Phytochemical analysis and bioactive potential of Moringa, Eucalyptus, and Nerium extracts against microbial, diabetic, inflammatory, and oxidative stress challenges.

Phytochemical screening of ethanolic and aqueous leaf extracts from Moringa oleifera, Eucalyptus globulus, and Nerium oleander confirmed alkaloids, flavonoids, phenols, tannins, and terpenoids. Antimicrobial activity assessed by agar well diffusion against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae showed ethanolic extracts as more effective (p < 0.05) than aqueous extracts. Eucalyptus globulus ethanolic extracts exhibited the highest inhibition zone (32 ± 1.5 mm at 150 µL) against P. aeruginosa, followed by Nerium oleander (29 ± 1.2 mm) and Moringa oleifera (26 ± 1.0 mm), with superior activity against E. coli and S. aureus (MIC: 125 ± 10 µg/mL). Linear regression analysis revealed strong dose-dependent effects for K. pneumoniae (R 2 = 0.982-0.992), moderate effects for P. aeruginosa (R 2 = 0.775), and weaker effects for S. aureus (R 2 = 0.981). Anti-oxidant activity by DPPH assay showed Moringa oleifera (93.1 ± 1.5% at 400 µg/mL), Eucalyptus globulus (91.8 ± 1.8% at 400 µg/mL), and Nerium oleander (93.5 ± 2.0% at 400 µg/mL) as potent. Anti-diabetic activity, measured by α-amylase inhibition, showed Nerium oleander (78.3 ± 3.1% at 75 µg/mL), Moringa oleifera (70.0 ± 2.8% at 75 µg/mL), and Eucalyptus globulus (90 ± 3% at 1000 µg/mL). Anti-inflammatory activity of Nerium oleander (97.3 ± 2.0% at 25 µg/mL) and Moringa oleifera (93.1 ± 1.8%) outperformed the standard. Time-dependent α-amylase inhibition increased significantly after 30 min (p = 4.9 × 10⁻5). These findings highlight the therapeutic potential of these extracts and might suggest further in vivo studies in diabetic and inflammatory models.