Phytochemical and biological studies of two Algerian medicinal plants

Abstract

Natural products are important sources of novel therapeutic agents. Bioactive secondary metabolites isolated from natural sources, can act as drugs or as lead compounds for synthetic drugs. In our work, two plants have been studied; the endemic species of Hypericum afrum Lam.(Hypericaceae) and Cytisus villosus Pourr. (Fabaceae). Fractions of the aerial parts of these two plants have been screened in vitro for several biological assays including cannabinoid and opioid receptors agonist assays, antifungal, antibacterial, antimalarial, antileishmanial, antiproliferative, antioxidant, anti-inflammatory and MAO inhibition. The chloroform, ethyl acetate and n-butanol fractions of H. afrum showed significant antioxidant activity and potent antitrypanosomal activity against T. brucei. The n-butanol fraction of C. villosus showed highly potent antitrypanosomal activity against T. brucei. In addition, the ethyl acetate fractions of both plants showed potent inhibition of recombinant human monoamine oxidases (MAO-A and -B). A bioassay-guided fractionation paradigm has been used for the isolation of bioactive compounds of these plants and hence the subfractions that showed significant activity were further purified. This study led to the isolation and identification of 20 compounds, three of which belonging to phloroglucinols, terpenoids and isoflavonoids are new. The structures of the isolated compounds were elucidated through various spectroscopic methods, including high- resolution mass spectrometry, one and two-dimensional nuclear magnetic resonance spectroscopy. Computational study was carried out by conformational search and docking techniques to provide insight into the binding mode of molecules on the active site of MAO’s isoenzymes.