Phenols displaying tyrosinase inhibition from Humulus lupulus

Abstract

Tyrosinase is the rate-limiting enzyme for the production of melanin and other pigments via the oxidation of L-tyrosine. The methanol extract from Humulus lupulus showed potent inhibition against mushroom tyrosinase. The bioactivity-guided fractionation of this methanol extract resulted in the isolation of seven flavonoids (1-7), identified as xanthohumol (1), 4 0 -Omethylxanthohumol (2), xanthohumol C (3), flavokawain C (4), xanthoumol B (5), 6-prenylnaringenin (6) and isoxanthohumol (7). All isolated flavonoids (1-7) effectively inhibited the monophenolase (IC 50 s ¼ 15.4-58.4 mM) and diphenolase (IC 50 s ¼ 27.1-117.4 mM) activities of tyrosinase. Kinetic studies using Lineweaver-Burk and Dixon-plots revealed that chalcones (1-5) were competitive inhibitors, whereas flavanones (6 and 7) exhibited both mixed and non-competitive inhibitory characteristics. In conclusion, this study is the first to demonstrate that the phenolic phytochemicals of H. lupulus display potent inhibitory activities against tyrosinase.

Natural and Bioinspired Phenolic Compounds as Tyrosinase Inhibitors for the Treatment of Skin Hyperpigmentation: Recent Advances

“…IC 50 values in the range 28-42 µM have been reported for two lignans isolated from Opilia amentacea leaves [112] (Figure 13), whereas particularly effective against the monophenolase activity of the enzyme were flavonolignans from the seeds of Silybum marianum (IC 50 in the range 1.7-4.9 µM) ( Figure 13) [113] as well as, although with a lower strength, hydroxylated phenones from Syzygium polyanthum leaves [114] (Figure 14). Higher inhibition against monophenolase than diphenolase activity of mushroom tyrosinase were reported also for xanthohumol and other chalcones isolated from Humulus lupulus [115] ( Figure 14). Higher inhibition against monophenolase than diphenolase activity of mushroom tyrosinase were reported also for xanthohumol and other chalcones isolated from Humulus lupulus [115] ( Figure 14).…”

“…Higher inhibition against monophenolase than diphenolase activity of mushroom tyrosinase were reported also for xanthohumol and other chalcones isolated from Humulus lupulus [115] ( Figure 14). Higher inhibition against monophenolase than diphenolase activity of mushroom tyrosinase were reported also for xanthohumol and other chalcones isolated from Humulus lupulus [115] ( Figure 14). Higher inhibition against monophenolase than diphenolase activity of mushroom tyrosinase were reported also for xanthohumol and other chalcones isolated from Humulus lupulus [115] (Figure 14).…”

“…Higher inhibition against monophenolase than diphenolase activity of mushroom tyrosinase were reported also for xanthohumol and other chalcones isolated from Humulus lupulus [115] ( Figure 14). Higher inhibition against monophenolase than diphenolase activity of mushroom tyrosinase were reported also for xanthohumol and other chalcones isolated from Humulus lupulus [115] (Figure 14).…”

Depigmenting effect of Xanthohumol from hop extract in MNT-1 human melanoma cells and normal human melanocytes

“…XH has previously been reported to possess inhibitory effects on melanogenesis in B16F10 mouse melanoma cells [ 26 ] while it inhibits activity of mushroom tyrosinase in a cell-free system [ 25 ]. However, to date, there are no reports on the effects of XH on melanogenesis in human melanocytes; this is a critical issue since most depigmenting candidates in the flavonoid group have shown opposite effects on melanogenesis in mouse and human cells in earlier studies [ 33 , 34 ].…”

“…Previous studies have reported that XH inhibited mushroom tyrosinase activity in an acellular system [ 25 ] and inhibited melanin synthesis in B16F10 mouse melanoma cells. The authors concluded that XH is a skin-whitening agent [ 26 ].…”