Apigenin, Tyrosinase Inhibitor Isolated from the Flowers of Hemisteptia lyrata Bunge

Abstract

From the flowers of Hemisteptia lyrata Bunge, two flavonoids, apigenin (1) and acacetin (2), were isolated. Their structures were established by UV, one- and two-dimensional NMR, and mass spectroscopic methods. Apigenin showed significant inhibition against mushroom tyrosinase with an IC_50 value of 4.56㎍·ml^-1, and appeared to inhibit the polyphenol oxidase activity of tyrosinase in a competitive manner (K_1=2.5×10 exp (-5) M) when L-tyrosine was used as a substrate, but did not inhibit the melanin production of Streptomyces bikiniensis.