Antistaphylococcal Activity of Xanthium cavanillesii Lactones.

Objective: The genus Xanthium L., of the Asteraceae Dum. family, (tribe Heliantheae) comprises 30 species of cosmopolitan distribution, many of which, as X. spinosum and X. strumarium are used as medicinal plants. This genus has been the object of numerous phytochemical investigations being sesquiterpene lactones with guaiane or secoguaiane frameworks the main secondary metabolites. Several sesquiterpene lactones have been demonstrated to have antimicrobial activity, in particular against Gram+ bacteria and in Uruguay the infusion of Xanthium cavanillesii Show (common name "Abrojo" or "Abrojo grande") which grows wild, is used as antiseptic in popular medicine. In this work we present the results of the antibacterial analysis of several extracts, fractions and pure compounds from X. cavanillesii against both sensitive and resistant strains of Staphylococcus aureus. Materials and Methods: Compounds were isolated from X. cavanillesii aerial parts by several chromatographic and spectroscopic methods antimicrobial analysis were performed according to Clinical and Laboratory Standards Institute guidelines. Results: The minimum inhibitory concentration (MIC) found were high for the sensitive 6538p strain when compared with common antibiotics. For the resistant strains, the pure compounds activity clearly outperformed the antibiotics, especially in the case of the multiresistant 700,699 strain with MICs of 31, 236 and 356 μg/mL for the Xanthium compounds, gentamicin and oxacillin respectively. [ABSTRACT FROM AUTHOR]