Study On Antioxidant Activity Of Proanthocyanidin Extracts From Syconia Of Ficus Pumilia L.

Ficus pumila L. is an evergreen scandent shrub with edible, medicinal and ecological value. For the purpose of rational development and utilization of F. pumila resources, in this work, based on optimization of the extraction and purification conditions of polyphenol compounds from defatted achene, the structures of polyphenol compounds were preliminary indetificated. Furthermore, systematic researches were carried out on free radical scavenging capacity and antioxidant activity of proanthocyanidin compounds from syconia of F. pumila. The main results are as follows:GC-MS analysis demonstrated that, F. pumila seed oil was rich in unsaturated fatty acids such as a-linolenic acid (54.44%) and linoleic acid (23.14%). By using response surface analysis, the optimal conditions for the ultrasonic-assisted extraction of polyphenols from defatted achene were as follows:ethanol concentration,70%, solid to liquid ratio,37:1, temperature,31℃. The average validation extraction ratio of defatted achene polyphenols was 4.82%, compared with the theoretical prediction value (4.91%), the relative error was 1.87%.X-5 resin was selected as a suitable material for purificating the defatted achene polyphenols from five kinds of macroporous resins. The factors that affecting the adsorption-desorption process were researched. The results showed the optimum adsorption-desorption conditions were as follows:intial extract solution concentration about 2.4 mg·mL-1, pH value between 3.4～4.5 and adsorption time for about 6 h. The adsorbed defatted achene polyphenols could be well eluted by 90% ethanol under 1.0 mL·min-1 elution rate. Under above optimal conditions, the yield and purity of polyphenol extracts were 3.12%,71.49%, respectively. After treated with X-5 resin, the mass fraction content of polyphenol in the extracts had increased from 4.82% to 71.49%, which was about 15-fold of those in the defatted achene. The results showed that X-5 resin revealed a good ability to separate defatted achene polyphenols. Therefore, X-5 resin could be applied as an effective adsorbent for the production at large-scale.Ultrasonic-assisted extraction technology and macroporous adsorption resin technology were used to separate and purify polyphenol compounds from different parts of syconia of F. pumila respectively. According to the UV-Vis spectrums and HPLC chromatograms analysis of before and after acid hydrolysis of the polyphenolic extracts from three different parts of syconia, the extracts probably contained oligomeric and polymeric proanthocyanidins. The product of acid hydrolysis was analyzed with LC-MS. Our results demonstrated that the main constituent of acid hydrolyzed products was delphinidin probably. Hence the main structural unit of syconia proanthocyanidins was prodelphinidin possibly.The extracts of defatted achene had the highest contents of total phenolics (714.86 TAE mg·g-1), proanthocyanidin (466.57 CE mg·g-1), and flavanol (156.84 CE mg·g-1) in three different extracts. The proanthocyanidin accounted for 65.30% of the total phenolics. In addition, defatted achene extracts had the highest yield of 3.12%. The anti-oxidative activities of proanthocyanidin extracts of different parts were compared. The results showed that, among the 7 kinds of anti-oxidative systems the defatted achene extracts exhibited perfect free radical scavenging capacity and antioxidant effect which deserves further studied. However, perianth and receptacle of inflorescence could not be neglected in the view of utilization resource.The defatted achene proanthocyanidin compounds were purified by column chromatography with Sephadex LH-20. Three purified fractions namely, FracⅠFracⅡand FracⅢwere obtained, and the highest yield was FracⅡ, which accounted for 58.08% of the all purified fractions. In addition, FracⅡhad the highest contents of phenolics (774.70 TAE mg·g-1), flavanol (191.09 CE mg·g-1), and proanthocyanidin (552.33 CE mg·g-1), and it was also higher than that of the unpurified defatted achene extracts.BHT and Vc were used as positive controls, the antioxidant activities of three purified fractions were compared and the correlation between antioxidant activity and polyphenol compounds content was also analyzed. These results are as follows:In FRAP assay, the total antioxidant capacity of three purified fractions and positive controls were followed this order:FracⅡ>Vc>FracⅢ≈BHT>FracⅠ. Moreover, statistical analysis indicated that there was good linear correlation between total antioxidant capacity and proanthocyanidin contents with correlation coefficients (R2) of 0.9862. The three different purified fractions had clear scavenging activity on DPPH-and ABTS·+ radicals. FracⅡhad the strongest scavenging activity with half-inhibiton concentrations (ρEC50) of 0.062 mg·mL-1 on DPPH·, and value of TEAC on ABTS·+was 5.987 TE mmol·g-1. The DPPH radical scavenging activity of samples were as followed: FracⅡ>FracⅢ>Vc>BHT> FracⅠ, the ABTS·+ scavenging activity of samples were as followed:FracⅡ>Vc>FracⅢ>BHT>FracⅠ. Analysis of correlation revealed that proanthocyanidin was the main active constituents on scavenging DPPH·and ABTS·+ radicals. The three different purified fractions displayed stronger scavenging activity on hydroxyl and superoxide anion radicals (OH·, O2-·). FracⅡhad the strongest scavenging ability with half-inhibiton concentrations (ρEC50) of 0.075 mg·mL-1,0.029 mg·mL-1, respectively. Hydroxyl radical (OH·) scavenging activity of samples were as followed: FracⅡ>FracⅢ≈FracⅠ>Vc, superoxide anion radical (O2-·) scavenging activity of samples were followed the order:FracⅡ>Vc>FracⅢ>FracⅠ. Correlation analysis demonstrated that lower molecular weight polyphenols may be the major contributor about scavenging hydroxyl radical (OH·). However, proanthocyanidins and flavonols were the main active constituents on scavenging superoxide anion radical (O2-·). To sum up, syconia proanthocyanidin displayed stronger scavenging free radical ability. Therefore, syconia proanthocyanidin could be served as a new source of natural radical scavenger with great potential.The three purified fractions were showed certain inhibition of lipid peroxidation in two lipsome systems (β-cartone/linoleic acid and mice liver homogenizations), FracⅡhad the strongest inhibiting activity in three fractions, but inferior to that of BHT. The lipid peroxidation-inhibiting activiy of samples in two lipsome system were followed the order:BHT>FracⅡ> FracⅢ>FracⅠ.