Isostearic Acid is a mixture of fatty esters consisting mainly of methyl branched isomers of octadecanoic acid and is used at concentrations up to 10% in a wide variety of cosmetic products. In rats, the acute oral LD50 is estimated to be greater than 32 ml/kg. The raw ingredient produced no significant skin or eye irritation in Draize rabbit irritation tests.
In clinical studies, 100 subjects showed no signs of irritation after a 24 h single insult skin patch with undiluted Isostearic Acid. Thirty-four percent Isostearic Acid was neither an irritant nor a sensitizer in 168 subjects, and gave no indication of phototoxicity in a subset of this population.
It is concluded that Isostearic Acid is safe as a cosmetic ingredient in the present practices of use. Consideration for the compound's potential for production of human comedogenicity is noted.
4. COSMETIC, TOILETRY AND FRAGRANCE ASSOCIATION (CTFA). (October, 1980). Submission of unpublished data. CTFA Cosmetic Ingredient Chemical Description.
5.
5. CTFA. (Sept. 27, 1982). Submission of unpublished data. Isostearic Acid, Method of Manufacture.
6.
6. Fordyce, C.R., and Johnson, J.R. (1933). Branched-chain aliphatic acids. Isomyristic isopalmitic and isostearic acids. J. Am. Chem. Soc.55, 3368–72.
7.
7. Hougen, F.W. Ilse, D. Sutton, D.A. and De Villiers, J.P. (1953). Wool wax. III. Synthesis of some iso acids. J. Am. Chem. Soc. pp. 98-102.
8.
8. Milburn, A.H. and Truter, E.V. (1954). J. Am. Chem. Soc. pp. 3344.
9.
9. Stenhagen, E. and Tagtstrom-EKETORP, B. (1945). Ark-Kemi. Min. Geol. A.19, 8.
10.
10. Weitkamp, A.W. (1945). J. Am. Chem. Soc.67, 447.
11.
11. Abrahamson, S., and Lunden, B.M. (1972). Crystal structure of isostearic acid. Acta Crystallogr.B28(Pt. 8), 2562–7.
12.
12. Arosenius, K.E., Stallberg, G., Stenhagen, E., and Tagtstrom-EDETORP, B. (1948). Long chain iso-acids. II. Synthesis of acids with 13, 15, 17, 24, 25, 26, and 35 carbon atoms, and an x-ray study of synthetic acids and amines. Arkiv. Kemi. Mineral, Geol.26A(19), 20 pp.
13.
13. Fischmeister, I. (1963). Infrared spectra of crystalline long-chain methyl fatty acids. I. The methyl group near the carboxylic acid group. Arkiv. Kemi. Min. Geol.20(29), 353–67.
14.
14. Vanlerberghe, G. and Handjani-VILA, R.M. (1978). Surface chemistry as a tool for evaluating cosmetic products. Cosmet. Toiletries93(1), 29–30, 32, 34–7, 40–2.
15.
15. Kaerkkacinen, V.J. (1964). Minor fatty acids in milk fat. Kiel. Milchwirtsch. Forschungsber.16, 331–9.
16.
16. Kurkova, M.F., and Belousov, A.P. (1966). Minor fatty acids in milk fat. Izv. Vysshikh Uchebn. Zavedenii. Pishchevaya Tekhnol.4, 41–3.
17.
17. Bjorkhem, I., and Danielson, H. (1970). Omega-oxidation of branched-chain fatty acids in rat liver homogenates. Eur. J. Biochem.14(3), 473–7.
18.
18. Balsam, M.S., and Sagarin, E.. (1972). Cosmetic Science and Technology, Vol. 1. New York, NY: Wiley-Interscience.
19.
19. FOOD AND DRUG ADMINISTRATION (FDA). (1981). Cosmetic product formulation data. FDA Computer Printout.
22. Hymer, W.C., and McSHAN, W.H. (1963). Isolation of rat pituitary granules and the study of their biochemical properties and hormonal activities. J. Cel. Biol.17(1), 67–86.
23.
23. Hansen, R.P., Shorland, F.B.Cooke, N.J. (1956). The branched-chain fatty acids of mutton fat. 3. The isolation of 16-methylheptadecanoic acid (isostearic acid). Biochem. J.64(2), 214–6.
24.
24. Renner, E., and Melcher, F. (1978). Studies on minor fatty acids of milk fats. 3. Saturated fatty acids. Milchwissenschaft33(5), 281–5.
25.
25. Dryden, F.D., and Marchello, J.A. (1970). Influence of total lipid and fatty acid composition upon the palatability of three bovine muscles. J. Anim. Sci.31(1), 36–41.
26.
26. Rodwell, A.W., and Peterson, J.E. (1971). Effect of straight-chain saturated, monoenoic, and branched-chain fatty acids on growth and fatty acid composition of mycoplasma strain Y. J. Gen. Microbiol.68(Pt. 2), 173–86.
27.
27. Blough, H.A., and Tiffany, J.M. (1969). Incorporation of branched-chain fatty acids into myxoviruses. Proc. Nat. Acad. Sci. U.S.62(1), 242–7.
28.
28. Lippel, K. (1973). Activation of branched and other long-chain fatty acids by rat liver microsomes. J. Lipid Res.14(1), 102–9.
