rubusoside and steviol

High content of steviol glycosides in stevia leaves is a cause of their high popularity as. a natural sweetener of various sugar-free food products. Stevioside (13-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic acid β-d-glucopyranosyl ester) is one of the main steviol glycosides in stevia leaves known for its hydrolytic instability responsible for the formation of simple steviol glucosides (steviolbioside, rubusoside, steviol monoside) and steviol. However, the formation of hydroxy and alkoxy adducts of stevioside and of its hydrolysis products has not yet been reported. The performed experiments prove that water and alkoxy adducts are formed not only during temperature processing of stevioside but also of stevia and stevia-containing food products. Their quantities depend on environment pH, water concentration and food composition. Although they are formed in small amounts their biological activity is unknown and should be recognized.

Topics: Diterpenes, Kaurane; Food Analysis; Glucosides; Hydrogen-Ion Concentration; Hydrolysis; Methanol; Plant Leaves; Stevia; Sweetening Agents; Temperature; Water

Two new diterpene glycosides in addition to five known glycosides have been isolated from a commercial extract of the leaves of Stevia rebaudiana. Compound 1 (rebaudioside KA) was shown to be 13-[(O-β-d-glucopyranosyl)oxy]ent-kaur-16-en-19-oic acid 2-O-β-d-glucopyranosyl-β-d-glucopyranosyl ester and compound 2, 12-α-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy]ent-kaur-16-en-19-oic acid β-d-glucopyranosyl ester. Five additional known compounds were identified, rebaudioside E, rebaudioside M, rebaudioside N, rebaudioside O, and stevioside, respectively. Enzymatic hydrolysis of stevioside afforded the known ent-kaurane aglycone 13-hydroxy-ent-kaur-16-en-19-oic acid (steviol) (3). The isolated metabolite 1 possesses the ent-kaurane aglycone steviol (3), while compound 2 represents the first example of the isomeric diterpene 12-α-hydroxy-ent-kaur-16-en-19-oic acid existing as a glycoside in S. rebaudiana. The structures of the isolated metabolites 1 and 2 were determined based on comprehensive 1D- and 2D-NMR (COSY, HSQC, and HMBC) studies. A high-quality crystal of compound 3 has formed, which allowed the acquisition of X-ray diffraction data that confirmed its structure. The structural similarities between the new metabolites and the commercially available stevioside sweeteners suggest the newly isolated metabolites should be examined for their organoleptic properties. Accordingly rebaudiosides E, M, N, O, and KA have been isolated in greater than gram quantities.

Topics: Diterpenes, Kaurane; Glucosides; Minnesota; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Plant Leaves; Stevia; Sweetening Agents

Meeting the rising consumer demand for natural food ingredients, steviol glycosides, the sweet principle of Stevia rebaudiana Bertoni (Bertoni), have recently been approved as food additives in the European Union. As regulatory constraints require sensitive methods to analyze the sweet-tasting steviol glycosides in foods and beverages, a HILIC-MS/MS method was developed enabling the accurate and reliable quantitation of the major steviol glycosides stevioside, rebaudiosides A-F, steviolbioside, rubusoside, and dulcoside A by using the corresponding deuterated 16,17-dihydrosteviol glycosides as suitable internal standards. This quantitation not only enables the analysis of the individual steviol glycosides in foods and beverages but also can support the optimization of breeding and postharvest downstream processing of Stevia plants to produce preferentially sweet and least bitter tasting Stevia extracts.

Topics: Chromatography, High Pressure Liquid; Diterpenes, Kaurane; Food Analysis; Glucosides; Glycosides; Plant Leaves; Reference Standards; Sensitivity and Specificity; Stevia; Sweetening Agents; Tandem Mass Spectrometry

In a search for potential cancer chemopreventive agents from natural resources, stevioside (1), a sweetener, and six related compounds, including two aglycones steviol (6) and isosteviol (7), were screened in an in vitro assay for inhibitory effects on Epstein-Barr virus early antigen activation. Compounds 1, 6 and 7 showed significant activity in this assay and also exhibited strong inhibitory effects in a two-stage carcinogenesis test using mouse skin induced by 7,12-dimethylbenz[a]anthracene (DMBA) and 12-O-tetradecanoylphorbol-13-acetate (TPA). The inhibitory effects of these three compounds were greater than that of glycyrrhizin. Furthermore, these three compounds significantly inhibited mouse skin carcinogenesis initiated by peroxynitrite and promoted by TPA. Their activities were comparable to that of curcumin. These results suggested that 1, as well as 6 and 7, could be valuable as chemopreventive agents for chemical carcinogenesis.

Topics: Animals; Antineoplastic Agents; Carcinogenicity Tests; Chemoprevention; Curcumin; Diterpenes, Kaurane; Glucosides; Glycyrrhizic Acid; Herpesvirus 4, Human; Mice; Skin Neoplasms

Steviol (ent-13-hydroxykaur-16-en-19-oic acid), the aglycone of various plant-derived glycoside sweeteners consumed by human populations, is known to be mutagenic toward Salmonella tymphimurium strain TM677 when metabolically activated using a 9000 x g supernatant fraction derived from the liver of Aroclor 1254-pretreated rats. Mass spectral analysis of this diterpenoid and some analogs revealed characteristic patterns reflecting differential stereochemistry at the C/D rings and variations in the nature of the substituents present. Such information has been used to help identify several in vitro metabolites of steviol in conditions known to produce a mutagenic response, when analyzed by gas chromatography/mass spectrometry. The major pathways of such steviol mammalian metabolism proved to be allylic oxidation and epoxidation. 15-Oxosteviol, a product of oxidation of the major steviol metabolite, 15alpha-hydroxysteviol, was found to be a direct-acting mutagen [corrected].

Topics: Biotransformation; Diterpenes; Diterpenes, Kaurane; Glucosides; Glycosides; Mass Spectrometry; Mutagens; Sweetening Agents; Terpenes