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

•BLPs showed potent chemical, cellular antioxidant and antiproliferative capacities.•TPC and PAs content were in strong relation with chemical antioxidant activities.•Ultrasound treatment significantly degraded the mDP of PAs and improved CAA value.•Antiproliferative activity was in strong relation with PA contents.

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.