Tyrosinase Inhibitory Activity of Chemical Constituents of Euphorbia macrostegia

The chloroform extract of the aerial parts of E. macrostegia has yielded a new compound, 2-(4-hydroxyphenyl)-ethylhentriacontanoate (1), along with hentriacontan-1-ol (2), lupenone (3), cycloart-22-ene-3,25-diol (4), 3,3′,4′-tri-O-methylellagic acid (5), cleomiscosin (6), and glucoclioniasterol (stigmast-5-en-3-O-β-glucopyranoside) (7), and from the ethyl acetate extract of aerial parts of the plant isoquercetin (8), quercetin-3-O-α-arabinofuranoside (avicularin) (9), and rutin (10) have been isolated. Compounds 1–10 were tested for their tyrosinase inhibitory activity, and 2 exhibited an IC50 value of 71.4 μM, almost comparable to standard kojic acid (IC50 58.2 μM). Compounds 1–4 also showed good activity with IC50 values of 77.2, 78.6, 71.4, and 77.5 μM, respectively.