FAO Nutrition Meetings Report Series No. 40A,B,C WHO/Food Add./67.29 TOXICOLOGICAL EVALUATION OF SOME ANTIMICROBIALS, ANTIOXIDANTS, EMULSIFIERS, STABILIZERS, FLOUR-TREATMENT AGENTS, ACIDS AND BASES The content of this document is the result of the deliberations of the Joint FAO/WHO Expert Committee on Food Additives which met at Rome, 13-20 December, 19651 Geneva, 11-18 October, 19662 1 Ninth Report of the Joint FAO/WHO Expert Committee on Food Additives, FAO Nutrition Meetings Report Series, 1966 No. 40; Wld Hlth Org. techn. Rep. Ser., 1966, 339 2 Tenth Report of the Joint FAO/WHO Expert Committee on Food Additives, FAO Nutrition Meetings Report Series, 1967, in press; Food and Agriculture Organization of the United Nations World Health Organization 1967 ETHYL p-HYDROXYBENZOATE Synonyms Ethyl p-oxybenzoate; Ethylparaben Chemical name Ethyl p-hydroxybenzoate; ethyl ester of p-hydroxybenzoic acid Empirical formula C9H10O3 Structural formulaMolecular weight 166.18 Definition Ethyl p-hydroxybenzoate, after drying for 2 hours at 80°, contains not less than 99 per cent. of C9H10O3. Description Ethyl p-hydroxybenzoate is a white, almost odourless, crystalline solid. Use As an antimicrobial agent. Biological Data This additive was evaluated by the Joint FAO/WHO Expert Committee on Food Additives in its Sixth Report (FAO/WHO, 1962). Since its publication some new experimental work has been carried out on these compounds. This and other work not included in the Sixth Report is presented and discussed in this monograph. Biochemical aspects The metabolism of the ethyl ester is similar to that of the methyl ester. Dogs given 1000 mg/kg body-weight orally or 50 mg/kg i.v. excreted 66-70 per cent. in the urine. Very low plasma levels, just detectable, were found two hours after oral administration or at 5 and 15 minutes after i.v. injection (Sokol, 1952). Human studies on six subjects involved administration of 10 or 20 mg/kg body-weight of ester orally. After 60, 135 and 255 minutes, n-hydroxybenzoate but not the ester, was detectable in serum. The maximum serum level attained was 4.5 µg/ml (Heim, 1960-1). Acute Toxicity Animal Route LD 50 References (mg/kg body-weight) Mouse oral 8 000 Sokol, 1952 Guinea-pig oral 2 000-2 400 Heyden, 1939 Rabbit oral 5 000 Sabalitschka & Neufeld- Crzellitzer, 1954 Dog oral 5 000 Sabalitschka & Neufeld-Crzellitzer, 1954 Short-term studies Rabbit. Suspensions of 0.5 and 7.5 per cent. ethyl p-hydroxybenzoate had the same local anaesthetic effect on the cornea as 0.12 and 0.27 per cent. solutions of cocaine hydrochloride. Therefore, the local anaesthetic activity of the ester is 3-4 times less than that of cocaine and twice that of procaine (Truhaut, 1962). Using the same method of Regnier & Quevauviller (1939), Adler-Hradecky and Kelentey (1960) found no local anaesthetic effect on the cornea by 0.25-0.30 per cent. solutions of methyl, ethyl, propyl or butyl p-hydroxybenzoates. Long-term studies Rat. Forty rats were fed 15 mg/kg body-weight, 20 animals 150 mg/kg body-weight and 20 animals 1500 mg/kg body-weight of a mixture of 40 per cent. ethyl ester and 60 per cent. propyl ester as the sodium salts for 18 months in the diet. The rate of weight gain showed some growth stimulation at the 15 and 150 mg/kg body-weight levels. The group on 1500 mg/kg body-weight showed initial retardation followed later by normal growth. Mortality rate and pathological examination of the major organs in all treated groups showed no significant difference from the control group (Heyden, 1940; Heyden, 1942). A group of 65 rats (35 males and 30 females) was fed a diet containing 2 per cent. of the ethyl ester for the life span, with 50 animals as the control group. All animals were autopsied on death. No adverse effects could be detected on weight gain, except a small retardation during the first month, and the mortality rate, haematology, tumour incidence and histopathology of major organs did not differ from the controls (Truhaut, 1962). A group of 39 rats (19 males and 20 females) was injected weekly with 1 ml of an aqueous solution of 10 per cent. sodium ethyl p-hydroxybenzoate for their life span. The 27 controls (16 males and 11 females) were injected with 1 ml of a 3 per cent. sodium chloride solution. Because of irritation by the high p.H of the ester solution, the frequency of injection had to be reduced to 1 in 2 weeks from the 4th to the 10th month and later to 1 injection a month up to the end of the experiment. No effect on mortality and tumour incidence could be detected (Truhaut, 1962). Comments The long-term studies in rats are adequate for assessment, taking into consideration the data on methyl and propyl p-hydroxybenzoates. However, further biochemical studies in man and animals are desirable and further studies on the local anaesthetic action should also be undertaken. Evaluation (See propyl p-hydroxybenzoate) REFERENCES Adler-Hradecky, C. & Kelentey, B (1960) Arch. int. Pharmacodyn., 128, 135 FAO/WHO (1962) FAO Nutrition Meetings Report Series, No. 31; Wld Hlth Org. techn. Rep. Ser., 228 Heim, F. (1960-1) Sitzber. Physik-Med. Soz. Erlangen, 81, 14 Heyden,-. (1939) Unpublished Report from Applied Research Inc., MX-124 Heyden, -. (1940) Unpublished Report from Applied Research Inc., MX-185 Heyden, -. (1942) Unpublished Report from Applied Research Inc., MX-185 Regnier, M. & Quevauviller, A. (1939) Arch. exp. Path. Pharm., 193, 48 Sabalitschka, T. & Neufeld-Crzellitzer, R. (1954) Arzneimitt.- Forsch.,4, 575 Schübel, K. & Manger, J. (1929) Arch. exp. Path. Pharmak., 146, 208 Sokol, H. (1952) Drug Stand., 20, 89 Truhaut, R. (1962) Estratto dai Rendiconti dell'Instituto Superiore di Sanità (Document submitted to WHO in 1964)
See Also: Toxicological Abbreviations