ABSTRACT
Over the past centuries, the "chemodiversity” of the kingdom plantae has gained utmost importance in securing mankind's future and overall well-being of people across the globe. In this context, phytochemicals with distinct stereochemical profiles have been particularly intriguing because of their indispensable roles in various clinical and industrial applications. The phytochemicals are broadly classified into primary and secondary/specialized metabolites. While the proteins, amino acids, chlorophyll, and purines/pyrimidine of nucleic acids are considered as primary metabolites, the remaining phytochemicals, namely, alkaloids, flavonoids, terpenes, steroids, curcumins, and phenolics, are regarded as specialized plant metabolites. In recent times, these high-valued phytochemicals are being extracted from the wasted fruits and vegetables, aiding in the sustainable crop management and cultural economy practices. Historically, these bioactive phytoconstituents have been widely used as a therapeutic agent in different ethnopharmacological cultures. With the advent of novel research technologies, these metabolites are now being screened extensively against both acute and chronic disorders like SARS-CoV-2, cancers, human immunodeficiency virus (HIV), coronary heart disease, multidrug-resistant microbial infections, diabetic conditions, and neural complications as well. Phytochemicals exhibit this wide range of biological activities via their cytotoxic, free radical scavenging, nutraceutical, and apoptotic properties by interfering with the cellular metabolic and signaling pathways. Besides, phytochemicals are widely recognized as flavoring agents and cosmeceuticals due to their antioxidant, stabilizing, emulsifying, chelating, and aromatic properties. The present chapter highlights the multifaceted role of phytochemicals in therapeutic, food/flavoring, and cosmetic industries. It further discusses the current research trends in phytochemical science, including their relevance in circular economy and future approaches for human benefit. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022.