The book presents the role of phytochemicals in drug discovery, highlighting their therapeutic potential, mechanisms of action, and challenges related to their study and production. The wide applications of phytochemicals such as flavonoids, alkaloids, terpenoids, and others in both traditional medicine and modern biotechnology are discussed. The book covers multifaceted issues, from biotechnological synthesis and chemical analysis, through research on Covid-19, to the future possibilities of using medicinal plants in disease therapy. The book emphasizes an interdisciplinary approach to phytochemicals, combining chemistry, molecular biology, and medicine. Special attention is paid to ethical and ecological aspects of bioprospecting and the need for sustainable use of plant resources.