Tyrosinase inhibitory activity of three new glycosides from Breynia fruticosa

Two new flavanone glycoside derivatives and one new sulfur-containing spiroacetal glycoside, (2R, 3R)-3-acetyl-7-methoxy-(−)-epicatechin 5-O-(6-isobutanoyl)-β-d-glucopyranoside (1), (2R, 3R)-3-acetyl-7-methoxy-(−)-epicatechin 5-O-[6-(2-methylbutanoyl)]-β-d-glucopyranoside (2) and 4-[(carboxymethyl)thio]-5′-hydroxy-phyllaemblic acid O-β-d-glucopyranosyl-(1 → 2)-β-d-glucopyranoside ester (3), along with twelve known flavonoids and one known sulfur-containing spiroacetal glycoside, were isolated from Breynia fruticosa. Their structures were elucidated by the use of extensive spectroscopic methods (UV, IR, HR-ESI-MS, 1D and 2D NMR, and CD). The in vitro inhibition of tyrosinase activity by all of these compounds was also evaluated, and we concluded that the flavanol-containing 5-O- and 7-O-sugar moieties possessed more potent effects than the other compounds examined herein.