| Consumption of raw natural plant foods or minimally processed foods with high levels of bioactive compounds is becoming a trend worldwide.This is due to increasing evidence and consumer awareness of the benefits of natural antioxidants.In particular,potato and sweet potato crops have been underscored in many previous studies as good sources of natural antioxidants.However,information regarding phenolic composition in different potato and sweet potato edible parts is scant.Moreover,the application of these natural antioxidants is limited by their low bioavailability and stability.In this study,polyphenols in edible parts(leaf,stalk,stem,skin,flesh)of four sweet potato cultivars(Simon No.1,Yuzi No.7,Shangshu 19,and Pushu 32),and polyphenols in edible parts(skin and flesh)of four potato cultivars(Hei Jingang,Favorita,Kexin No.1,and Shepody)were extracted,identified and quantified.Moreover,an attempt was made to prepare and characterize composites formed by the main phenolic compound(3,5-di-O-caffeoylquinic acid,3,5diCQA)and?-lactoglobulin(?lg)with potential applications as supplements in the food and pharmaceutical industry.The specific findings were as follows:(1)The total polyphenol content(TPC),total flavonoid content(TFC)and total anthocyanin content(TAC)values ranged from 440±0.17–12080±0.58 chlorogenic acid equivalent(CAE)mg100 g-1 dry weight(DW),94±0.08–4210±0.74 quercetin equivalent(QE)mg 100 g-1 DW,and 7±0.01–1010±0.54 cyanidin 3-glucoside equivalent(CGE)mg 100 g-1 DW,respectively,in edible parts of sweet potato.Yuzi No.7 sweet potato cultivar contained significantly higher amounts of TPC,TFC,TAC,and antioxidant activity(AA)in all its edible parts,followed by Pushu 32,Simon No.1,and Shangshu 19 in that order.On average,the TPC in sweet potato leaf was 11.70 times,12.02 times,11.98 times and 14.14 times higher than in the stalk,stem,skin,and flesh,respectively.High performance liquid chromatography(HPLC)revealed 19 individual phenolic compounds.In general,3,5-di-O-caffeoylquinic acid,astragalin,and cyanidin were the predominant phenolic acid,flavonoid,and anthocyanin compounds,respectively.The correlation analysis suggested that higher AA could be attributed to higher polyphenol content.Taken together,edible parts of Yuzi No.7 sweet potato cultivar presented the highest amounts of polyphenol content and AA suggesting the possibility of utilizing this cultivar by farmers and the food industry as a functional food product.(2)TPC,TFC,and TAC values in potato skin ranged from 157.20±0.15–360.61±0.22 CAE mg100 g-1 DW,55.12±0.04–112.19±0.12 QE mg 100 g-1 DW and 3.61±0.00–94.48±0.23 CGE mg100 g-1 DW,respectively.Likewise,TPC,TFC and TAC in potato flesh ranged from 101.82±0.05–299.13±0.11 CAE mg 100 g-1 DW,11.97±0.13–76.69±0.21 QE mg 100 g-1 DW and 3.34±0.01–44.96±0.03 CGE mg 100 g-1 DW,respectively.On average,TPC,TFC and TAC in potato skin were1.59 times,2.91 times and 1.46 times higher than in the flesh,respectively.As well,the AA measured by FRAP,DPPH and ABTS were 1.64 times,2.19 times and 1.66 times higher than in the flesh,respectively.A total of thirteen individual phenolic compounds were identified by HPLC.Phenolic acid(chlorogenic acid)and anthocyanidins(petunidin and peonidin)were predominant in both potato peels and flesh.In addition,a very high positive correlation was found between TPC,TFC and AA,suggesting that AA could be attributed to high polyphenol content.In general,Hei Jingang potato cultivar exhibited the highest amount of TPC,TFC,TAC and AA in all the edible parts(skin and flesh)followed by Favorita,Kexin No.1 and Shepody,respectively.Potato peel could be used as an important source material in production of functional food for consumers and food industry.(3)The main interactions between?lgor?lgnanoparticles(NPs)with 3,5-di-O-caffeoylquinic acid(3,5diCQA)was found to be due to hydrogen bonding and hydrophobic effects.The 3,5diCQA caused a decrease in?-helix and?-sheet structure with a corresponding increase in unordered structure.Compared to?-lgalone,composite?-lgor?-lgNPs-3,5diCQA slightly decreased the particle size but increased their negative surface potentials especially for?-lgor?-lgNPs at a molar ratio of 5:1.The addition of 3,5diCQA appreciably improved the AA in a dose-dependent manner.These results shed light on the structural,physicochemical,and AA of composite?-lgor?-lgNPs-3,5diCQA non-covalent complexes,important for application as functional ingredients in food solutions as well as in the pharmaceutical industry.In conclusion,sweet potato leaves currently discarded or used as animal feed could be utilized as a major source of phenolic compounds and be applied in the development of supplements with potential health benefits in the food and pharmaceutical industry. |
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