INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY WORLD HEALTH ORGANIZATION SAFETY EVALUATION OF CERTAIN FOOD ADDITIVES WHO FOOD ADDITIVES SERIES: 42 Prepared by the Fifty-first meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA) World Health Organization, Geneva, 1999 IPCS - International Programme on Chemical Safety gamma-CYCLODEXTRIN First draft prepared by Dr P.J. Abbott Australia New Zealand Food Authority, Canberra, Australia Explanation Biological data Biochemical aspects Absorption, distribution, biotransformation, and excretion Toxicological studies Acute toxicity Short-term studies of toxicity Genotoxicity Developmental toxicity Special studies Ocular irritation and dermal sensitization Cell membrane effects Impurities Estimate of dietary intake Comments Evaluation References 1. EXPLANATION gamma-Cyclodextrin is a ring-shaped molecule made up of eight glucose units linked by alpha-1,4-bonds. It is produced by the action of the enzyme, cyclodextrin-glycosyl transferase (EC 2.4.1.19) on hydrolysed starch syrups. Cyclodextrin-glycosyl transferases are amylolytic enzymes that are produced naturally by various strains of Bacillus and other organisms. The gene coding for the cyclodextrin- glycosyl transferase used for the manufacture of gamma-cyclo-dextrin was isolated from Bacillus firmus and Bacillus lentus (both of which are considered non-pathogenic) and cloned into a strain of Escherichia coli K12. Mixtures of alpha-, ß-, and gamma-cyclodextrin are formed during the reaction, and the formation of gamma-cyclodextrin is optimized by the addition of the complexant, 8-cyclohexadecen-1-one, which causes precipitation of the gamma-cyclodextrin-8-cyclohexadecen-1-one complex, which can then be further purified. The final product contains > 98% gamma-cyclodextrin. Cyclodextrin-glycosyl transferase is inactivated by heat and removed from the final gamma-cyclodextrin product. The complexant, 8-cyclohexadecen-1-one, is extracted from the gamma-cyclodextrin with n-decane which, in turn, is separated from the final dry gamma-cyclodextrin product. The circular structure of gamma-cyclodextrin (Figure 1) provides a hydrophobic cavity which enables complexes to be formed with a variety of organic molecules, while the hydrophilic outer surface makes gamma-cyclodexrin water soluble. Because of these properties, gamma-cyclodextrin can be used in a variety of ways in food, with a potential intake in the order of grams per person per day.gamma-Cyclodextrin has not been reviewed previously by the Committee; however, the structurally related ß-cyclodextrin (seven glucose units) was evaluated at the forty-first and forty-fourth meetings of the Committee (Annex 1, references 107 and 116). 2. BIOLOGICAL DATA 2.1 Biochemical aspects 2.1.1 Absorption, distribution, biotransformation, and excretion Early experiments provided some evidence that gamma-cyclodextrin (unlike alpha- or ß-cyclodextrin) is hydrolysed by salivary amylase (French, 1957). More recent studies have confirmed that both human salivary amylase and human or porcine pancreatic amylase can readily hydrolyse gamma-cyclodextrin, yielding mainly maltose, some maltotriose, and smaller amounts of glucose (Abdullah et al., 1966; Marshall & Miwa, 1981; Kondo et al., 1990). The fate of intravenously administered gamma-cyclodextrin was examined in three male and two female rabbits and one male dog. The rabbits were each given a dose of 7.5 g in saline (30 ml of a 25% w/v solution), while the dog was given a dose of 25 g in saline (500 ml of a 5% w/v solution at 8.3 ml/min). Blood and urine samples were collected and examined by high-performance liquid chromatography (HPLC) for gamma-cyclodextrin over 4 h. The half-life of gamma-cyclo-dextrin in blood was about 50 min in rabbits and 30 min in the dog. In rabbits, about 77% of the injected dose was recovered as unchanged gamma-cyclodextrin in the urine within 24 h, while in the dog, nearly 80% of the injected dose was recovered as unchanged gamma-cyclodextrin in the urine within the first 4 h (Matsuda et al., 1985). Two male Wistar rats were given 14C-gamma-cyclodextrin (94% radiochemical purity) as single oral or intravenous doses. After an oral dose of 14C-gamma-cyclo-dextrin (25 µCi/kg bw diluted to 200 mg/kg bw), 50% of the radiolabel was excreted in the exhaled air within 24 h, while 2% was excreted in the urine and 5% in the faeces; 35% of the radiolabel was retained in the body after 24 h. No detectable gamma-cyclodextrin was found in blood during 8 h after administration, suggesting metabolism in the gastrointestinal tract. After the intravenous dose of 14C-gamma-cyclodextrin (25 µCi/kg bw diluted to 100 mg/kg bw), 90% of the radiolabel was excreted in the urine within 8 h, mainly as unchanged gamma-cyclodextrin. After 8 h, small amounts of radiolabel were excreted in exhaled air (1.1%), while 0.5% was detected in the faeces; 6% was retained in the body after 24 h (de Bie & van Ommen, 1994). Groups of four male Wistar rats were given single oral or intravenous doses of 14C-gamma-cyclodextrin. The oral dose was 1000 mg/kg bw, and the concentration of radiolabel was either 25 or 100 µCi/kg bw. In order to examine the role of the gut microflora in the metabolism of gamma-cyclodextrin, a separate group of germ-free male rats was given 25 µCi/kg bw gamma-cyclodextrin diluted to 1000 mg/kg bw. The intravenous dose was 600 mg/kg bw, and the concentration of radiolabel was 25 µCi/kg bw. In the first experiment, the time-course and routes of metabolism were examined after oral administration. After administration of 1000 mg/kg bw (25 µCi/kg bw) 14C-gamma-cyclodextrin, 62% of the radiolabel in males and 71% in females was excreted within 48 h. The majority was excreted in expired air (57% in males and 65% in females), with maximum excretion between 1 and 2 h after dosing. Little was excreted in the urine (2.1% for males and 2.5% for females) or faeces (2.9% for males and females) during the 48-h sampling