Curcumin analogues exert potent inhibition on human and rat gonadal 3ß-hydroxysteroid dehydrogenases as potential therapeutic agents: structure-activity relationship and in silico docking.

ABSTRACT

Curcuminoids are functional food additives, and the effect on gonadal hormone biosynthesis remains unclear. Gonads contain 3ß-hydroxysteroid dehydrogenase isoforms, h3ß-HSD2 (humans) and r3ß-HSD1 (rats), which catalyse pregnenolone into progesterone. The potency and mechanisms of curcuminoids to inhibit 3ß-HSD activity were explored. The inhibitory potency was bisdemethoxycurcumin (IC50, 1.68 µM) >demethoxycurcumin (3.27 µM) > curcumin (13.87 µM) > tetrahydrocurcumin (109.0 µM) > dihydrocurcumin and octahydrocurcumin on KGN cell h3ß-HSD2, while that was bisdemethoxycurcumin (1.22 µM) >demethoxycurcumin (2.18 µM) > curcumin (4.12 µM) > tetrahydrocurcumin (102.61 µM) > dihydrocurcumin and octahydrocurcumin on testicular r3ß-HSD1. All curcuminoids inhibited progesterone secretion by KGN cells under basal and forskolin-stimulated conditions at >10 µM. Docking analysis showed that curcuminoids bind steroid-active site with mixed or competitive mode. In conclusion, curcuminoids inhibit gonadal 3ß-HSD activity and de-methoxylation of curcumin increases inhibitory potency and metabolism of curcumin by saturation of carbon chain losses inhibitory potency.