Quinolines are a prominent heterocyclic motif and crucial building blocks in creating physiologically active compounds. Due to the fast development of novel medicines with a quinoline nucleus, numerous research papers have been published in a short amount of time. Therefore, to comprehend the present state of the quinoline nucleus in medicinal chemistry science, it is necessary to combine new information with older data. So far, several traditional synthesis techniques have been reported in the literature to synthesize this scaffold. Pfitzinger, Gould–Jacob, Friedlander, Skraup, Doebner–von Miller, and Conrad–Limpach are examples of old synthetic methods. However, they need expensive and demanding conditions, such as high temperature, the use of non-biodegradable chemical compounds degrade the ecosystem, create irritation or harm as pollutants, and represent a threat to the environment. However, traditional synthesis processes need a difficult and time-consuming apparatus set-up, resulting in high costs and pollutants. As a result, scientists are presently developing new and innovative techniques to decrease the use of chemicals, solvents, and catalysts, which are detrimental to both humans and the environment. Therefore, we have attempted to shed light in this current review on various reactions to produce quinolines and their derivatives using various green synthetic methods. GRAPHICAL ABSTRACT

Background and Purpose: The blood-brain barrier (BBB), a critical interface of specialized endothelial cells, plays a pivotal role in regulating molecular and ion transport between the central nervous system (CNS) and systemic circulation. Experimental Approach: This review aims to delve into the intricate architecture and functions of the BBB while addressing challenges associated with delivering therapeutics to the brain. Historical milestones and contemporary insights underscore the BBB's significance in protecting the CNS. Key Results: Innovative approaches for enhanced drug transport include intranasal delivery exploiting olfactory and trigeminal pathways, as well as techniques like temporary BBB opening through chemicals, receptors, or focused ultrasound. These avenues hold the potential to reshape conventional drug delivery paradigms and address the limitations posed by the BBB's selectivity. Conclusion: This review underscores the vital role of the BBB in maintaining CNS health and emphasizes the importance of effective drug delivery through this barrier. Nanoparticles emerge as promising candidates to overcome BBB limitations and potentially revolutionize the treatment of CNS disorders. As research progresses, the application of nanomaterials shows immense potential for advancing neurological therapeutics, albeit with careful consideration of safety aspects.

: The benzimidazole and its derivatives are privileged heterocyclic motif and important building block for the development of the biologically active compound. However, several research reports are produced in a short period of time due to the rapid production of new drugs having a benzimidazole nucleus. In order to understand the current status of the benzimidazole nucleus in medicinal chemistry science, it is therefore important to combine the latest knowledge with earlier information. Hence, synthetic organic chemists concentrated on inventing an effective green methodology for synthesizing benzimidazole derivatives. In addition to this, non-degradable chemical compounds cause the ecosystem to become fragile, damage or irritation as contaminants and pose a danger to the environment. However, conventional methods of synthesis need longer heating time, complicated and tedious apparatus set up which result in high cost and pollution in contrast to greener methods which are inexpensive. In the present review, therefore, we have attempted to shed light on various synthetic strategies leading to the synthesis of different benzimidazole derivatives through the direct condensation reaction between o-phenylenediamine and aromatic aldehydes using green chemistry approaches such as mechanochemistry, ultrasound irradiation, microwave irradiation, environmentally benign solvents/catalysts, reactant immobilized on a solid support and blue light irradiation.

Cancer is a frightful disease that still poses a 'nightmare' worldwide, causing millions of casualties annually imposing one of the human race's greatest health-care challenges that entail a pragmatic treatment strategy. Plants are repositories for new chemical entities and have a promising cancer research path, supplying 60% of the anticancer agents currently used. However, plants and plant-derived products revolutionize the field, as they are quick, cleaner, eco-friendly, low-cost, effective, and less toxic than conventional treatment methods. Alkaloids are important chemical compounds that serve as a rich reservoir for drug discovery and development. However, some alkaloids derived from natural herbs display anti-proliferation and antimetastatic activity on different forms of cancer both in vitro and in vivo. Alkaloids have also been widely formulated as anticancer medications, such as camptothecin and vinblastine. Based on the information in the literature, this review focuses on the naturally-derived bioactive alkaloids with prospective anticancer properties. Still, more research and clinical trials are required before final recommendations can be made on specific alkaloids.