Isoxazoles are five-membered aromatic heterocyclic compounds in which oxygen and nitrogen atoms are present at positions 1 and 2 of the ring system. Isoxazole derivatives play a vital role due to their diverse biological activities, such as antimicrobial, antifungal, anti-viral, anti-tubercular, anti-epileptic, anti-diabetic, anticancer, anthelmintic, antioxidant, antipsychotic, antimalarial, analgesic, anti-inflammatory, etc. Isoxazole scaffold is present in various drug molecules, such as leflunomide (antirheumatic), valdecoxib (non-steroidal anti-inflammatory drug), and zonisamide (anti-convulsant). Similarly, isoxazole derivatives such as isocarboxazid act as monoamine oxidase inhibitors. It is used to treat symptoms of depression that may include anxiety, panic, or phobias. Whereas the isoxazole derivatives, including sulfamethoxazole, sulfisoxazole, and oxacillin, are used clinically for the treatment of bacterial infections. Isoxazole pharmacophore is also present in β-lactamase resistant antibiotics such as cloxacillin, dicloxacillin, and flucloxacillin. Cycloserine is a naturally occurring antibiotic that possesses isoxazole moiety with anti-tubercular, activity. This study focuses on the therapeutic potentials of isoxazole derivatives in new drug development.

Drug repurposing or drug repositioning has emerged as an efficient, very popular and alternative technique in modern drug discovery to identify old drugs for new targets cost-effectively and dynamically. This concept gets a tremendous boost, especially in the century's most challenging healthcare concern of the Covid-19 pandemic across the globe. In this approach, scientists seek new indications and clinical use of the drugs at minimum risk, which have previously already been pharmacologically established and approved. The methods developed for drug repositioning include computational approaches and biological methodologies, and with the fast technological advancement, various new drug-target- diseases are discovered, and thereby immense information is now available in the different databases, such as DrugBank, OMIM, ChemBank, KEGG, Pubmed, Genecard, and many more. The information available on all the above public domain databases has been utilized successfully in many drug repositioning projects. The present chapter discusses the concept of drug repurposing and its impact on academia, industries and, of course, their social implications. Besides this, the chapter will also cover details on tools and techniques to identify drugs for repositioning and their application in identifying drugs for various diseases and disorders. The current work will also foresee the recent market analysis and updates on the cost of drug discovery and development by drug repurposing, its comparison with traditional drug discovery approaches, challenges involved with drug repurposing, and future perspectives. 

Antiviral drugs are a class of medicines particularly used for the treatment of viral infections. Drugs that combat viral infections are called antiviral drugs. Viruses are among the major pathogenic agents that cause a number of serious diseases in humans, animals and plants. Viruses cause many diseases in humans, from self-resolving diseases to acute fatal diseases. The strategies for the development of antiviral drugs are generally focused on two different approaches, i.e., targeting the viruses themselves or the host cell factors. Antiviral drugs that directly target viruses include the inhibitors of virus attachment, inhibitors of virus entry, uncoating inhibitors, polymerase inhibitors, protease inhibitors, nucleotide reverse transcriptase, inhibitors of nucleoside and the inhibitors of integrase. The inhibitors of protease (ritonavir, atazanavir and darunavir), viral DNA polymerase (acyclovir, tenofovir, valganciclovir and valacyclovir) and integrase (raltegravir) are listed among the top 200 drugs by sales during the2010. Still, there are no effective antiviral drugs available for many viral infections. There is a couple of drugs for herpes viruses, many for influenza and some new antiviral drugs for treating hepatitis C infection and HIV. This chapter gives an overview of the pyrimidines and hetero annulated pyrimidines that have been reported to be active against viral infections; identification of novel pyrimidine leads may be used in the designing of new potent, selective and less toxic novel therapeutic agents having promising antiviral activity. An effort has been made to compile all the possible information regarding antiviral pyrimidines and bring them together to make easy availability of the existing literature on the subject. The objective of this chapter is to provide the structural and antiviral activity information as well as methods being used for the screening of the antiviral activity and antiviral potential IC50/ED50/CC50 values of the reported active pyrimidines are briefly discussed.

Cancer which is basically uncontrolled cell division and, thereby, the formation of tumors, has been a prominent cause of death across the world. More than 10 million people have lost their lives due to different types of cancer such as breast, lung, prostate, gastrointestinal, etc. Several pathways, including metabolic, signalling, etc., get altered to support uncontrolled cell division and their growth in case of cancer. Despite an increasing understanding of this disease over the period of time, still, specific causes could not be held responsible for the occurrence. Therefore, various different strategies mainly focused on preventing and killing cancerous cells have been explored. This chapter will primarily focus on the different drugs, including different types of chemotherapeutic agents such as DNA-alkylating agents like nitrogen mustard, cyclophosphamide, drug-peptide, drug-steroid conjugates, antimetabolites, antibiotics, etc. In addition to that, phytochemicals, which have also been investigated for their anti-cancerous activities and are under clinical trial, have also been discussed. 

