SOME NEW KEYS TO COSMETIC CHEMISTRY --1956. Presented at the May loth, 1957, Meeting of the Society of Cosmetic Chemists, New York City. By PAUL G. I. LAUFFER* COSMETIC CHEMISTRY is 13. vast province with the vaguest of boundaries. Its vastness makes impossible a comprehensive review in tabloid form, and necessitates a critical approach whereby only the more significant advances are mentioned. Its vague demarcation justifies the use of some judgment in selecting the areas to be included. In 1955, the writer attempted, in an article entitled "The Emerging Cosmetic Chemistry"•½, to describe and delineate the body of cosmetic chemistry that had taken form in the previous ten years. This is a review of chemical advances made in late 1955 and in !956 which may be expected to result in improved cosmetic technology. It will follow the thesis put forward in the 1955 article, that the first concern of cosmetic chemists is with knowledge of the structure, composition, and functioning of the skin, and that all exact data and concepts regarding these subjects come within the purview of cosmetic chemistry. SKIN A wealth of up-to-date information, with stress upon the anatomical features, was made available by the publication of Montagna's "The Struc- ture and Function of the Skin, "• which complements effectively Rothman's earlier "Physiology and Biochemistry of the Skin. "a Newer methods of investigation added to our knowledge of the skin surface and its maintenance. Examination by the stripping method • revealed that normal adults had from 0.66 to 1.39 million non-nucleated keratin cells per square centimetre on the forearm, and about 50 per cent less on shoulder and thigh it was estimated that keratin cells make up over 10 per cent of the total cells of human epidermis, and that reported mitotic rates are sufficient to account for the normal loss of surface cells. Polarised light studies 5 of serial sections cut parallel to the surface of human callus showed that beneath the surface grooves keratin is disposed with the long axis of its chain molecules along the grooves while beneath the ridges, the keratin molecules lie crosswise, and around the sweat ducts they form rings. Blank's earlier demonstration G that water content is the major factor influencing flexibility and softness of the outer skin has led to attempts * House of Tangee. Title appeared erroneously as "The Emerging Cosmetic Industry." 233

234 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS to' evaluate various cosmetic ingredients in • terms of their ability to increase or maintain water content, and has led to the use of the Shore Durometer for assessing skin softness. 7 Another study 8 indicated that: (1) oil-in- water emulsions are more effective in hydrating keratin than water-in-oil (2) high-viscosity emulsions are superior to those of low viscosity (3) water- miscible adjuvants increased water loss, even if they increased viscosity (4) hygroscopic substances did not increase water absorption by dried keratin. Administration of cortisone or ACTH increased the resistance of skin capillaries in humans or in rabbits while that of testosterone to females or of progesterone to males decreased the resistance. The capillary resistance in females was increased by estrone in small doses and by progesterone it was decreased by large doses of estrone. • Polarigraphic measurement of oxygen in human skin •ø disclosed wide changes in oxygen tension with variations in circulation and metabolism. The rate of carbon dioxide elimination from human skin was reported • to be increased by 15 to 20 per ,cent within an hour after drinking tea, indicating increase in skin metabolism under control of the cerebral cortex. Methionine was added • to the list of amino-acids previously found on the skin. Extraction of human epidermis with 6M urea failed to yield a TM protein similar to the "epidermin" similarly extracted •4 from cow snout epidermis. A hydrogen-bond breaker, 75 per cent lithium bromide solution, did, however, extract from human epidermis a fibrous protein different from any previously obtained and postulated to be a keratin precursor. Rats fed a diet containing only C-8, C-10, and C-12 fatty acid glycerides had fat from skin and subcutaneous tissue with higher saponification number and lower iodine number than similar fat from controls, indicating that the medium-weight fats can be deposited in the skin. •' Incubation of skin with acetate-l-C TM gave results leading to the hypothesis" that the main site of sterol synthesis is the keratinising epidermis, while the main site of squalene synthesis is the sebaceous gland. Electron-microscopic studies •8 have greatly expanded our knowledge of cellular components in the epidermal layers, and have confirmed the existence of tonofibrils crossing cell boundaries. The observations suggest that the tonofilaments are synthesised in the basal layer and transformed in the stratum granulosum into a non-filamentous but densely packed material which is presumably keratin. At this Society's 1956 Seminar, a symposium on keratinisation included reviews TM of the biochemical, physiological, and pathological aspects of keratinisation. New observations have demonstrated the presence and/or the •1ocation of the enzymes cholinesterase•, •, monoamine oxidase •, guanine deaminase" (in rat skin but not in human skin), and phosphomonoesterase. •