This invention relates to bio synthesis of novel nano gold through environment friendly process with the aid of plant materials classified under the taxonomical genus Dalbergia, Citrus, Ferula and Dolichos or Macrotyloma. The present inventive product novel nano gold finds utility in, the treatment of humans and animals, nutraceutical, cosmeceutical and herbal composition, the field of technology including but not limited to nano technology, green technology and bio technology. The invention also relates to the use of plant materials in the purification and particle size reduction of metals.