Chemical, Mineralogical, and Biological Properties of Pistacia atlantica subsp. atlantica Essential Oils from the Middle Atlas of Morocco

This study focused on Atlas pistachio (Pistacia atlantica subsp. atlantica), an endangered species from the Moroccan Middle Atlas, analyzing its leaves to assess their antioxidant and antimicrobial activity. Essential oils (EOPA) were extracted by distillation using a Clevenger apparatus, and their phytochemical compounds were identified by gas chromatography–mass spectrometry (GC/MS). Antioxidant activity tests were carried out using the DPPH and FRAP methods. In addition, antimicrobial activity was tested against Candida albicans to determine its antifungal effect, and against two Gram-positive strains (Staphylococcus aureus and Bacillus subtilis) and three Gram-negative strains (Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae) to determine the antibacterial effect. The results show that the essential oils contained between 23 and 49 compounds, depending on the extraction area, with (-)-germacrene D as the main compound. Antioxidant activity varied by study area, with IC50 ranging from 0.414 mg/mL (Amghas) to 1.520 mg/mL (Ait Naamane), and EC50 from 2.132 mg/mL to 5.4 mg/mL. In terms of antimicrobial activity, Afourgah essential oils showed the best results, with significant inhibition diameters against bacteria and low MIC. In particular, Amghas essential oils inhibited Staphylococcus aureus well, while Ait Naamane essential oils were less effective. This variability in phytochemical composition, as well as antioxidant and antimicrobial activities, may be attributed to climatic differences specific to the distribution zones of the Atlas pistachio tree. This study contributes to a better understanding of the botanical and chemical characterization of the Pistacia genus, and highlights its potential as a source of bioactive agents.