Synopsis The knowledge of medicinal plants can be traced back from Vedic period.  The Rigveda and Atharvaveda, which date back to ca 2000-1000 BC, and several post Vedic treatise, viz. Charak (Carak) Samhita (ca 100 AD), Sushruta Samhita (ca 8000-900 AD), Ashtanga Hridiyam Samhita (ca 700 AD), Dravyaguna Sangrah (ca 1060 AD), Shodal Nighantu (ca 1374 AD), Raj Nighantu (ca 1600 AD), Bhava Prakash Nighantu (ca 1600 AD), Rajballah Nighantu (ca 1760 AD), etc. are important sources of information on medicinal plants.  The modern Ayurvedic and Unani literature and several other medico-botanical text (Kirtikar & Basu, 1935; Chopra et al., 1956 etc) have further added to our knowledge regarding plant based remedies.