Chemical Constituents With Tyrosinase Inhibitory Activity In The Fruit Of Pyracantha Fortueana

Pyracantha fortuneana (Maxim.) Li, Chinese name Huo-ji, is a evergreen shrub plant of pyracantha roem. genus in rose family, widely distributed throughout the southern and northwestern parts of China. Its fruit is used as a traditional Chinese medicine for treatment of indigestion. Recent pharmacological studies showed that P. fortuneana possessed some antioxidation activities and could significantly improve the lipoprotein metabolism of rats. Its fruit extract showed inhibitory activity against tyrosinase and was widely used in cosmetics as a skin-whitening agent.In our investigation for compounds with inhibitory activity against tyrosinase, 34 compounds were isolated from the 60% ethanol extract of the fruit of this plant through various chromatographic techniques. The structures were established on the basis of their physicochemical properties and spectroscopic analysis as Fortuneanoside A (1)~*, Fortuneanoside B (2)~*, Fortuneanoside C (3)~*, Fortuneanoside D (4)~*, Fortuneanoside E (5)~*, Fortuneanoside F (6)~*, Fortuneanoside G (7)~*, Fortuneanoside H (8)~*, Fortuneanoside I (9)~*, Fortuneanoside J (10)~*, Fortuneanoside K (11)~*, Fortuneanoside L (12)~*, 2,4,6-trihydroxy-acetophenone-4-O-β-D-glucopyranoside (13), 2,4,6-trihydroxy-acetophenone-6-O-β-D-glucopyranoside (14), Pyrafortunoside A (15)~*, 2,4,6-trihydroxy-benzophenone-6-O-β-D-glucopyranoside (16), Pyrafortunoside B (17)~*, Pyrafortunoside C (18)~*, Isoquercitrin (19), Hyperoside (20), Rutin (21),4',5,7-trihydroxy-3'-methoxy-flavonol-3-O-(α-L-rhamnopyranosyl)-(1-6)-β-D-gluco-pyranoside (22), kaempferol-3-O-(α-L-rhamnopyranosyl)-(1-6)-β-D-glucopyranoside (23), kaempferol-3-O-β-D-glucopyranoside (24), kaempferol-3-O-β-D-galactopyranoside (25), quercetin (26), kaempferol (27), (+)-epicatechin (28), phenylmethyl-O-(α-L-arabinofuranosyl)-(1-6)-β-D-glucopyranoside (29), phenylethyl-2'-O-(α-L-arabinofuranosyl)-(1-6)-β-D-glucopyranoside (30), (+)-Isolarisiresinol-9'-O-β-D-glucopyranoside (31), ursolic acid (32),β-sitosterol (33), and daucosterol (34), respectively. Among them, 15 compounds (1-12, 15, 17-18) were new compounds, and 11 compounds (13-14, 16, 22-25, 28-31) were isolated from the pyracantha genus for the first time.All the compounds isolated from the active fractions were evaluated for inhibitory activity against tyrosinase. The results showed that 11 compounds (2-10, 29-30) possessed inhibitory activity on different levels. Most of biphenyl glycosides and dibenzofuran glycosides showed potent activity, and some of them were more potency compared with arbutin. All the potent compounds possessed the 4'-dihydroxy-3', 5'-dimethoxy moiety in the structure, suggesting that the special moiety might contribute to the inhibitory activity against tyrosinase.Five biphenyl compounds were synthesized, and evaluated for inhibitory activity against tyrosinase. Some of the synthetic compounds displayed potent activity, which also possessed the 4'-dihydroxy-3', 5'-dimethoxy moiety in the structure. It confirmed that the special moiety contributed to the inhibitory activity.The LC-MS~n study of the active fraction of the fruit extract was also performed on the basis of MS~n data of the compounds isolated from P. fortuneana. Seventeen peaks in the chromatograph were assigned, and 12 peaks were deduced by the loss of mass and the relative abundance of fragment ions in MS~n data.