Characterisation of polyphenol constituents of Linderae aggregate leaves using HPLC fingerprint analysis and their antioxidant activities.

The leaves of Linderae aggregate (LAL) has been used as a type of tea in China and other Southeast Asian countries. In this study, 11 polyphenols in LAL were clarified for the first time using multiple high-performance liquid chromatographic techniques. An optimal extracting method was developed through the comparison of the amount of quercetin-3-O-α-L-rhamnoside using a uniform design method. From the fingerprint liquid chromatography data, 11 common peaks in the 8 samples collected from April to November were semi-determined. The antioxidant capacities were examined using the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay and the ferric reducing/antioxidant power assay. All 8 samples contained the same 11 polyphenols in similar ratios. Three samples, S2, S5 and S6 contained higher amount of quercetin-3-O-α-L-rhamnoside and were demonstrated to have stronger antioxidant capacities in both antioxidant assays. These results are critical in optimising harvest time and quality control of LAL.