Current Medicinal Chemistry - Volume 13, Issue 1, 2006

Imidazoles are an important class of heterocycles and include many substances of both biological and chemical interest. They are part of a large number of highly significant biomolecules such as the essential amino acid histidine and related compounds, biotin, and the imidazole alkaloids. Insertion of the imidazole nucleus is an important synthetic strategy in drug discovery. Imidazole drugs have broad applications in many areas of clinical medicine. The imidazoles are a class of antifungal azole derivatives and have a broad spectrum of activities both in vitro and in vivo. The imidazole moiety is also contained in many histaminergic ligands for histamine H1, H2, and H3 receptors. These are currently used as tools in pharmacological studies. The important therapeutic properties of imidazole related drugs have encouraged the medicinal chemists to synthesize and test a large number of novel molecules. Some of these have chemotherapeutic properties, such as for example several FTase inhibitors with an imidazole moiety. Imidazole derivatives have also been shown to have antibacterial activity and recently several P38 MAP Kinase inhibitors and 5-Lipoxygenase inhibitors containing the imidazole moiety have been synthesized. This review reports current progress in the area of new biologically active imidazoles and recently discovered naturally occurring imidazole.

The β3-adrenergic receptor (β3-AR) has been shown to mediate various pharmacological and physiological effects such as lipolysis, thermogenesis, and relaxation of the urinary bladder. Activation of the β3-AR is thought to be a possible approach for the treatment of obesity, type 2 diabetes mellitus, and frequent urination. Therefore, the β3-AR is recognized as an attractive target for drug discovery. On the other hand, activation of the β1- or β2-AR can cause undesirable side effects such as increased heart rate or muscle tremors. Consequently, a number of recent efforts in this field have been directed toward the design of selective agonists for the β3-AR. This review summarizes recent advances in β3-AR agonists with an emphasis on recent attempts to create potent, selective and orally bioavailable small-molecule agonists.

Invertebrate animals, such as sponges, tunicates and bryozoans, are among the most important sources of biomedically relevant natural products. However, as these animals generally contain only low quantities of the compounds, further pharmacological development is in most cases difficult. There is increasing evidence that many metabolites, in particular polyketides and nonribosomally synthesized peptides, are not produced by the animals themselves but by associated bacterial symbionts. This symbiont hypothesis currently attracts considerable interest, since it implicates that animal-independent production systems based on bacterial fermentation processes could be created. This review gives an overview about recent developments in the research on natural product symbiosis. Different techniques will be discussed that have been employed to pinpoint the actual producer. Since bacterial symbionts are highly fastidious and have been generally resistant to cultivation attempts, emphasis will be laid on culture-independent strategies, such as cell separation approaches and the cloning of biosynthetic genes. These strategies have provided insights into possible sources of several natural products, e.g. the bryostatins, pederin, the onnamides, swinholide A and theopalauamide. Finally, potential techniques for the generation of renewable supplies of symbiontderived drug candidates will be discussed. Cultivation approaches and the heterologous expression of cloned biosynthesis genes from uncultured symbionts could in future provide access to several important marine drug candidates, including bryostatin 1, halichondrin or ET-743.

Heptahelical receptors are coupled to heterotrimeric GTP-binding proteins (G-proteins) which transduce most signals through their α and βγ subunits to effectors, enzymes and ion channels. Of the 367 heptahelical receptors for endogenous ligands, about 330 are potential targets for drug discovery with agonist, antagonist or inverse agonist properties. The term G-protein-coupled receptors (GPCRs) is a broader functional definition rather than a structural one referring to heptahelical receptors specifically. Non-heptahelical putative GPCRs include some transmembrane receptors with tyrosine-kinase activity on their cytosolic endings (EGF, insulin and IGF-1 receptors), other transmembrane receptors (mannose-6-phosphate/IGF-2 receptor and integrin-associated protein IAP or CD47), and some receptors belonging to the class of glycosylphosphatidylinositol (GPI)-anchored proteins and located on the outer face of the plasma membrane. Also, activators of G-protein signaling (AGS) proteins that regulate vesicular trafficking activate heterotrimeric G-proteins in the Golgi independently of receptor activation. Main effectors activated through their direct interactions with α subunits or βγ dimers of heterotrimeric G-proteins include adenylylcyclases, cGMPphosphodiesterase, phospholipases Cβ, phosphoinositide 3-kinase γ, CaV2 calcium channels, GIRK/Kir3 potassium channels, and guanine nucleotide exchange factors RasGEF and RhoGEF leading to small G-proteins and MAP-kinases activation. Current signaling cascades leading to final cell responses are depicted.

Among the strategies that can lead to the discovery of new drugs, the identification and use of privileged structures, molecular fragments that are able to interact with more than one target, gained particular attention, in an attempt to find new drugs in a shorter time with respect to other strategies. These structures, that have been identified mainly by empirical observations, can target only a given protein family, or can be able to interact with more, unrelated targets. This review deals with structures not covered in recent papers on this topic, and emphasizes the importance of understanding the structure-target relationships, that confer the privileged status.

Resveratrol (3,4',5-trihydroxystilbene, RESV) is a natural phenolic compound that exists as cis and trans isomers [c-RESV or (Z)-RESV and t-RESV or (E)-RESV, respectively]. t-RESV is a natural component of Vitis vinifera L. (Vitaceae), abundant in the skin of grapes (but not in the flesh) and in the leaf epidermis, and present in wines, especially red wines. In in vitro, ex vivo and in vivo experiments t-RESV exhibits a number of biological activities, including anti-inflammatory and anticarcinogenic properties. RESV also exists in wines as a cis isomer, which (unlike t-RESV) is not currently available commercially; as a result, little is known about this isomer's pharmacological activity. In this review, I will focus on the few comparative studies of the antioxidant effects of the two RESV isomers in different experimental models.

The sol-gel process is an inorganic polymerization process taking place in mild conditions, allowing the association of mineral phases with organic or biological systems. The possibility to immobilize drugs, enzymes, antibodies and even whole cells without loss of their biological activity led to the development of diagnostic tools, drug delivery carriers as well as new hosts for artificial organ design. These systems take profit from the wide variety of chemical compositions, dimensions and forms that can be achieved via sol-gel chemistry. Recent advances involve multifunctional "smart" devices combining biocompatibility, biological activity and stimuli-responsive materials. The design of such novel devices with significant added value when compared to current products is probably a key factor when foreseeing industrial developments of sol-gel materials in medicinal science.

The number of people with diabetes is expected to rise from the current estimated 150 million to 220 million in 2010 and 300 million in 2025, and 90% is Type 2 diabetes or non-insulin dependant diabetes mellitus (NIDDM). Voglibose, one of the most important α-glucosidase inhibitors, delays the digestion and absorption of carbohydrates, thereby inhibiting postprandial hyperglycemia and hyperinsulinemia, and is the aid in the treatment of diabetes. In this paper, properties and the preparation of voglibose are reviewed.