period. Retention of radiolabel after 48 h was 27% in males and 22% in females, with the most significant retention in the liver (11% in males, 5.2% in females). The amounts in all other organs were low: intestine, 0.42% for males, 0.36% for females; kidney, 0.13% for males. In the second experiment, the excretion kinetics and time-course in blood over 24 h were examined after a single oral dose of 1000 mg/kg bw (100 Ci/kg bw) 14C-gamma-cyclodextrin. The major route of excretion was exhaled air (55% for males; 53% for females) during the 24-h sampling period. The carcass retained 35% of the radioactive dose in males and 25% in females at 24 h after treatment. The maximum concentration in blood was reached 40 min after treatment, but this concentration decreased by 50% after 0.5 h in males and after 6 h in females. The urine of animals of each sex contained a peak that eluted before glucose at all times and a small peak that co-eluted with glucose (6% of total radiolabel). A small amount of unchanged gamma-cyclo-dextrin was detected in urine after 4 h (< 0.02% of the ingested dose). HPLC analysis of the stomach contents 24 h after dosing revealed the presence of gamma-cyclodextrin and a minor peak that co-eluted with glucose. HPLC analysis of the blood revealed the presence of a radioactive peak that co-eluted with glucose. In the third experiment, the excretion kinetics and time-course in blood over 24 h were examined after a single intravenous dose of 600 mg/kg bw (25 µCi/kg bw) 14C-gamma-cyclodextrin. The major route of excretion was the urine (87% for males, 91% for females), and the faeces contained about 1% and the gastrointestinal tract about 0.5% of the radiolabel; the exhaled air contained 7.8% of the dose for males and 3.2% for females. The carcass contained 3.9% of the dose in males and 2.2% in females, the liver having the most residue (0.41% in males, 0.42% in females). Radiolabel was removed rapidly from the blood, with calculated initial half-lives of 20 min in males and 15 min in females. HPLC analysis of blood revealed predominantly gamma-cyclodextrin. In the fourth experiment, excretion kinetics over 24 h was examined in germ-free rats given a single oral dose of 1000 mg/kg bw (25 µCi/kg bw) gamma-cyclodextrin. About 73% of the radiolabel was excreted in expired air (68% in males, 65% in females). Peak exhalation of 14C-carbon dioxide occurred at about 90 min. Low concentrations of radiolabel were found in faeces and urine. The gastrointestinal tract contained 9.2% in males and 11% in females, with the majority in the caecum. The results indicate that gastrointestinal microflora play little part in the metabolism of gamma-cyclodextrin. Overall, this study indicates that gamma-cyclodextrin is metabolized to glucose, other low-molecular-mass sugar metabolites, and carbon dioxide by luminal and/or epithelial enzymes of the gastrointestinal tract (de Bie & van Ommen, 1994; de Bie et al., 1998). 2.2 Toxicological studies 2.2.1 Acute toxicity The acute toxicity of gamma-cyclodextrin was examined in mice and rats; the results are summarized in Table 1. In each study, groups of 10 animals of each sex were tested at three doses or served as controls. There were no deaths at the highest doses tested (Matsuda et al., 1983). Table 1. Acute toxicity of gamma-cyclodextrin Species Sex Route LD50 Reference (mg/kg bw) Mouse Male and female Oral >16 000 Matsuda et al. (1983) Mouse Male and female Subcutaneous > 4 000 Matsuda et al. (1983) Mouse Male and female Intravenous > 4 000 Matsuda et al. (1983) Mouse Male and female Intravenous 10 000 Riebeek (1990a) Rat Male and female Oral > 8 000 Matsuda et al. (1983) Rat Male and female Subcutaneous > 2 400 Matsuda et al. (1983) Rat Male and female Intravenous > 3 750 Matsuda et al. (1983) Rat Male and female Intravenous > 3 750 Riebeek (1990b) Rat Male Intraperitoneal > 4 600 Riebeek (1990c) In a test for micronucleus formation (see section 2.2.3), groups of 15 Swiss mice of each sex were given a single dose of 15 g/kg bw gamma-cyclodextrin by gavage and were killed in groups of five at 24, 48, and 72 h. All of the animals survived until termination (Immel, 1991). The toxicity of intravenously administered gamma-cyclodextrin was examined in groups of five male and five female Crl:CD mice and five male and five female Crl:W1(WU)BR rats. The mice were given gamma-cyclodextrin (purity, > 98%) at doses of 5000, 7500, or 10 000 mg/kg bw, while the rats were given doses of 2500, 3750, or 5000 mg/kg bw as a solution in sterile saline. The animals were observed for clinical signs over 14 days after treatment. They were examined for gross pathological changes on day 14 after treatment. Both mice and rats showed dose-related signs of toxicity, such as piloerection and sluggishness, within 1 h to a few days after treatment. Deaths occurred within a few days in both species, but the surviving animals recovered and appeared to be healthy at the end of the observation period. Macroscopic examination revealed no gross treatment-related alterations (Riebeek, 1990a,b). The toxicity of intraperitoneally administered gamma-cyclodextrin was examined in groups of three male rats after single doses of 2000 or 4600 mg/kg bw as a solution in sterile saline. The animals were observed for clinical signs during 14 days after treatment and were examined grossly for pathological changes on the last day. There were no signs of toxicity and no deaths. Macroscopic examination revealed no gross treatment-related alterations (Riebeek, 1990c). 