Inhibitory Effects of Sterols Isolated from Chlorella vulgaris on 12-O-Tetradecanoylphorbol-13-acetate-Induced Inflammation and Tumor Promotion in Mouse Skin

Abstract

Inhibitory activity against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation in mice was observed in the methanol extract of Chlorella vulgaris, a green alga. The hexane soluble fraction obtained from the methanol extract exhibited marked inhibitory activity from which were isolated two Δ^{5, 7}-sterols (ergosterol and 7-dehydroporiferasterol), two Δ^{5, 7, 9(11)}-sterols [9(11)-dehydroergosterol and 7, 9(11)-bisdehydroporiferasterol], two 5α, 8α-epidioxy-Δ⁶-sterols (ergosterol peroxide and 7-dehydroporiferasterol peroxide), and a 7-oxo-Δ⁵-sterol (7-oxocholesterol), among others. The Δ^{5, 7}-sterols, 5α, 8α-epidioxy-Δ⁶-sterols and 7-oxo-Δ⁵-sterol inhibited TPA-induced inflammation in mice. The 50% inhibitory dose of these compounds for TPA-induced inflammation was 0.2-0.7 mg/ear. Furthermore, ergosterol peroxide markedly inhibited the tumor-promoting effect of TPA in 7, 12-dimethylbenz[a]anthracene-initiated mice.