Pharmacological basis of the use of the root bark of Zizyphus nummularia Aubrev. (Rhamnaceae) as anti-inflammatory agent

BACKGROUND The root bark of Zizyphus nummularia (Rhamnaceae) is traditionally used as an anti-inflammatory agent. The current study aimed to explore the anti-inflammatory activity (in vivo) of a crude ethanolic extract (EE) and the pure identified octadecahydro-picene-2,3,14,15-tetranone (IC) in the root bark of Z. nummularia. IC was further subjected to suitable in vitro and in silico studies to find out the mechanistic pharmacology. METHODS EE (100 and 200 mg/kg, p.o.) and (IC) (400 and 600 μg/kg, p.o.) were subjected to in vivo anti-inflammatory assays to evaluate the anti-inflammatory activity and predict the probable mechanism(s) of action. Suitable acute (carrageenan-induced paw edema, arachidonic acid-induced ear edema, xylene-induced ear edema) and chronic (cotton pellet granuloma) models were employed to investigate in vivo the anti-inflammatory activity. Based on in vivo observation, IC was further subjected to in vitro assays to estimate the inhibition of nitric oxide (NO), prostaglandin-E2 (PGE-2) and tumor necrosis factor-α (TNF-α) production in PBS stimulated RAW 264.7 cells. Based on the observation of in vitro studies, finally, ADME prediction and molecular docking studies of IC were performed for better understanding of interaction of IC with TNF-α. RESULTS Oral administration of EE (100 and 200 mg/kg) exhibited significant inhibition of carrageenan (p < 0.05) and arachidonic acid (p < 0.05) induced oedema, and the reduced the granuloma tissue formation (p < 0.05) in experimental mice. IC (400 and 600 μg/kg, p.o.) exhibited significant (p < 0.01) inhibition of carrageenan, xylene and arachidonic acid-induced edema, and reduced the granuloma tissue formation. In in vitro assays, IC caused a concentration-dependent inhibition of LPS stimulated NO (up to ~ 67.4% at 50 μM) and TNF-α (~84.5% at 50 μM) production. However, the PGE-2 inhibition did not follow dose dependent pattern. Based on in vitro observations, the molecular docking has been performed on the basis of interaction with TNF-α. In in silico studies, it was observed that IC showed hydrogen bonding with GLN 47 amino acid residue of TNF-α protein. CONCLUSIONS IC possibly produces anti-inflammatory activity through inhibition of TNF-α and NO production.