Glycosidic Inhibitors of Melanogenesis from Leaves of Passiflora edulis

A new flavonoid glycoside, chrysin 6‐C‐β‐rutinoside (chrysin α‐L ‐rhamnopyranosyl‐(1→6)‐C‐β‐glucopyranoside; 2 ), and two new triterpene glycosides, (31R)‐31‐O‐methylpassiflorine ( 7 ) and (31S)‐31‐O‐methylpassiflorine ( 8 ), along with 14 known glycosides, including three flavonoid glycosides, 1, 3 , and 4 , six triterpene glycosides, 5, 6 , and 9 – 12 , three cyano glycosides, 13 – 15 , and two other glycosides, 16 and 17 , were isolated from a MeOH extract of the leaves of Passiflora edulis (passion flower; Passifloraceae). The structures of new compounds were elucidated on the basis of extensive spectroscopic analysis and comparison with literature data. Upon evaluation of compounds 1 – 17 against the melanogenesis in the B16 melanoma cells induced with α‐melanocyte‐stimulating hormone (α‐MSH), three compounds, isoorientin ( 1 ), 2 , and (6S,9R)‐roseoside ( 17 ), exhibited inhibitory effects with 37.3–47.2% reduction of melanin content with no, or almost no, toxicity to the cells (90.8–100.2% cell viability) at 100 μM . Western blot analysis showed that compound 2 reduced the protein levels of MITF, TRP‐1, and tyrosinase, in a concentration‐dependent manner while exerted almost no influence on the level of TRP‐2, suggesting that this compound inhibits melanogenesis on the α‐MSH‐stimulated B16 melanoma cells by, at least in part, inhibiting the expression of MITF, followed by decreasing the expression of TRP‐1 and tyrosinase. In addition, compounds 1 – 17 were evaluated for their inhibitory effects against the Epstein? Barr virus early antigen (EBV‐EA) activation induced by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in Raji cells.