Antimicrobial and antifungal activities of ethanolic extracts from five medicinal plants indigenous to southeastern Nigeria

Background: The global rise of antimicrobial resistance necessitates the exploration of novel therapeutic agents. Plants represent a promising source of bioactive compounds due to their diverse phytochemical constituents.Objectives: This study aimed to evaluate the in vitro antibacterial and antifungal activities of ethanolic extracts from the rhizomes of Zingiber officinale and Curcuma longa, the leaves of Annona muricate and Piper guineense, and the gel of Aloe barbadensis.Methods: Plant materials were collected, authenticated, dried, and powdered. Ethanolic extracts were prepared using Soxhlet extraction for all materials except Aloe barbadensis gel, which was obtained through mechanical separation and filtration. The extracts were subjected to qualitative phytochemical screening and assessed for antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans using the agar well diffusion method. The minimum inhibitory concentration (MIC) was determined for each active extract.Results: Phytochemical analysis confirmed the presence of alkaloids, flavonoids, tannins, saponins, steroids, triterpenoids, glycosides, reducing sugars, proteins, and amino acids. The extracts demonstrated varying degrees of antimicrobial activity. Curcuma longa extract exhibited the strongest and broadest activity, with MICs of 6.25 mg/mL against S. aureus, 12.5 mg/mL against P. aeruginosa, and 3.13 mg/mL against C. albicans. Zingiber officinale and Piper guineense extracts were active against all three test organisms, with MICs ranging from 12.5 to 50 mg/mL. Annona muricate extract showed selective antifungal activity against C. albicans (MIC = 50 mg/mL), while Aloe barbadensis gel extract showed no detectable activity against any of the tested pathogens at the concentrations used.Conclusion: The results validate the traditional use of these plants, particularly Zingiber officinale, Piper guineense, and Curcuma longa, in treating infections. The significant antimicrobial efficacy observed, especially for Curcuma longa, underscores their potential as sources of lead compounds for developing new antimicrobial agents to combat drug-resistant pathogens.