Antimelanogenic Effect of Isoquinoline Alkaloids from Plumula Nelumbinis

Plumula Nelumbinis, the green embryo of a lotus seed, is widely consumed in China as a well-known food with medicinal effects. In this study, 14 alkaloids, including 4 new and 10 known alkaloids, were isolated from it, which were elucidated by comprehensive spectroscopic analysis, and were investigated for their antimelanogenic effects in vitro and in vivo. As a result, melanogenesis in alpha-MSH-stimulated B16F10 cells was reduced significantly by a new compound 4 and known compound 12 at a concentration of 0.5 mu g/mL, and the tyrosinase (TYR) activities were inhibited by 78.7 and 82.0% at 4 mu g/mL, prior to alpha-arbutin (41.3%). Additionally, compounds 4 and 12 also exhibited superior antimelanogenic effects compared to alpha-arbutin on a zebrafish assay model at equivalent concentrations. Mechanistically, our preliminary findings suggested that compounds 4 and 12 exerted antimelanogenesis effect probably by inhibiting key proteins involved in melanin production such as microphthalmia-associated transcription factor, TYR, TRP-1, and TRP-2. The findings highlight the potential use of Plumula Nelumbinis containing compounds 4 and 12 as functional foods for treating hyperpigmentation.

Automated summary

In this study, 14 alkaloids were isolated from Plumula Nelumbinis and investigated for their antimelanogenic effects. Two compounds, compound 4 and compound 12, showed significant reduction in melanogenesis and inhibition of tyrosinase activity. Mechanistically, these compounds exerted their effects by inhibiting key proteins involved in melanin production. These findings highlight the potential use of Plumula Nelumbinis containing compound 4 and compound 12 as functional foods for treating hyperpigmentation.