Longistyline A, a natural stilbene isolated from leaves of Cajanus cajan, exhibits significant anti-MRSA activity.

Longistyline A (LLA), an abundant stilbene form the leaves of Cajanus cajan (L.) Millsp, was isolated. However, the antibacterial effect of LLA was still not understood. A detailed investigation of LLA against bacterial, particularly Methicillin-resistant Staphylococcus aureus (MRSA), was conducted. In vitro, LLA exhibited strong antibacterial activities against MRSA with the minimum inhibitory concentration (MIC) of 1.56 µg/mL and displayed much more rapid bactericidal efficacy (a 3-log decrease in MRSA cell-survival curve within 8 h) than that of vancomycin. The membrane-targeting experiment implied that antibacterial capability of LLA was associated with the perturbation of bacterial membrane potential and permeability. Notably, LLA had relatively weak cytotoxicity to murine macrophage cells (IC50 = 8.61± 0.57 µg/mL). In vivo, topical treatment of the injury with LLA improved wound healing and closure in a MRSA-infected wound healing mouse model consisting of 48 mice. After 3 days treatment, LLA decreased MRSA bacterial counts in the wounded region, reduced accumulation of immune cells at the injury site and alleviated induction of TNF-α (180.74±10.78 vs. 606.57±68.99 pg/mL) and IL-6 (87.25±10.19 vs.280.58±42.27 pg/mL) in serum .