2.2.2 Short-term studies of toxicity Rats Groups of 15 Wistar rats of each sex were given gamma-cyclodextrin intravenously as single daily doses of 0, 200, 630, or 2000 mg/kg bw for 30 days. A group of five animals of each sex were allowed to recover for 27 days after treatment. The animals were examined throughout the study, and the body weights recorded weekly. Clinical chemical parameters were examined at the end of treatment and after the recovery period. Ten animals from each group were killed at the end of treatment and the remainder at the end of the recovery period. There were no clinical signs of toxicity throughout the study. The body-weight gain of males at 630 and 2000 mg/kg bw per day was slightly decreased, but the difference was not significant. Food consumption was decreased in a dose-related manner only during the first few days of treatment. Significantly decreased mean values for haemoglobin concentration and haemacrit were seen in males at doses > 630 mg/kg bw per day, and significantly decreased erythrocyte count in males at 2000 mg/kg bw per day. In females, the erythrocyte count, haemoglobin concentration, and haematocrit were significantly decreased only at 2000 mg/kg bw per day. The reticulocyte counts were significantly increased in both males and females at 2000 mg/kg bw per day. These changes were reversed after the recovery period. The only significant clinical chemical change was an increase in creatinine and urea in both males and females at 2000 mg/kg bw per day, which was reversed at the end of the recovery period. Urinalysis revealed a significantly increased incidence of haemoglobin in the urine of rats at 2000 mg/kg bw per day, which was reversed at the end of the recovery period. Pathological examination at autopsy showed that the majority of animals at 2000 mg/kg bw per day had light-coloured and, in some cases, irregularly coloured kidneys. A dose-dependent increase in spleen weight was found in all groups, which was significant in males at doses > 630 mg/kg bw per day and in females at all doses. Liver weights were significantly increased in females at > 630 mg/kg bw per day, and kidney weights were significantly increased at 2000 mg/kg bw per day. Lung and adrenal weights were significantly increased in both males and females at 2000 mg/kg bw per day. These changes were partially reversed after the recovery period, but a significant increase in kidney and spleen weights was still present in females at 2000 mg/kg bw per day. Histopathological examination revealed marked vacuolation of renal epithelial cells in the proximate convoluted tubules, which may have been related to administration of a substance that causes hyperosmolarity. There was also extensive pulmonary histiocytosis (massive accumulation of alveolar macrophages) in all animals at 2000 mg/kg bw per day. These changes were seen only in some animals at 630 mg/kg bw per day and at lesser severity. Considerable reversibility was observed after the recovery period. The NOEL was 200 mg/kg bw per day (Fuchs et al., 1992). Groups of 15 Wistar rats of each sex were given gamma-cyclodextrin intravenously as single daily doses of 0, 60, 120, or 600 mg/kg bw for 90 days. Groups of five animals of each sex were allowed to recover at the end of the treatment period. The animals were examined throughout the study, and body weights were recorded weekly. Haematological and urinary parameters were examined after one month, at the end of the study, and on day 37 (males) or 36 (females) of recovery. Clinical chemical parameters were examined at the end of the treatment period and after recovery. Animals were killed after 90 days, their organs were examined, and tissues were taken for histopathological examination. There were no clinical signs of toxicity. Body-weight gain was slightly decreased only in males at the high dose, and food consumption was decreased in a dose-related manner only during the first few days of treatment. Haematological examination revealed a slight decrease in the mean erythrocyte count, haemaglobin concentration, and haemacrit in females at one month, and these values were significantly decreased at three months only in females at the high dose. The reticulocyte counts were significantly increased in females at the high dose at three months. At the end of the recovery period, all of these values were normal. The only clinical chemical changes were a slight decrease in bilirubin concentration in males and females at the high dose and a slight increase in alkaline phosphatase activity in males at the high dose. At the end of the recovery period, all of the values were normal. The slight changes observed in urinary parameters were considered not to be treatment-related. Histological examination at autopsy revealed an increased incidence of enlarged iliac lymph nodes in males and females at the high dose, which was probably related to inflammation at the injection site. Increases in the relative weights of lungs, liver, and spleen were seen in males and in the relative weights of heart, lungs, kidneys, spleen, and adrenal glands in females at the high dose. All of these changes were reversed after the four-week recovery period. Histopathological examination revealed hyperplasia of the mucosa of the urinary bladder, which was reversed after four weeks, and pulmonary histiocytosis (macrophage aggregates), which tended to reverse after four weeks, in males and females at the high dose. The reversibility of the urinary bladder changes indicates that the hyperplasia was not preneoplastic. The NOEL was 120 mg/kg bw per day (Ehling et al., 1992). Groups of five male Wistar rats were fed diets containing gamma-cyclo-dextrin at concentrations of 0, 5, 10, 15, or 20%, equivalent to 0, 2500, 5000, 7500, or 10 000 mg/kg bw per day, for 14 days. A control group was fed 20% lactose. The animals were examined for clinical signs of toxicity, and food and water consumption was monitored throughout the study. On day 14, the animals were killed, and blood samples were taken for examination of clinical chemical parameters. The animals were also examined macroscopically for pathological changes. There were no deaths. The incidence of soft stools was slightly higher in treated than control animals, and the mean body weights of treated animals were slightly lower than those of controls, although this difference was not statistically significant. Food intake was slightly lower