Synthesis and Antibacterial Activities of Amidine Substituted Monocyclic ß-Lactams.

BACKGROUND: Mononcyclic ß-lactams are regarded as the most resistant class of ß-lactams against a series of ß-lactamases, although they possess limited antibacterial activity. Aztreonam, being the first clinically approved monobactam, needs broad-spectrum efficacy through structural modification. OBJECTIVE: We strive to synthesize a number of monocyclic ß-lactams by varying the substituents at N1, C3, and C4 positions of azetidinone ring and study the antimicrobial effect on variable bacterial strains. METHODS: Seven new monobactam derivatives 23a-g, containing substituted-amidine moieties linked to the azetidinone ring via thiazole linker, were synthesized through multistep synthesis. The final compounds were investigated for their in vitro antibacterial activities using the broth microdilution method against ten bacterial strains of clinical interest. The minimum inhibitory concentrations (MICs) of newly synthesized derivatives were compared with aztreonam, ceftazidime, and meropenem, existing clinical antibiotics. RESULTS: All compounds 23a-g showed higher antibacterial activities (MIC 0.25 µg/mL to 64 µg/mL) against tested strains as compared to aztreonam (MIC 16 µg/mL to >64 µg/mL) and ceftazidime (MIC >64 µg/mL). However, all compounds, except 23d, exhibited lower antibacterial activity against all tested bacterial strains compared to meropenem. CONCLUSION: Compound 23d showed comparable or improved antibacterial activity (MIC 0.25 µg/mL to 2 µg/mL) to meropenem (MIC 1 µg/mL to 2 µg/mL) in the case of seven bacterial species. Therefore, compound 23d may be a valuable lead target for further investigations against multi-drug resistant Gram-negative bacteria.

Synthesis and antibacterial evaluation of new monobactams.

Monobactams play an important role in antibiotic drug discovery. Based on the structural characteristics of aztreonam and its biological targets, six new monobactam derivatives (2a-c and 3a-c) were synthesized and their in vitro antibacterial activities were investigated. Compounds 2a-c showed higher activities against tested gram-negative bacteria than that of parent aztreonam. Monobactam 2c exhibited the most potent activities, with MIC ranging from 0.25 to 2 µg/mL against most bacteria.

Flavonoids and Stilbenoids of the Genera Dracaena and Sansevieria: Structures and Bioactivities.

The genera Dracaena and Sansevieria (Asparagaceae, Nolinoideae) are still poorly resolved phylogenetically. Plants of these genera are commonly distributed in Africa, China, Southeast Asia, and America. Most of them are cultivated for ornamental and medicinal purposes and are used in various traditional medicines due to the wide range of ethnopharmacological properties. Extensive in vivo and in vitro tests have been carried out to prove the ethnopharmacological claims and other bioactivities. These investigations have been accompanied by the isolation and identification of hundreds of phytochemical constituents. The most characteristic metabolites are steroids, flavonoids, stilbenes, and saponins; many of them exhibit potent analgesic, anti-inflammatory, antimicrobial, antioxidant, antiproliferative, and cytotoxic activities. This review highlights the structures and bioactivities of flavonoids and stilbenoids isolated from Dracaena and Sansevieria.

Bioactive Phytochemical Constituents of Wild Edible Mushrooms from Southeast Asia.

Mushrooms have a long history of uses for their medicinal and nutritional properties. They have been consumed by people for thousands of years. Edible mushrooms are collected in the wild or cultivated worldwide. Recently, mushroom extracts and their secondary metabolites have acquired considerable attention due to their biological effects, which include antioxidant, antimicrobial, anti-cancer, anti-inflammatory, anti-obesity, and immunomodulatory activities. Thus, in addition to phytochemists, nutritionists and consumers are now deeply interested in the phytochemical constituents of mushrooms, which provide beneficial effects to humans in terms of health promotion and reduction of disease-related risks. In recent years, scientific reports on the nutritional, phytochemical and pharmacological properties of mushroom have been overwhelming. However, the bioactive compounds and biological properties of wild edible mushrooms growing in Southeast Asian countries have been rarely described. In this review, the bioactive compounds isolated from 25 selected wild edible mushrooms growing in Southeast Asia have been reviewed, together with their biological activities. Phytoconstituents with antioxidant and antimicrobial activities have been highlighted. Several evidences indicate that mushrooms are good sources for natural antioxidants and antimicrobial agents.