Anti-Inflammatory Effects of Seven Compounds Isolated from the Ethyl Acetate Fraction of the Extract of Red Cultivar Allium Cepa L. Bulb in Wistar Rats

Abstract

The use of medicinal plants in traditional medicine is done by the administration of various forms of crude extracts for the treatment of diseases. Allium cepa is one of the oldest medicinal foods traditionally used for several health disorders. This study is a follow-up to previous published reports on anti-inflammatory activities of the crude extract, and four other solvent extracts of Nigerian-grown red cultivar Allium cepa (RCAC) in which the ethyl acetate extract exhibited the highest anti-inflammatory effect. Compound isolation from ethyl acetate extract was done using Thin Layer Chromatography and Silica-gel Open Column Chromatography system, The anti- inflammatory effects of the seven compounds were evaluated using Carrageenan-induced Paw Oedema in Wistar rats. The most active compound was chemically identified using Infrared and proton-NMR spectroscopy. All seven compounds isolated from the ethyl acetate extract of RCAC exhibited good anti-inflammatory activities with a rapid onset of action. The most effective of these compounds (labelled as OJF1) manifested excellent anti-inflammatory activity by inhibiting paw oedema formation up to 88.6% at 120 minutes post-induction in Wistar rats. OJF1 also exhibited faster onset and longer anti-inflammatory activities compared with indomethacin. OJF1 was chemically identified to be a triglyceride, an acyl compound. The results in this study indicated that the isolated acyl compound possesses excellent anti-inflammatory activities with a rapid onset and long-lasting action. This research further confirms the previous recommendation of red cultivar Allium cepa as a potential natural source of painkillers.