A biofilm is a community of stable microorganisms encapsulated in an extracellular matrix produced by themselves. Many types of microorganisms that are found on living hosts or in the environment can form biofilms. These include pathogenic bacteria that can serve as a reservoir for persistent infections, and are culpable for leading to a broad spectrum of chronic illnesses and emergence of antibiotic resistance making them difficult to be treated. The absence of biofilm-targeting antibiotics in the drug discovery pipeline indicates an unmet opportunity for designing new biofilm inhibitors as antimicrobial agents using various strategies and targeting distinct stages of biofilm formation. The strategies available to control biofilm formation include targeting the enzymes and proteins specific to the microorganism and those involved in the adhesion pathways leading to formation of resistant biofilms. This review primarily focuses on the recent strategies and advances responsible for identifying a myriad of antibiofilm agents and their mechanism of biofilm inhibition, including extracellular polymeric substance synthesis inhibitors, adhesion inhibitors, quorum sensing inhibitors, efflux pump inhibitors, and cyclic diguanylate inhibitors. Furthermore, we present the structure–activity relationships (SAR) of these agents, including recently discovered biofilm inhibitors, nature-derived bioactive scaffolds, synthetic small molecules, antimicrobial peptides, bioactive compounds isolated from fungi, non-proteinogenic amino acids and antibiotics. We hope to fuel interest and focus research efforts on the development of agents targeting the uniquely complex, physical and chemical heterogeneous biofilms through a multipronged approach and combinatorial therapeutics for a more effective control and management of biofilms across diseases.

Background: Bacterial cells communicate via small extracellular molecules that facilitate gene expression which is dependent on cell density and this mechanism is known as Quorum Sensing (QS). At low cell density, these bacteria show a single cellular type of behavior but once they reach the threshold level they alter to a multicellular type and hence a QS is established by the transfer of signalling molecules called autoinducers. Quorum sensing inhibitors (QSI) are those that hinder the quorum sensing pathway. Main body of the The emergence of antimicrobial resistance has become a threat to mankind with quorum sensing being one of the mechanisms responsible for this resistance. Hence Quorum Quenching can be considered to interrupt bacterial communication. This review focuses on the effects of different synthetic and natural quorum-sensing inhibitors on different organisms and how it affects their gene regulation. Conclusion: Different natural and synthetic agents can quench quorum sensing by various mechanistic pathways. The various quorum-sensing inhibitors against both Gram-positive and Gram-negative bacteria provide a wider scope to prevent emerging antimicrobial resistance.

Cancer, the second leading cause of death worldwide, is a major health problem. Chemotherapy, radiation therapy and surgery are current treatments for cancer. Most anticancer drugs have severe toxic effects and are required to be administered in cycles to reduce toxicity and prevent resistance. Plant-based drugs have shown a potential for treatment of cancer, and various plant secondary metabolites have shown promising antitumor activity against several cancer cell lines, such as leukemia, colon cancer, prostate cancer, breast cancer and lung cancer. Vincristine, etoposide, topotecan and paclitaxel, which are of natural origin, are successfully used in clinical practice, and this has generated interest in natural compounds as anticancer agents. Some phytoconstituents like curcumin, piperine, allicin, quercetin and resveratrol have been extensively researched and reviewed. In the current study, we have reviewed several plants like Athyrium hohenackerianum, Aristolochia baetica, Boswellia serrata, Panax ginseng, Berberis vulgaris, Tanacetum parthenium, Glycine max, Combretum fragrans, Persea americana, Raphanus sativus, Camellia sinensis, and Nigella sativa for their source, key phytoconstituents, and anticancer activity along with their toxicity profile. Few phytoconstituents like boswellic acid, sulforaphane and ginsenoside showed excellent anticancer activity compared to standard drugs and are potential clinical candidates.

Pyrimidines serve as key structural components in chemical frameworks and biological processes. Several pyrimidine analogues have been produced over the years by means of traditional methods that necessitated large amounts of solvents, reagents, and, most importantly, additional time, which has led them to become prohibitive. These procedures are now being replaced with more cost-effective adaptive methodologies that incorporate one-pot synthesis and greener approaches involving various green solvents and catalysts. The current review covers a number of green synthetic techniques, including ultrasound-assisted synthesis, visible light irradiation synthesis, solvent-free synthesis, catalyst-free synthesis, microwave-assisted synthesis, and green catalyst synthesis for the synthesis of pyrimidine derivatives. Accordingly, it integrates different strategies to synthesize heterocyclic pyrimidine analogues in a well-organized manner.