Strain-specific and photochemically-activated antimicrobial activity of berberine and two analogs

Berberine, a natural product alkaloid, and its analogs have been reported to have a wide range of medicinal properties, including antibacterial activity. Berberine has been shown to be a photosensitizer - photochemical excitation at the correct wavelengths generate highly reactive singlet oxygen species in situ, and this has biomedical applications in photodynamic therapy. Here, we explore the antibacterial effects of berberine and two semisynthetic berberine analogs, dihydroberberine and 8-methyl-7,8-dihydroberberine, as a result of photoirradiation across three strains of bacteria. Through two antibiotic susceptibility assays, the Kirby Bauer assay and an infused agar assay, it was determined that the antibacterial activities of berberine and two semisynthetic analogs were more potent upon photoirradiation. An understanding of the photosensitizing ability of berberine may inform the design of future compounds towards the photodynamic therapy of bacterial infections.