A randomized Phase I study of Atuna racemosa: A potential new anti-MRSA natural product extract

Aim: We previously reported significant antimicrobial activity against Gram-positive bacteria from the extract of the Atun tree (Atuna racemosa), identified through rapid digital bioprospecting of a 400-year-old historic herbal text. Toxicity studies in human cell lines showing safety, combined with the ethnomedical descriptions of botanical use, suggested that this extract might be clinically useful against topical Gram-positive bacteria infections. Materials and methods: Using a minimal inhibitory concentration assay, we examined the susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) to an extract of the kernel of the Atun tree (Atuna racemosa). Additionally, a maximum tolerated topical application of the extract was determined in a randomized, double-blind, placebo-controlled pilot clinical trial. Results: Here we report that the effectiveness of this Atuna racemosa extract against MRSA (MIC = 16-32 μg/mL) is on par with currently available last-line antibiotics, while it remains well tolerated in short-term topical applications of 10 times the minimally inhibitory concentration. Conclusions: Although further studies are needed to determine safety and clinical efficacy, this effective extract, identified in a 400-year-old historic herbal text, may prove to be clinically useful in the treatment of MRSA.