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Analysis on extractable and non-extractable polyphenols in blueberry leaves.

[Objective]The present experiment was conducted to study the effects of solvent type,volume and pH on the content of extractable polyphenols and non-extractable polyphenols in blueberry leaves to provide basis for commercial extraction of polyphenols from blueberry leaves.[Method]The leaf of blueberry was used to extract the extractable polyphenol using two-step extraction method.The non-extractable polyphenols in leaves of blueberry were isolated by sulfuric acid hydrolysis,and both polyphenol contents were determined by Folin-Ciocalteu colorimetric method.[Results]The results showed that the content of total extractable polyphenol(TEPP)was the highest under condition of 50∶50 extractant to H2O ratio and pH 2 irrespective of the extractant used(carbinol or ethanol),while the non-extractable polyphenol(NEPP),on the contrary,showed lowest content.Therefore,low pH value and 50∶50 extractant to H2O ratio and pH 2 were beneficial for extraction of TEPP,and not for NEPP.The content of total polyphenols in different treatments differed little and was over 82.00 mg/g.The analysis showed that the content of extractable polyphenol on the 1s t step was mainly affected by pH value,while that content on 2 n d step was affected significantly by single factor and complex factors,and these factors had no significant effects on the extraction of total polyphenol.The complex factors also have no significant effects on non-extractable polyphenol.[Conclusion]The pH value of extractant has significant effect on extraction of polyphenols,and the content of extractable polyphenol was similar to that of non-extractable polyphenols in the leaf of blueberry.The average total polyphenol content was recorded as 85.49 mg/g.