Antimicrobial Endophytes from the Antimicrobial Botanical Yerba mansa (Anemposis californica)

A common practice in traditional medicine is the topical application of botanical preparations to treat infections. It has generally been assumed that the anti-infective properties of such plant medicines are a result of compounds of botanical origin. However, plants are known to harbor endophytic fungi, and many fungi produce potent antimicrobials. With this study, we investigated the role of endophytic fungi in the antimicrobial activity of the plant Anemopsis californica (Nutt.) Hook. & Arn (Saururaceae) (yerba mansa). A. californica, which is native to the southwestern United States and Northern Mexico, has a long history of use in indigenous medicine for the treatment of infection. A number of endophytic fungi were isolated from A. californica, and several of these possessed antimicrobial activity against the pathogenic bacteria Staphylococcus aureus and/or Pseudomonas aeruginosa. Extracts prepared from these fungi were dereplicated with LC-HRMS and subjected to bioactivity-directed fractionation. A number of fungal secondary metabolites were identified, including verticillin A, 11-deoxyverticillin A, equisetin, 5'-epiequisetin, apicidin, and cochiliodone A. Several of these compounds possess antimicrobial activity. Our findings suggest a role for fungal endophytes in the antimicrobial activity of topical preparations from A. californica roots.