It is reported that salvianolic acid B, a bioactive phenolic compound contained in the root of Salvia miltiorrhiza, exhibits a much stronger activity in free radical scavenging and antioxidance than those of vitamin E. When a conventional refluxing method is adopted to extract salvianolic acid B from the root, in which the materials are subjected to higher temperature and longer time, the yield of this phenolic compound is lower due to the possibility of its hydrolysis to tanshinol. However, a higher extraction yield can be achieved over a shorter time period and lower temperature when an ultrasound-assisted extraction method is used. This paper investigated the parameters influencing the extraction of salvianolic acid B. Factors such as extraction time, frequency of the ultrasound, the ratio of solvent to material, and types of extraction solvent were examined. A comparison was also conducted between conventional refluxing and ultrasound-assisted extraction. Results showed that the optimal parameters to extract salvianolic acid B from the root of S. miltiorrhiza were as follows: ultrasonic frequency: 45 Hz; solvent: 60% aqueous ethanol; extraction temperature: 30 degrees C; extraction time duration: 25 min.; ratio of solvent to material: 20:1 (v/w, ml/g). Under these conditions, the yield of salvianolic acid B was 5.17 mg/g (33.93 mg/g) higher than those with conventional refluxing method (28.76 mg/g), indicating that the efficiency and the yield of ultrasound-assisted extraction method are higher than reflux method, and the hydrolysis of salvianolic acid B to tanshinol is effectively avoided.
Avibactam is a non‐β‐lactam based second generation β‐lactamase inhibitor containing diazabicyclooctane (DBO) ring as the β‐lactam mimic. We substituted C2 position of DBO scaffold by a number of amidine derivatives to form water soluble final compounds A1‐A14. The synthesized compounds were evaluated for their antibacterial and synergistic activity in combination with an antibiotic in vitro. The compounds, were tested against ten bacterial strains alone and in combination with existing antibiotic, meropenem. All compounds didn't show antibacterial activity when alone (MIC,>128 μM), however exhibited moderate to good synergistic activity in the presence of meropenem by lowering its MIC values. Compound A7 proved the most potent among other counterparts against all bacterial species with MIC from <0.29 μM to 2.34 μM, and showed comparable or improved activity to avibactam against eight bacterial strains. Compound A7 may prove a lead for next level in vivo and clinical studies.
Avibactam is a clinically approved non-β-lactam based β-lactamase inhibitor. Derivatization of this scaffold with improved inhibition profile is the demand of the day to cope with the future challenges. We successfully synthesized new derivatives of avibactam containing sulfonylamidine moieties at C2 position of the diazabicyclooctane ring. We tested in vitro antibacterial activities of newly synthesized compounds against 10 bacterial strains expressing variable β-lactamases. All compounds did not exhibit antimicrobial profile when assayed individually; however, all compounds minimized the MIC value of the imipenem in combination. Compound 5l proved most potent against all 10 bacterial strains, and showed improved inhibition against six bacterial strains as compared with the control inhibitor, relebactam. The compound 5l may be a lead hit for future development.
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