拟茎点霉侵染对采后龙眼果皮LOX活性和膜脂脂肪酸组分的影响

Effects of Phomopsis longanae Chi Infection on Lipoxygenas Activity and Fatty Acid Constituents of Membrane Lipids in Pericarp of Harvested Longan Fruit

摘要:

用拟茎点霉(Phomopsis longanae Chi)侵染福眼龙眼(Dimocarpus longan Lour. ‘Fuyan’)果实，研究龙眼果皮脂氧合酶(LOX)活性、膜脂脂肪酸组分和细胞膜透性的变化及其与果皮褐变的关系。结果表明：拟茎点霉侵染导致龙眼果皮褐变指数、LOX活性和细胞膜透性增加，不饱和脂肪酸组分[亚油酸(C18∶2)、亚麻酸(C18∶3)和花生一烯酸(C20∶1)]下降而饱和脂肪酸组分[棕榈酸(C16∶0)和硬脂酸(C18∶0)]增加，脂肪酸不饱和指数(IUFA)和脂肪酸不饱和度下降。拟茎点霉侵染提高龙眼果皮LOX活性和加速膜脂不饱和脂肪酸的降解，从而破坏细胞膜系统的完整性，导致膜系统区室化功能丧失，使多酚氧化酶与酚类物质接触，引起酚类物质的酶促氧化和黑褐色高聚物形成，导致龙眼果皮褐变。

Abstract:

After harvested longan (Dimocarpus longan Lour. ‘Fuyan’) fruits were infected by Phomopsis longanae Chi, the changes in lipoxygenase (LOX) activity, fatty acid constituents of membrane lipids and cellular membrane permeability in pericarp were studied. The results showed that the browning index, LOX activity and cellular membrane permeability increased in pericarp of longan fruits infected by P. longanae. The unsaturated fatty acids, such as linoleic acid (C18∶2), linolenic acid (C18∶3) and gondoic (C20∶1), decreased, while the saturated fatty acids, such as palmitic acid (C16∶0) and stearic acid (C18∶0), increased, and the index of unsaturated fatty acids (IUFA) and unsaturation degree of fatty acids decreased. These suggested that longan pericarp browning induced by P. longanae might be due to LOX activity increment and degradation of unsaturated fatty acids of membrane lipids acceleration, which caused the integrity of cellular membrane structure breakage, in turn, the cellular compartmentation function loss, resulting in the contact of polyphenol oxidase (PPO) with phenolic substrates and subsequent oxidation phenolics to form brown polymers.