| The kiwifruit,called 'the king of fruits',is an economically important fruit crop because of its remarkably high vitamin C content,balanced nutritional composition of dietary fiber,minerals and other health-beneficial metabolites.Actinidia chinensis,also known as golden kiwifruit,is particularly well-known for its abundant vitamin C contents as compared to other cultivars.Golden kiwifruit with yellow fruit flesh has prominent tropical flavor and soft hairless peel,which allow consumer to consume it without peeling.Several studies have illustrated the high amount of bioactive substances,such as phenolic compounds and fibers,in golden kiwifruit peel.However,the kiwifruit peel has been only used for the production of acids and alcohol through solid state fermentation currently.In China,the production of golden kiwifruit per year is 72 thousands MT,which leads to the formation of 793 MT peel waste every year.Therefore,further studies are needed to explore the biological properties of golden kiwifruit peel to prompt its full utilization.Considering the predominant bioactivities of polyphenols and the higher amounts of polyphenols in golden kiwifruit peel than flesh,our study firstly evaluated and compared the promising antioxidant,antimicrobial and anti-proliferative activity of polyphenols extracted from peel and flesh of golden kiwifruit.The phenolic profile of flesh and peel was examined by liquid chromatography mass spectrometry(LC/MS).To reflect the pattern of kiwifruit intake more realistically,the fleshes of two Actinidia chinensis(ACF),peels of two Actinidia chinensis(ACP)and fleshes with peels of two Actinidia chinensis(ACFP)were prepared.The potential functional properties of ACFP in comparison to ACF and ACP were evaluated in healthy and high fructose diet-fed Sprague Dawley(SD)rats.The main methodology and outcomes are defined as follows:1.The pericarp of golden kiwifruit was found to be more abundant in polyphenols and flavonoids than its flesh,with the contents of 12.8 mg/g and 2.7 mg/g,respectively.LC/MS analysis revealed that the contents of catechin,quercetin and epigallocatechin(the main polyphenols in kiwifruit)in peel were significantly higher than that in flesh(p<0.05).Antioxidant activity of extracted polyphenols of peel and flesh of Actinidia chinensis was checked by DPPH,ABTS,hydroxyl ion reducing and ion chelating ability.The antibacterial activity against Escherichia coli,Listeria monocytogenes and Staphylococcus aureus was checked by disc diffusion assay.As a result,the overall antioxidant and antibacterial activity of peel were significantly higher when compared to flesh.Moreover,the proliferation of HepG2 cells was time and dose-dependently inhibited by kiwifruit polyphenols,with 170?g/mL and 291?g/mL of IC50 values for peel and flesh polyphenols after 72 h of treatment time,respectively.Taken together,kiwifruit peel with higher contents of phenolics and flavonoids exerts more potent antioxidant,antibacterial and anticancer activity than flesh.2.The effects of fleshes of two Actinidia chinensis fruits(ACF)and fleshes with peels of two Actinidia chinensis fruits(ACFP)on lipid homeostasis,fatty acid metabolism and gut microbiota was investigated in healthy rats.Moreover,the phenolic contents of ACF and ACFP were identified and quantified by LC/MS.10 phenolic compounds including isoquercetin,epigallacatechin,chlorogenic acid,catechin,ferulic acid,epicatachin,caffiec acid,kaempferol,quercetin and rutin were identified and quantified in golden kiwifruit.Among them,catechin,epicatechin,epigallacatechin,kaempherol,quercetin and chlorogenic acid were the main polyphenols in ACF and ACFP.The contents of catechin,epicatechin,quercetin,epigallacatechin and chlorogenic acid in ACFP were 7.68 mg,5.74 mg,10.16 mg,3.22 mg and 6.92 mg,respectively,which were significantly higher(p<0.05)than the contents of catechin(6.20 mg),epicatechin(4.74 mg),quercetin(8.08 mg),epigallacatechin(2.58 mg)and chlorogenic acid(5.54 mg)in ACF.Intervention of ACF and ACFP for 4 weeks significantly reduced total cholesterol,total triglycerides,and increased the high-density lipoprotein levels in rats.But ACF or ACFP showed no significant effects on low density lipoprotein at any time interval.Besides,ACF and ACFP ameliorated lipid peroxidation in rats,by lowering hepatic MDA level and