Analyses of Nutritional Components and Antioxidant Activity of Polyphenol Extracts from Stems and Leaves of Moringa oleifera

The crude protein, ether extract, crude fiber, crude ash, nitrogen-free extract, calcium, total phosphorus and polyphenols in the stems and leaves of Moringa oleifera were analyzed. The antioxidant capacity of M. oleifera stems-leaves polyphenol extract were evaluated by DPPH, ABTS free radical scavenging, hydroxyl radical and ferrous reductive capacity. The results showed that the crude protein, ether extract, crude fiber, nitrogen-free extract, crude ash, calcium, total phosphorus and polyphenols were (17.98±0.87)%, (2.71±0.17)%, (27.74±0.02)%, (35.56±0.96)%, (9.01±0.15)%, (1.76±0.02)%, (0.62±0.01)%, and (4.01±0.01)% respectively. The polyphenols from the stems-leaves of M. oleifera had a strong ability to scavenge DPPH free radicals, the strongest scavenging ability was 91.08% at the concentration of 0.5 mg·mL⁻¹. The scavenging capacity of hydroxyl radicals was better than that of BHT. The scavenging rates of polyphenols from stems-leaves of M. oleifera and BHT were 97.50% and 13.87% respectively at polyphenol concentration 1.25 mg·mL⁻¹. The ABTS free radical scavenging activity of polyphenols M. oleifera stems-leaves was also strong. When the polyphenols concentration was 1.25 mg·mL⁻¹, the ABTS free radical scavenging rates of M. oleifera stems-leaves polyphenols and BHT were 97.80% and 99.18%, respectively. In addition, polyphenols from the stems-leaves of M. oleifera also have certain metal chelating ability. When the concentration of polyphenols in the stems-leaves of M. oleifera was 0.75 mg·mL⁻¹, the metal chelating ability of polyphenols from the stems-leaves of M. oleifera and EDTA was 78.99% and 98.03%, respectively.