Identification and Characterization of Plant Extract Pharmaceuticals Using Vibrational Spectroscopic Techniques

This paper reports the possibility of monitoring the sweetener content in the leaves of Stevia Rebaudiana and root extract of Ginseng using FT-IR, micro-Raman and SERS techniques. Fingerprint analysis is a direct, fast, nondestructive and effective method to discriminate and identify different species. Ginseng root contains ginsengoside saponin about 4% and other active compounds such as D-glucose, D-fructose, sucrose, maltose, trisaccharide A,B,C, cellulose, alkaloids, volatile oil, etc. Stevioside is a natural sweettasting glycoside isolated from the herb Stevia rebaudiana, composed of stevia, a diterpenic carboxylic alcohol with three glucose molecules, mainly used commercially as sugar substitute. Stevioside, comprising 6-18% of the stevia leaf, is also the most prevalent glycoside in the leaf and is considered 300 times sweeter than sucrose at 0.4% sucrose concentration, 150 times sweeter at 4% sucrose, and 100 times sweeter at 10% sucrose concentration. Other sweet constituents include steviolbioside, rebausiosides A-E, and dulcoside A. Vibrational analysis of Stevia Rebaudiana reveals the specific modes of the three glucose molecules and the diterpenoic carboxylic alcohol with the characteristic Raman bands at 1663, 1198, 1126, 746 cm -1 . Regarding the ginseng, the starch content is monitored through the band intensity at 1026 cm -1 . The peaks at 911, 856 and 766 cm -1 are assigned as characteristic absorption of the carbohydrate I, II and III whereas the week band at 990 cm -1 in the secondary derivative FT-IR is closely related to the content of saponin. It is well known that the content of saponin in wild American ginseng may reach 11%. The sensitivity of the FT-vibrational techniques allowed identifying the differences due to the cultivation origin and it can be applied to determine the composition of a plant mixture. Such analysis may be applied to test the authenticity of particular products and ensure their proper use. The results provide a useful tool in preventing the fraudulent substitution of one type of plant for another.