Biomolecules present in plant extracts can be used to reduce metal ions to nanoparticles in a single-step
green synthesis process. This biogenic reduction of metal ion to base metal is quite rapid, readily conducted
at room temperature and pressure, and easily scaled up. Synthesis mediated by plant extracts is environmentally
benign. The reducing agents involved include the various water soluble plant metabolites (e.g. alkaloids,
phenolic compounds, terpenoids) and co-enzymes. Silver (Ag) and gold (Au) nanoparticles have been the
particular focus of plant-based syntheses. Extracts of a diverse range of plant species have been successfully
used in making nanoparticles. In addition to plant extracts, live plants can be used for the synthesis. Here we
review the methods of making nanoparticles using plant extracts. Methods of particle characterization are
reviewed and potential applications of the particles in medicine are discussed.