Phytoconstituent Detection, Antioxidant, and Antimicrobial Potentials of Moringa oleifera Lam. Hexane Extract Against Selected WHO ESKAPE Pathogens

The holistic use of Moringa oleifera Lam. seeds is not as popular amongst rural South Africans. This study screened for the phytochemicals, antimicrobial, and antioxidant potentials as well identifying the compounds in the oils of South African Moringa seed oils using cost-effective thin layer chromatography bioautography and dot blot assays, because fewer studies have been conducted using seed samples from this country. The results obtained indicated that the best oil extract yield (24.04%) was obtained for hexane from 60.10 g of powdered seeds. The yield of the other extracts ranged from 6.2 to 9.5%. Positive test results were obtained for terpenoids, steroids, alkaloids, flavonoids, phenols, and tannins, with potentially good antioxidant properties for scavenging free radicals from 2,2-diphenyl-1-picrylhydrazyl (DPPH) and good antimicrobial activity against Acinetobacter baumannii (BAA 747), Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 27853), and Pseudomonas aeruginosa (ATCC 27853), with the best zone of inhibition of 314.2 mm² obtained for oil extracted with hexane, followed by dichloromethane, methanol, and acetone oil extracts, respectively. The best minimum inhibitory concentration (MIC) of 0.032 mg/mL against P. aeruginosa was recorded for the hexane oil, compared with ciprofloxacin, which had an MIC of 0.0039 mg/mL against the same pathogen. The identification of the in-oil compounds proposed to mitigate inhibitory activity against the test microbes was carried out through GC-MS analysis matching our results with the GC-MS library. These compounds included ursane-3,16-diol, azetidin-2-one, 1-benzyl-4à-methyl, dibutyl phthalate, 4-methyl-2,4-bis(p-hydroxyphenyl)pent-1-ene, 1H-pyrrole-2,5-dione, 3-ethyl-4-methyl, octopamine rhodoxanthin, 29,30-dinorgammacerane-3,22-diol, 21,21-dimethy, cholan-24-oic acid, 3,7-dioxo, and benzyl alcohol. These are in addition to the stability-indicating marker compounds like oleic acid (54.9%), 9-Octadecenoic acid (z)-, methyl ester (23.3%), n-hexadecanoic acid (9.68%), among others observed over a five year period.