in controls than in treated groups. Plasma alkaline phosphatase activity was increased in animals at 15 and 20%, while gamma-glutamyl transferase activity was decreased in all treated groups. The activity of aspartame and alanine aminotransferases were unchanged, as were the concentrations of total protein, albumin, urea, and bilirubin. Enlargement of the caecum was seen at all doses, the most significant effect occurring in the group fed 20% lactose. There were no macroscopic changes attributable to treatment (Lina & Jonker, 1989; Lina & Bär, 1998). Groups of 20 Wistar rats of each sex were fed diets containing gamma-cyclo-dextrin at concentrations of 0, 1.5, 5, or 20% (equivalent to 0, 750, 2500, or 10 000 mg/kg bw per day) for 13 weeks. A control group was fed 20% lactose. In order to examine the reversibility of any effects seen, a group of 10 animals of each sex were fed either 20% gamma-cyclodextrin or 20% lactose for 13 weeks and then control diet for one month. As a result of a feeding error, the groups receiving 20% gamma-cyclodextrin were discarded, and two additional groups were fed 0 or 20% gamma-cyclodextrin for 13 weeks and 10 animals receiving the 20% dose were fed control diet for an additional month at the end of the 13-week period. Animals were examined for clinical signs of toxicity, and food and water consumption was monitored throughout the study. Ophthalmoscopic examinations were conducted in animals at the high dose and those given lactose before treatment and at the end of the study. The animals were killed at the end of the study, and blood samples were taken for clinical chemistry. The animals were also examined macroscopically for pathological changes. There were no treatment-related deaths during the study. Soft stools were observed in some rats at 5 or 20% gamma-cyclodextrin and in those given lactose early in the study, but this effect disappeared subsequently. Ophthalmoscopic examination revealed no treatment-related effects. The body weights of males at 20% gamma-cyclodextrin were slightly but significantly decreased throughout treatment; a more significant body-weight decrease was seen in the males given 20% lactose. No difference was noted in these groups during the recovery period. Food conversion efficiency was also slightly decreased in males at 20% lactose. None of the changes in haematological parameters was considered to be of toxicological significance. Some changes in clinical chemistry were seen in females at the high dose, namely increased activity of aspartate and alanine aminotransferases, especially in one female. The sodium concentrations were slightly higher but within the historical control range. Urinary parameters were similar in control and treated groups, apart from a significant increase in the urinary calcium concentration at the end of treatment in males given 20% gamma-cyclodextrin and rats of each sex given 20% lactose; the effect was more pronounced in the latter group. The calcium:creatinine ratio was significantly increased in rats receiving 20% lactose. The increased calcium appeared to be associated with the increased load of osmotically active substances in the large intestine; there was no increase in calcium at the end of the recovery period. Analysis of organ weights revealed significant increases in both absolute and relative caecal weights in rats at 5 and 20% gamma-cyclodextrin and 20% lactose in comparison with controls. At the end of the recovery period, no difference from controls was seen for rats given 20% gamma-cyclodextrin, but the increase was still evident in those given 20% lactose. This effect is probably related to the retention of an osmotically active substance in the large intestine. Relative adrenal weights were increased in males given 20% gamma-cyclodextrin and the lactose control group at the end of the study. A very slight increase in relative liver weight was seen in males at 20% gamma-cyclodextrin and females given lactose. No changes in organ weight were seen at the end of the recovery period. There were no gross pathological changes attributable to treatment with gamma-cyclodextrin. Microscopic examination revealed increased cortico-medullary mineralization in the kidneys of rats at 1.5 and 5% gamma-cyclodextrin but not at the high dose. This change is considered to be relatively common in rats and not related to treatment with gamma-cyclodextrin. There was no evidence of hyperplasia of the mucosa of the urinary bladder or of pulmonary histiocytosis, which were observed after intravenous administration. The effects observed in rats after receiving gamma-cyclodextrin in the diet at concentrations up to 20% appeared to be largely related to the presence of high levels of an osmotically active substance in the large intestine and not of toxicological significance. Similar, and generally more pronounced, effects were observed when the diet contained 20% lactose. On the basis of this study, dietary levels of 20% gamma-cyclodextrin (equivalent to10 000 mg/kg bw per day) were considered to be tolerated without toxicological effects (Lina, 1992a; Lina & Bär, 1998). Dogs Groups of four male and four female beagle dogs were fed diets containing gamma-cyclodextrin at doses of 0, 5, 10, or 20% (equivalent to 0, 1250, 2500, or 5000 mg/kg bw per day). Body weight and food consumption were recorded weekly throughout the study. Ophthalmoscopic examinations were made at the beginning and end of the study. Blood was collected for clinical chemical and haematological examination before the start of treatment and at weeks 6 and 13. Urinalyses were performed at week 13. During week 14, all animals were killed, their organs were examined, and tissues were prepared for histopathological examination. There were no deaths during the study and no clinical signs of toxicity. Diarrhoea was noted in all groups, increasing in incidence and severity with increasing doses of gamma-cyclodextrin, and was more severe in females than in