In Vitro Evaluation of the Antioxidant, Cytoprotective, and Antimicrobial Properties of Essential Oil from Pistacia vera L. Variety Bronte Hull

Abstract

Although the chemical composition and biological properties of some species of the genus Pistacia has been investigated, studies on hull essential oil of Pistacia vera L. variety Bronte (HEO) are currently lacking. In this work, we have carried out an in-depth phytochemical profile elucidation by Gas Chromatography-Mass Spectrometry (GC-MS) analysis, and an evaluation of antioxidant scavenging properties of HEO, using several different in vitro methods, checking also its cytoprotective potential on lymphocytes treated with tert-butyl hydroperoxide. Moreover, the antimicrobial activity against Gram-positive and Gram-negative strains, both American Type Culture Collection (ATCC) and clinical isolates, was also investigated. GC-MS analysis highlighted the richness of this complex matrix, with the identification of 40 derivatives. The major components identified were 4-Carene (31.743%), α-Pinene (23.584%), d-Limonene (8.002%), and 3-Carene (7.731%). The HEO showed a strong iron chelating activity and was found to be markedly active against hydroxyl radical, while scarce effects were found against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. Moreover, pre-treatment with HEO was observed to significantly increase the cell viability, decreasing the lactate dehydrogenase (LDH) release. HEO was bactericidal against all the tested strains at the concentration of 7.11 mg/mL, with the exception of Pseudomonas aeruginosa ATCC 9027. The obtained results demonstrate the strong free-radical scavenging activity of HEO along with remarkable cytoprotective and antimicrobial properties.

Keywords: Pistacia vera L. variety Bronte; antimicrobial activity; antioxidant; cytoprotective activity; essential oil.

Figure 1

Antioxidant and free radical-scavenging activity of hull essential oil of Pistacia vera L. variety Bronte (HEO) towards Fe³⁺-TPTZ (A); ABTS^•+ (B); DPPH^• (C); and iron chelating capacity (D). The asterisks (**) indicate significant differences (p < 0.05).

Figure 2

Superoxide anion (A) scavenging assay in the absence (a) or in the presence of 60, 30, 15, 7.5, and 3.7 μg/mL of HEO (b–f, respectively); Hydroxyl radical (B) scavenging assay in the absence (a) or in the presence of 15, 7.50, 3.75, 1.85, and 0.92 μg/mL of HEO (b–f, respectively). The asterisks (**) indicate significant differences (p < 0.05). Each value represents mean ± SD (n = 3).

Figure 3

Beta-carotene bleaching curves of hull essential oil of Pistacia vera L. variety Bronte (HEO) at concentration range 0.5–4 mg/mL in respect to the reference compound butylated hydroxytoluene (BHT) (2 mg/mL). Results are expressed as mean (n = 3) of three independent experiments.

Figure 4

Cytoprotective effects of HEO on tert-butyl hydroperoxide (t-BOOH) treated lymphocytes. Lymphocytes plus 100 μM of t-BOOH were incubated for 24 h in the absence (b) or in the presence of 20, 17.5, 15, 12.5, 10, 7.5, 5, or 1 μg/mL of essential oil (c–l, respectively). Lymphocytes incubated under the same experimental condition without t-BOOH (a). Cell vitality and integrity were analysed by trypan blue staining (A) and lactate dehydrogenase (LDH) release (B). The asterisks (**) indicate significant differences (p < 0.05). Each value represents mean ± SD (n = 3).