Structure characterization of proanthocyanidins from Caryota ochlandra Hance and their bioactivities

Proanthocyanidins (PAs) from Caryota ochlandra fruit pericarp and fruit flesh were characterized by 13C nuclear magnetic resonance, high performance liquid chromatography-electrospray ionization mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry techniques. The fruit pericarp and flesh PAs were complex mixtures of homo- and heteropolymers of B-type procyanidins and prodelphinidins both with degrees of polymerization up to dodecamer. Their antioxidant and antityrosinase activities were investigated. The fruit pericarp PAs exhibited potent antioxidant activity with IC50 values of 142.86 ± 1.53 and 80.51 ± 0.4 μg/ml for DPPH and ABTS free-radical scavenging assays; with FRAP value of 373.09 ± 5.02 mg ascorbic acid equivalent/g dry weight. Furthermore, the fruit pericarp PAs had antityrosinase activity while the fruit flesh PAs could be oxidized by tyrosinase. The structure and antioxidant activities of the C. ochlandra fruit PAs together with their effects on tyrosinase activity would lay scientific foundation for their utilization in food and nutrition industry.