Currently, the development of anticancer drug resistance is significantly restricted the clinical efficacy of the most commonly prescribed anticancer drug. Malignant disease is widely prevalent and considered to be the major challenges of this century, which concerns the medical community all over the world. Consequently, investigating small molecule antitumor agents, which could decrease drug resistance and reduce unpleasant side effect is more desirable. 2-aminothiazole scaffold has emerged as a promising scaffold in medicinal chemistry and drug discovery research. This nucleus is a fundamental part of some clinically applied anticancer drugs such as dasatinib and alpelisib. Literature survey documented that different 2aminothiazole analogs exhibited their potent and selective nanomolar inhibitory activity against a wide range of human cancerous cell lines such as breast, leukemia, lung, colon, CNS, melanoma, ovarian, renal, and prostate. In this paper, we have reviewed the progresses and structural modification of 2-aminothiazole to pursuit potent anticancers and also highlighted in vitro activities and in silico studies. The information will useful for future innovation.

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: Heterocyclic compounds play a critical role in medicinal chemistry and many available drugs contain heterocyclic rings. A six-membered heterocyclic compound pyridine showed various applications that acts as an important solvent, reagent, and precursor in agrochemicals and pharmaceuticals. Due to the increase of drug resistance, there is an obvious medical need to develop new antiviral agents. Various derivatives of pyridine scaffold display abroad biological activities such as anti-microbial, anti-viral, antioxidant, anti-diabetic, anti-cancer, anti-malaria, analgesic and anti-inflammatory activities, psychopharmacological antagonistic, anti-amoebic agents, and anti-thrombic activity. Due to the high importance of pyridine derivatives, in the present review, we tried to collect and classify many pyridine derivatives based on their structures from 2000 to 2020. Pyridine derivatives were classified into two general categories including pyridine containing heterocycles and pyridine fused rings. Structure-activity relationship (SAR) and the action mechanism of derivatives were also investigated. According to the recent studies, these derivatives exhibited good antiviral activity against different types of viruses such as the human immunodeficiency viruses (HIV), the hepatitis C virus (HCV), the hepatitis B virus (HBV), Respiratory syncytial virus (RSV), and Cytomegalovirus (CMV). These derivatives inhibited viral application with different action mechanism such as RT inhibition, polymerase inhibition, Inhibition of RNase H activity, inhibition of maturation, inhibition of the viral thymidine kinase, AAK1 (Adaptor-Associated Kinase 1) inhibition, GAK (Cyclin G-associated kinase) inhibition, inhibition of post-integrational event, inhibition of HDAC6, CCR5 antagonistic activity, DNA and RNA replication inhibition, gene expression inhibition, cellular NF-jB signaling pathway and neuraminidase (NA) inhibition, protein synthesis inhibition, and generally inhibition of viral replication cycle. This paper summarily expressed the past and present results about the discovery of novel lead compounds with good antiviral activity. Studies exhibited that almost all of the evaluations were performed by way of in vitro testing and is necessary to investigate in vivo and clinical testing for having better evaluations in the future. We believe that pyridine derivatives can be used as promising antiviral agents and needs to perform more broad investigations in this field.

Quercetin as a valuable natural flavonoid has shown extensive biological activities, including anticancer, antioxidant, antibacterial, antiinflammatory, anti-Alzheimer, antifungal, antiviral, antithalassemia, iron chelation, antiobesity, antidiabetic, antihypertension, and antiphospholipase A2 (PLA2) activities, by the modulation of various targets and signaling pathways that have attracted much attention. However, the low solubility and poor bioavailability of quercetin have limited its applications; therefore, the researchers have tried to design and synthesize many new derivatives of quercetin through different strategies to modify quercetin restrictions and improve its biological activities. This review categorized the O-glycoside derivatives of Quercetin into two main classes, 3-O-glycoside and other O-glycoside derivatives. Also, it studied biological activities, structure-activity relationship (SAR), and the action mechanism of O-glycoside quercetin derivatives. Overall, we summarized past and present research for discovering new potent lead compounds. Highlights• Quercetin is a natural flavonoid with a valuable scaffold.• O-Glycoside quercetin derivatives represents broad-spectrum biological activities.• The structure-activity relationship investigation is discussed after modifying the scaffold of quercetin.• This review can help researchers to rationally design/develop various drugs.

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