Effets anti-inflammatoire, antioxydant et antibactérien des extraits aqueux et méthanolique de Plantago lanceolata L.

Abstract

The present study was devoted to evaluate the in vitro antioxidant and antibacterial properties, the in vivo anti- inflammatory activities of the aqueous (Aq. E) and methanolic (Met. E) extracts of the aerial part of Plantago lanceolata L. The obtained results showed that methanolic extract is richer on total polyphenols, flavonoids and tannins. The orally pretreatment of rats with 200 or 400 mg/kg of Aq. E, prevents significantly the paw edema induced by λ carrageenan from the 4th hour with an inhibition percent of 82 % and 84 % respectively. These effects are higher than that of the Met. E but similar to those of aspirin used as an anti-inflammatory standard. On the other hand, the local treatment of mice with 2 mg/ear of Aq. E or Met. E, inhibited ear inflammation induced by croton oil with 77% and 89% respectively. These values are better than those obtained with indomethacin used as reference. The antioxidant potential of the two extracts was evaluated using the DPPH test, the metal chelating assay and reducing power tests. Compared to the synthetic antioxidant BHT, both extracts exhibited high antiradical activity against the free radical DPPH, with IC50 of 38.94  0,83 and 66,44  1.04 µg/ml for Aq E. and Met E respectively. The Aq. E and Met. E have also, a good chelating activity with EC50 of 53.61 ± 1.51 and 105.78 ± 14.56 mg/ml respectively. These values are lower than that of standard chelator (EDTA). Both extracts showed a good concentration dependent reducing power. The antibacterial effect of Aq. E and Met. E was determined by agar diffusion assay toward ten bacterial strains. The obtained results revealed that Aq. E has the broadest spectrum of activity because it inhibited the growth of 4 strains (Proteus mirabilis ATCC 35659, Pseudomonas aeruginosa ATCC 27853, Salmonella typhimurium ATCC 13311 and Bacillus cereus ATCC 10876) causing inhibition zones of 8-22 mm. While Met. E inhibited the growth of 3 strains (Listeria monocytogenes ATCC 15313, Salmonella typhimurium ATCC 13311 and Proteus mirabilis ATCC 35659) with inhibition zones of 8-17 mm. In conclusion, aqueous and methanolic extracts of aerial parts of Plantago lanceolata L. have anti- inflammatory, antioxidant and antibacterial activities which supports the traditional medicinal use of this plant.