A sphingolipid and tyrosinase inhibitors from the fruiting body of Phellinus linteus

This paper for the first time reports the isolation of 5 compounds from Phellinus linteus. A sphingolipid (1) and two tyrosinase inhibitory compounds (2, 3) along with two carboxylic acids (4, 5), were isolated from the fruiting body of Phellinus linteus (Berk & Curt) Aoshima. The structure of compound 1 was identified as 1-O-beta-D-glucopyranosyl-(2S, 3R, 4E, 8E)-2-[(2R)-2-hydroxyhexadecanoylamino]-9-methyl-4,8-octadecadiene-1,3-diol, known as cerebroside B, based on spectroscopic methods such as 1 D and 2D NMR as well as by acid hydrolysis. Compounds 2similar to5 were identified as protocatechualdehyde (2), 5-hydroxymethyl-2-furaldehyde (HMF) (3), succinic acid (4), and fumaric acid (5) based on the spectroscopic evidence. Compounds 2 and 3 inhibited the oxidation of L-tyrosine catalyzed by mushroom tyrosinase with an IC50 of 0.40 and 90.8 mug/mL, respectively. The inhibitory kinetics, which were analyzed by the Lineweaver-Burk plots, were found to be competitive and noncompetitive inhibitors with a K-i of 1.1 muM and 1.4 mM, respectively.