Mini Reviews in Medicinal Chemistry - Volume 16, Issue 2, 2016

Tyrosine kinase inhibitors (TKIs) are molecules that compete with ATP on tyrosine kinase receptors (TKRs), blocking tyrosine kinase (TK) activation and then oncogenic pathways; they have been studied, and some of them are right approved for the treatment of many types of cancer. Among TKIs, one of the most explored chemical template is the pyrazolo[3,4-d]pyrimidine (PP) heterocyclic core, which proved to be a useful scaffold for the obtainment of effective compounds. Actually, derivatives belonging to this structural class show a large spectrum of activity, thus standing out as multi-target agents. Different PP compounds have been shown to act as: a) ABL inhibitors and antiproliferative agents against human leukemia cell lines; b) Src kinase inhibitors in neuroblastoma, medulloblastoma and osteosarcoma; c) Phospholipase D inhibitors in different neoplasias; d) Urokinase plasminogen activator inhibitors, in breast cancer. In thyroid cancer (TC), PP1 and PP2 (inhibitors of RET, Hck, lck, and fynT kinases, and a good inhibitor of c-Src and platelet-derived growth factor receptor) showed antineoplastic actvity in human papillary TC cell lines that carry spontaneous RET/PTC1 rearrangements. More recently, new derivatives, (R)-1-phenethyl-N-(1-phenylethyl)-1H-pyrazolo[3,4-d]pyrimidin-4- amine, namely, CLM3 and CLM29, have been demonstrated to exert a multiple signal transduction inhibition (including the RET-TK, BRAF, EGFR, and with antiangiogenic activity), showing antineoplastic activity, in vitro and in vivo, in papillary dedifferentiated, medullary and anaplastic TC. These data have shown the antineoplastic activity of PP in different neoplasias, opening the way to a future clinical evaluation in human cancers.

The amino acid, L-Arginine (L-Arg) plays an important role in the cardiovascular system. Data from the literature show that L-Arg is the only substrate for the production of nitric oxide (NO), from which L-Arg develops its effects on the cardiovascular system. As a free radical, NO is synthesized in all mammalian cells by L-Arg with the activity of NO synthase (NOS). In states of hypertension, diabetes, hypercholesterolemia and vascular inflammation a disorder occurs in the metabolic pathway of the synthesis of NO from L-Arg which all together bring alterations of blood vessels. Experimental results obtained on animals, as well as clinical studies show that L-Arg has an effect on thrombocytes, on the process of coagulation and on the fibrolytic system. This mini review represents a summary of the latest scientific animal and human studies related to L-Arg and its mechanisms of actions with a focus on the role of L-Arg via NO pathway in cardiovascular disorders. Moreover, here we present data from recent animal and clinical studies suggesting that L-Arg could be one of the possible therapeutic molecules for improving the treatment of different cardiovascular disorders.

Berberine is one of the most widely known alkaloids belonging to the protoberberine group exhibiting myriad therapeutic properties. The anticancer potency of berberine appears to derive from its multiple actions including strong interaction with nucleic acids exhibiting adenine-thymine base pair specificity, inhibition of the enzymes topoisomerases and telomerases, and stabilizing the quadruplex structures. It was realized that the development of berberine as a potential anticancer agent necessitates enhancing its nucleic acid binding efficacy through appropriate structural modifications. More recently a number of such approaches have been attempted in various laboratories with great success. Several derivatives have been synthesized mostly with substitutions at the 8, 9 and 13 positions of the isoquinoline chromophore, and studied for enhanced nucleic acid binding activity. In this article, we present an up to date review of the details of the interaction of berberine and several of its important synthetic 8, 9 and 13 substituted derivatives with various nucleic acid structures reported recently. These studies provide interesting knowledge on the mode, mechanism, sequence and structural specificity of the binding of berberine derivatives and correlate structural and energetic aspects of the interaction providing better understanding of the structure- activity relations for designing and development of berberine based therapeutic agents with higher efficacy and therapeutic potential.

Diabetes mellitus occurrence has been associated to the modification of the physiological levels of glucose and is often accompanied by several long-term complications, namely neuropathy, nephropathy, retinopathy, cataract, and cardiovascular. Aldose reductase (AR) is an enzyme of aldoketo reductase super-family that catalyzes the conversion of glucose to sorbitol in the polyol pathway of glucose metabolism. In this context, aldose reductase inhibitors (ARIs) have received much attention worldwide. Decreased sorbitol flux through polyol pathway by ARIs could be an emerging target for the management of major complications of diabetes. The present review article describes a brief overview of the role of aldose reductase in the diabetic complications, advances achieved on ARIs and their potential use in the treatment and management of the major diabetic complications such as cataract, retinopathy, neuropathy, nephropathy and cardiovascular. The ARIs developed vary structurally, and representative structural classes of ARIs include i) carboxylic acid derivatives (such as Epalrestat, Alrestatin, Zopalrestat, Zenarestat, Ponalrestat, Lidorestat, and Tolrestat), ii) spirohydantoins and related cyclic amides (such as Sorbinil, Minalrestat, and Fidarestat), and iii) phenolic derivatives (related to Benzopyran-4-one and Chalcone). Among these inhibitors, Epalrestat is the only commercially available inhibitor till date. In addition, some other ARIs such as Sorbinil and Ranirestat had been advanced into late stage of clinical trials and found to be safe for human use. The role of various natural ARIs in management of diabetic complications will be discussed. Adapting ARIs could prevent sepsis complications, prevent angiogenesis, ameliorate mild or asymptomatic diabetic cardiovascular autonomic neuropathy and appear to be a promising strategy for the treatment of endotoxemia and other ROS-induced inflammatory diseases. The role of ARIs in non-diabetic diseases will also be discussed.

Chinese herbal medicine (CHM), an alternative and complementary medicine, has been applied in various diseases. Recently, a number of anti-liver fibrogenesis compounds exhibiting antiliver fibrosis effects have been discovered in CHM. In this review, we reviewed the published data on their anti-fibrosis effects and discussed the possible underlying mechanisms. More investigations are needed to improve the insight into therapeutic effect of CHM on liver fibrosis.