Tyrosinase inhibition of major secondary metabolites isolated from endangered Meconopsis bhutanica Tosh.Yoshida & Grey-Wilson

Meconopsis bhutanica Tosh.Yoshida & Grey-Wilson (Meconopsis Vig., fam: Papaveraceae), is a Critically Endangered species utilized in Tibetan medicine. Due to the very limited numbers of wild individuals, the chemical and biological basis of its medicinal value has not been studied. The objective of this study was to explore the chemical constituents of Meconopsis bhutanica and to determine the antityrosinase activity and influence on human melanoma cell lines A375. The chemical constituents were mainly isolated through column chromatography and semipreparative high performance liquid chromatography, and the structures were elucidated by nuclear magnetic resonance spectra. The inhibition on tyrosinase was examined by microplate reader. High performance liquid chromatography, spectrofluorophotometer, and molecular docking were used to analyze the effects on the function and structure of tyrosinase. The influence on A375 cells were measured by the Cell Counting Kit. Finally, a total of eleven phenolic compounds were isolated and identified from Meconopsis bhutanica. All of these compounds were found in this plant for the first time. The results of antityrosinase activity assay showed that compound 9 exhibited tyrosinase inhibition obviously. Furthermore, compound 9 could decrease the oxidation products and fluorescence emission intensity of tyrosinase. However, compound 9 had no effect on the proliferation of human melanoma A375 cells at high concentrations. The present paper uncovered the chemical composition of Meconopsis bhutanica and assessed the tyrosinase inhibition activity, which will provide data for comparing bioactive chemical constituents between the wild and cultivated ones. This study paved the way for the conservation, cultivation, and application of Meconopsis bhutanica.