In Vitro Antioxidant and Antimicrobial Activities of Three African Spices Commonly Utilized in Postpartum Healthcare Practice in Southern Nigeria

Abstract

Spices such as Xylopia aethiopica, Piper nigrum, and Tetrapleura tetraptera are traditionally employed in postpartum healthcare in Southern Nigeria due to their perceived therapeutic properties. However, scientific validation of their antioxidant and antimicrobial activities, particularly against multidrug-resistant (MDR) pathogens, remains limited. Aqueous and methanol extracts of the three spices were evaluated for their phytochemical constituents, total phenolic content (TPC), total flavonoid content (TFC), antioxidant capacity (DPPH, FRAP, and metal chelating assays), and antimicrobial activity against MDR bacterial isolates using agar well diffusion, MIC, and MBC assays. Methanol extracts generally exhibited higher TPC and TFC values, with X. aethiopica showing the highest flavonoid content (81.0 mg QE/g) and T. tetraptera the highest phenolic content (29.1 mg GAE/g). Antioxidant assays revealed superior activity in methanol extracts, particularly P. nigrum (FRAP IC₅₀: 36.09 µg/mL). Antimicrobial tests showed that methanol extracts had greater inhibitory and bactericidal effects than aqueous counterparts, with P. nigrum methanol extract demonstrating the lowest MIC (25 mg/mL) and the highest activity index (AI up to 0.95) against Bacillus sp. and Pseudomonas aeruginosa. The methanol extracts, especially from Piper nigrum, exhibited potent antioxidant and antimicrobial activities, supporting their traditional use in postpartum therapy and suggesting potential for pharmaceutical applications. This study provides empirical evidence linking the phytochemical richness of these spices to their bioactivities, emphasising the need for further compound isolation, characterisation, and clinical evaluation in the fight against antimicrobial resistance.