Extraction,Recovery And Bioaccessibility Enhancement Of Phenolics From Lotus (Nelumbo Nucifera Gaertn.) Seedpods And Seed Kernels

Lotus(Nelumbo nucifera Gaertn.)seeds and their processed by-products are widely consumed in Asia,the Americas,and Oceania due to its high content of physiologically active substances.While lotus seedpods are normally considered as the byproduct of lotus seed processing,which is often discarded,leading to a large quantity of waste.Both lotus seed kernels(LSKs)and seedpods(LSPs)contain considerably high phenolic content,and LSP is the only part of lotus that is rich in type-B procyanidin and oligomeric procyanidins.Besides,LSKs also contain high starch content with relatively high amylose.Although both LSKs and LSPs have been used in Chinese traditional medicine,but there is still a lack of industrial application.The increasing number of reports published on the potential beneficial properties of flavonoids for human health,has led to increasing interest on their flavonoids.An extraction of LSK phenolics was optimized using response surface methodology(RSM)and glycerol as an extracting solvent.Both single factor experiment and RSM results indicated an extraction of phenolics from LSKs was affected by the presence of LSK starch and high amylose content;and thus,starch was isolated from LSK to observe changes in its properties under heat treatment and to study their relationships to phenolic content during extraction.Moreover,as HPLC-UV result of LSP phenolics suggested purification of LSP phenolics should be done prior to separation and identification of phenolic compounds,thus,polar macroporous resins were selected for the recovery of LSP phenolics after extraction.Then starch-phenolic complexes were formed via acidification of an alkaline solution,and the stability of the complex over wide ranges of p H and temperature,were studied.Both bioaccessibility and bioavailability of the complex were also studied,using in vitro gastrointestinal digestion model.The main results are as follows:1).LSKs possess many bioactivities,which are mainly attributed to its phenolics.In the present study,RSM with A three-level-three-factor,Boxbehnken design,was adopted to optimize phenolics extraction from LSKs,and glycerol was used as an extracting agent.The result showed extraction temperature,glycerol concentration and time significantly affected response variables.LSKs,extracted for 93.95 min at 79.98°C,using glycerol concentration of8.72%,contained as high as 60.60 and 11.75 mg/g sample for total phenolic content(TPC)and total flavonoid content(TFC),respectively.A total of ten phenolics were detected from LSK extracts,including six phenolic acids and four flavonoids,using HPLC-UV while a total of 18flavonoids were detected from LSP extracts,using ultra-performance liquid chromatography triple-time of flight/mass spectrometry(UPLC-triple-TOF/MS).The result suggested optimization of the extraction conditions was successfully achieved using Boxbehnken design,and that glycerol can be used as an effective extracting solvent for phenolics.2).In the previous chapter,LSK phenolics were extracted using aqueous glycerol,and thus,in this chapter,the obtained phenolics and the properties of the isolated LSK starch under heat treatment were observed for their correlations.RSM indicated significant quadratic effect of temperature and significant linear effect of glycerol on LSK phenolics(p<0.05).In this chapter,temperature also showed a significant effect on LSK starch solubility and swelling power as well as%leaching amylose(p<0.05).Also,leaching amylose in the presence of glycerol and swelling power showed positive correlations with LSK phenolics in a linear relationship(r=0.825,p<0.01)below 50°C and a monotonic relationship(r_s=0.933,p<0.01)above 60°C,respectively.A building block backbone model was adopted to illustrate the possible interaction between amylose/amylopectin-glycerol,and most importantly,their relationship to LSK phenolics.3).Macroporous resins have been employed in the effective recovery of flavonoids from plants.In this study,S8 polar resins were used to recover flavonoids and procyanidins from LSPs.Adsorption kinetics,isotherms,and thermodynamics studies revealed that the adsorption process involved physico-chemical interactions,including flavonoid–resin and flavonoid–flavonoid electrostatic interactions,-aromatic stacking,moderate and strong hydrogen bonding,and repulsive forces.These forces worked complementarily in adsorption,except for the repulsive force,which opposed the adsorption.Further,adsorption temperature determined the adsorption behavior,with multilayer adsorption enhancing adsorption capacity.In dynamic desorption tests,an acetone/water/acetic acid mixture(58.77:39.34:1.89)designed by the D-optimal design method was able to desorb 95.57%and 89.85%of total flavonoids and procyanidins,respectively,using less than two bed volumes of solvent.UPLC-triple-TOF/MS analysis showed that 26 flavonoids,including 5 procyanidins,were detected after the recovery.4).Chlorogenic acid(CA)possesses numerous health-promoting properties;however,its usage CA is currently limited because of low stability and poor bioaccessibility.In the present study,amylopectin-CA complexes were formed.FTIR studies confirmed that the new complex was formed via hydrogen bonding and CH-bonding,and involved the reorganization of the skeletalα-1,4 glucosidic linkages of amylopectin.DSC,and XRD studies suggested that complexation affected starch crystallinity and increased the size of the amorphous region.Complex degradation was found to follow first-order reaction’s kinetics(0.76<R~2<0.99).The complex retained maximum CA content under low acidity at p H 2.5.The water adsorption capacity and swelling power of the complex were found to be 7.75 g/g and17.1 g/g,respectively.Results of the in vitro gastrointestinal(GI)digestion studies showed that maximum digestion of the complex was observed during the gastric phase(39.2%).The digestion in the oral phase and the intestinal phase was found to be 23.21%and 17.08%,respectively.Also,more than 81.14%of the retained CA in the complex can be absorbed after GI digestion.