| Abstract: |
The escalating burden of antimicrobial resistance has renewed scientific interest in ethnopharmacologically important plants as sources of antibacterial metabolites. This empirical study compared the phytochemical profiles and antibacterial efficacy of 70% ethanolic extracts of five medicinal plants widely used in central India: Azadirachta indica (leaf), Ocimum sanctum (leaf), Curcuma longa (rhizome), Andrographis paniculata (aerial parts) and Tinospora cordifolia (stem). Shade-dried powders were macerated, concentrated under reduced pressure and screened qualitatively for ten metabolite classes. Total phenolic content, total flavonoid content, alkaloids, tannins and saponins were quantified colorimetrically. Antibacterial activity against Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Klebsiella pneumoniae ATCC 13883 was determined by CLSI-aligned disk diffusion and broth microdilution. Curcuma longa and Andrographis paniculata recorded the highest phenolic loads (148.62 ± 3.41 and 132.45 ± 2.87 mg GAE/g), whereas Ocimum sanctum led in flavonoids (86.53 ± 2.14 mg QE/g). Mean inhibition zones at 100 mg/mL ranged from 10.9 to 22.4 mm. Ocimum sanctum was most active against Gram-positive strains and Andrographis paniculata against Gram-negative strains. Minimum inhibitory concentrations spanned 0.312–5.000 mg/mL. Pearson analysis demonstrated a strong positive correlation between total phenolics and mean zone of inhibition (r = 0.874, p = 0.023) and between flavonoids and Gram-positive inhibition (r = 0.912, p = 0.008). One-way ANOVA confirmed significant inter-species differences for every strain (p < 0.001). The data therefore establish a quantitative phytochemical–activity relationship and identify Ocimum sanctum and Andrographis paniculata as priority candidates for bioassay-guided fractionation. |
