Pharmacological evaluation of extract and isolated compounds from the root bark of Ziziphus Abyssinica Hochst ex. A rich (Rhamnaceae)

Abstract

The diversity offered by natural products has timelessly positioned it as a good source for novel therapeutics for the management of various medical conditions, including pain and CNS disorders. This study evaluated hydro-ethanolic root bark extract (ZAE) and isolated compounds from Ziziphus abyssinica for analgesic, anti-inflammatory, anxiolytic and antidepressant properties. Established in vitro and in vivo experimental models were adopted in assessing ZAE and the isolated compounds for these pharmacological properties. Elucidation of structure of the isolated compounds was carried out using infra-red spectroscopy, mass spectrometry, nuclear magnetic resonance and X-ray crystallography. Two pentacyclic triterpenes, β-amyrin and polpunonic acid, were for the first time isolated from the plant. This is also the first time the crystal structure of polpunonic acid is reported. ZAE was found to be relatively safe in acute and sub-chronic toxicity studies in rats. ZAE exhibited analgesic effect that is possibly mediated via opioidergic, ATP-sensitive potassium channels and nitric oxide - cyclic guanosine monophosphate pathways. ZAE also exhibited anti-inflammatory activity via membrane stabilisattion as well as inhibition of protein denaturation, neutrophil degranulation and activity of inflammatory mediators (TNF-α, IL-1β, prostaglandin E2 and bradykinin). The isolated compounds, β-amyrin and polpunonic acid, also exhibited analgesic, anti-inflammatory (anti-arthritic), anxiolytic and antidepressant properties in murine models. It is concluded that ZAE, β-amyrin and polpunonic acid possess analgesic, anti-inflammatory, anxiolytic and antidepressant properties.