期刊
JOURNAL OF THE AMERICAN OIL CHEMISTS SOCIETY
卷 79, 期 7, 页码 677-683出版社
AMER OIL CHEMISTS SOC A O C S PRESS
DOI: 10.1007/s11746-002-0542-2
关键词
C-13 NMR; H-1 NMR; 3,5,7,3 ',4 ',5 '-hexahydroxyflavone; isolation; melting point; Moringa oleifera; myricetin; natural antioxidants; seed oil gums; ultraviolet absorption spectroscopy
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 a-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 a-tocopherol. The identification of HPLC3 was done using H-1 NMR, C-13 NMR, MS, melting point, and UV absorption spectroscopy and proved to be 3,5,7,3',4',5'-hexahydroxyflavone (myricetin).
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