males. This effect was attributed to the slow digestion and intestinal absorption of gamma-cyclodextrin. Ophthalmoscopic examination revealed no differences between treated and control animals. Weight gain was comparable in all groups, except for a slight, non-significant decrease in males at 20% during the last six weeks of the study. Treated dogs had slightly decreased food intake during the first two weeks of the study, particularly at the high dose. This effect persisted throughout the study only in dogs at the high dose. No differences in haematological parameters were seen, and clinical chemical parameters were similar in treated and control groups. Urinalysis revealed a slight decrease in urinary pH in the group receiving 20% gamma-cyclodextrin, which was considered to be associated with the intake of poorly digestible carbohydrates and increased fermentation in the large intestine. Both the absolute and relative weights of the ovary were increased in animals at 10 and 20% gamma-cyclodextrin, but no histopathological changes were seen, and the weight of the ovaries in the control group was lower than that of other dogs in the same laboratory. The changes observed are considered unlikely to be toxicologically significant. There was no change in absolute liver weight, although the relative liver weight was increased in males at the high dose as a result of the slight decrease in body weight at this dose. This change is likely to be adaptive and was considered not to be toxicologically significant. Caecal weights were increased in the dogs at 10 and 20% gamma-cyclodextrin but statistically significantly only in females. This change is considered to be related to the presence of high levels of an osmotically active substance in the large intestine. Pathological examination at the end of the study revealed no treatment-related change. Similarly, the histopathological findings were unremarkable. On the basis of this study, dietary levels of 20% gamma-cyclodextrin (equivalent to 5000 mg/kg bw per day) were considered to be tolerated without toxicological effects (Til & van Nesselrooij, 1992; Til & Bär, 1998). 2.2.3 Genotoxicity The results of assays for genotoxicity with gamma-cyclodextrin are shown in Table 2. 2.2.4 Developmental toxicity Rats In a study of embryotoxicity and teratogenicity, groups of 25 presumed pregnant Wistar Crl:(WI)WU BR rats were fed diets containing gamma-cyclodextrin (purity, >98%) at concentrations of 0. 1.5, 5, 10, or 20% (equivalent to 0, 2500, 5000, or 10 000 mg/kg bw per day) on days 0-21 of gestation. A separate group received a diet containing 20% lactose instead of pre-gelatinized potato starch. The animals were examined throughout the study, and body weight and food consumption were recorded. The rats were killed on day 21 and examined for parameters of reproductive performance. Fetuses were examined for signs of toxicity, external malformations, and soft-tissue defects and were stained for detection of skeletal anomalies. No deaths occurred during the study. Maternal body-weight gain was similar in all groups except for a slight reduction at the 20% dose on days 0-16 of gestation. Necropsy of the dams showed no adverse effects that could be related to treatment. The number of viable litters, the number of corpora lutea, and the mean number of implantation sites were similar in all groups. Fetal length and body weight were also similar in all groups. Examination of the fetuses revealed no treatment-related increase in gross, skeletal, or visceral abnormalities. Under the conditions of this assay, gamma-cyclodextrin was not teratogenic (Verhagen & Waalkens-Berendsen, 1991). Rabbits In a study of embryotoxicity and teratogenicity, groups of 16 presumed pregnant New Zealand white rabbits were fed diets containing gamma-cyclodextrin (purity, > 98%) at concentrations of 0, 5, 10, or 20% (equivalent to 0, 1500, 3000, or 6000 mg/kg bw per day) on days 0-29 of gestation. The animals were examined throughout the study, and body weights and food consumption were recorded regularly. The animals were killed on day 29 of pregnancy, and the fetuses were examined for signs of toxicity, external malformations, and soft-tissue defects and were stained for detection of skeletal anomalies. Table 2. Results of assays for the genotoxicity of gamma-cyclodextrin End-point Test object Concentration Result Reference Bacterial gene S. typhimurium TA1535, 2-20000 Negativea Blijleven (1991) mutation TA1537, TA 1538, µg/plate TA98, TA100 Chromosomal Human lymphocytes 10-5000 Negativea de Vogel & van aberrationb µg/ml Delft (1996) Micronucleus CD-1 mouse bone 15 g/kg bw Negative Immel (1991) formationb marrow (single dose) a With and without exogenous metabolic activation b Two assays conducted: treatment times, 6, 24, and 48 h; harvest times, 24 and 48 h No deaths occurred during the study. Diarrhoea was seen in several treated animals. Maternal body weight was significantly decreased at the 20% dose during the first week of treatment but not thereafter. Necropsy of the does showed no adverse effects that could be related to treatment. The number of viable litters, the number of corpora lutea, and the mean number of implantation sites were similar in all groups. One abortion occurred in the control group and one in rabbits at the 10% dose. Fetal length and body weight were similar in all groups. Examination of the fetuses revealed no treatment-related increase in gross, skeletal, or visceral abnormalities. An increase in the incidence of haemorrhagic fluid in animals at the 5 and 20% doses was considered unlikely to be treatment-related. Under the conditions of this assay, gamma-cyclodextrin was not teratogenic (Waalkens-Berendsen & Smits-van Prooije, 1992). 2.2.5 Special studies 2.2.5.1 Ocular irritation and dermal sensitization gamma-Cyclodextrin was not irritating or corrosive to the eyes of albino rabbits (Prinsen, 1990). In a skin sensitization assay in guinea-pigs, a 30% solution of gamma-cyclodextrin induced no signs of sensitization (Prinsen, 1992). 