Potential substitution of the root with the leaf in the use of Moringa oleifera for antimicrobial, antidiabetic and antioxidant properties

Abstract

A study was conducted to assess variation in antioxidant, antimicrobial, antidiabetic and phytochemical properties between the leaves, and the main and lateral roots of Moringa (Moringa oleifera). Standard antioxidant models including the DPPH scavenging, ferric reducing power (FRAP) as well as α-glucosidase inhibitory activity were used to evaluate and compare their bioactivity. Antimicrobial efficacy was also tested against Gram-positive (Staphylococcus aureus; Bacillus subtilis) and Gram-negative (Escherichia coli) strains and the yeast-like fungus Candida albicans using the microdilution method. Acetone extracts of all plant parts exhibited good antibacterial activity (MIC < 1 mg/mL) against E. coli, B. subtilis and S. aureus, except for lateral root which exhibited weak activity against E. coli (MIC values > 1 mg/mL). However, all the plant part extracts exhibited low activity against C. albicans (MIC values < 1 mg/mL). Variation in the antioxidant activity was observed, with the main and lateral roots exhibiting better activity than the leaves. All the plant parts had better antioxidant activity than the reference compound ascorbic acid. Leaf extracts had significantly good antidiabetic activity as compared to the reference compound, acarbose. Variations were observed in the total phenolic, condensed tannins and flavonoid contents among the different plant parts tested. The leaf extracts exhibited the highest amount of total phenolics, while the lateral roots had higher amounts of condensed tannins and flavonoid contents. The roots can be used as a better source of antioxidants than the leaves. All the leaf extracts had significantly good antidiabetic and antimicrobial activity as compared to the roots. This study ascertains that these different plant parts of Moringa can be suitable candidates for antimicrobial, antioxidant and antidiabetic supplementations, particularly as it is already frequently used in animal and human diets.