This research seeks to address the problem of methicillin-resistant Staphylococcus aureus (MRSA) by discovering synergistic antibacterial natural substances from traditional Chinese herbs using antibacterial bioassays. Six compounds, including three neolignans (À)-acuminatin (1), (À)-denudatin B (2), puberulin D (3), and three benzocyclohexane oxide derivatives ferrudiol (4), ellipeiopsol B (5) and zeylenol (6), were isolated and purified by silica gel and reverse-phase silica gel column chromatography, and the chemical structures were determined through NMR spectroscopy, MS, together with CD and calculated CD spectroscopic methods. Synergistic activity was determined using strain SA1199B, a strain that overexpresses the major S. aureus multidrug transporter, NorA. Compounds 1-6 showed synergistic activity combined with norfloxacin against SA1199B, with FICI values of 0.13, 0.25, 0.25, 0.52, 0.08 and 0.27 respectively. The synergistic effects of the benzocyclohexane oxide derivatives with norfloxacin were further demonstrated through strain growth kinetics experiments. In the mechanistic experiment, the compounds showed significant accumulation and/or inhibition effects for EtBr efflux in SA1199B.These active compounds showed no toxicity to HEK293T cells at a concentration of 100 mM in the cytotoxicity evaluation experiments. Combined with efflux pump inhibitors, classic antibiotics that are substrates for efflux pumps may yet play a role in the therapy of drug-resistant bacteria where a lower dose could result in improved safety. View Article Onlinea (1) FICI # 0.5 is dened as synergy; 0.5 < FICI # 1 as additive; 0.5 < FICI # 4 as indifferent; 4 < FICI as antagonistic.(2) All six compounds have no direct inhibitory effects on ve strains and no synergetic effects combined with the other four strains, so data about those was not listed in above table. 43522 | RSC Adv., 2016, 6, 43518-43525This journal is

A phytochemical investigation of an extract of the leaves of Piper betle, guided by a synergistic antibacterial screen, led to the isolation and structural elucidation of 10 new neolignans, Pibeneolignan A−J (1−10), together with 11 known compounds. The structures and absolute configurations of the new compounds were elucidated on the basis of spectroscopic data, single-crystal X-ray diffraction analysis, and experimental and calculated ECD investigations. Compounds 1 and 2 are new naturally occurring neolignan skeleton, based on the cyclohept-2-ene-l,4-dione framework. We propose that these natural products are biosynthetically formed from bicyclic [3.2.1] neolignans by oxidative cleavage and ring opening at C-1′ and C-2′. Among these compounds, 9, 13, 15 and 16 in combination with norfloxacin against an effluxing S. aureus strain (SA1199B), exhibited significant synergistic activity with fractional inhibitory concentration indices (FICIs) of 0.078, 0.156, 0.125 and 0.25 respectively. Bacterial growth curves, ethidium bromide (EtBr) efflux, and qRt-PCR were further employed to verify their synergistic antibacterial mechanism. Furthermore, computational molecular modeling suggested the binding of compounds 14-17 and 19 to the active site of the modeled structure of the NorA efflux pump, which is the main efflux pump in SA1199B.

No abstract

Measurement and control system usually set measurement and control module separately. In this paper, we give the technique combing measurement and control. Using computer integration, multithreading, the technique is based on data acquisition. The automatic control system of Hydraulic Support Experimental Bench successfully applies the method to realize the function of A/D conversion and DA/DO control. After the local operation, the system gains better response, measurement and control accuracy.