The effect of seasonality on the phytochemical composition of two Limonium species naturally growing in a Mediterranean arid-salt marsh: Harvesting time optimization by modeling approach

Abstract

Limonium species are widely considered as potential ornamental candidates for dry and saline areas in arid zones. Limonium pruinosum and Limonium tunetanum are perennial halophytic herbs occurring in extreme biotopes; they are polyphenol-rich herbal medicine with antioxidant potentials. This paper outlines the effect of seasonality on the phytochemical profile as well as the antioxidant potential of these species using a modeling approach to establish the optimum harvesting time. Accordingly, the shoots of L. pruinosum and L. tunetanum were monthly harvested over 1 year from the shott of Sebkha of Aïn Maider – Boughrara (Tunisia). Both species were affected by the seasonal fluctuation, as was evidenced by the high levels of lipid peroxidation, hydrogen peroxide, and electrolyte leakage during the dry period. The harvesting time had a significant effect on the polyphenols, flavonoids, condensed tannins, and antioxidant potentials. Generally, the shoots harvested during the dry season had significantly greater content of bioactive compounds and consequently, higher antioxidant activity, when compared to those collected during the wet period, as confirmed by the adopted exponential model. Indeed, the oxidative stress markers, the phytochemical contents, and the antioxidant capacity were highly and positively correlated with the soil sodium content and the air temperature. Moreover, 18 and 14 individual phenolic compounds were confirmed in L. pruinosum and L. tunetanum extracts, respectively, which mostly consisted of quinic acid, gallic acid, 4,5-di-O-caffeoylquinic acid, hyperoside, quercetrin, catechin, and rutin. The identified phenolic acids and flavonoid compounds were highly and differently affected by seasonality. Considering the phytochemical analysis and the established model, the dry season could be the optimal harvest time.