Light-enhanced antibiotic activity of Brazilian medical plants (Croton campestris A, Ocimum gratissimum L and Cordia verbenaceae DC)

Background: Although broad-band ultraviolet (UV)-A has been described as a therapeutic option for various skin diseases, there are few studies investigating the efficacy of UV-A irradiation in treating diseases related to infectious agents. Objective: Evaluate the light-enhanced antibacterial activity of Brazilian medical plants, Croton campestris A (Euphorbiaceae), Ocimum gratissimum L. (Lamiaceae), and Cordia verbenaceae DC (Boraginaceae). Methods: Hexane extracts of Croton campestris A., Ocimum gratissimum L., and Cordia verbenaceae DC were assayed using a UV-A exposure method against strains of Staphylococcus aureus and Escherichia coli. Assays were performed in triplicate with and without exposure to UV-A radiation to test for light-activated or lightenhanced antibacterial activity. Results: All extracts showed activity against the S. aureus strain. Extracts of O. gratissimum and C. verbenaceae were the most active after exposure to UV-A light, with an increase in antibacterial activity of 140 and 100%, respectively. No extract showed light-activated antibacterial activity against E. coli. Conclusion: C. campestris, O. gravissimum and C. verbenaceae showed light-enhanced antibiotic activity. This suggests that phytochemical investigations may be warranted.