Phytochemical and anti-MRSA constituents of Zanthoxylum nitidum.

Infectious diseases caused by multidrug-resistant bacteria such as methicillin-resistant Staphylococcus aureus, pose a significant threat to humanity. Persistent and repeated invasive infection with MRSA led to higher morbidity and mortality, and required comprehensive measures in treatment and prevention. Zanthoxylum nitidum (Roxb.) DC. is used as detoxifying, analgesic, and hemostatic herbal medicine for thousands of years. Previously pharmacological studies showed that Z. nitidum had antibacterial bioactivity, but only the MIC of a few compounds, crude extracts, and fractions were reported. In our ongoing endeavor to explore bioactive compounds, two new coumarins, 6-(3-oxo-butyl)-limettin (1) and toddalin I (2), and 24 known compounds were isolated from the roots of Z. nitidum, in which two isoquinoline alkaloids, 6-acetonyl-dihydrofagaridine (16) and 6-acetonyl-dihydrochelerythrine (17) showed anti-MRSA bioactivity in vitro and in vivo. Both 16 and 17 showed synergistic action with ampicillin, which decreased the MIC significantly, and both compounds had a significant ability to destroy bacterial biofilm combined with ampicillin. The combined administration showed a strong scavenging effect on the planktonic bacteria in vitro and cleared skin infection effectively in the model of wound infection in vivo. Furthermore, compound 16 inhibited the efflux of the drug by combining with ampicillin or EtBr, resulting in the MIC decreased obviously. Our investigation supported the traditional use of Z. nitidum in treating infections caused by bacteria, and might provide new natural products to reduce the use of antibiotics and the treatment of drug-resistance bacteria.

Phytochemical and Antibacterial Constituents of Edible Globe Amaranth Flower against Pseudomonas aeruginosa.

Globe amaranth flower, the edible inflorescence of Gomphrena globose L., was used to treat dysentery and ulcer as well as other infectious diseases caused by microbes in Southwest China, but its function and bioactive components need experimental support. In this study, phytochemical constituents and antibacterial bioactivity of globe amaranth flower against P. aeruginosa were carried out. As a result, two new (1 and 2) and eleven known (3-11) compounds were isolated, in which compounds 4-7 displayed anti P. aeruginosa bioactivity with the minimum inhibitory concentration (MIC) from 0.008 to 0.256 mg/mL. Furthermore, with aid of the scanning electron microscope (SEM) and a superficial skin infection model in mice, the most potent compound 4 can significantly destroy the structure of bacteria in vitro and restore bacterial infection damage in vivo.