Rasa to Visha: An Evolutionary Perspective on the Taxonomy of Rasa Dravyas

Rasa Śāstra is an important branch of Ayurveda concerned with the identification, processing, pharmaceutical transformation, and therapeutic use of metals, minerals, and other Rasa Dravyas. Rasa Dravya Vargikarana provides a systematic framework for understanding these substances based on their properties, pharmaceutical applications, therapeutic importance, and role in Parada Karma. The present review examines the development of Rasa Dravya classification through a comparative study of major classical Rasa granthas. Descriptions of Maharasa, Uparasa, Sādhāraṇa Rasa, Dhatu, Upadhatu, Ratna, Uparatna, Sudha, Sikata, Lavana, Kshara, Visha, and Upavisha Vargas were reviewed, with emphasis on differences in nomenclature, composition, and grouping. The review shows that classification systems gradually evolved alongside the development of Rasashastra and its pharmaceutical practices. Earlier texts mainly emphasized substances associated with Parada Karma, whereas later works introduced additional groups based on material properties and pharmaceutical requirements. Differences in the classification of certain substances may reflect variations in the understanding and practices of individual authors. Sandigdha, Kritrima, and Anupalabdha Dravyas require further investigation. Correlating classical classifications with chemical and mineralogical information may support accurate identification, standardization, quality control, and appropriate utilization of Rasa Dravyas in contemporary Ayurvedic pharmaceutics.