2.2.5.2 Cell membrane effects The interactions between alpha-, beta-, and gamma-cyclodextrin and membrane phospholipids, liposomes, and human erythrocytes were studied in vitro. gamma-Cyclodextrin and the other cyclodextrins did not increase the permeability of dipalmityol-phosphatidylcholine liposomes, nor did they affect the active transport of 42K+ into erythrocytes at a concentration of 10-2 mol/L. ß-Cyclo-dextrin but not gamma-cyclodextrin or alpha-cyclodextrin increased the release of 42K+, 86Rb+, and 137Cs+ from erythocytes by passive transport at a concentration of 1.7 × 10-2 mol/L (Szejtli et al., 1986). gamma-Cyclodextrin induced haemolysis of human erythrocytes in vitro in isotonic saline after 30 min, with a threshold concentration of 16 mmol/L (approximately 20 mg/L). A similar effect was seen with alpha-cyclodextrin at 6 mmol/L and with ß-cyclodextrin at 3.5 mmol/L. At 15 mmol/L, gamma-cylodextrin caused a 2% release of cholesterol from erythrocytes, indicating that cyclodextrin-induced haemolysis is associated with removal of membrane components from erythrocytes (Irie et al., 1982). Other studies have confirmed that gamma-cyclodextrin causes erythrocyte haemolysis at concentrations of 15-30 mmol/L (Okada et al., 1988; Yoshida et al., 1988; Leroy-Lechat et al., 1994). In a study on the differential effects of cyclodextrins on human erythrocytes in vitro, alpha-, ß-, and gamma-cyclodextrin were incubated at increasing concentrations with erythrocytes for 30 min. The cyclodextrins induced a change in shape, from discocyte to spherocyte, but with ß-cyclodextrin haemolysis occurred before the change was complete. gamma-Cyclodextrin was less potent than either alpha- or ß-cyclodextrin in releasing potassium and haemoglobin from erythrocytes and in solubilizing various components of erythrocytes, including phospholipids, cholesterol, and proteins. A concentration of 4 mmol/L gamma-cyclodextrin was required to induce release of phospholipid, and > 20 mmol was required for release of cholesterol or protein (Ohtani et al., 1989). The potential cytotoxicity of the cyclodextrins to P388 murine leukaemia cells was examined by exposing the cells to increasing concentrations of cyclodextrins for 48 h in medium containing 10% fetal calf serum. Initial cytotoxicity was elicited at 11 mmol/L alpha-cyclodextrin, 2.5 mmol/L ß-cyclodextrin, and 55 mmol/L gamma-cyclodextrin (Leroy-Lechat et al., 1994). Potential reductions in the luminescence of a strain of E. coli after incubation with various concentrations of cyclodextrins were examined. Luminescence was reduced by 20 and 50% by ß-cyclodextrin at concentrations of 0.03 and 0.5%, respectively. With gamma-cyclodextrin, a concentration of 2% was required to reduce the luminescence by 20%, and a 50% reduction could not be achieved even at the highest concentration of 10% gamma-cyclodextrin (Bär & Ulitzur, 1994). 2.2.5.3 Impurities Cyclodextrin-glycosyl transferase The gene coding for cyclodextrin-glycosyl transferase is derived from a strain of the Bacillus firmus-lintus complex. This is a ubiquitous group of aerobic, gram-positive, alkalophilic microorganisms which form sub-terminal endospores. Both B. firmus and B. lintus are considered to be non-pathogenic. After isolation from this strain, the gene was cloned into pUC18, isolated again and inserted into an expression and secretion vector derived from pJF118EH by introduction of a DNA fragment coding for an appropriate signal peptide. The vector, pJF118EH, is derived from pBR322, a widely used vector which is considered to be safe. All genetic modifications were made by directed mutagenesis by standard techniques. The gene that has been introduced for production of the signal peptide is cleaved off during exportation of cyclodextrin-glycosyl transferase and degraged with the E. coli cell. A strain derived from E. coli K12 was used as the host for the cyclodextrin-glycosyl transferase expression and secretion vector. E. coli K12 is considered to be a non-pathogenic strain and is used for production of enzymes for food use. For the production of cyclodextrin-glycosyl transferase, the recombinant E. coli strain was cultured in a standard medium. The pH of the fermentation broth was adjusted by adding food-grade ammonia or phosphoric acid. The E. coli was grown to a certain density, after which enzyme production was initiated by addition of isopropyl thiogalactoside. The bacteria were then removed by fermentation and the supernatant filtered and concentrated to the crude cyclodextrin-glycosyl transferase preparation. Groups of 20 Wistar rats of each sex were given an aqueous solution of a cyclodextrin-glycosyl transferase preparation at doses of 0, 5, 10, or 20 ml/kg bw per day, equivalent to 0, 65, 130, or 260 mg/kg bw per day of total organic solids (TOS), by gavage for 13 weeks. The animals were examined for clinical signs of toxicity, and food and water consumption was monitored throughout the study. Ophthalmoscopic examinations were conducted in rats at the high dose before treatment and at the end of the study. Haematological parameters were examined before treatment, on days 30 and 60, and at the end of the study. The animals were killed at the end of the study, and blood samples were taken for examination of clinical chemical parameters. The animals were also examined macroscopically for pathological changes, and samples were taken for histopathological examination. Two animals (one control male and one female at the low dose) died as a result of dosing accidents. There were no clinical signs of toxicity in the treated animals which survived. Ophthalmoscopic examination of animals at the high dose revealed no treatment-related changes. There was no significant difference in body weight between treated and control rats, and food consumption was unchanged in the treated group. There were no treatment-related haematological, clinical chemical, or