Growth suppression of hamster flank organs by topical application of catechins, alizarin, curcumin, and myristoleic acid

Hamster flank organ growth, as measured by an increase in the area of the p igmented macule, is androgen-dependent. When flank organs of a castrated ha mster are treated topically with testosterone, the flank organ becomes larg er and darker. Since this growth is known to be dependent on the intracellu lar active androgen, 5 alpha -dihydrotestosterone (DHT), inhibitors of 5 al pha -reductase which converts testosterone to DHT can inhibit the growth of the flank organ. Certain unsaturated aliphatic fatty acids, such as gamma -linolenic acid and myristoleic acid, as well as other natural compounds, i ncluding alizarin and curcumin, are 5 alpha -reductase inhibitors and inhib ited flank organ growth. Green tea catechins, including (-)-epicatechin-3-g allate, and (-)-epigallo-catechin-3-gallate (EGCG) are also 5 alpha -reduct ase inhibitors and inhibited flank organ growth. However, (-)-epicatechin a nd (-)-epigallocatechin, which are not 5 alpha -reductase inhibitors, also inhibited flank organ growth. EGCG also inhibited DHT-dependent growth of f lank organs. These catechins, therefore, may act by a mechanism other than inhibition of 5 alpha -reductase. The effect of EGCG and other compounds wa s localized at the site of application; they did not affect the growth of t he contralateral flank organ in the same animal. Since these compounds do n ot appear to exhibit systemic effects, they may be potentially useful for t reatment of androgen-dependent skin disorders.