Harnessing Costus species for sustainable nanoparticle synthesis and biological applications

Green nanotechnology is a rapidly advancing field of science which primarily focuses on the sustainable nanoparticle (NP) production using biological pathways of living systems. Metallic nanoparticles, whether composed of metal or metal oxide, have become highly popular because of their remarkable chemical, physical, biological, optical, and magnetic characteristics. Various physical, chemical, and biological approaches can be used to prepare metal-based NPs. Biological processes employing green synthesis methods have become valuable for producing nanoparticles (NPs) within 1 to 100 nm size range, due to their safety, environmental sustainability, reduced toxicity, and cost efficiency. Costus species (family Costaceae), is found in Africa, Asia, and America. Many plants of this family have diverse pharmacological activities, due to the presence of unique phytoconstituents such as tannins, saponins, steroids, phenolic compounds, flavonoids and alkaloids. Metal NPs have been found to enhance the activity of herbal extracts. The NPs of various Costus species developed are highly stable, economical, non-toxic, and environmentally safe. These are found to exhibit a broad spectrum of biological activities such as antibacterial, antifungal, antioxidant, anticancer, and antidiabetic activity. This review collates information on green metal NPs of a variety of Costus species, which have improved biomedical and environmental applications.