Extraction of Phytosterols from the Green Hull of Pistacia vera L. var and Optimization of Extraction Methods

Abstract

Phytosterols, as valuable compounds with known health-beneficial effects, are extensively used in nutrition, pharmaceuticals, and cosmetics. Pistachio green hull (PGH) is a cost-effective agricultural waste that contains bioactive compounds. This study aimed to identify and quantify the types and levels of phytosterols in the PGH and kernel of Abbasali, Akbari, and Khanjari pistachio cultivars of Damghan (Iran) and to optimize the phytosterol extraction using the Soxhlet and Folch methods.The phytosterol types and quantities were analyzed using gas chromatography with flame ionization detection, following the methods established by the International Olive Council. The Soxhlet and the Folch methods underwent delicate modifications, including adjustments in the concentration of potassium chloride (KCl) and the transesterification condition. A total of eleven phytosterols were identified in the oil extracted from PGHs and Kernels of the studied cultivars. β-sitosterol was the most abundant sterol in all samples. The kernel of Abbasali cultivars had the greatest phytosterol amount (1887 mg/kg), followed by Akbari (1828 mg/kg) and Khanjari (1758 mg/kg). The ratio of total phytosterol content in the kernel to that in the PGH for the studied cultivars was as follows: Abbasali: 3.3, Akbari: 2.3, and Khanjari: 2.9. The most effective fat removal and the maximum amount of phytosterol were observed at 25 ºC with a 1 M KCl solution using the modified Soxhlet method. The mild conditions along with the modifications to the methanol: sulfuric acid ratio and time seem to be an appropriate approach for extracting phytosterols from PGH using the Soxhlet method.