Abstract

Many exotic vegetables remain uninvestigated as potential sources of bioactive nutrients. The objective was to determine and compare nutrients, selected phytochemicals and antioxidant and antimicrobial activities in three types of leafy vegetables and a spice, including Hibiscus sabdariffa, Centella asiatica, Moringa oleifera, and Murraya koenigii. Proximate analysis, vitamin C, beta-carotene, phenolics and flavanoids contents including antioxidant capacity and antimicrobial activity were determined. Soluble dietary fiber, vitamin C and lutein contents were highest in the leaf of H. sabdariffa including high contents of flavanoids and phenolic acids. M. oleifera leaf had the highest contents of carotenoids, (-) epicatechin and o-coumaric acid while M. koenigii’s leaf had the highest content of benzoic acid. The anti-radical power values were 1.03, 0.63, 0.41, and 1.19 mg DPPH/mg extract for the ethanolic extracts from C. asiatica, M. koenigii, H. sabdariffa, and M. oleifera leaves, respectively. Total phenolic contents of the ethanolic extracts significantly affected their anti-radical power with a strong positive correlation between the total phenolic contents and their anti-radical power values. Antimicrobial activity of the three leaf extracts against Listeria monocytogenes,Salmonella typhimurium, and E. coli O157:H7 resulted in H. sabdariffa L. to exhibit the most antibacterial activity among all extracts evaluated in this study showing pathogen reduction to non-detectable limits. These leaves can be used as potential sources of vitamins, minerals, phenolics with antioxidant activity and as antimicrobial agents with potential medicinal value.

Key words: Phytochemicals, Moringa oleifera, Hibiscus sabdariffa, Murraya koenigii,antioxidant, antimicrobial.