Comparative Phytochemical Composition and Antibacterial Activities of Aqueous, Ethanolic and n-hexane Fruit Pulp Extracts of Adansonia digitata, Tamarindus indica and Vitellaria paradoxa

Abstract

The increasing prevalence of antimicrobial resistance has intensified the search for alternative therapeutic agents from natural sources. Adansonia digitata, Tamarindus indica, and Vitellaria paradoxa are important indigenous African fruit species traditionally utilized for nutritional and medicinal purposes. This study evaluated the phytochemical composition and antibacterial activities of aqueous, ethanolic, and n-hexane fruit pulp extracts of these species. Fruit pulps were extracted by percolation using the three solvents. Qualitative and quantitative phytochemical analyses were performed using standard methods, while antibacterial activity was evaluated against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Streptococcus pneumoniae using the agar well diffusion method at concentrations of 300, 150, 75, and 37.5 mg/mI, with three replicates per treatment. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were also determined. Data were analysed using analysis of variance (ANOVA), with statistical significance set at p < 0.05. Qualitative screening revealed the presence of alkaloids, tannins, flavonoids, phenols, glycosides, terpenoids, saponins, and steroids in varying proportions across the extracts. Quantitative analysis showed that phenols were predominant in most extracts, with the ethanolic extract of A. digitata exhibiting the highest phenolic content (90.10 mg/g), while T. indica showed the highest tannin (80.20 mg/g) and flavonoid (62.40 mg/g) contents. Antibacterial activity varied among extracts, concentrations, and bacterial isolates, with ethanolic and n-hexane extracts generally showing greater activity than aqueous extracts. V. paradoxa exhibited the broadest antibacterial spectrum and produced the highest inhibition zone (31 mm) against K. pneumoniae. MIC values ranged from 32 to 280 mg/mI, whereas MBC values ranged from 37.5 to 300 mg/mI, with some MBC values exceeding the highest concentration tested for individual extracts. ANOVA revealed significant differences among bacterial isolates for A. digitata (p = 0.000002) and T. indica (p = 0.00000079), whereas significant differences among extract treatments were observed for V. paradoxa (p < 0.001). The findings demonstrate that the fruit pulps of A. digitata, T. indica, and V. paradoxa contain diverse bioactive phytochemicals and exhibit antibacterial activity, suggesting that these fruits may serve as promising sources of antibacterial phytochemicals for further pharmaceutical, nutraceutical, and functional-food research.