Medicinal Plant Phytochemicals as Natural Ligands for Metal Coordination Complexes: Advances in Bioinorganic Chemistry and Drug Discovery

Medicinal plants constitute one of the richest sources of structurally diverse phytochemicals that serve as promising natural ligands for the synthesis of metal coordination complexes with enhanced pharmacological activities. Bioactive compounds such as flavonoids, polyphenols, alkaloids, terpenoids, phenolic acids, tannins, coumarins, and glycosides possess functional groups capable of coordinating with biologically important metal ions, including copper, zinc, iron, cobalt, manganese, nickel, ruthenium, vanadium, and silver. Metal complexation often improves the physicochemical properties of phytochemicals by increasing their chemical stability, aqueous solubility, lipophilicity, bioavailability, and therapeutic efficacy while reducing toxicity. Recent advances in bioinorganic chemistry, medicinal chemistry, nanotechnology, and green synthesis have accelerated the development of plant-derived metal coordination complexes for applications in antimicrobial therapy, cancer treatment, antioxidant defense, anti-inflammatory therapy, antiviral research, and targeted drug delivery. Sophisticated analytical techniques including UV–Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), mass spectrometry (MS), X-ray diffraction (XRD), electron microscopy, thermogravimetric analysis (TGA), and computational modeling have substantially improved structural characterization and mechanistic understanding of these complexes. This review discusses the chemistry of medicinal plant phytochemicals as natural ligands, coordination mechanisms, synthesis strategies, structural characterization, biological activities, applications in drug discovery, current challenges, and future perspectives in medicinal bioinorganic chemistry.