Antioxidant and antiproliferative activities of proanthocyanidins from Chinese bayberry (Myrica rubra Sieb. et Zucc.) leaves

Chinese bayberry leaves proanthocyanidin (BLPs) contain epigallocatechin-3-O- gallate (EGCG) as its terminal unit and most of its extension units, which is unusual in the plant kingdom. The present study compared the antioxidant and anti-proliferative activities of BLPs prepared from different purification stages. Low-molecular-weight BLPs were prepared by ultrasonic treatment. Results revealed that the antioxidant activities of BLPs were strongly related to the content of total phenolics and proanthocyanidins; however, the cellular assay indicated that the mean degree of polymerization (mDP) played a vital role in the cellular antioxidant activity (CAA) of BLPs. The ultrasonic depolymerized BLPs with lower mDP (3.6 +/- 0.3) exhibited a much higher CAA (EC50 = 0.042 +/- 0.005 mg/mL) than other groups, which suggests that bioavailability is crucial to the cellular antioxidant potential of BLPs. Additionally, BLPs strongly inhibited HepG2 proliferation in a dose-dependent manner. Our results indicated that BLPs could be a valuable resource of bioactive compounds to promote consumer health. (C) 2016 Elsevier Ltd. All rights reserved.