GC-MS profiling and antimicrobial activity of Moringa oleifera leaf and Citrus sinensis peel extracts and their individual and combinational effects

The plant-based antimicrobials have emerged as an alternative source of medicine to synthetic antibiotics due to their cost-effectiveness, cause lesser side effects and have a broad range of activity. The present study deals with the assessment of antibacterial efficiency of ethanolic leaf extracts of Moringa oleifera Lam., as well as ethanolic peel extracts of Citrus sinensis L., against Vibrio harveyi (Gram-negative bacteria) and Bacillus subtilis (Gram-positive bacteria). The M. oleifera and the C. sinensis are widely available, inexpensive and eco-friendly botanical materials with wide range of phytochemical content. The crude extracts were obtained through Soxhlet extraction process with 70 % ethanol. The preliminary qualitative phytochemical analysis showed the presence of alkaloids, tannins, saponins, phenols, flavonoids and terpenoids. Antibacterial activity was assessed by agar well diffusion, broth microdilution (MIC/MBC) and checkerboard synergy testing methods. Findings indicated that the two extracts reduced the growth of bacteria in a dose-dependent manner. Moringa oleifera and Citrus sinensis extracts exhibited a potent antimicrobial activity against B. subtilis (MIC-3.125 ± 0.11 and 12.50 ± 0.00 mg/mL respectively) and V. harvevi (6.25 ± 0.17 and 3.125 ± 0.05 mg/mL respectively). Against B. subtilis, a synergistic effect was defined (fractional inhibitory concentration index (FICI) = 0.31), whereas against V. harveyi, an indifferent effect was observed (FICI = 1.03). Through gas chromatography-mass spectroscopy (GC-MS) analysis we were able to identify some antibacterial compounds in M. oleifera extract such as n-hexadecanoic acid, phytol and α-linolenic acid. Similarly, limonene, 5-hydroxymethylfurfural and phenolic derivatives in C. sinensis. The results support the feasibility of widely used plant resources such as M. oleifera and C. sinensis and their natural antibacterial capacity at an affordable cost and potential anti-microbial usage in food safety and disinfectant spray formulations.