Antibacterial Activities of Phytosterol Extracted from Kernels and Fresh Green Hulls of <i>Pistacia vera</i> L., Damghan Varieties

Abstract

Background: Phytosterols (PSs) are plant-derived steroids known for their health-promoting effects, including anti-obesity, hypoglycemic, antimicrobial, anti-inflammatory, antioxidant, and immunomodulatory properties. Previous studies have demonstrated that ethanolic and hydroalcoholic extracts from various parts of Pistacia vera L. (e.g., leaves and fruit) possess antioxidant properties. The consumption of nuts, including pistachios, appears to contribute to improved intestinal microbial composition. Furthermore, evaluations of key sterols such as campesterol, β-sitosterol, stigmasterol, and epicoprostanol against a range of bacteria have shown notable antibacterial properties. Objectives: This is the first study to report on the antibacterial activities of PSs extracted from the kernel and pistachio green hull (PGH) of three Damghan pistachio cultivars. Methods: The Soxhlet method was employed to extract total PSs from the kernel and PGH of the Abbasali, Akbari, and Khanjari cultivars of Damghan pistachios, sourced from Damghan Gardens. The antibacterial activities of the extracted PSs were tested against Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) bacteria in duplicate. Statistical analysis of the antioxidant activity results was conducted using SPSS software (version 27). Results: The extracted PSs showed no antibacterial activity at concentrations ranging from 1.6 to 10,000 mg/mL. Conclusions: In contrast to previous reports, no antibacterial effect was observed for the extracted total PSs. Further investigation is recommended to explore the reasons behind this discrepancy.