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Phytochemical, Antioxidant, and Antibacterial Activities of Stem Bark Fractions of Eucalyptus globulus Against Multidrug-Resistant Bacterial Isolates Abaka, AbdulAzeez Mumsiri; Dominic, Nazuwa; Emmanuel, Alex Yeri; Aliyu, Zayyad Dahiru
Biology, Medicine, & Natural Product Chemistry Vol 14, No 1 (2025)
Publisher : Sunan Kalijaga State Islamic University & Society for Indonesian Biodiversity

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14421/biomedich.2025.141.513-518

Abstract

The growing challenge of antimicrobial resistance (AMR) has intensified the need for alternative therapeutic agents, with medicinal plants offering promising solutions due to their bioactive compounds. This study investigated the antimicrobial and antioxidant properties of Eucalyptus globulus bark extracts against multidrug-resistant bacteria (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus). Plant samples were collected from Adamawa State Polytechnic, Nigeria, authenticated (voucher ASP-765), and subjected to reflux extraction using hexane and water. Phytochemical analysis revealed alkaloids, phenols, tannins, glycosides, and terpenoids in both methanol and aqueous extracts, while flavonoids and steroids were absent in aqueous extracts, and methanol extracts lacked saponins. Antibacterial activity was assessed through agar well diffusion and broth dilution assays, demonstrating a concentration-dependent effect. Methanol extracts showed greater efficacy against E. coli and P. aeruginosa (12.8–13.8 mm inhibition zones), while aqueous extracts were most effective against S. aureus (19.3 mm at 100 mg/mL). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values ranged from 25 to 50 mg/mL, with E. coli exhibiting the lowest MIC (25 mg/mL), highlighting the extract’s antimicrobial potential. The antioxidant activity was evaluated using phosphomolybdate and ferricyanide assays. The methanol extract exhibited strong free radical scavenging activity, with a total antioxidant capacity (TAC) expressed in ascorbic acid equivalents (AAE), although lower than pure ascorbic acid. Statistical validation (one-way ANOVA, p < 0.05) confirmed the significance of the results. These findings support the traditional medicinal use of E. globulus and its potential for combating antibiotic-resistant infections and oxidative stress-related conditions. Further studies are recommended to isolate bioactive compounds, determine mechanisms of action, and develop optimized therapeutic formulations for AMR management.
Phytochemical, Acute toxicity, and Antibacterial Activity of Tamarindus indica Against Antimicrobial-Resistant Staphylococcus aureus Dominic, Nazuwa; Joel, Ewansiha Uyi; Abaka, AbdulAzeez Mumsiri; Yau, Ibrahim
Biology, Medicine, & Natural Product Chemistry Vol 14, No 2 (2025)
Publisher : Sunan Kalijaga State Islamic University & Society for Indonesian Biodiversity

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14421/biomedich.2025.142.1537-1545

Abstract

The escalating public health crisis of antimicrobial resistance (AMR), driven by pathogens like methicillin-resistant Staphylococcus aureus (MRSA), demands an urgent expansion of the therapeutic arsenal. This study provides a comprehensive scientific validation of Tamarindus indica L., a plant with extensive ethnobotanical uses, by systematically evaluating its phytochemical composition, antibacterial efficacy, and acute toxicity profile. Phytochemical analysis revealed that methanol extraction was superior to n-hexane, yielding a rich array of bioactive compounds from the leaves, including alkaloids, flavonoids, saponins, and phenolic compounds. Quantitative assessment confirmed substantial levels of key metabolites, with saponins (550–1400 mg/100g), total phenolics (800–2000 mg/100g), and flavonoids (450–1100 mg/100g) being the most abundant. Antibacterial assays demonstrated that the methanolic extract possessed potent, strain-specific activity against clinical isolates of S. aureus. A notable finding was the significant susceptibility of one strain (SaD), which showed a zone of inhibition of 23.00 mm at 80 mg/mL, exceeding the activity of the cefoxitin control. The methanol fruit extract exhibited Minimum Inhibitory Concentration (MIC) values between 4.69 and 9.38 mg/mL. Crucially, the Minimum Bactericidal Concentration (MBC) was identical to the MIC for most strains, indicating a primarily bactericidal, rather than bacteriostatic, mode of action. In stark contrast, the n-hexane extract showed minimal efficacy, highlighting the critical influence of solvent polarity on the recovery of antibacterial constituents. A pivotal component of this research was the toxicological evaluation. An acute oral toxicity study conducted in rats established an excellent safety profile, with no mortality or significant adverse effects observed at the limit dose of 5000 mg/kg, classifying the extract as practically non-toxic according to OECD guidelines. This finding confirms a wide therapeutic window for potential applications. In conclusion, this study definitively links the traditional use of Tamarindus indica to a scientifically verified, bactericidal phytochemical profile effective against S. aureus and a compelling safety margin. These results firmly position T. indica as a promising candidate for the development of standardized herbal medicines to address the growing threat of antibiotic-resistant infections.