Inflammatory diseases are a real public health problem worldwide. Many synthetic drugs used in the treatment of inflammatory diseases such as steroidal anti-inflammatory drugs, nonsteroidal anti-inflammatory drugs (NSAIDs) and immunosuppressive drugs have harmful side effects. However, there are natural products like propolis, which is traditionally used in the treatment of pain. The objective of this work was to evaluate the anti-inflammatory and analgesic activities of the ethyl ester of arachic acid, a compound isolated from Cameroonian propolis. The ethyl ester of arachic acid was isolated by chromatography of the ethanolic extract of propolis harvested at Tala-Mokolo (Far North Region of Cameroon) and identified by nuclear magnetic resonance (NMR) spectra and the 1H-1H correlated spectroscopy. The anti-inflammatory and analgesic properties of oral administration of arachic acid ethyl ester (12.5, 25.0, and 50.0 mg/kg bw) were evaluated using carrageenan-induced paw edema, xylene-induced ear edema, cotton pellets-induced granuloma formation, and hot plate test in rat. Arachic acid ethyl ester produced maximum inhibition at 50.0 mg/kg for carrageenan-induced paw edema (62.5%), xylene-induced ear edema (54.5%), cotton pellet-induced granuloma (47.4%), and increased mean latency for hot plate test in rats. These results show clearly that the arachic acid ethyl ester has acute and chronic anti-inflammatory properties as well as central analgesic properties. This justifies the use of propolis in the treatment of pain in traditional medicine.

Five extracts of propolis of Adamawa Cameroon were obtained by percolation and maceration with five different solvents: hexane, ethyl acetate, ethanol, methanol and water, in order of increasing polarity. Phytochemical screening was carried out on the extracts and the total content in flavonoids and polyphenols were evaluated by photometric methods. The total flavonoid content was evaluated using the Neu reagent (2-aminodiethyl diphenylborinate) and quercetin as standard and the results varied from 0.84±0.02 gQE/100gRM in ethyl acetate extract to 1.52±0.06 gQE/100gRM in ethanol extract. The total polyphenol content was evaluated using Folin-Ciocalteu reagent and gallic acid as standard and results varied from 2.32±0.37 gGAE/100gRM in the ethyl acetate extract which is the least to 8.64±0.47 gGAE/100gRM in the aqueous extract. The antiradical activities of the extracts were evaluated through their inhibition on DPPH• and IC50 values varied from 1.88 mg/mL in the aqueous extract which showed highest antioxidant power to 5.06 mg/mL in the ethyl acetate extract with the least antioxidant power. BHT and vitamin C were used as synthetic and natural standards respectively and they showed higher antioxidant power compared to the propolis extracts. Ferrous iron chelating capacities of the extracts were determined using potassium ferricyanide reagent and EDTA as standard. Using Stat Graphics software and Durbin-Watson statistics test, the extracts showed significant correlation between flavonoid content and polyphenol content with DPPH• scavenging activity. The ethyl acetate extract showed least ferrous ion chelating capacity while the methanol extract showed highest ferrous ion chelating capacity.

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