Effects Of Chlorogenic Acid On Postharvest Ripening And Senescence Of Nectarine And Apple Fruit

Phenolic compounds are important secondary metabolites in plants,and are well known by their antioxidant properties in human body.Many researches have foucused on the changes of phenolic compounds during fruit ripening and senescence,but there were few researches about whether/how phenolic compounds influence postharvest ripening and senescence of fruit.Our purpose here was to find whether/how fruit phenolic compounds influence postharvest ripening and senescence of fruit by regulating senescence-related proteins and the enzymatic activities.We presented that chlorogenic acid(CHA)could more prominently reduce ethylene production,retard firmness and soluble solids content decreases of nectarine fruit pulp discs than neo-chlorogenic acid,which is also a major phenolic compound of nectarine pulp.Our results showed that the CHA treatment significantly reduced respiration rate,ethylene production,softening,decay rate and malondialdehyde accumulation of nectarine fruit during postharvest ripening.Meanwhile,CHA also retarded peel color turning,increase of soluble solids content and decline of titratable acid in the fruit.Total phenolics content and antioxidant property of the fruit were also influenced by CHA.Antioxidant activity,radical scavenging activity and reducing power in the pulp were remarkably enhanced by CHA.Among the 74 proteins,which are related to the fruit ripening and influenced by CHA,identified with 2-dimensional gel electrophoresis and MALDI-TOF-TOF/MS,levels of the enzymes involved in plant respiration,including NADP-malic enzyme,malate dehydrogenase and NAD-dependent malate dehydrogenase,were significantly reduced in CHA treated fruit;levels of allergen Pru p1 and pathogen-related protein that are known playing multifunctional roles in plants,enhanced by CHA.Accumulations of some proteins related to carbohydrate metabolism,including a-amylase,sucrose synthase,UGPase,UDP-glycosyltransferase and a-galactosidase in nectarine fruit during ripening,were also significantly influenced by the CHA-treatment.And CHA also significantly reduced the accumulation of 1-Aminocylopropane-l-carboxylic acid oxidase(ACO)in nectarine fruit during postharvest ripening.In apple pulp,174 proteins which have affinity with apple polyphenols were identified by iTRAQ(isobaric tags for relative and absolute quantification).These proteins include:lipoxygenase,glycosytrasferase,a-amylase,starch branch enzyme,cellulose synthase,sucrose phosphate synthase,P-galactosidase?1-Aminocylopropane-l-carboxylic acid synase(ACS)?ACO and ethylene receptor.Apple pulp discs were used as models to study the influences of CHA(a major polyphenol in apple pulp)on apple fruit senescence.Compared to the control samples,treatment with CHA significantly reduced ethylene production and respiration rate,and enhanced levels of firmness and soluble solids content of the pulp discs during incubation at 25?.Proteomics analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and MALDI-TOF/TOF revealed that the expressions of several key proteins correlated to fruit senescence were affected by the treatment with CHA.Treating the pulp discs with CHA remarkably reduced levels of lipoxygenase,?-galactosidase,NADP-malic enzyme,and enzymatic activities of lipoxygenase and UDP-glucose pyrophosphorylase,all of which are known as promoters of fruit ripening and senescence.To determine whether CHA influences senescence-related enzymes of apple fruit,we analyzed them in vitro.In vitro,ACS,ACO,a-amylase,lipoxygenase(LOX),?-glucosidase,?-galactosidase,polygalacturonase,pectin methylesterase,NADP-malic enzyme,peroxidase(POD),polyphenol oxidase(PPO)were all inhibited by apple pulp polyphenols and CHA which is the principle phenolic compound of apple pulp polyphenols.And there was no significant difference between them.During observation,we found ACS,ACO,a-amylase,LOX,?-glucosidase,?-galactosidase,NADP-ME,POD,PPO enzymes of apple pulp discs were inhibited by CHA during observation,while some enzymes,such like PG and PME were not influenced by chlorogenic acid.