꾸지뽕나무(Cudrania tricuspidata(Carr.) Bureau) 뿌리껍질에서 3종의 xanthones 화합물을 분리하였으며, 분광학적인 자료를 바탕으로 cudraxanthone L (1), cudraxanthone D (2), 그리고 cudraxanthone M (3)으로 구조동정되었다. 분리된 화합물을 L-tyrosine이 기질로 작용할 때 tyrosinase 저해 활성을 측정한 결과 cudraxanthone M (3)의 $IC_{50}$ 값이 $16.5{mu}M$로 가장 높은 저해 효능을 보였으며, kinetic type은 uncompetitive inhibition로 저해 상수($K_i$)는 $1.6{mu}M$로 측정되었다. 또한 이 화합물은 $20{mu}M$의 농도에서 lag time이 310초로 측정 되어 대조화합물인 kojic acid와 유사한 저해능을 나타내었다.
The methanolic roots bark extract of Cudrania tricuspidata (Carr.) Bureau was chromatographed, which yielded three xanthones 1-3 by tyrosinase inhibitory activity-guided fractionation. The structures were fully characterized by analysis of physical and spectral data. Among them, furano prenylxanthone 3, never reported as tyrosinase inhibitor, showed potent activity with $IC_{50}$ value of $16.5{mu}M$, and appeared to inhibit the polyphenol oxidase activity of tyrosinase in an uncompetitive inhibitor($K_i=1.6{mu}m$) when L-tyrosine was used as a substrate. Moreover, potent inhibitor furano prenylxanthone 3 had an extended lag time of 310 sec at $20{mu}M$, while lag time of kojic acid as positive control was prolonged with 350 sec at the same concentration.
