Sanguisorba hybrida: pharmacognostic studies and antimicrobial activity evaluation of crude extracts

Resumen

The genus Sanguisorba L. (Rosaceae) includes perennials that are distributed throughout the northern hemisphere. Some species of this genus are known by their medicinal interest. In the present work the pharmacognostic characterization and the potential antimicrobial activity of several extracts of Sanguisorba hybrida, endemic in Portugal, were evaluated. The leaves of the plant have been observed under microscopy techniques, tector and secretor multicellular trichomes were seen on both leaf surfaces. With histochemical tests the in situ localization of compounds was recognized and the most relevant were mucilages, phenols and terpenoids. Powdered plant material was extracted with n-hexane, dichloromethane, ethyl acetate, methanol and water. Their phytochemical survey, through TLC on silica gel plates and the proper reagents, was performed and the previous results with histochemical tests were confirmed. All extracts were tested against reference and multiresistant bacterial strains: Gram-positive (Enteroccocus faecalis, Staphylococcus aureus, Staphylococcus epidermidis and Mycobacterium smegmatis); Gram-negative (Pseudomonas aeruginosa, Salmonella typhimurium, and Klebsiella pneumoniae) and the yeast Candida albicans. The minimum inhibitory concentrations (MIC) were determined by the serial broth micro dilution method. Appropriated antibiotics were used as controls. The methanol and water extracts showed better antimicrobial activity than n-hexane, dichloromethane, ethyl acetate extracts. Gram-positive bacteria were the most sensitive and the MIC values of 3.50-1.75 µg/mL were obtained using those polar extracts against Staphylococcus aureus, including strains resistant to meticillin (MRSA).