Brahmi (Bacopa monnieri Linn.) is a well-known therapeutic herb used in a broad spectrum of conventional medicines to alleviate various ailments, prominently those involving intellect, anxiety and mental health. In Ayurveda, it is classified as Medhya rasayanas (meaning intellect rejuvenator) and claimed to be a cognitive nutrient and memory enhancer. Although the plant possesses a plethora of compounds, its neurological activity is mainly attributed to its major phytochemical constituents, i.e., bacoside saponins. Majorly isolated compounds are dammarane triterpenoids glycone and aglycones. There are several reports published with neurological activities on Bacopa monnieri to validate traditional claims through scientific findings. Some therapeutic formulations containing standardized extracts of Bacopa monnieri have also been developed for the betterment of mental health. Besides, being neuroprotective, the plant is reported to possess anti-inflammatory, analgesic, and antipyretic properties and systemic disorders like cardiovascular, hepatic, gastrointestinal, myocardial ischemia, respiratory problems, opioid-related nephrotoxicity and hepatotoxicity. The present chapter described the phytochemical profiling, extraction and isolation, neurological properties, as well as toxicological and clinical studies of the plant. 

Hexavalent chromium has been a potential threat to human beings due to its toxicity and carcinogenesis. The pathway of entry of hexavalent chromium in an aqueous medium is both anthropogenic and natural through ores of chromium. Prolonged exposure to hexavalent chromium may cause DNA mismatch and gene mutation, resulting in cancer. Cr(VI)- induced malignant cell and its study has become very important towards the possible mechanism of Cr(VI) binding. When a cell of the human lungs adsorbs hexavalent chromium due to prolonged ingestion of Cr(VI) contaminated water or inhalation, oxidative DNA damage is caused in the specific gene. This causes mutations in adenine and guanine bases of DNA in cases of lung cancer.

Humans, since their evolution, have always been in close contact with mother nature. Early life has been dependent solely on environmental resources for their livelihood. The trial-and-error approach in utilizing different resources came up with incorporating plants as a whole or their parts for food and survival. Gradually, the knowledge of medicinal plants was gained by our ancestors, and there started the Indian medical history of Ayurveda. In the current scenario, a huge number of medicinal herbs are being consumed in day-to-day life, which imparts tremendous benefits to human health. Our interest in gaining knowledge of medicinal components present in these herbs has led to many important discoveries in the area of drug development. Nowadays, numerous plants derived compounds are being used in modern medicines. In view of utilizing these natural resources efficiently, we need to understand their components in a better way. This chapter is towards gaining a deeper knowledge about medicinal plants, their role in different diseases, and insights into drug discovery.

Shikonin is a red naphthaquinone pigment present in the roots of plants of the Boraginaceae family. This pigment is an as active ingredient in several pharmaceutical and cosmetics preparations, and as a dye for fabrics and food items. It shows many bioactivities such as stimulation of peroxidase, protection against UV-radiation, inhibition of microsomal monooxygenase and induction and secretion of nerve growth factor. In this book chapter, we have provided detailed information on its biosynthesis and prospects for pharmaceutical use.

With changing the scenarios of living style, professional work culture, and daily hectic routine, liberal and global thoughts are impacting our dietary patterns and normal food consumption. So the preference for foods is changing, and foods that can be ready in a shorter time, like “fast foods”, are gaining popularity among the masses, especially young generations. The fast food business has become one of the fastest-growing industries across the globe. This growing trend of fast food consumption has also brought several health-associated issues, like obesity and heart-related problems. Therefore, health-conscious people do like to know the chemical ingredients embedded in fast foods as well as their packaging and storage. For this purpose, the chemistry relating to quality aspects of fast foods, including nutritional, physiological, sensory, flavor, microbiological and packaging, is very important for healthy consumption of fast food for a healthy life. In this book chapter, we have made efforts to bring updated information related to fast food, its chemical composition and implications for human health.

Breast cancer is the most prevalent neoplasm diagnosed in women worldwide. There are many factors responsible for breast cancer susceptibility. Mutation in tumor suppressor genes BRCA1 and BRCA2 predispose women to the early onset of breast cancer. The BRCA genes are involved in multiple cellular processes in response to DNA damage, including checkpoint activation, gene transcription, and DNA repair. Several DNA-acting agents act as effective anticancer used for treating cancer disease. Certain groups of chemicals are known to affect specific phases of cell division, such as, Cyclophosphamide is the most potent and successful anticancer agent that acts by alkylating the N-7position of guanine to cause crosslinking of DNA’s double helix, resulting in DNA breaks that interfere with the DNA replication and RNA transcription. This chapter deals with the classification of DNA-acting agents according to their modes of action.

Liver cancer is the sixth most commonly diagnosed cancer and the fourth leading cause of cancer death worldwide. Research over the last two decades has revealed that medicinal plants have been used for the treatment of various neoplastic diseases. Aloe vera is a ubiquitously naturally occurring and drought-resisting herbal medicinal plant. Some reports suggest that Aloe vera possesses wound and burn healing activities and anti-inflammatory as well as immunomodulatory effects. There are no direct studies available on the role of the Aloe vera extract and its active ingredient like aloe-emodin that modulates antiaging and anticancer activities, particularly on immune cells as well as liver cancer cells. Aloe vera has many bioactive compounds and pharmacological properties that may show an important role in liver cancer prevention and treatment through the enhancement of regeneration, antiaging activity, antioxidant activity, anticancer activity and modulation of genetic pathways. Here, we discuss the study of the anticancer effect and modulation of expression of various genes in response to Aloe vera in liver cancer.