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Abstract Plant extracts are used worldwide for treating microbial diseases due to their biologically active compounds. This study investigated the phytochemical constituents and the synergistic antimicrobial and antioxidant potential of three medicinal plants namely Ocimum gratissimum, Tetradenia riparia, and Dysphania ambrosioides. Antibacterial studies against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were performed using the broth dilution method. Antioxidant activity was assessed using the DPPH method. UPLC analysis identified several metabolites in the plant extracts, including phenolics and flavonoids. The phytochemical analysis revealed the presence of alkaloids, saponins, flavonoids, iridoids, and anthraquinones in all extracts. The extract of T. riparia had the highest phenolic content (299.146 ± 0.143 mg GAE/g extract), while O. gratissimum had the highest flavonoid content (138.256 ± 0.277 mg QE/g extract). Decocted extracts of O. gratissimum exhibited the highest antioxidant activity. The combination of O. gratissimum + T. riparia demonstrated synergistic antioxidant activity (CI = 0.57). Antibacterial activity was highest with percolated extracts of O. gratissimum and T. riparia against S. aureus (MIC = 500 µg/mL), with their combination showing additive antibacterial activity (FICI = 1). This study concludes that these plant extracts are promising sources of natural antimicrobial and antioxidant agents for pharmaceutical and food industries.
Ngolo et al. (Tue,) studied this question.