Effects of age and extraction solvent on phytochemical content and antioxidant activity of fresh Moringa oleifera L. leaves

摘要

Antioxidant activity (AOA) and phytochemical content of Moringa oleifera Lam leaves were determined as a function of their age and extraction solvent. Fresh Moringa leaves aged 30, 45, and 60 days were harvested and extracted with three solvents; methanol, ethanol, and water. AOA of leaf extracts was measured using radical scavenging assays (DPPH, ABTS, antiperoxide activity [APA]) and reducing assays (FRAP and total antioxidant capacity [TAC]), and these were correlated with total polyphenols (TPC), total flavonoids (TFC), and chlorophyll contents of leaves. Significant variability (p < 0.05) in TPC and AOA of Moringa leaf extracts was observed with age and extraction solvent as well as their interaction. TPC and TFC increased with maturity, except in aqueous extract. The 60‐day‐old leaves showed highest TPC, TFC, and tocopherol contents with highest DPPH activity. On their part, 30‐day‐old leaves recorded better vitamin C, chlorophyll, and carotenoids with highest style="fixed-case">ABTS activity and style="fixed-case">APA. Methanol was best extraction solvent for style="fixed-case">TPC (4.6 g style="fixed-case">GAE/100 g style="fixed-case">DM) while ethanol was for flavonoids (1.8 g style="fixed-case">CE/100 g style="fixed-case">DM). Ethanol extracts exhibited the highest style="fixed-case">DPPH activity (53.3%–71.1%), while both ethanolic and methanolic extracts had similar and higher style="fixed-case">ABTS ⁺ activity (3.83–3.86 g style="fixed-case">AAE/100 g style="fixed-case">DM). Strong positive correlations (r ≥ 0.8; p < 0.05) were observed between chlorophyll content and style="fixed-case">DPPH, style="fixed-case"> ABTS, and style="fixed-case">APA, suggesting that chlorophyll was the major contributor to style="fixed-case">AOA. style="fixed-case">TAC was highest in aqueous solvent. Free radical scavenging activity in Moringa leaves is positively correlated to chlorophyll, style="fixed-case">TFC, and style="fixed-case">TPC while reducing power is positively correlated to chlorophyll and style="fixed-case">TPC. style="fixed-case">AOA of fresh Moringa leaf extract is a function of its phytochemical content and is influenced by both the age of the leaves and the extraction solvent used. Methanolic and ethanolic extracts of 45‐day‐old Moringa leaves exhibited best antioxidant potentials.