Characteristics Of Polyphenol Compounds Accumulation In Muscadine Grapes

The muscadine grapes have high biological activity and strong resistance in comparison with non-muscadine grapes,which are mainly due to the distinctive polyphenol composition among them.By using UPLC Triple TOF MS/MS,we analyzed the polyphenol compositions and concentrations in muscadine grapes,including in different cultivars(red and bronze),growing locations(new South China and original USA),berry developmental stages(from small to fully ripened berries),and berry parts(skins,seeds,and pulps).Furthermore,we emphasisly discussed the major polyphenol of ellagic acids and their precursors(EP)accumulation and transfer characteristics in different growing tissues of muscadine and non-muscadine grapes with berry maturation,included berries,pedicels,stems,young/mature leaf blades,and young/mature petioles.By evaluating these,it will laid theoretical foundation for the Grape Germplasm Resources evaluating in South China,in-depth understanding the nutrition character,and in further analyzing the molecular mechanism of EA biosynthesis in muscadine grapes.The results are summarized as follows:1)The UPLC Triple TOF MS/MS method for polyphenol detection in muscadine grapes were built.Among them,156 kinds of polyphenol compounds were detected,and 17 unknown ellagitannins were newly found.Then the structure and fragmentation reactions of the main polyphenols were analyzed.2)The polyphenol compositions and concentrations in skins and seeds of five muscadine grapes(red 'Noble','Alachua',and bronze 'Carlos','Fry' and 'Granny Val')cultivated in newly locations of South China(Nanning-Guangxi,NN-GX,and Pu'er-'Yunnan,PE-YN)has unique characteristics,when compared with their native origin of United States(Tallahassee-Florida,TA-FL).In general,the grapes grown in NN-GX accumulated higher contents of ellagic acid,methyl brevifolin carboxylate and ellagic acid glucoside in skins,and penta-O-galloyl-glucose in seeds.In PE-YN,more flavonols were detected in skins,and higher contents of flavan-3-ols,ellagic acid and methyl gallate were identified in seeds.Abundant seed gallic acid and flavonols were found in TA-FL.Based on PCA of 54 evaluation parameters,various cultivars grown in different locations could be grouped together and via versa for the same cultivar cultivated in different regions.This is the result of interaction beetween genotype and environmental conditions which apparently influence the polyphenol synthesis and accumulation.3)The color of 'Noble' fruit changing to 5%,50%and 100%on 70,77 and 84 days post flowering(DPF)in Nanning-Guangxi,respectively,and 'Carlos' have one week delay compared with 'Noble'.With berry development,fruit horizontal and vertical diameter have double S features,while the fruit weight was increased rapidly at small berry stage,and increased slowly after veraison to ripening.The sugar and acid contents increased and decreased significantly,respectively,but the sugar/acid ratio was lowest on the small berry stage,then increased from veraison,and accumulated highest when berry ripening.Moreover,the variation were different when the total phenolic content(TPC)expressed as either dry weight or fresh weight.When as the former,the TPC in seeds decreased significantly on the small berry stage,then decreased slowly after veraison,while as the latter,the TPC was highest on the veraison stage.4)A total of 141 kinds of polyphenols were identified and quantified in berry skins,seeds,and pulps of the two Muscadinia rotundifolia grapes 'Noble' and 'Carlos')and two Vitis vinfera grapes('Cabernet Sauvignon' and 'Riesling')during berry maturation.These were consisted of 61 EP,38 flavonols,11 flavan-3-ols,21 hydroxybenzoic acids,6 hydroxycinnamic acids,and 4 stilbenes.In contents,EP was the most common category,followed by flavonols and flavan-3-ols.Great differences were found for the polyphenol compositions among different berry parts like skins,seeds and pulps.For example,ellagic acids(EA)and flavonols were highest in skins,whereas the precursors(PC)of EA biosynthesis and flavan-3-ols were abundant in seeds.The polyphenols were differed among the berry developmental stages,for instance,the EP in pulps were significantly decreased,while in skins and seeds they also had cultivar and year differences.EP,total flavonols,galloylate and dimer of flavonols in skins were significantly higher in 2014 than in 2013,whereas the glycosylate and trimer were not affected by the year.Further,flavan-3-ols in skins and pulps were mainly found on small berry stage and before veraison,however in seeds they were highest at veraison.5)Compared with Vitis vinifera grapes('Cabernet Sauvignon' and 'Riesling'),significantly higher contents of EP were found in the different growing tissues of Muscadinia rotundifolia grapes 'Noble'and 'Carlos')during berry maturation.Among them,the highest values were showed in young leaf blades,and the lowest were exhibited in berries.Moreover,the EP composition and the proportion of total EP varied significantly in different tissues.The young leaf blades of Vitis vinifera grapes also had significantly highest EP values,even though no EA were detected in the berries.As berry development,the EP in red cultivar 'Noble' young leaf blades were gradually decreased,whereas the contents were increased significantly in berries.Nevertheless the EP decreased gradually in berries,young leaf blades and young petioles of bronze cultivar 'Carlos',and significantly increased in mature leaf blades and mature petioles.The EA biosynthesis pathway was mostly related to the grape genus(Muscadinia rotundifolia Michx.vs Vitis vinifera),while the color factor was relatively small.We concluded the EA biosynthesis pathway were both existed in young leaf blades of the two grape genus,and the EA in muscadine berries may be transported from other growing tissues.However,the transfer did not happen in Vitis vinifera berries,which may be due to the deficiency accumulation of the precursors,and/or the loss of the transfer enzyme,and with the interreaction of the gene expression regulation.