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

Introduction: Rhamnus alaternus L. belongs to the genus Rhamnus (Rhamnaceae). It is a medicinal plantgrowing 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 activitiesof R. alaternus L. aerial parts extracts. Methods: Total contents of bioactive components were estimated and the antioxidant potential was assessedby DPPH and hydroxyl radical scavenging assays, ferric reducing antioxidant activity and total antioxidantcapacity. Additionally, the haemolytic activity was evaluated towards human red blood cells and thecytotoxicity was performed using Brine shrimp lethality test. Furthermore, the antibacterial activity wasestimated in vitro against five bacteria. Seven known secondary metabolites have been established usingdifferent spectroscopic techniques such as 1D- and 2D-NMR experiments and ESI mass spectrometry andby comparison to data reported in the literature. Results: The chemical investigation of the aerial portions’ ethyl acetate extract of R. alaternus allowed thecharacterization of three triterpenoids, two phytosterols and two flavonoids. High levels of phenols andflavonoids were estimated in both ethyl acetate (EtOAc) and n-butanol (n-BuOH) extracts. These extractsexhibit strong ferric reducing antioxidant activity and significant hydroxyl and DPPH radicals scavengingeffects. Moreover, the petroleum ether (PE) extract shows a very strong hemolytic 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.