Current Medicinal Chemistry - Volume 8, Issue 4, 2001

a-Conotoxins are small disulfide rich peptides from the venoms of marine cone snails. They target specific nicotinic acetylcholine receptor (nAChR) subtypes with high affinity and potency and are therefore valuable as neuropharmacological probes and potential drug leads. This article gives a general overview of the chemical and biological features of a-conotoxins, including their pharmacology, binding interactions and structure. A detailed analysis of recently reported three-dimensional structures from members of different subfamilies of the a-conotoxins, including those with 3/5, 4/3, 4/6 and 4/7 spacings of their two intracysteine loops is given. The structures are generally well defined and represent useful frameworks for the display of amino acid residues to target molecules.

Due to their ability to perform reactions in a stereo- and regiospecific manner, while functioning under mild conditions of temperature and pH, enzymes are increasingly used for chiral synthesis in the pharmaceutical industry, in medicinal chemistry, agriculture, cosmetic and food industry. The oxidoreductases as catalysts require a coenzyme (cofactor) which functions as an electron carrier. If used in stoichiometric amounts the cost of coenzymes makes synthetic applications of redox enzymes prohibitively expensive for industrial applications. The present review updates previous discussions about the objectives of cofactor regeneration as a requirement for the applicability of enzymatic redox reactions, and about the strategies customarily used to this end. Different types of chiral syntheses coupled successfully to coenzyme regeneration (amino acid synthesis, lactone synthesis, synthetic reactions involving alcohols, hydroxy acid and steroid synthesis, deracemization) are then discussed. New catalysts, cross-linked enzyme crystals, prepared from redox enzyme are presented in a small paragraph together with some of their applications. Special attention is given to whole cells used in this type of synthesis and their advantages and disadvantages are presented in one paragraph. Finally, different reactors, within which were conducted chiral syntheses catalyzed by oxireductases and coupled to cofactor regeneration, are briefly discussed.

This review focuses on the most recent research findings on adverse reactions caused by quinolone antibiotics. Reactions of the gastrointestinal tract, the central nervous system (CNS) and the skin are the most often observed adverse effects. Occasionally major events such as phototoxicity, cardiotoxicity, arthropathy and tendinitis occurr, leading to significant tolerability problems.Over the years, several structure-activity and side-effect relationships have been developed, in an effort to improve overall antimicrobial efficacy while reducing undesiderable side-effects. In this article we review the toxicity of fluoroquinolones, including the newer derivatives such levofloxacin, sparfloxacin, graepafloxacin and the 7-azabicyclo derivatives, trovafloxacin and moxifloxacin. A special attention is given to new data on mechanistic aspects, particularly those regarding CNS effects.In recent years extensive in vivo and in vitro experiments have been performed in an attempt to explain the neurotoxic effects of quinolones sometimes observed under therapeutic conditions. However, the molecular target or receptor for such effects is still not exactly known. Several mechanisms are thought to be responsible. The involvement of g-aminobutyric acid (GABA) and excitatory aminoacid (EAA) neurotransmission and the kinetics of quinolones distribution in brain tissue are discussed. In addition, quinolones may interact with other drugs theophylline and nonsteroidal antinflammatory drugs (NSAID s )in producing CNS effectsThis article provides information about the different mechanisms responsible of quinolones interaction with NSAID s , methylxanthines, warfarin and antiacids.

In the search for effective, selective, and nontoxic antiviral and antitumour agents, a variety of strategies have been devised to design nucleoside analogs. These strategies have involved several formal modifications of the naturally occurring nucleosides, especially, alteration of the carbohydrate moiety. Since the naturally occurring purine nucleoside analog oxetanocin A and its derivatives have been found to be effective as anti-HIV-1 and anti-herpes virus agents in 1986, the syntheses of different types of sugar-modified nucleoside analogs have been reported. In this review we will give an overview of the sugar-modified nucleosides synthesized since the late 1990 according to their structural types along with the synthetic routes of some selected nucleosides.

Matrix metalloproteinases (MMPs) are a family of zinc-containing enzymes involved in the degradation and remodeling of extracellular matrix proteins. The activities of these enzymes are well regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs). Chronic stimulation of MMP activities due to an imbalance in the levels of MMPs and TIMPs has been implicated in the pathogenesis of a variety of diseases such as cancer, osteoarthritis, and rheumatoid arthritis. Thus, MMP inhibitors are expected to be useful for the treatment of these disorders. This article reviews briefly the biochemistry of MMPs and evidence for their pathogenic roles using molecular biology approaches. Biomolecular structures used in the design of MMP inhibitors are thoroughly covered. Major emphasis is on recently published potent, small molecular weight MMP inhibitors and their pharmacological properties. Finally, available clinical results of compounds in development are summarized.