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.
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.
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%.
These findings propose that pistachio hull extracts can be a valuable source of bioactive compounds.