urinary changes. The organ weights of control and treated groups were similar, and there were no treatment-related gross pathological changes. Histopathological examination revealed an increased incidence of pulmonary changes in the treated animals which were considered to be related to aspiration of test material. The NOEL was 20 ml/kg bw per day, equivalent to 260 mg/kg bw per day of TOS, the highest dose tested (Jonker, 1994). The cyclodextrin-glycosyl transferase preparation was tested for mutagenic activity in S. typhimurium strains TA1535, TA1537, TA98, and TA100 with and without metabolic activation at concentrations of 19-1500 µg/plate or 62-500 µg/plate. The assay was slightly complicated by the growth-stimulating effects of some of the components of the crude preparation, but the overall result confirmed that cyclodextrin-glycosyl transferase had no mutagenic activity in these strains. 8-Cyclohexadecen-1-one 8-Cyclohexadecen-1-one is a colourless, waxy, solid product. The commercial preparation has a purity of > 98%. The acute toxicity of 8-cyclo-hexadecen-1-one was examined in five male and five female mice at a dose of 5 ml/kg bw (4.6 g/kg bw) and in five male and five female rats at doses of 5 and 10 g/kg bw. The animals were observed for 14 days. Two of the five mice died during the study, but there were no deaths among the rats. It was concluded that the LD50 was > 4.6 g/kg bw in mice and > 10 g/kg bw in rats (Dickhaus & Heisler, 1985; Spanjers, 1986). Groups of five CD-1 mice of each sex were fed diets containing 8-cyclo-hexadecen-1-one at doses of 0, 500, 1500, or 7500 mg/kg diet (equivalent to 0, 75, 230, or 1100 mg/kg bw per day) for four weeks. The animals were examined for clinical signs of toxicity, and food and water consumption were monitored throughout the study. Haematological and clinical chemical parameters were examined before treatment and at the end of the study. The animals were also examined macroscopically for pathological changes, and samples were taken for histopathological examination. There were no deaths and no clinical signs of toxicity. The body-weight gain of mice at the high dose was decreased, but food and water intake were similar in treated and control groups. There were no treatment-related haematological changes. The only clinical chemical change was a decrease in the albumin:globulin ratio in males at the high dose. An increase in relative liver weight was seen in males and females at the high dose. No treatment-related gross abnormalities were seen, but microscopic examination revealed effects in the cytoplasm of four males at the high dose. The NOEL was 1500 mg/kg diet, equivalent to 230 mg/kg bw per day (Lina, 1992b). Groups of five male and five female Wistar rats were fed diets containing 8 cyclohexadecen-1-one at doses of 0, 600, 3000, or 15 000 mg/kg diet (equivalent to 0, 30, 120, or 750 mg/kg bw per day) for four weeks. The animals were examined for clinical signs of toxicity, and food and water consumption was monitored throughout the study. Haematological and clinical chemical parameters were examined before treatment and at the end of the study; the animals were also examined macroscopically for pathological changes, and samples were taken for histopathological examination. There were no deaths and no clinical signs of toxicity. A number of effects were seen in animals at the high dose. Body-weight gain and food intake were decreased, and the red blood cell counts and packed cell volume were increased. Clinical chemistry revealed increased plasma urea and creatinine concentrations in males and decreased albumin in females, and urinalysis showed increased urinary density in animals of each sex. The absolute and relative liver weights were increased in animals of each sex at the high dose and also in males at the intermediate dose. The absolute and relative adrenal weights were decreased in females at the high dose. Gross examination revealed no remarkable findings, but microscopic examination showed treatment-related hepatocellular cytoplasmic alterations in animals of each sex at the high dose. There was no evidence of degeneration or necrosis. The NOEL was 600 mg/kg diet, equivalent to 30 mg/kg bw per day (Lina et al., 1986). 8-Cyclohexadecen-1-one was tested for mutagenic activity in S. typhimurium strains TA1535, TA1537, TA1538, TA98, and TA100 with and without microsomal activation. There was no increase in the number of revertants of any of the strains tested (Wilmer, 1986). 8-Cyclohexadecen-1-one was also tested for its capacity to induce micronuclei in animals treated in vivo. Groups of 30 CD-1 mice of each sex were given the compound by gavage at a dose of 3 or 5 ml/kg bw (equivalent to 2.8 and 4.6 g/kg bw). Five animals of each sex were killed at 24 and 48 h and two of each sex at 72 h after treatment. Examination of the bone marrow showed no increase in the number of normochromatic erythrocytes over that in control mice (Willems, 1986). 3. ESTIMATE OF DIETARY INTAKE gamma-Cyclodextrin can be used as a carrier for flavours, sweeteners, and colours, and it has been proposed for use in this manner in dry mixes for beverages, soups, dressings, gravies, sauces, puddings, gelatines, and fillings and also in instant coffee and instant tea, coffee whiteners, compressed sweets, chewing gum, breakfast cereals, savoury snacks, crackers, and spices and seasonings. It is also proposed for use as a carrier for vitamins and polyunsaturated fatty acids in dry food mixes and in dietary supplements, as a flavour modifier in soya milk, and as a stabilizer in bread spreads, frozen dairy desserts, baked goods, bread, fruit-based fillings, fat-based fillings, processed cheese, and dairy desserts. The estimated daily intake of gamma-cyclodextrin from its use in food has been calculated by the dietary survey approach (Amann et al., 1998), which is based on food consumption data from the 1989-91 Continuing Survey of Food Intakes by Individuals, in which data