OPTIMIZATION OF DIFFERENT PARAMETERS FOR THE EXTRACTION OF POLYPHENOLS AND PROANTHOCYANIDINS FROM PISTACIA VERA HULLS

Objective: Pistachio (Pistacia vera L.) hull are usually discarded as waste, which can lead to environmental pollution even a significant portion of polyphenols are often present in high concentrations in the outer parts of fruits. In this way, using a pistachio hull as a source of bioactive compounds will increase the value of pistachio production and offer valorization for a useless by-product. Methods: Different ethanol concentrations (5, 10, 25, 50, 75 and 95 %) were investigated and the extraction efficiency at extraction temperature from 20 to 90 °C and extraction times from 5 to 45 min was studied. The extraction yield of total polyphenols and proanthocyanidins from the pistachio hull and the antioxidant activity of the extract were evaluated. Results: The obtained results indicated relationships between the tested parameters and extraction yield. The maximum yield for total polyphenols and proanthocyanidins was obtained with 25% ethanol at 60 °C for 15 min (13.91±0.72 and 5.86±0.45 g/100g dry weight, respectively). DPPH radical scavenging activities of extracts were proved to have a linear relationship with the polyphenols yield in the extracts (R2=0.9907) with a maximum DPPH radical scavenging activity of 60.25%. Conclusion: These findings propose that pistachio hull extracts can be a valuable source of bioactive compounds