Prenylated flavonoids from Artocarpus altilis: Antioxidant activities and inhibitory effects on melanin production

Compounds 1–5, together with 12 known compounds, were isolated from the heartwood and cortex of Artocarpus altilis. Several of these showed free radical scavenging activity, and some reduced melanin production without affecting cell viability. These compounds could be considered as cosmetic agents in the future. [Display omitted] ► Five flavonoids, and 12 known compounds, were isolated from Artocarpus altilis. ► Natural antioxidants and tyrosinase inhibitors of A. altilis were identified. ► The inhibition modes of active compounds on tyrosinase were identified. ► Some prenylated flavones were demonstrated to reduce melanin production. Flavonoids, 10-oxoartogomezianone (1), 8-geranyl-3-(hydroxyprenyl)isoetin (2), hydroxyartoflavone A (3), isocycloartobiloxanthone (4), and furanocyclocommunin (5), together with 12 known compounds, were isolated from heartwood and cortex of Artocarpus altilis, and their structures were identified by comparing their spectra with those of similar compounds. To identify natural antioxidants and whitening agents, the ability of these prenylated flavonoids was assessed to scavenge the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) radical cation, and the superoxide anion (O2−), and their abilities to inhibit tyrosinase and melanin production. It was found that compounds 3, 4, and artoflavone A (15) had moderate DPPH-scavenging activity, whereas compound 4 exhibited significant ABTS+-scavenging activity, and that norartocarpetin (7) and artogomezianone (8) exhibited moderate ABTS+-scavenging activity, with compounds 2, 7, and artocarpin (6) displaying good superoxide anion-scavenging activity. In addition, compounds 7, 8, cudraflavone A (14), and artonin M (17), inhibited melanin production by strongly suppressing tyrosinase activity. Compound 6 reduced the melanin content without inhibiting tyrosinase activity. These results suggest that flavonoids isolated from A. altilis may be candidate antioxidants and/or skin-whitening agents. However, further investigations are required to determine their mechanisms of action.