| Vine tips and storage roots of sweetpotato [Ipomoea batatas (L.) Lam.] contain sugars, proteins, vitamins and other nutrients. In addition, they are rich in chlorogenic acid, flavonoids, anthocyanins and other natural antioxidants with the functions of lowering blood pressure, regulating immunity, scavenging free radicals effectively, anti-aging and so on. The antioxidant activity of different natural antioxidants mixture is more than single antioxidant, which is regarded as antioxidant synergistic. In order to fully use the leaves of sweetpotato,80%ethanol extraction from mixtures, which made of different vine tips or roots among sweetpotato varieties with distinct use type through150:50,100:100,50:150mg mass ratio by the methods of pre-mixed and then extracted or of pre-extrcated and then mixed, were measured their indexes such as DPPH-scavenging quantities, reaction rate at concentrations of0.1,0.2,0.4,0.8,1.6,2.0mg·mL-1and their EC50. Their antioxidant synergistic effect determined by campared these indexes with those of single component of mixture and with their theoretical values. While the total phenolic content, chlorogenic acid (ChIA) and its isomer content of mixtures and single component were determined.The major results obtained in present study are as follows:1. There are synergistic, negative effects in different vine tips or roots mixture extraction on DPPH scavenging reaction, determined by the capacites of antioxidant of single component, mass ratio and the concentrations of extraction.The extraction of mixture with the strongest anoxidant capacity cultivars Pusu53and Yusu162performenced synergistic effect at some concentration and the DPPH-scavenging activity increased with the mass increasing of strong antioxidant Yusu162in mixture. YusuNo.8,2010061with weaker DPPH· scavenging capacity mixed with Yusul62separately, the mixtures showed easily synergistic effects on DPPH-scavenging when increased the Yusu162. Synergistic effects was also infuluenced by mass concentrations of mixture extract and it performenced more scavenging capacity at the0.2,0.4mg·mL-1.2. The DPPH-scavenging reaction rates at0-5min were different when the mixture ingredients and their mass ratio were varied. Increased the ingredient with stronger antioxdant, the reaction rates at0-1min,1-3min,3-5min among mixtures elevated differently. 3. The DPPH-scavenging activities of vine tips and roots of sweetpotato were related positively to polyphenolic content and chlorogenic acid and its isomer content. The contents of polyphenolic and chlorogenic acids in combinations of types of A and B were not related with DPPH scavenging activity because the contents of polyphenolic and chlorogenic acids were beyoned the DPPH reaction linear range. The EC50of types of B, C, D combinations were significantly negative related with their polyphenolic contents and chlorogenic acids contents. The relationships between EC50and DPPH-scavenging quantities at0.1-0.8mg·mL-1were possitive significant.4. When ingredients mixed with different mass ratio, their increase of polyphenolic content, chlorogenic acids ratio in polyphenolic and DiCQA content could enhance their DPPH-scavenging capacity so that performanced synergistic effects. When Pushu53and Yusu162mixed with150:50mg, the ratio of3,4-diCQA in mixture added to12.68%,3,5-diCQA added to8.46%, the ratio of chlorogenic acids was increased and higher than those of single components. When2010061and Yusu162mixed with50:150mg, the ratio of3,4-diCQA in mixture added to7.75%,3,5-diCQA added to6.23%, the ratio of chlorogenic acids was lower than that of single Yusu162. Yanzishu761and Pushu53mixed with50:150mg, the ratio of DiCQA in mixture added to47.29%, the ratio of chlorogenic acids in polyphenolic content added to51.76%and higher than those of single components. When Yusuzi43mixed Yusu162with150:50mg,100:100mg,50:150mg, the contents of chlorogenic acids and polyphenolic decreased, moreover, the percentage of5chlorogenic acids were higher than those of single ingredient, the150:50mg,100:100mg mixtures performanced synergistic effects.In conclusion, there are synergistic, additive and negative effects in mixture between vine tips or roots with different antioxidant capacities by different mass ratio on DPPH scavenging reaction. The synergistic and additive effects of different sweetpotato varieties mixtures were related to the contents of polyphenolic, chlorogenic acids and the ratios of chlorogenic acids in polyphenolic content. This phenomenon and their mechanism provides guidances for breeding and industrialization of sweetpotato. |
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