Abstract
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 ABTS activity and APA. Methanol was best extraction solvent for TPC (4.6 g GAE/100 g DM) while ethanol was for flavonoids (1.8 g CE/100 g DM). Ethanol extracts exhibited the highest DPPH activity (53.3%–71.1%), while both ethanolic and methanolic extracts had similar and higher ABTS + activity (3.83–3.86 g AAE/100 g DM). Strong positive correlations (r ≥ 0.8; p < 0.05) were observed between chlorophyll content and DPPH, ABTS, and APA, suggesting that chlorophyll was the major contributor to AOA. TAC was highest in aqueous solvent. Free radical scavenging activity in Moringa leaves is positively correlated to chlorophyll, TFC, and TPC while reducing power is positively correlated to chlorophyll and TPC. 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.
Highlights
Oxidative stress is a physiological condition resulting from an imbalance between reactive oxygen species (ROS) and antioxidants in favor of the former
To study the effect of extraction solvent and age on phenolic content and antioxidant activity, fresh leaf samples were pounded in a porcelain mortar to a smooth paste; 1 g of fresh sample was mixed with 20 ml of solvent in a conical flask
The phytochemical content and antioxidant activity of fresh M. oleifera leaves are influenced by the age of the leaves and the extraction solvent used, as well as the interaction between them
Summary
Oxidative stress is a physiological condition resulting from an imbalance between reactive oxygen species (ROS) and antioxidants in favor of the former. M. oleifera leaf extracts exhibit significant pharmacological activities against inflammation (Galuppo et al, 2014), diabetes and hyperglycemia (Azad et al, 2017; Fombang & Willy Saa, 2016; Jaiswal, Kumar Rai, Kumar, Mehta, & Watal, 2009), cancer (Boonsirichai & Jetawattana, 2014), and neurodegeneration (Hannan et al, 2014). They constitute a potential material for nutraceutical formulation. Influence of extraction solvent on the phytochemical content and antioxidant activity of vegetables
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