Gigantolevisins A–C, tyrosinase inhibitory benzylidenes from the shoots of Gigantochloa levis

The excessive tyrosinase activity has been linked to the overproduction of melanin which can lead to hyperpigmentation, oxidative stress, browning, and an increased risk of melanoma. Due to these detrimental effects associated with the overexpression of tyrosinase, research efforts are focused on finding bioactive compounds that can inhibit this enzyme efficiently. This study, conducted to find tyrosinase inhibitors utilizing the shoots of Gigantochloa levis (G. levis), produced three previously undescribed benzylidene derivatives (1–3) and two known compounds, with promising anti-tyrosinase activity. The new compounds were designated as gigantolevisins A–C, and the two known compounds as (E)-3-(4-hydroxyphenyl)-2-phenylacrylaldehyde (4) and (E)-2,3-bis(4-hydroxyphenyl)acrylaldehyde (5), respectively, based on the spectroscopic data and X-ray crystallographic analysis. The isolated compounds showed inhibition effects against tyrosinase, ranging from 42 % to 58 % (IC₅₀ values of >400–286 ± 15 μM) in comparison to the positive control Kojic acid with 100 % inhibition (IC₅₀ value of 43 ± 3 μM). The findings suggest that, while the isolated compounds are less potent than Kojic acid, they can be effective in inhibiting tyrosinase activity. Thus, the study highlights the therapeutic potential of G. levis shoots for treating melanin-related conditions.