Spectrofluorimetric estimation of puerarin in Pueraria tuberosa.

Pueraria tuberosa (Roxb. ex. Willd.) DC. (Fabaceae) is the important plant used in Indian medicine, commonly known as Vidarikand. The plant is described as rasayana and tonic in Ayurvedic Pharmacopoeia of India (1). It is an extensive perennial climber, growing throughout tropical parts of India, mostly in moist regions, monsoon-forests and coastal tracts (2). The tuber of pueraria is sweet in taste and used in indigenous system of Indian medicine as tonic, aphrodisiac, antirheumatic, diuretic and galactogogue (3). It is an important constituent of Ayurvedic medicines including Chywanprash, a popular tonic (4). Phytoconstituents like: puerarin, daidzein, βsitostreol, stigmasterol, puerarone and coumestan, isoflavone C-glycoside-4,6-diacetyl-puerarin, pterocarpintuberosin, puetuberosanol and hydroxytuberosone have been isolated and characterized from the species (5). Puerarin is an important isoflavone-C-glucoside also found in a number of plants like Radix puerariae (6), Pueraria lobata (7) and Pueraria phaseoloides (8). Puerarin and its preparations (injections) are official in Chinese Pharmacopeia (9). Its pharmacological activities like: anticancer (10), hepatoprotective (11), estrogenic (12), antioxidant (13), antidiabetic (14), neuroprotective (15) and in learning-memory disorder (16) have been reported. The methods previously reported for estimation of puerarin include HPLC, HPTLC and liquid chromatography-mass spectrometry (17ñ19). The above methods for estimation of puerarin are time consuming and costly. Methanolic solution of puerarin showed intense blue fluorescence when observed under UV light (366 nm); therefore, it was thought to develop a more sensitive and simple spectrofluorometric method for the estimation of puerarin. Using standard sample preparation procedures and fluroscence spectrometry detection, we established a rapid and simple assay for puerarin quantitation in any herbal formulation and plasma samples. This analytical method achieves the highest sensitivity of any method reported to date, enabling improved characterization of puerarin pharmacokinetics. The methods give leads to scientist to use spectroflurometry to estimate fluorescence compound.