Effects of different extraction on the antibacterial and antioxidant activities of phenolic compounds of areca nut (husks and seeds)

Phenolic compounds are bioactive metabolites in plants. The phenolic compounds in husks and seeds of areca nut (AN) were extracted via conventional liquid–solid extraction and ultrasonic-microwave synergistic extraction (UMSE), and abbreviated as CHP, CSP, UHP, and USP, respectively. The extraction conditions of UHP and USP were optimized (solid/solvent ratio of 1:40 and 1:50, the ethanol concentration of 50%, microwave power of 600 and 300 W, and extraction time of 360 and 540 s, respectively). The total phenolic content (TPC) yield, purity, antioxidant activity, and antibacterial activity of four samples were determined and compared. The USP has excellent TPC yield (270.92 mg GAE/g DW), purity (42.84%), antioxidant activities (the IC 50 of DPPH, ABTS, and Superoxide anion were 55.40, 81.87, 138.65 µg/mL, respectively), and antibacterial activities (the MIC of Streptococcus mutans , Staphylococcus aureus , Escherichia coli , and Pseudomonas aeruginosa were 2.50, 5.00, 15.00, and 25.00 mg/mL, respectively). The HPLC–MS showed that USP rich in phenolic compounds, especially proanthocyanidin polymers. Moreover, we speculated that the antibacterial and antioxidant activity might be due to proanthocyanidin polymers. Therefore, UMSE is an efficient method to obtain phenolic compounds of AN, and USP is a potential antibacterial agent and antioxidant.