Isolation of melanin biosynthesis inhibitory compounds from the seeds of Plantago asiatica L.

Seven compounds were isolated from the MeOH extract of the seeds of Plantago asiatica L. and their structures were identified as β-sitosterol (1), (24R)-6β-hydroxy-24-ethyl-cholest-4-en-3-one (2), acteoside (3), geniposidic acid (4), 1-octen-3-ol 3-O-β-D-xylopyranosyl(1→6)-β- D-glucopyranoside (5), plantainoside D (6) and plantamajoside (7) on the spectroscopic analysis. Among them, (24R)-6β-hydroxy-24-ethyl-cholest-4-en- 3-one (2) and 1-octen-3-ol 3-O-β-D-xylopyranosyl (1→6)-β-D- glucopyranoside (5) were first isolated from this plant. Among them, geniposidic acid (4) showed the most potent inhibitory effect on melanogenesis, with inhibition rate of 41%.