| Rice(Oryza sativa L.)is a leading commercial cereal crop and a pivotal source of nourishment and energy homeostasis for more than half of the global population,particularly in Asian countries.Whole rice grains are one of the consumable rice forms,which are produced by paddy milling and removal of the husk layer with bran layers(pericarp,testa,and aleurone)are still intact.Rice bran is one of the most abundant underutilized agricultural by-products of rice polishing,which harbor about 60-97%of the grain phenolic compounds depending on rice genotype.Therefore,efforts were made to profile rice and rice bran phenolic constituents and document the in vitro abilities associated with the management of type 2 diabetes mellitus.Additionally,the influence of phenolic compounds on starch physicochemical characteristics was also investigated.1)In this chapter,aqueous glycerol was explored as a food-grade solvent for rice bran phenolic antioxidant extraction.Further,the in vitro inhibitory activity against digestive enzymes and AGEs of the extract and its major phenolics were investigated.Response surface methodology(Box-Behnken design)was implemented to optimize experimental conditions for rice bran phenolics and antioxidants extraction.The extraction conditions were optimized using Box-Behnken design at the conditions of 15.9%glycerol concentration(w/v),31.6 m L g-1liquid/solid ratio,and extraction temperature of 90?.These conditions provided a very satisfactory outcome in total phenolic contents(TPC)(549.6±8.05 mg GAE/100 g dry weight)and DPPH scavenging activity(57.83±1.8%).The chromatographic separation of the extract showed higher concentrations of ferulic acid,and?-coumaric acid,followed by chlorogenic acid,caffeic acid,syringic acid,and rutin.Moreover,the extract inhibition of??amylase,??glucosidase,and lipase activity was34.2±3.2%at 20??L,29.9±1.0%at 50??L,and 12.4±2.3%at 20??L,respectively.Furthermore,fructose was found to readily form Advanced Glycation End Products(AGEs)fluorescence with essential amino acids in low concentration in simulated intestinal digestion conditions.The extract inhibited AGEs formation by 52.6%at 20?L/m L.Additionally,ferulic acid and?-coumaric acid showed pronounced(p?<?0.05)inhibitory activity against lipase and AGEs formation,while ferulic acid showed weaker activity for starch hydrolyzing enzymes compared to the standard drugs.Our study indicated that the in vitro enzyme and glycation inhibitory potentials of rice bran extract was mainly driven by the extract phenolic compounds.2)Due to the low phenolic recovery from the aqueous glycerol extract observed in the previous study,the purpose of this work was to develop a fast and efficient strategy for the purification of rice bran phenolic compounds using macroporous resins,and to acquire insightful knowledge into the impact of purification on its chemical constituents,antioxidants,and inhibition of digestive enzymes,and glycation.Among the eight macroporous resins investigated,HPD-300 resin was verified to bosses superior adsorption and desorption ratio,which accounts for 62.5 and 94%TPC of rice bran extract,respectively.Purification parameters were optimized,including the initial extract concentration of 0.07 mg/m L,p H 6.3 at temperature 30°C for 12 h and desorption with70%ethanol(v/v).Also,rice bran phenolic adsorption on HPD-300 resin was adequately modelled on the Freundlich equation.Eighteen phenolic compounds were identified using HPLC-PDA,the contents of ferulic acid(71.58 mg/100 g)and syringaldehyde(66.96 mg/100 g)were significantly(p<0.05)higher than other phenolic constituents.However,phenolic compounds concentrations varied significantly(p<0.05)after HPD-300 resin purification.In addition,the extract exhibited a significant(p<0.05)increase in total flavonoid contents(TFC),in vitro antioxidants(DPPH and FRAP),and in vitro?-glucosidase and BSA-glycation inhibition after HPD-300 resin treatment.3)This chapter evaluated the effect of thermal treatments(i.e.,roasting and frying),and the subsequent cooking on phenolic composition,total antioxidant activity(TAA),inhibitory potentials against digestive enzymes and BSA-glycation of black,red and brown rice varieties.Quantification of 16 phenolic compounds in rice grains revealed that black rice dominated by cyanidin-3-glucoside(156.8±30.5 mg/100g)and protocatechuic acid(143.2±35.0 mg/100g),red rice was dominated by protocatechuic acid(14.1±0.2 mg/100g)and followed by(-)-epicatechin(7.6±1.6 mg/100g),whereas brown rice showed higher contents of?