enhancing GSH-Px and SOD activities.In addition,ACFP more significantly decreased the saturated fatty acids in serum and increased the polyunsaturated fatty acids in hepatic and serum of rats.Analysis of gut microbiota revealed that ACF and ACFP evidently increased the microbial richness and diversity of gut microbiota.The microbiota composition was significantly altered in both ACF and ACFP group while ACFP more significantly reduced the abundance of Firmicutes(66%to 51%)and increased the Bacteroidetes(21%to 38%).The Firmicutes/Bacteroidetes(F/B)ratio for ND,ACF and ACFP was 3.04,2.12 and 1.34,respectively.Moreover,ACF and ACFP significantlyincreased the abundance of Lactobacillus by 35.15%and 50.59%,respectively,when compared to the ND rats(18.69%).Similarly,ACF and ACFP significantly increased the abundance of beneficial bacteria Barnesiella from 9.83%for ND rats to 14.69%and 17.24%,respectively,suggesting that kiwifruit flesh,especially the whole kiwifruit could be considered as a great prebiotic.Moreover,ACF and ACFP reduced the harmful bacteria(Enterococcus,Escherichia,Staphylococcus).Overall,ACFP exerts more potent health-improving effects than ACF.3.The protective effects of ACF,ACP and ACFP on HF diet-induced liver injury and fatty acid metabolism disorders were investigated.Phenolic contents of ACF,ACP and ACFP were identified and qualified by the LC/MS.The contents of catechin,epigallacatechin,epicatechin,quercetin and chlorogenic acid(the dominant polyphenols in golden kiwifruit)in ACFP were 7.68 mg,3.22 mg,5.74 mg,10.16 mg and 6.92 mg,respectively,which were significantly higher(p<0.05)than that in ACF.And the contents of catechin(1.48 mg),epigallacatechin(0.64 mg),epicatechin(1.00 mg),quercetin(2.08 mg)and chlorogenic acid(1.38 mg)in ACP were even lower than that in ACF.Moreover,the total pectin contents of ACF,ACP and ACFP were determined as the calcium pectate.The amount of pectic substances in ACP(1.34%)were significantly higher(p<0.05)as compared to the ACFP(0.76%)and ACF(0.63%).Healthy male SD rats fed with HF water(20%)for 10 consecutive weeks displayed significant dyslipidemia,hepatic steatosis,oxidative stress,insulin resistance and fatty acids metabolism disorder.While continuous administration of ACF and ACFP for 10 weeks prevented the damage caused by HF-diet in rats.ACFP significantly reduced the HF dietinduced elevation of body weight,organ weight,serum total cholesterol,total triglycerides and low density lipoprotein,as well as AST and ALT activities,while markedly increased the HF-induced decline of high density lipoproteins levels in the serum when compared to HF-fed rats.Moreover,ACFP significantly recover the hyperglycemia and hyperinsulinemia induced by HF diet in rats.Meanwhile,oral administration of ACFP alleviated the HF diet induced oxidative stress in rats by reducing the MDA level and increasing the SOD and GSH-Px activities,as compared to HF-fed rats.Furthermore,intervention of ACFP for 10 weeks significantly(p<0.01)decreased serum saturated fatty acids,serum and hepatic monounsaturated fatty acids and increased serum and hepatic polyunsaturated fatty acids levels,as compared to the HF-fed rats.Similarly,the ACFP elevated the HF diet-caused decrease in the contents of acetic acid(from 46.32 to 63.67 mM/g,p<0.05),propionic acid(from 8.62 to 20.69 mM/g,p<0.05)and butyric acid(from 11.36 to 22.76 mM/g,p<0.05),which could be considered as biomarkers for the improving effects of golden kiwifruit on HF-caused abnormalities.Furthermore,histopathology of the liver by HE staining confirmed the liver steatosis induced by HF-diets and the hepatic protective effects of ACFP.Our findings suggest that golden kiwifruit alleviates the HF diet-induced dyslipidemia,hepatic steatosis,oxidative stress,insulin resistance and fatty acids metabolism disorder in rats,and ACFP exerts more potent protective effects against HF diet-induced disorders than ACF and ACP.To sum up,golden kiwifruit,especially its peel,effectively improved the glucolipid metabolism,hepatic oxidative stress,fatty acid profile and gut microbiota in both healthy and high-fructose-fed rats.Our study provides a scientific foundation for developing kiwifruit(including peel)-based dietary supplements with significant health benefits. |
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