Chemical composition, antioxidant and anti-tyrosinase activities of fractions from Stenoloma chusanum

Abstract

Stenoloma chusanum is a traditional Chinese medicine with very high total flavonoid content (TFC) and the total phenolic content (TPC). To explore its phytochemicals and potential in therapeutic applications, the antioxidant activity and tyrosinase inhibitory activity of S. chusanum fractions prepared by extraction with petroleum ether (PF), chloroform (CF), ethyl acetate (EF), n-butanol (NF) and water fractions (WF) as well as their flavonoid profiles were investigated. All these five fractions contained appreciable quantities of flavonoids and phenols, but the EF fraction was richest one with TPC and TFC values of 385.5mg gallic acid equivalents/g and 746.8mg rutin equivalents/g, respectively. The EF, NF, and CF fractions showed significant antioxidant activity, presumably due to their high flavonoid and phenol contents. All five fractions also caused dose-dependent inhibition of tyrosinase activity, and the PF fraction was a stronger inhibitor than the positive control inhibitor arbutin. However, the compounds responsible for this activity are currently unknown. These fractions’ chemical profiles were analyzed by LC/MS, revealing that their most abundant secondary metabolites were flavonoids and alkaloids. The EF and NF fractions contained similar compounds, including flavonols, flavones, isoquinolines, filicinic acid, and gigantecine. Further work on S. chusanum to isolate these compounds and explain the mechanisms responsible for their antioxidant activity and anti-tyrosinase activity is warranted.