Study of the antioxidant activity of Pistacia atlantica Desf. Gall extracts and evaluation of the responsible compounds

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Defensive gall traits against natural enemies, such as predators and parasitoids, attracted much attention of ecologists and evolutionary biologists. To our knowledge, naturally occurring antioxidant compounds present in Pistacia atlantica Desf. Galls have not yet been reported and characterized. The objective of this study is to evaluate the effects of the harvest period and plant gender on these antioxidant activities. Furthermore, peaks present in chromatographic fingerprints, probably showing significant antioxidant activities, were identified. Three antioxidant assays, 2,2 diphenyl-1-picrylhydrazyl (DPPH) and 2,2 azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging besides the ferric reducing antioxidant power (FRAP), were applied to determine the total antioxidant activity in galls from both genders of Pistacia atlantica. Fingerprints of ten P. atlantica gall extracts were obtained by Ultra Performance Liquid Chromatography (UPLC). Extensive pre-treatment of the data and a linear multivariate calibration technique, Partial Least Squares (PLS), were used for model construction. Our findings highlighted that gender and harvest period affected the antioxidant activities. Major peaks, potentially influencing the antioxidant activity of the samples, were indicated by studying the regression coefficients of the PLS models. Individual antioxidant compounds of P. atlantica galls were identified by UPLC coupled to a hybrid quadrupole orthogonal time-of-flight mass spectrometer (Q-TOF/MS). The phenolic compounds methyl gallate and valoneic acid dilactone were considered to be important antioxidants in the FRAP and scavenging ABTS assays, while quinic acid showed to be the main component influencing the antioxidant activity measured with the DPPH method. The findings of the present study suggest that P. atlantica gall might be used as an accessible source of natural antioxidants and for the treatment of diseases resulting from oxidative stress.