Mini Reviews in Medicinal Chemistry - Volume 11, Issue 12, 2011

The 14-position of natural opiates (e.g. morphine) are unsubstituted, however synthetic approaches have uncovered that functionalizing position 14 gives rise to a wide range of diverse activities. This review focuses on SAR of the position, with the aim of aiding in the search for opioid analgesics with improved clinical profiles.

The continuing emergence of bacterial resistance has provided an incentive for recent intensified research on macrolide antibiotics. Belonging to the macrolide family, 16-membered macrolides also experience a renewed interest in further exploration. The medicinal potential of 16-membered macrolides in search for new antibacterials stems from some advantages over 14-membered macrolides, such as gastrointestinal tolerability, structural flexibility, and lack of inducible resistance. Thus, compared with abundant articles on various 14-membered macrolide derivatives in the literature, this review will highlight some representative 16-membered macrolide antibiotics and their recently discovered analogs. Furthermore, the action and resistance mechanisms of 16-membered macrolide antibiotics will be elucidated as well to assist the drug design.

Covalent EGFR irreversible inhibitors showed promising potential for the treatment of gefitinib-resistant tumors and for imaging purposes. They contain a cysteine-reactive portion forming a covalent bond with the protein. Irreversible kinase inhibitors have been advanced to clinical studies, mostly characterized by an acrylamide or butynamide warhead. However, the clinical usefulness of these compounds has been hampered by resistances, toxicity and pharmacokinetic problems. Investigation on the structure-activity and structure-reactivity relationships may provide useful information for compounds with improved selectivity and pharmacokinetic properties. This review focuses on the exploration of the cysteine-trap portions able to irreversibly inhibit EGFR and other erbB receptors.

The ligand-gated ion channels and seven transmembrane domain receptors are the greatest families of transmembrane receptors (TMR) expressed in mammalians and the major target of current available drugs. Recently, boron containing compounds (BCC) have shown capability of acting as ligands on these targets. This mini-review is focused on the description of BCC that target TMR which were evaluated under experimental models. The results in experimental models are related with the theoretical interaction studies of these ligands on the target proteins as 3D-models in order to explore the biological effects of BCC in molecular detail.

Dihydroorotate dehydrogenase (DHODH) is a flavin-dependent mitochondrial enzyme that catalyzes fourth reaction of pyrimidine de-novo synthesis. Pyrimidine bases are essential for cellular metabolism and cell growth, and are considered as important precursors used in DNA (thymine and cytosine), RNA (uracil and cytosine), glycoproteins and phospholipids biosynthesis. The significance of pyrimidines biosynthesis in DNA and RNA makes them ideal targets for pharmacological intervention. Inhibitors of DHODH have proven efficacy for the treatment of malaria, autoimmune diseases, cancer, rheumatoid arthritis and psoriasis. Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) represents an important target for the treatment of malaria. Many of the clinically relevant anti-tumor and immunosuppressive drugs target human dihydroorotate dehydrogenase (hDHODH), and the two most promising drugs of such kinds are brequinar (antitumor and immunosuppressive) and leflunomide (immunosuppressive). X-ray crystal structures of DHODH in complex with inhibitors reveal common binding region shared by each inhibitor. A number of compounds are identified by high-throughput screening (HTS) of chemical libraries and structure-based computational approaches as selective DHODH inhibitors. Based upon the understanding of molecular interaction of DHODH inhibitors with binding site, some of the common structural features are identified like ability of compounds to interact with ubiquinone (CoQ) binding site and substituents linked to a variety of heterocyclic and heteroaromatic rings responsible for H-bonding with binding site. These findings provide new approaches to design DHODH inhibitors and highlights DHODH as a target for chemotherapeutics. This review is mainly focused on the recent developments in the medicinal chemistry and therapeutic potential of DHODH inhibitors as a target for drug discovery.

Endophytic fungi are a seemingly inexhaustible source of novel bioactive natural products. Currently, more than 140 fungal metabolites have shown confirmed activity in tumor cell line bioassays. We present the chemical structures of these antitumor metabolites, their corresponding fungal endophytes and host plants, and the activities they exhibited, and briefly discuss some of their action mechanisms. This review emphasizes the role of endophytic fungi as an important source of leads for drug discoveries.

In the last years novel therapeutic approaches for the treatment of cancer have been proposed: specific inhibitors of serine/threonine and tyrosine kinases, angiogenesis inhibitors, antibodies against receptors/surface molecules on cancer cells, gene therapy approaches and others. In a lot of cases the clinical trials have confirmed the efficacy of these approaches. Here, we will review the discovered new potential molecular targets for the treatment of human testicular seminomas.

Although the clear mechanism of T2DM is still to be elucidated, it has been well established that reactive oxygen species (ROS) derived from multiple sources plays a causal role in multiple types of insulin resistance and contributes to β-cell dysfunction thus enhances the development and progression of T2DM. What is incomprehensible is that the detrimental ROS also plays a substantial role in the normal insulin signal transduction and glucose-stimulated insulin secretion (GSIS) in β-cell, which forces us to re-recognize the role of ROS under physiological and pathological conditions in a more broad way. Redox homeostasis is tightly controlled by the transcriptional factor nuclear factor erythroid 2-related factor 2 (Nrf2), whose abnormality is believed to be related with diabetes. Accumulating evidences suggest that there are important cross-talks between Nrf2 and PPARγ, PGC1α, PI3K/Akt on regulating antioxidant enzymes and the development of diabetes. Therefore, these evidences indicate that Nrf2 may be a critical element in taking survival and death decisions when cells are exposed to an oxidant environment. In conclusion, enhancing GSIS and insulin sensitivity through the regulation of Nrf2 levels is a potential avenue for developing new therapeutics. Nrf2 may become a promising target for the treatment of T2DM.