Antioxidant activity and phenolic profile of a collection of medicinal plants from Tunisian arid and Saharan regions

Abstract

Desert plants are a potentially sustainable source of bioactive molecules. This paper investigates phenolic profile, total polyphenols, flavonoids and condensed tannins in a collection of desert shrubs of Tunisian flora (Pituranthos tortuosus; Retama raetam; Ephedra alata; Ziziphus lotus; Capparis spinoza; Calligonum comosum). The collection was build according to people traditional tendency uses. The chemical composition was estimated in ethanol extracts of aerial parts together with a comparison of antioxidant activities. The results were significantly dependent on plant material source. Phenolic contents ranged from 15.52 to 37.5 mg of gallic acid equivalents (GAE)/g of Dry Weight (DW) of plant, and flavonoids ranged from 2.92 to 9.14 mg of rutin equivalents (RE)/g DW. The phenolic profile was composed of 23 compounds identified through LC-ESI–MS analysis. Five phenolic acids (quinic acid, gallic acid, syringic acid, p-coumaric acid, and trans-Ferulic acid) and five flavonoids (catechin, epicatechin, rutin, quercetrin and naringenin) were predominant and common between plants. Based on all data visualized within the heatmap, plants were clustered into two groups. The tow species Z. lotus and E. alata were selected for their highest antioxidant potential. These results allowed us to select the combination of three phenolic acids (rutin, qurectrin, quinic acid) that seems determinant in the strong antioxidant capacity. In addition, the possible domestication and cultivation of the two selected plants are discussed.