Rafael I. San Miguel

Synthesis and Sensory Evaluation of ent-Kaurane Diterpene Glycosides

Catalytic hydrogenation of the three ent-kaurane diterpene glycosides isolated from Stevia rebaudiana, namely rubusoside, stevioside, and rebaudioside-A has been carried out using Pd(OH)2 and their corresponding dihydro derivatives have been isolated as the products. Synthesis of reduced steviol glycosides was performed using straightforward chemistry and their structures were characterized on the basis of 1D and 2D NMR spectral data and chemical studies. Also, we report herewith the sensory evaluation of all the reduced compounds against their corresponding original steviol glycosides and sucrose for the sweetness property of these molecules.

Chemical Constituents from the Polar Fraction of Rubus suavissimus

Systematic phytochemical study of the n-BuOH fraction of the aqueous extract of Rubus suavissimus resulted in the isolation of three diterpene glycosides namely rubusoside, suavioside-A and sugeroside; a phenolic glycoside quercetrin; and a lignan glycoside arctiin. The structures of the isolated compounds were characterized on the basis of extensive spectral data (1D and 2D NMR; and MS) and chemical studies which has not been reported earlier. This is the first report of the isolation of quercetrin and arctiin not only from the plant R. suavissimus but also from the genus Rubus. Also, herewith we are reporting the sweetness recognition threshold and sweetness enhancement effect of rubusoside, the major constituent of R. suavissimus.