Inhibitory Activity Of Kumquat Extracts On Lipid Oxidation Of Mackerel And It’s Effective Compounds

• Main Authors: Liou, Jiunyi, 劉俊毅
• Other Authors: Lou, Shyineng
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/76219508361150060962

碩士 === 國立宜蘭大學 === 食品科學系碩士班 === 100 === In this study immature kumquat was extracted by hot water, ethanol, and ethyl acetate. The obtained extracts were added in oil of mackerel, separately, to evaluate the inhibitory activity on lipid oxidation under heating condition. In order to confirm the effective compounds, a semi-preparative C18 column was used to separate and fractionate the target substances. Furthermore, the inhibitory model of antioxidant and identification of the effective compounds were also investigated. The results exhibited that DPPH free radical scavenging effect of extracts from hot water and ethanol extracts were better than ethyl acetate extract, while the scavenging potency were 7.51±0.67 and 6.98±0.30 % / mg / mL, respectively, which also equal to 158.96 ±5.39 and 119.93 ±3.81 M trolox. After addition of ethanol extract of kumquat into oil of mackerel, evaluation of inhibitory activity against lipid oxidation was carried out under heating storage. The results showed that 2000 ppm ethanol extract could retard the induction time to 5 days against lipid oxidation. Besides, it could decrease the formation of conjugated diene substances and also postpone the degradation of EPA and DHA, effectively. The ethanol extract was separated to six fractions via semi-preparative C18 column, and each fraction was added to oil of mackerel for the accelerated storage test. Fraction I could delay the oxidation induction time to third day, while fraction V and fraction VI could inhibit the formation of conjugated diene. These hinted that the compounds in fraction I, V and VI might relate to the antioxidant activity. The results of antioxidant activity test revealed that fraction I had better DPPH free radical and superoxide anion radical scavenging activity, with values of 22.79 ± 6.10 % and 46.04 ± 19.91 %, respectively. Moreover, the highest ORAC（oxygen-radical absorbance capacity）of fraction V with 1785±9 M trolox was also observed. We used different mixtures of kumquat ethanol extract（K）, fraction I（I）, fraction V（V）, and BHA in the ORAC assay. A increasing effect of ORAC assay to 419% was observed with the ratio of K：BHA=5:1. A increase of 20.6% ORAC of I：B=10：1 was also found. In fraction I, many compounds existed, however, there was only a major compound in fraction V. The compound was detected by UV scan and the maximum absorptions were 267 and 332 nm. The molecule weight was certified as 592 dalton. The main breaking ion for MS1 was 447 [M+H–146]+ and for MS2 was 285 [M+H–146–162]+. It was identified as acacetin 7-O-neohesperidoside in comparing with literature data. The level of acacetin 7-O-neo- hesperidoside in immature kumquat was 0.56 g / 100 g d.w.