Contents of extractable and non-extractable polyphenols in the leaves of blueberry

The contents of extractable polyphenols (EPP), non-extractable polyphenols (NEPP), extractable proanthocyanidins (EPAC), non-extractable proanthocyanidins (NEPAC) and extractable anthocyanidins (EAC) in blueberry leaves were investigated. An experiment was conducted to analyse the effect of solvent types (methanol and ethanol), concentration (50 and 70%) and pH (2 and 6) on the extraction of bioactive compounds. Total extractable polyphenols (TEPP), total extractable proanthocyanidins (TEPAC), and total extractable anthocyanidins (TEAC) were analysed in methanol/ethanol/water extracts, NEPP were determined in acidic hydrolysates and NEPAC were quantified by depolymerisation in HCl/butanol. The results showed that ethanol and methanol did not affect the extraction of TEPP, while methanol was better for TEPAC and TEAC. The contents of TEPP and TEAC in 50% solvent were higher than those in 70% solvent. When solvent pH dropped to 2, the contents of EPP and EPAC were increased, while the EAC content was decreased.