Maximizing total phenolics, total flavonoids contents and antioxidant activity of Moringa oleifera leaf extract by the appropriate extraction method

Abstract

Moringa oleifera L. (Moringaceae) has been used as traditional medicines in many tropical and sub-tropical countries. Having phenolics and flavonoids as major constituents, the leaf extract has been reported to exhibit antioxidant activity both in vitro and in vivo. To obtain the maximum yields of these compounds, which consequently influence the antioxidant activity, varying extraction methods were examined. Squeezing, decoction, maceration, percolation and soxhlet extraction were used to extract fresh and dried leaves of M. oleifera. Distilled water was used in squeezing and decoction, while 50 and 70% ethanol were used in the other methods. The contents of total phenolics and total flavonoids, free radical scavenging activity and ferric reducing power (FRP) of each extract were quantitatively determined. Quantitative analysis of active compounds was accomplished through high performance liquid chromatography (HPLC). Extract from the most effective extraction method was then selected for reactive oxygen species assay (ROS) in HEK-293 cells. Maceration with 70% ethanol of dried leaves promoted the extract with maximum amounts of total phenolics (13.23g chlorogenic acid equivalents/100g extract) and total flavonoids (6.20g isoquercetin equivalents/100g extract). This extract also exhibited high DPPH-scavenging activity (EC50 62.94μg/mL) and the highest FRP value (51.50mmol FeSO4 equivalents/100g extract). At the concentration of 100μg/mL, the extract could significantly reduce relative amount of intracellular ROS. The contents of major active components, crypto-chlorogenic acid and isoquercetin, in the dried plant powder were 0.05 and 0.09% (w/w), respectively. Considering various factors involved in the extraction process, maceration with 70% ethanol was advantageous to other methods with regards to simplicity, convenience, economy, and providence of the extract containing maximum contents of total phenolics and total flavonoids with the highest antioxidant activity. Maceration and 70% ethanol were recommended as the extraction method and solvent for high quality antioxidant raw material extract of M. oleifera leaves for pharmaceutical and nutraceutical development.