were collected from a representative sample of individuals residing in households in the United States. Each individual was surveyed over three successive one-day periods, and the foods consumed were coded into one of about 6000 different categories. For the purposes of the calculation, it was assumed that each food (or food component) that contains gamma-cyclodextrin contains this substance at the highest feasible concentration. When gamma-cyclodextrin was used as a component of the food, the intake of that component was calculated from data on food consumption. The estimated daily intake was calculated for each food in which gamma-cyclodextrin may be used from data on one- and three-day food intake. Intakes were calculated both per capita and per user. Users were defined as individuals who consumed a food of at least one of the categories concerned on at least one occasion. The largest amounts of gamma-cyclodextrin are consumed with soya milk and dairy desserts. Relatively high intakes (> 2 g/day) also result from its use in bread spreads and fruit-based fillings. The mean one-day intake of gamma-cyclodextrin from all its food uses was estimated to be 4.1 g. The 90th percentile user was estimated to ingest about 8.8 g on any one day. The three-day averages are 4 g for the mean intake and 7.5 g for the 90th pecentile consumer. The intake of gamma-cyclodextrin from chewing gum was estimated from a separate survey on chewing-gum intake in the United States, and the average consumer was estimated to ingest about 0.07 g gamma-cyclodextrin per day. These data represent a 'worst-case' scenario and are based on the assumption that gamma-cyclodextrin is used simultaneously in all possible applications and at the highest feasible concentrations. The realistic average daily intake of gamma-cyclodextrin would therefore be lower than the levels indicated above. 4. COMMENTS The Committee noted that the close structural similarity between gamma-cyclodextrin and ß-cyclodextrin allows some comparisons to be made of the metabolism and the toxicity of these two compounds. The metabolism of gamma-cyclodextrin is different from that of ß-cyclodextrin, as demonstrated both in vitro and in vivo. In rats in vivo, gamma-cyclodextrin (at single doses up to 1000 mg/kg bw) is rapidly metabolized to glucose, presumably by the luminal and/or epithelial enzymes of the gastrointestinal tract. In contrast to the metabolism of ß-cyclodextrin, there was little involvement of the gastrointestinal microflora. Similarly, in contrast to ß-cyclodextrin, much less gamma-cyclodextrin was absorbed and only very low levels could be detected in the urine. After intravenous injection, gamma-cyclodextrin (at single doses up to 600 mg/kg bw) was rapidly cleared from the blood and was excreted, largely unchanged, in the urine. Although no studies of metabolism in humans in vivo were available, gamma-cyclo-dextrin, unlike ß-cyclodextrin, can be readily hydrolysed by human salivary and pancreatic amylases in vitro. Short-term (28- and 90-day) studies of toxicity indicate that gamma-cyclodextrin has little toxicity when given intravenously or orally to rats or orally to dogs. After administration of a very high dietary concentration (20%), caecal enlargement and associated changes were seen in both species. This effect is likely to result from the presence of a high concentration of an osmotically active substance in the large intestine. This result suggests that the metabolism of gamma-cyclodextrin is less efficient at doses higher than those used in the studies of metabolism. The results of the studies in rats treated intravenously indicate that gamma-cyclodextrin is well tolerated, even when given systemically, and may be less toxic than ß-cyclodextrin. Studies conducted in rats and rabbits with gamma-cyclodextrin at doses up to 20% of the diet did not indicate any teratogenic effects. Similarly, the results of a battery of studies of genotoxicity were negative. Long-term studies of toxicity, carcinogenicity, and reproductive toxicity have not been conducted, but, given the rapid metabolism of this substance to glucose and its lack of genotoxicity, the Committee concluded that such studies were not required for an evaluation. In vitro, gamma-cyclodextrin, like ß-cyclodextrin, sequestered components of the membranes of erythrocytes, causing haemolysis. The threshold concen-tration for this effect was, however, higher than that of ß-cyclodextrin. Furthermore, gamma-cyclodextrin was not detected in blood after dietary administration of high doses to animals in vivo. It was considered unlikely that interaction of gamma-cyclodextrin with lipophilic vitamins would impair their bioavailability, because of the rapid digestion of gamma-cyclodextrin in vivo. Also, there was no evidence that vitamin deficiency was induced in experimental animals given high doses of gamma-cyclodextrin. The Committee considered studies on the short-term toxicity and genotoxicity of the enzyme, cyclodextrin-glycosyl transferase, used in the production of cyclodextrins, and of the complexant, 8-cyclohexadecen-1-one, used to optimize formation of gamma-cyclodextrin. The data indicated that these substances are unlikely to be of toxicological concern in final preparations of gamma-cyclodextrin that comply with the specifications. The Committee also considered information on genetic modifications in the organism used to produce the enzyme, which raised no concern. Although no studies of human tolerance to gamma-cyclodextrin were submitted to the meeting, the Committee was aware that such a study was available. Although it was unable to review the data, the Committee was reassured by the relatively low toxicity of this compound in animals and the fact that it is less toxic than ß-cyclodextrin, for which studies of human tolerance were available. 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See Also: Toxicological Abbreviations Cyclodextrin, gamma- (WHO Food Additives Series 44)