ANTIBACTERIAL ACTIVITY OF AQUEOUS AND METHANOLIC EXTRACTS OF POLYALTHIA LONGIFOLIA AND HYPTIS SUAVEOLENS AGAINST CLINICALLY RELEVANT ISOLATES FROM NIGERIAN DEFENCE ACADEMY HOSPITAL, KADUNA, NIGERIA

Abstract

The escalating threat of antibiotic resistance necessitates innovative strategies leveraging plant-derived antimicrobials. This study evaluates the antibacterial activity of aqueous and methanolic leaf extracts of Polyalthia longifolia and Hyptis suaveolens against multidrug-resistant clinical isolates (Staphylococcus aureus, Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Streptococcus pyogenes) from the Nigerian Defence Academy Hospital, Kaduna, compared to ciprofloxacin. Extraction yields were solvent- and species-dependent: methanol optimized P. longifolia yields (15.8%), reflecting its mid-polar phytochemicals (flavonoids, terpenoids), while water maximized H. suaveolens yields (49.6%), indicative of hydrophilic metabolites (glycosides, glycerol). GC-MS profiling revealed antimicrobial constituents, including lauric acid derivatives (31.0%) and cyclic ketones (20.6%) in P. longifolia, and γ-sitosterol (9.6%) and glycerin (10.3%) in H. suaveolens. Both species shared key membrane‐active and antioxidant constituents, including phytol, palmitic and linoleic acid esters, and vitamin E. Both extracts exhibited dose-dependent antibacterial activity, with P. longifolia achieving MICs as low as 1.0 mg/mL (rivaling ciprofloxacin at higher concentrations) and H. suaveolens showing Gram-positive specificity. Ciprofloxacin retained superior potency (MICs: 0.25–0.50 mg/mL). Finally, 16S rRNA gene sequencing confirmed species identities with 99.6–100 % accuracy and revealed a plasmid associated amplicon in H. influenzae. These findings highlight the multi‐target, synergistic mechanisms of these plant extracts such as, membrane disruption, enzyme inhibition, and free radical scavenging, and support their potential as cost effective, plant-based adjuncts to conventional antibiotics in resource limited settings.