Phytochemical constituents and assessment of crude extracts from Boerhavia diffusa L. and Lonchocarpus sericeus (Poir.) Kunth ex DC. leaves for antioxidant and antibacterial activities

Abstract

Medicinal plants have been used by humans for therapeutic purposes since ancient times. Hence, this study investigated the human health benefits of aqueous and ethanolic extracts of Boerhavia diffusa and Lonchocarpus sericeus leaves after these solvents’ extraction. The ethanolic L. sericeus extract (ELS), aqueous L. sericeus extract (ALS), ethanolic B. diffusa extract (EBD) and aqueous B. diffusa extract (ABD), were respectively evaluated for their phytochemical constituents, antioxidant and antibacterial properties. Results showed that both plant species have various constituents such as flavonoid (7.11–21.05%), alkaloid (2.00–8.00%), oxalate (1.98- 3.51 mg/g), saponin (3.00–16.00%), tannin (9.70–18.10 mg/100 g), total phenol (7.36- 18.26 mg/100 g) and phytate (225.64–394.88 mg/100 g), respectively. The ethanolic extracts of the leaves showed higher phytochemicals values than the aqueous extracts, with the highest values in the L. sericeus species, which might be due to the less polarity nature of ethanol solvent when compared to the aqueous solvent. The antioxidant results showed that the ethanolic extracts of the L. sericeus species had higher DPPH (78.61%), ABTS (75.57%), Fe2+ chelation (72.13%), FRAP (2.89 mg AAE/g) and hydroxyl radical scavengers (79.81%) than the ethanolic extracts of the B. diffusa species (58.20%, 71.46%, 61.03%, 2.72 mg AAE/g, 66.58%), respectively. The leaves extracts possessed remarkable antibacterial effects against the selected bacterial strains such as Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and S. typhimurium. For instance, the ethanolic leaves extracts showed better inhibitory performances (2–14 mm) than the aqueous extracts (1–8 mm). Therefore, the study recorded the best activities from the ethanolic extracts of Lonchocarpus sericeus plant. Hence, the study substantiated the fact that the effective antibacterial performances of the ethanolic leaves extract is dependent on its high antioxidant capacities as well as the species of plants being used.