| Luffa is a medical and edible dual purpose plant,with its soft and juicy fruit by the people's favorite,widely cultivated in China.Luffa flesh prone to browning,affecting its commodity value,revealing the mechanism of luffa browning breeding and post-harvest physiology research focus.Phenolics are closely related to the browning of fruits and vegetables,which is one of the main conditions for enzymatic browning of fruits and vegetables.In this paper,11 varieties of luffa were used as test materials to optimize the extraction method of phenolics in luffa,and the luffa ultra-performance liquid chromatography(UPLC)was established in order to explore the components of the main phenolic compounds caused by enzymatic browning of luffa.The chromatographic rapid detection system was used to analyze the components and contents of gourd phenolic compounds.The enzymatic browning process of phenolic compounds was simulated by in vitro.The main phenolic components of enzymatic browning were determined by UPLC,and screened anti-browning luffa varieties.Key enzymes of luffa phenolic compounds biosynthesis LcPAL1,LcPAL2 gene expression patterns were analyzed.This study provided the theoretical basis and method for the anti-browning breeding of luffa.The main results are as follows:1.Optimize the extraction method of luffa phenolic compounds.The results showed that the extraction of phenolic compounds was the best in the environment of ethanol as the extractant,the ratio of the material to solvent was 1:20(g:mL),and in the strong acid(pH3?4).2.The method of ultra performance liquid chromatography was used to analyze the components and contents of gourd and phenolic compounds.The results were as follows The liquid phase was ACQUITY UPLC BEH C18(2.1 mm × 100 mm,1.7 ? m).The mobile phase consisted of methanol(A)/0.3%acetic acid aqueous solution(B),the column temperature was 32 ?,the injection volume was 2 ? L,MLˇmin-1.Using the gradient elution,elution program 0?0.5 min,95%B;0.5?17.5 min,95%?75%B;17.5?18 min,75%?95%Detection wavelength selection 283nm.14 kinds of phenolic compounds were completely separated within 18 min,and 14 phenolic acids were detected in the samples.The linear range was 0.05?4.0 mg ˇ L-1,the detection limit(S/N = 3)was 0.001?0.049 mg ˇ L-1,the coefficient of determination was more than 0.999,and the relative standard deviation of precision,repeatability and stability Less than 5%.The average recoveries were between 95.36%and 105.58%and the relative standard deviations were 0.80%?3.64%.3.The phenolic compounds caused by enzymatic browning of luffa were identified as chlorogenic acid,p-hydroxybenzoic acid and 4-methylcatechol,and chlorogenic acid was the main browning Things.According to the content of browning substrate,the varieties of chrome-resistant luffa varieties C1,C7 and C9 were screened.4.LcPAL1 and LcPAL2 genes in the biosynthesis of the luffa phenolic compounds were analyzed.The results showed that the two genes had tissue specificity,the highest expression level in the leaves,and the expression level in the roots was also significantly higher than that in the stem The expression order of LcPAL1 gene was leaf>root>stem>flower>fruit.The expression of LcPAL1 and LcPAL2 genes were different in different varieties,among which the expression level of luffa acutangula was significantly lower than that of luffa cylindrica.The LcPALl and LcPAL2 genes were expressed as the first ascending and descending expression in the low-temperature treatment at 25 ? and 4 ?.At the same time,the LcPAL1 and LcPAL2 genes of the luffa were Fresh and frozen during the regulation of phenylalanine ammonia enzyme synthesis of phenolic substances,to promote the occurrence of enzymatic browning luffa. |
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