Antimicrobial activity of extracts isolated from Plantago sp.

The aim of the paper is to present the results of research studies concerning the effect of three main solid extracts E1, E2, E3, isolated from Plantago sp. from alcoholic and aqueous media on some pathogenic bacteria. In the first step, the disk diffusion Kirby Bauer method was applied for in vitro testing of the biological effects of the three extracts by using the following pathogenic microorganisms: Staphyloccocus aureus, Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis [1–3]. The obtained results were quantified in comparison with the effect generated by the usual antibiotics on the same pathogenic microorganisms. Each biological test was made by more repetitions and the Student method was applied for results' validation. The biological tests results showed that E1 had no biological effect, E2 had a moderate bactericidal effect and E3 presented a significant bactericidal effect. In the second step the solid extracts E1, E2, E3 were characterised by physico-chemical analyses. For this purpose, qualitative and quantitative analyses were performed by energy dispersive X-ray fluorescence and by atomic emmission with inductively coupled plasma, respectively. The obtained results indicated the presence of C, H, P, and some microelements in all the solid extracts as well as the presence of K and Cl in extracts E2 and E3. The physical properties investigated by thermogravimetric analyses and differential thermal analysis showed the thermolability of all extracts and the presence of organic compounds in all extracts E1, E2, E3. The infrared spectrum analysis performed for all the extracts indicated the presence of polysaccharide chains in E1, the existence of flavonoides in E2 and the presence of iridoid compounds in E3. In conclusion, the biological and physico-chemical tests performed for the solid extracts E1, E2, E3 isolated from Plantago sp. indicate a significant bactericidal effect of E3 which contains iridoid compounds.

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