Study On The Nrenaration And Activity Of Pectic Oligosaccharides And Their Sulfated Derivatives

Canning operation on mandarin results in the production of a large amount of discharged water and without further treatment,this will pollute the environment.Citrus pectin,whose molecular weight is 792kDa,is the most common pectic polysaccharide extracted from the discharged water.Citrus pectin is a class of macromolecures that is abundant in nature and exhibits multiple activities.These include various biological benefits,such as anticancer activies,antioxidant activities and anticoagulant activities.Current studies showed that the molecular weight(Mw)and structure of pectic polysacchraides directly correlates with their biological activities.Also,the high molecular weight and low solubility resulted in a limited biological activities of the pectic polysaccharides.Therefore,more and more studies are focused on the mild and efficient way to reduce its molecular weight and improve the related biological activities.At the moment,ultrasound,enzymatic hydrolysis,acid hydrolysis and free radicals are the most commonly used degradation methods.However,the industrialized production of enzyme is a difficulty,ultrasonic degradation capacity is limited,acid degradation is environmentally unfriendly and can cause structural damage of sugar chains and the reaction of free radical degradation is hardly controllable.Researchers hope to figure out a more effective and green method to degrade the pectic polysaccharides.In this work,two methods,free radical combined Cu2+(H2O2-Cu2+)and ultrasound combined with free radical and ascorbic acid(US-H2O2-VC),were applied to degrade pectic polysaccharides.The related factors,structure and activities were systematically conducted to optimize and predict the mechanism of degradation.The main results are as follows:H2O2 concentration,Cu2+ concentration and reaction time had a direct influence on the degradation efficiency.According to the single factor experiments,the optimal degradation parameters obtained were 4%(v/v)H2O2 concentration,3 mmol/L Cu2+concentration and 3 h reaction time.Six pectic oligosaccharides with different molecular weights were obtained through the purification of the degradation products under these optimal conditions.The molecular weight determination,monosaccharide composition analysis,FTIR,1H NMR and HILIC-MS analysis of those pectic oligosaccharides showed the differences of the structure and the significant changes in the monosaccharide composition.Antitumor experiments were carried out on sulfated pectic oligosaccharides(POS1 and POS2).The results showed that sulfation can increase the antitumor effect of the pectic oligosaccharides.US-H2O2-VC system had more effcient degradation than H2O2,Vc,US-Vc,US-H2O2 and H2O2-Vc respectively.At the beginning of the reaction,ultrasound intensity and temperature can increase the rate of degradation which subsequently decreased in the later period.With the increase of Vc concentration,the degradation rate increased firstly and then decreased.However,the reverse is true for the Mw of the degradation products.Three typical degrading conditions were selected to prepare the corresponding degradation products(LMP1,LMP2 and LMP3).In comparison with the pectc polysaccharide,the structure of the three low molecular weight products has not changed significantly.Combined with the composition of monosaccharide,FTIR,1H NMR analysis,it can be concluded that the US-H2O2-VC system mainly attacks galacturonic acid in the HG domain.Additionally,results of the analysis of antitumor activity of LMP3 indicated that,the degradation of pectic polysaccharide can produce a stronger antitumor activity,plus a dose-dependent relationship.The reduced molecular weight,increased solubility and more active group exposure may have a major impact on its activity.