Phytochemical Content and Biological Activity of Pistachio (Pistacia vera L.) Shells

Pistachio Pistacia vera L. (Anacardiaceae) production generates many different wastes, one of which is pistachio shells. Pistachio shells were collected from the region of Gafsa (Tunisia), in a natural place, in August 2019. Then, the secondary metabolites were extracted using a conventional technique (maceration). The obtained extract was characterized by determining total phenolic content (TPC), total flavonoid content (TFC), and the biological activity by the free radical scavenging assay using DPPH. The results were expressed as mg of trolox equivalent (TE)/g extract. Finally, the anti-microbial activity was evaluated using disk diffusion method against four strains of bacteria species, two gram-positive bacteria (Staphylococcus aureus and Enterococcus sp.), and two gram-negative bacteria (Klebsiella pneumoniae and Escherichia coli). The pistachio shell was rich in phenolic compounds (69.18 ± 0.3 mg AGE/g). In contrast, the scavenging capacity against the radical DPPH was good (49.76 ± 0.7 mg TE/g) and had a strong anti-microbial activity. The highest activity of shell extract was against gram-positive bacteria. The pistachio shell can be used as potential feedstock to provide natural antioxidant and anti-microbial agents.