Phenolic contents and in vitro antioxidant, anti-tyrosinase, and anti-inflammatory effects of leaves and roots extracts of the halophyte Limonium delicatulum

Abstract

Limonium delicatulum is a halophyte growing in extreme conditions and therefore constituted a possible source of bioactive compounds. In the present study, total phenolic, flavonoids, and condensed tannins were quantified. DPPH, ABTS, Galvinoxyl radical (GOR), CUPRAC, reducing power, O-phenanthroline, silver nanoparticle, and β-carotene bleaching assays were used to evaluate the antioxidant capacity. The inhibitory effect on tyrosinase activity and denaturation of BSA were also investigated. The results showed that extraction solvent, as well as plant organ, significantly influenced the contents of phenolic compounds. Methanolic roots extract contained the highest phenolic content with a value of 772.52 ± 5.12 µg GAE/mg consisting mainly of condensed tannins (678.87 ± 0.11 µg EC/mg of extract), while methanolic leaves extract recorded the highest content of flavonoids (212.77 ± 1.19 µg QE/mg extract). Methanolic extracts with high phenolic contents exerted the strongest antioxidant activity compared to the aqueous extracts. Moreover, methanolic roots extract exhibited high tyrosinase inhibition ability with an IC50 of 9.87 ± 0.15 µg/ml better than that of methanolic leaves extract and kojic acid (24.77 ± 0.5 and 25.23 ± 0.21 µg/ml, respectively), The studied extracts also inhibited the denaturation of BSA in dose-dependent manner. Methanol extracts presented higher inhibition percentages than aqueous extracts and similar to that obtained with diclofenac sodium. L. delicatulum can be considered as a promising source of therapeutic bioactive compounds.