Differences in the Composition of Archidendron Clypearia at Different Harvest Periods and Spectrum–Effect Relationship and Structure–Activity Analysis of Antioxidant Components

Abstract

Archidendron clypearia, a specialty plant in Southeast Asia, is expected to be developed as a natural antioxidant due to its rich polyphenolic compounds. In this study, the ultra-performance liquid chromatography (UPLC) fingerprints of 16 different harvest period batches of A. clypearia were evaluated using hierarchical clustering analysis (HCA), principal component analysis (PCA), and partial least squares discrimination analysis (PLS-DA). The antioxidant activities of 70% aqueous ethanol extracts from the above 16 batches of samples were assessed using diphenyl picryl hydrazyl (DPPH), 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric reducing antioxidant assay (FRAP). The spectrum–effect relationship between UPLC fingerprints and antioxidant activity of A. clypearia was evaluated to screen for the antioxidant activity of substances based on three chemometrics, i.e., orthogonal partial least squares analysis (OPLS), gray correlation analysis (GRA), and bivariate correlation analysis (BCA). The results revealed that P7 (ethyl gallate), P14 (5,3',4',5'-tetrahydroxyflavan-7-gallate), P16 (quercitrin), P15 and P18 (7,3’-O-di-gallyoltricetiflavan /7,4’-O-di-galloyltricetiflavan) were the main changing components between different harvest periods and P3 (gallic acid), P6, P7, P8 (3,5,3',4',5'-pentahydroxyflavan-7-gallate), P9, P13, P14, P15, P17 and P18 played an essential role in the antioxidant effects of A. clypearia . Six monomer components and a pair of isomonomer mixtures were also isolated to verify the antioxidant activity combined with structure-activity analysis by density functional theory (DFT) calculations. Our results prove the potential of A. clypearia as an antioxidant for some common and unique components, and at the same time provides a reference for the selection and utilization of A. clypearia .

Keywords: Archidendron clypearia, Spectrum-effect relationship, chemometrics, antioxidant activity, column separation, structure-activity analysis