Anthocyanins were extracted from the berries according to the method described by Wang et al. (2014) with some modifications. Approximately 2 g of fresh berries were placed in 10 mL centrifuge tubes containing 5 mL 2% formic acid methanol (v/v), and then the
mixtures were shaken by a QL-861 vortexer for 30 s. The samples were subsequently sonicated in a KQ-500DE ultrasonic cleaner at 20 C for 20 min and then centrifuged using SIGMA 3K30 centrifuge at 12,000g for 10 min. The supernatants were then collected in 50 mL centrifuge tubes. The steps above were repeated until the extracts were colorless. Thereafter, 5 mL extracts were dried using multifunction sample concentrator with nitrogen. The residue was re-dissolved in 1 mL of 2% formic acid methanol (v/v) and then passed through 0.22 lm millipore membrane filters prior to the HPLC analyses.