2,4-二硝基苯酚对采后龙眼果皮脂氧合酶活性和膜脂脂肪酸组分的影响

Effects of 2,4-dinitrophenol on Lipoxygenase Activity and Fatty Acid Constituents of Membrane Lipids in Pericarp of Harvested Longan Fruits

以‘福眼’龙眼(Dimocarpus longan Lour.‘Fuyan’)果实为材料,研究呼吸解偶联剂2,4-二硝基苯酚(DNP)对采后果皮脂氧合酶(LOX)活性、膜脂脂肪酸组分和细胞膜透性的影响及其与果皮褐变的关系。结果表明:DNP处理导致龙眼果皮细胞膜透性、LOX活性和褐变指数增加,膜脂脂肪酸组分中的棕榈酸(C16:0)、硬脂酸(C18:0)等饱和脂肪酸的组分增加,亚油酸(C18:2)、亚麻酸(C18:3)和花生一烯酸(C20:1)等不饱和脂肪酸的组分下降,脂肪酸不饱和指数和脂肪酸不饱和度下降。因此认为,DNP促进了龙眼果实果皮褐变可能是由于提高了LOX活性,促进了膜脂不饱和脂肪酸的降解而引起膜系统完整性受损,最终导致细胞膜结构的破坏,使酚酶与酚类物质接触而引起酚类物质氧化的结果。

The effects of 2,4-dinitrophenol （DNP, a uncouple agent for respiratory） on lipoxygenase （LOX） activity, fatty acid constituents in membrane lipids and cellular membrane permeability in harvested longan （Dimocarpus longan Lour. ‘Fuyan＇） pericarp were investigated and the relationship to pericarp browning was analysed. The results showed that the cellular membrane permeability, LOX activity and browning index increased treated with DNP, the saturated fatty acids, such as palmitic acid （C16：0） and stearic acid （C18：0） increased, and the unsaturated fatty acids, such as linoleic acid （C18：2）, linolenic acid （C18：3） and （C20：1）, and index of unsaturated fatty acids （IUFA） and unsaturation degree of fatty acids decreased. It suggested that the pericarp browning of longan induced by DNP might be due to increasing LOX activity, enhancing degradation of membrane unsaturated fatty acid and reducing integrity of cellular membrane, which it lead to finally the contact of phenolase with phenolic substrates to produce browning polymers.