Effect of soaking and air-resting on the phytochemical, antioxidant, and antimicrobial properties of Piper guineense (Schum and Thonn) seeds

BACKGROUNDSoaking and air-resting are processing steps in malting. This has been reported to increase metabolic and enzyme activities in rice paddy as a result of exposure of the grain to atmospheric oxygen. The present study evaluated the effect of soaking and air-resting on the phytochemical composition of Piper guineense seeds. The seed extracts were prepared by: soaking the seeds in water for 4 h; air-resting for 30, 60, 90, and 120 min; and re-soaking for another 4 h. The out-of-steep seeds were milled and an extract was formed by tissue homogenization and maceration using ethanol. The phytochemical, antioxidant, and antibacterial properties of the seed extract were determined using standard methods. RESULTSThe alkaloid, flavonoid, saponin, tannin, and total phenol contents were 0.126-0.268, 0.091-0.172, 0.080-0.123, 0.00-0.107, and 0.447-0.908 g kg(-1) respectively. The antioxidant properties (reducing power) of the seed extracts were concentration-dependent and were in the range 1.08-3.24 g kg(-1) at 8 mg mL(-1), 1.14-3.47 g kg(-1) at 16 mg mL(-1), 1.30-3.35 g kg(-1) at 24 mg mL(-1), 1.26-3.11 g kg(-1) at 32 mg mL(-1), and 1.13-3.04 g kg(-1) at 40 mg mL(-1), respectively. The antibacterial activities against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa showed that, at 100 mg mL(-1), the inhibition zone diameters of the seed extracts were in the range 10-23 mm. CONCLUSIONSoaking and air-resting of P. guineense seeds increased the phytochemical components of the seeds. The extracts from the seeds air-rested for 30 min showed the highest phytochemical contents and had the highest antioxidant and antimicrobial properties. (c) 2022 Society of Chemical Industry.