Ursane And Olenane Triterpenes From Astragalus Propinquus.

Continuation on the phytochemical studies of the dichloromethane (CH2Cl2) fraction of the aqueous extract of Astragalus propinquus furnished two triterpenes namely α-amyrin and β-amyrin. The structures of the two isolated compounds were characterized on the basis of extensive spectral studies and literature search. The complete 1H and 13C NMR spectral assignments of the two isolated compounds are reported on the basis of 1D (1H and 13C) and 2D (COSY, HSQC, and HMBC) NMR spectral data.

Isolation of Stigmasterol and β-Sitosterol from the dichloromethane extract of Rubus suavissimus.

Purification of the dichloromethane (CH2Cl2) fraction of the aqueous extract of Rubus suavissimus resulted in the isolation of two sterols namely stigmasterol and β-sitosterol. The structures of the isolated compounds were characte-rized on the basis of extensive spectral data (1D and 2D NMR; and MS) and in comparison with their literature data.

Spectral Analysis and Chemical Studies of the Sweet Constituent, Rebaudioside A.

Aim: To study NMR spectral analysis and hydrolysis products of Rebaudioside A (1) that has been isolated from Stevia rebaudiana. Study Design: Acquiring NMR and high resolution mass spectral (HRMS) data of Rebaudioside A for structural characterization, and identification of hydrolysis products. Place of Study: Organic Chemistry Department of The Coca-Cola Company, Atlanta, GA 30313, USA. Methodology: The 1D (1H & 13C) and 2D (COSY, HSQC, and HMBC) NMR spectral data of was acquired using Varian Unity Plus 600 MHz instrument using standard pulse sequences. Hydrolysis studies were performed on Rebaudioside A using acid, base and enzymatic studies to identify partial degradation products, aglycone and sugar residues. Results: The proton and carbon values of Rebaudioside A were assigned based on NMR and HRMS data as well as chemical studies. The aglycone was identified as steviol on the basis of enzymatic hydrolysis, sugar was identified as D-glucose from acid hydrolysis and the partial hydrolyzed product was identified as Rebaudioside B from alkaline hydrolysis.

Isolation of Stigmasterol and β-Sitosterol from the dichloromethane extract of Rubus suavissimus.

Purification of the dichloromethane (CH2Cl2) fraction of the aqueous extract of Rubus suavissimus resulted in the isolation of two sterols namely stigmasterol and β-sitosterol. The structures of the isolated compounds were characte-rized on the basis of extensive spectral data (1D and 2D NMR; and MS) and in comparison with their literature data.

Acid and Alkaline Hydrolysis Studies of Stevioside and Rebaudioside A.

Hydrolysis studies of the two diterpene glycosides stevioside and rebaudioside A that were isolated from Stevia rebaudiana were performed using acid and alkaline conditions. Acid hydrolysis was carried out using H2SO4 whereas alkaline hydrolysis was performed using NaOH. Using these methods, partial hydrolyzed glycosides of stevioside and rebaudioside A and their sugar residues were identified from the alkaline and acid hydrolysis studies respectively. The structures of the acid and alkaline hydrolysis products were achieved on the basis of extensive NMR and high resolution mass spectral data, and in comparison with the data reported in the literature as well as TLC comparison with their corresponding standard compounds.