RESUMO
Three new flavonoids, ephedroside A (1), ephedroside B (2), ephedroside C (3), together with fifty-four known compounds 4-57 were isolated from the EtOH extract of the herbaceous stems of Ephedra sinica. The structures of these compounds were elucidated by spectroscopic techniques, as well as by comparison with literature data. Thirty-eight of these compounds were isolated from the genus Ephedra for the first time. The antimicrobial activities of eight compounds were tested by measuring the minimum inhibitory concentrations (MIC) against bacteria (both Gram positive and Gram negative) and fungi, and were found to be in the range of 0.105-0.926 mM. Among them, compound 2 showed the best antimicrobial activity against Pseudomonas aeruginosa with MIC value of 0.105 mM.