Rasa Nirdhāraṇa (assessment of taste) of Leonotis nepetifolia (L.) R. Br.: A preliminary study in healthy volunteers

BACKGROUND: Rasa (a concept corresponding to taste) is the only perceivable parameter for drug identification in Ayurveda. The Ayurvedic pharmacological principles such as guṇa (quality), vīrya (potency) and vipāka (effect of biotransformation) are inferred based on the identified Rasa of a drug. All these principles together predict the probable spectrum of drug action in Ayurveda. It is mandatory to screen a drug in the Ayurvedic pharmacological perspective to incorporate it into Ayurvedic materia medica. AIM: To assess the rasa of a non classical herb, Leonotis nepetifolia (L.).R.Br. based on the lakṣaṇas (characteristics) described in Ayurvedic texts for the identification of individual rasa. SETTINGS AND DESIGN: The study was conducted at the Department of Dravyaguna, Institute for Post Graduate Teaching and Reaseach in Ayurveda, Gujarat Ayurved University, Jamnagar. MATERIALS AND METHODS: The whole plant powder (3g) of Leonotisnepetifolia was administered to 50 participants (trained Ayurvedic physicians) and their responses after intake of the drug were elicited using a structured questionnaire. RESULTS AND CONCLUSION: On analyzing the data it was found that Leonotis nepetifolia possess predominantly tikta rasa (bitter taste) followed by Kaṣāya rasa (astringent taste). Recent researches and ethnomedicinal claims on Leonotis nepetifolia stand comparable with the pharmacological activities attributed to tikta and Kaṣāya rasa in Ayurvedic classics. Rasa nirdhāraṇa can be one of the preliminary steps to initiate the process of screening of an unknown drug along the lines of Ayurvedic pharmacology specially because rasa is the only perceivable parameter. According to Ayurveda, rasa of a dravya has a bearing on its karma (pharmacological action) and the identification of rasa could be one of the subjective means for inferring pāñcabhautika constitution of a substance which in turn could help in tentatively inferring guṇa, vīrya and vipāka of the dravya. This paper demonstrates how a simple method can be used without any instruments to do a preliminary assessment of the rasa or taste of a plant.