Extraction Optimization,Physicochemical Properties And Antioxidant Activity Of Polysaccharides From Camellia Oleifera

Camellia oleifera is a perennial plant of the Theaceae family,an important edible oil crop in China.C.oleifera has accumulated rich nutrients during more than one year from flowering to harvest.In addition to the main product of seed oil,its resources such as flowers,leaves,fruit shells and seed cakes also have the value of development and utilization.They are rich in natural polysaccharides with strong antioxidant effects.Researchers have obtained polysaccharides from C.oleifera leaves,fruit shells and seed cakes,but there is still a lack of systematic research on its antioxidant activity.In addition,there are few reports on C.oleifera flower polysaccharides.Therefore,C.oleifera flowers,leaves,fruit shells and seed cakes were used as materials to extract polysaccharides,the extraction process was optimized by response surface method in this study.The physicochemical properties of C.oleifera polysaccharides were investigated.The antioxidant activity in vitro and the protective effect on oxidative damage of Caenorhabditis elegans were studied.The aim was to provide theoretical basis for the development and utilization of C.oleifera resources and natural antioxidant additives.The main results were as follows:1.The yield of polysaccharides from C.oleifera was successfully improved by Box-Behnken design.Under the optimal conditions,the yields of polysaccharides from C.oleifera flowers,leaves,fruit shells and seed cakes were 9.32±0.11%,7.57±0.11%,7.25±0.07%and 8.69±0.16%,respectively.2.The polysaccharides of C.oleifera flowers（P-CF）,leaves（P-CL）,fruit shells（P-CS）and seed cakes（P-CC）were obtained by removing protein（Sevag method combined with freeze-thaw）and freeze-drying.The carbohydrate contents were 59.48±0.59%,64.37±0.66%,52.13±0.16%and 50.72±0.57%,respectively.The contents of uronic acid were3.31±0.05%,7.90±0.07%,10.48±0.12%and 5.94±0.03%,respectively.P-CF,P-CL,P-CS and P-CC were mainly composed of mannose,rhamnose,galacturonic acid,glucose,galactose and xylose.In addition,P-CF,P-CL and P-CS contained arabinose,P-CC contained fucose.The monosaccharide molar ratio of P-CF was 10.88:6.34:5.92:11.32:23.78:41.19:0.57.The molecular weight of the four polysaccharides ranged from 3.31 k Da to 128.06 k Da,which were heterogeneous polysaccharides with typical polysaccharide characteristics,and P-CC had a triple helix structure.3.P-CF,P-CL,P-CS and P-CC showed different degrees of antioxidant activity in vitro,among which P-CF had the best activity.The ability of P-CF to scavenging DPPH·,ABTS·+,·OH and chelating Fe²⁺were 84.19±2.65%,94.80±0.22%,79.97±3.04%and 44.67±1.04%,respectively.Under oxidative stress,compared with the injury group which pretreated with t-BHP,P-CF（400μg/m L）could reduce the fluorescence intensity of ROS and mitochondrial membrane potential of Hep G2 by 34.03±3.74 and 21.69±1.68,respectively,thereby reducing apoptosis and improving the survival rate of Hep G2 cells.4.P-CF,P-CL,P-CS and P-CC showed antioxidant activity in vivo,P-CF and P-CL had the best activities.Compared with the control group that without polysaccharide treatment,P-CF,P-CL,P-CS and P-CC increased the fluorescence intensity of sod-3 by 7.77±0.31,8.88±0.15,5.45±0.28 and 1.65±0.15,respectively,which by increasing the nucleation rate of DAF-16,thereby activating the oxidation system and reducing the levels of ROS by56.10±0.67%,59.37±1.79%,27.55±2.62%and 16.63±2.51%,respectively.Furthermore,the survival rates of C.elegans under heat stress were increased by 75±5%,33.33±2.89%,62.72±2.53%and 50.87±3.77%,respectively,and finally showed a strong protective effect on C.elegans under oxidative stress.