-hydroxybenzoic acid(4.3±0.2 mg/100g),(-)-epicatechin(3.8±0.3 mg/100g)and syringaldehyde(3.9±0.4 mg/100g).Among the processed grains,phenolic contents significantly altered,but no variances among phenolic profiles were noted.Pearson's correlation study revealed that TAA of processed grains was mainly dependent on phenolic contents.Roasting the grains sustained higher contents of TPC,TFC,and total proanthocyanidins contents(TPAC).Brown rice frying and subsequent cooking boosted TFC and maintained carbohydrate hydrolyzing enzyme inhibition.Thermal decomposition of anthocyanin(TAC)and cyanidin-3-glucoside was evident across all processing methods of black rice,while TPAC was more susceptible to cooking treatments in pigmented rice.The thermally treated pigmented rice grains showed pronounced activity against?-glucosidase,with cooking procedures boosted anti-lipase activity for black rice.Meanwhile,processing excluding Fr.C boosted glycation inhibition for brown and black rice grains while thermal treatments enhanced the activity for red rice.4)In this chapter,the effect of the previous domestic processing techniques on the physiochemical characteristics of the three rice varieties was evaluated.Native starch granules were isolated and used as control.Our results showed that different processing methods significantly influenced the physical and chemical characteristics of rice grains(p?<?0.05).Processing profoundly influenced the color parameters of brown and black grains,which was mainly driven by the changes in phenolic profiles.Fourier transform infrared spectroscopy indicated that intermolecular hydrogen bonds formed between native starch and phenolic compounds in rice grains and starch-lipid complex in fried grains.The waxy brown rice had low apparent amylose contents(AAC)that influenced the grain's thermal performance and digestibility characteristics.Cooking and frying enhance AAC of the three varieties,while roasting led to a significant reduction.Notably,the native starch of the samples showed considerably higher AAC,gelatinization enthalpy,and digestion ratio compared to rice grains.Oil-frying significantly increased damage starch,reduce gelatinization enthalpy,enhanced resistance starch(RS),and reduced the estimated glycemic index(e GI)of the three varieties.Our results suggested that the synergistic action of thermal treatments and cooking can significantly alter the starch molecular structure,which is a feasible technique to slow starch digestibility.5)This chapter aimed to investigate the modulation in recovery and bioaccessibility of the phenolic,anthocyanin,total antioxidant activity,and starch digestibility by rice matrix during digestion.For this purpose,cooked black rice(R.C),native starch(Ns),and phenolic extract(E)were subjected to in vitro gastrointestinal digestion.HPLC profiling evidenced that the phenolic profile of R.C and E was dominated by cyanidin-3-glucoside(31.54±2.66 mg/100g and 31.37±0.24 mg/g),followed by protocatechuic acid(14.53±0.38 mg/100g and 1.03±0.02 mg/g),respectively,showing clear variances of the detected phenolic profiles.The matrix of R.C immediately decreased the TPC,TAC,DPPH,ABTS,and FRAP during oral digestion by 69.7,67.7,63.4,57.5,and 72.2%as well as gastric digestion by 66.4,72.6,76.3,45.4 and 70.3%,respectively,compared with the undigested sample.While intestinal digestion of R.C slightly elevated TPC and significantly enhanced ABTS 1.6-fold,but further reducing TAC,DPPH,and FRAP compared with the undigested sample by 20.2,56.9,and 29.8%,respectively.Contrary,E digestion significantly enhanced TPC(12.5,21.6,and 112.1%),DPPH(24.6,102,and121.5%),ABTS(17.7,17.4,and 341.1%),and FRAP(49.8,50.1,and 56.2%),while causing significant loss of TAC(61.0,11.2,and 71.0%)compared to undigested sample for oral,gastric and intestinal digestion,respectively.Further,the enzymatic catabolism of cyanidin-3-glucoside was evident in both samples after digestion and followed by a significant increase in gallic acid and protocatechuic acid.TAA of the digested samples was influenced by the synergistic and/or antagonist effect of the recovered phenolic compounds.Further,phenolics and cooking influenced the grains'starch structure,as confirmed by FTIR and XRD.On the same note,phenolics inhibit starch hydrolysis,reduced glycemic index,lower gelatinization transition temperatures,and reduced gelatinization enthalpy,while rice matrix found to significantly(p?<?0.05)reduce phenolic antioxidant recovery and bioaccessibility and simultaneously enhance anthocyanins recovery and bioaccessibility.These findings could influence the formulation of rice-based functional foods to maximize the bioaccessibility of targeted phenolic molecules. |
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