Extraction and identification of natural antioxidant from the seeds of the Moringa oleifera tree variety of Malawi

The oil from the dried seeds of the Moringa oleifera tree (variety of Malawi) was extracted with a mixture of chloroform/methanol (50∶50). The induction period measurements demonstrated a great resistance to oxidative rancidity. After degumming, there was a reduction of 74% in induction periods. The gums produced were extracted with diethylether, n-butanol, and water, yielding four fractions: Fraction 1 (81.8% w/w), Fraction 2 (0.04% w/w), Fraction 3 (0.05% w/w), and Fraction 4 (17.0% w/w). These fractions were tested for their protection of fresh sunflower oil against rancidity, at 50°C, using a UV accelerated method. The oxidation of the sunflower oil was measured using PV; absorbance E _1cm ^1% and malondialdehyde concentration were measured by HPLC. The fraction that showed the highest antioxidant activity was further fractionated by HPLC, yielding seven fractions. Fraction HPLC 3 (present in a quantity of 330.8 and 29.11 ppm in gums and oil, respectively) showed the highest antioxidant activity. Its activity was also compared with that of the commonly used antioxidants BHT and α-tocopherol on sunflower oil using the same methods. At the same level of addition (200 ppm), HPLC 3 showed higher antioxidant activity than BHT and α-tocopherol. The identification of HPLC3 was done using ¹H NMR, ¹³C NMR, MS, melting point, and UV absorption spectroscopy and proved to be 3,5,7,3′,4′,5′-hexahydroxyflavone (myricetin).