Protective Effects Of The Main Flavonoid Compounds Of Citrus Peel Against High-Glucose Induced Intracellular Oxidative Damage In Saccharomyces Cerevisiae

Citrus is the most improtant fruits which grown more than 90 countries and regions in the world.In China,Citrus is the second fruit behand apple in fruit industry.It dominates the cultivation of fruit trees in China,especially pummelo and orange.Citrus fruits are full of nutrition,colorful,good taste,and rich in flavonoids which are the main secondary metabolites.Flavonoids can be used as an antioxidant,which have the the function of anti-inflammatory,anti-aging,anti-cancer,anti-diabetes and cardiovascular disease prevention.It is widely used in the fields of medicine and cosmetics.Therefore,scientific exploitation of citrus fruit which will provides a certain role for human health and nutrition.It not only improves the economic value,but also effectively improves the citrus market and medicinal value.At present,the research on extraction of citrus flavonoids is not only related to the active ingredients of different citrus resources evaluation,active ingredient analysis and identification of the active components of the metabolic regulation of the synthesis of new material and technology,but also the bioactivity of flavonoids and flavonoids and human disease prevention.Therefore,the scientific research on nutritional components of citrus fruit,especially citrus flavonoids,not only provides the foundation for the study of human disease,also provides guidance for human nutrition and health food.It provides a scientific basis for the future development and application of natural antioxidant flavonoids,and will also improve citrus market value,medicinal value and the full realization of the economic value of citrus.Three varieties of pomelos(Liangping,Shatian,Hua Rongshan)and sweet oranges(Fengjie Navel,Washington navel,and Sunkist navel 3107)were chosen as the plant materials in this study.The total contents of fifteen flavonoids in extracts were detected by UPLC-PDA.At the same time,Saccharomyces cerevisiae S288 c was used as a model organism and quercetin was used as a positive antioxidant flavonoids to establish a new system in growing curve,levels of reactive oxygen species,the activities of catalase,superoxide dismutase,peroxidase,and expression levels of mRNA related to glucose metabolism at log phase(8~16 h).The main results were as follows:(1)HR and WN were detected in the most flavonoids in peel extract of pomelos and sweet oranges,respectively.The highest content of flavonoids was NAR in the peel of pomelos,and the highest content of NAR was in ST.In the peel of sweet oranges,the highest content of flavonoids was Hsd,and the highest content of Hsd was in WN;(2)Treatment of Hsd and NAR did not affect on the growth of S.cerevisiae under high-glucose(HG)-induced stress;(3)In yeast cells: Hsd and NAR could effectively reduce intracellular ROS levels induced by high glucose-induced stress in Saccharomyces cerevisiae.Hsd could promote the activity of these three enzymes,including intracellular CAT,SOD and POD,respectively.Under the high and low concentration glucose-induced stress,the effect of Hsd on the reduction of intracellular CAT and SOD activity was observed.On the early period under low concentration of sugar stress,NAR promoted the enzyme activity of intracellular CAT and SOD,respectively.There was no significant difference at high concentration glucose-induced stress.On the early and mid period,the enzyme activity of POD was reduced.Moreover,POD activity was more sensitive to high glucose tolerance,and could be used as an important physiological index to measure the stress mechanism of high glucose-induced stress;(4)The gene expression resulted in yeast under the high glucose-induced early and mid log phase showed that Hsd could inhibit the expression of GPD1,GPD2,GUT1,HXT1,SUC2 and SUC2 which increased by high glucose-induced stress,and induced expression of GUT2 gene which reduced by the glucose-induced stress only in the early stage.But the expression of GPD1 and GPD2 were increased in the late stage.The expression of GPD1 gene was upregulated by NAR.In the early stage of stress,the expression of GUT1 and GUT2 which increased by the glucose-induced stress were inhabited,and regulating the expression of GUT2 or GUT1 to return to normal cells.NAR also could reduce the expression of SOD2 and HXT1 at the early and mid stage of high glucose-induced stress and the expression of SUC2 gene only reduced at the early stage of high glucose-induced stress.