Medicinal plants supply an array of bioactive compounds and play an important role in addressing chronic diseases. This review describes the status of advances in several major classes of plant-based compounds: flavonoids, alkaloids, terpenoids, phenolic acids, saponins, and tannins. It specifically addresses the biosynthesis of these compounds, discusses some of the emerging pharmacological mechanisms, and presents potential therapeutic applications. The review highlights the promising effects of these classes of compounds on the treatment of cardiovascular disease, type 2 diabetes, cancer, neurodegenerative disorders, and chronic inflammation. Mechanistic and translational evidence were the focal points of the recent articles reviewed (published 2015–2025) from the databases PubMed, Scopus, and Web of Science. Current evidence suggests that many of the class compounds exert therapeutic benefits through several overlapping mechanisms that include the control of oxidative and inflammatory processes, modulation of apoptosis, regulation of glucose, and sustain endothelial function. The evidence primarily rests on in vitro and preclinical studies, and there are many known hurdles to the therapeutic use of these compounds (e.g., poor bioavailability, lack of standardization, multiple-compound interactions, and insufficient and underpowered clinical studies). The use of omic, artificial intelligence, and nanotechnology will aid in the development of the bioactive plant compounds clinically, but more grounded translational practices will be necessary to successfully integrate the compounds for use therapeutically in the future.