Two New Flavonol Glycosides from Lamium amplexicaule L. and Their in vitro Free Radical Scavenging and Tyrosinase Inhibitory Activities

Two new flavonol glycosides, kaempferol 3-O-[beta-D-glucopyranosyl-(1 -> 4)][alpha-L-rhamnopyranosyl-(1 -> 6)]-beta-D-glucopyranoside and quercetin 3-O-[beta-D-glucopyranosyl-(1 -> 4)][alpha-L-rhamnopyranosyl-(1 -> 6)]-beta-D-glucopyranoside, together with three known flavonoids were isolated using column chromatography from the aerial parts of Lamium amplexicaule (Labiatae). In addition, the five isolates were evaluated for their in vitro free radical scavenging (EC50 values, 14.1 - 63.9 mu g/mL) and tyrosinase inhibitory activities (IC50 values, 110.4 - 193.5 mu g/mL).