Phytochemical composition, antioxidant, cytotoxic, haemolytic and antibacterial activities of the aerial parts of Rhamnus alaternus.

Introduction: Rhamnus alaternus L. belongs to the genus Rhamnus (Rhamnaceae). It is a medicinal plant growing in Algeria. This plant is used worldwide as effective pharmacological remedy. Objective: This study describes in detail the phytochemical composition and the in vitro biological activities of R. alaternus L. aerial parts extracts. Methods: Total contents of bioactive components were estimated and the antioxidant potential was assessed by DPPH and hydroxyl radical scavenging assays, ferric reducing antioxidant activity and total antioxidant capacity. Additionally, the haemolytic activity was evaluated towards human red blood cells and the cytotoxicity was performed using Brine shrimp lethality test. Furthermore, the antibacterial activity was estimated in vitro against five bacteria. Seven known secondary metabolites have been established using different spectroscopic techniques such as 1D- and 2D-NMR experiments and ESI mass spectrometry and by comparison to data reported in the literature. Results: The chemical investigation of the aerial portions’ ethyl acetate extract of R. alaternus allowed the characterization of three triterpenoids, two phytosterols and two flavonoids. High levels of phenols and flavonoids were estimated in both ethyl acetate (EtOAc) and n-butanol (n-BuOH) extracts. These extracts exhibit strong ferric reducing antioxidant activity and significant hydroxyl and DPPH radicals scavenging effects. Moreover, the petroleum ether (PE) extract shows a very strong haemolytic effect with 94.03 ± 0.21% at 50 µg/mL and induces the mortality of 78.57 ± 0.17% of Brine Shrimp nauplii at 20 µg/mL. Furthermore, the tested crude extracts (PE, EtOAc and n-BuOH) inhibit the growth of all the bacterial strains. Conclusion: R. alaternus constitutes a natural resource of bioactive substances with potential cytotoxic, antioxidant and antibacterial effects. [ABSTRACT FROM AUTHOR]