Sesquiterpenes,guaianolides and diterpenes from Stevia myriadenia

The investigation of Stevia myriadenia afforded in addition to known compounds a new clerodane and a labdane derivative, two guaianolides, a bisabolene and a germacrene derivative. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly.     

Steviamine,a new indolizidine alkaloid from Stevia rebaudiana

The novel iminosugar (1R,2S,3R,5R,8aR)-3-(hydroxymethyl)-5-methyloctahydroindolizine-1,2-diol (steviamine) was isolated from leaf material of Stevia rebaudiana and leaves and bulbs of Veltheimia capensis. This is the first report of an indolizidine iminosugar alkaloid from the Asteraceae and Hyacinthaceae. Steviamine may occur in some Stevia products and influence taste.     

Rebaudioside F, a diterpene glycoside from Stevia rebaudiana

The sweet diterpenoid glycoside, rebaudioside F, was isolated from leaves of a high rebaudioside C producing line of Stevia rebaudiana, and its structure was established by chemical and spectral studies.     

Diterpenes from Stevia monardaefolia

An investigation of Stevia monardaefolia resulted in the isolation of two new labdane type diterpenes, 6α-angeloyloxy nidorellol and 6α-angeloy     

Melampolides and germacranolides from Stevia amambayensis

From the aerial parts of Stevia amambayensis in addition to known compounds three new sesquiterpene lactones, a grazielic acid derivative and two melampolides were isolated. The roots gave two new bisabolene derivatives.     

Glucose, sucrose, and steviol glycoside accumulation in Stevia rebaudiana grown under different photoperiods

The amount of free glucose and sucrose within the leaves of Stevia rebaudiana has been evaluated under different photoperiods and related to steviol glycoside (SVgly) accumulation. The diurnal dynamics of glucose and sucrose in leaves, internodes, apices, and roots revealed considerable fluctuations. Within leaves, glucose and sucrose content decreased up to three-fold during the night whereas SVgly amounts did not show any significant diurnal fluctuations. Ontogenetic variations in glucose content was markedly different under long-day (LD) and short-day (SD) regimes. Under LD, glucose content increased two-fold after the onset of flower bud formation, whereas under SD, a stagnation or small decrease was observed. This increase under LD was already noticed in the upper sink leaves at the end of the vegetative stage, possibly acting as a metabolic trigger for the phase transition to reproductive development. Under SD, glucose content appeared more controlled resulting in a better linear relationship with dry matter and SVgly content. The increased sink demands of the transitional apex led to a rapid decline in leaf sucrose which showed little or no correlation with SVgly amounts. From our results, it becomes clear that the correlation between glucose or sucrose as substrates and SVglys as products is very dynamic and is significantly influenced by day-length and ontogeny.     

A guaianolide from Stevia breviaristata

Extraction of Stevia breviaristata furnished a new guaianolide breviarolide.     

Flavonoids and eupahakonenin B from Stevia satureiaefolia

Extraction of Stevia satureiaefolia furnished the flavonoids cirsimaritin and eupatorin and the guaianolide eupahakonenin B.     

Photoperiod and elicitors increase steviol glycosides,phenolics, and flavonoid contents in root cultures of Stevia rebaudiana

The establishment of green root cultures of Stevia rebaudiana Bertoni, and the effect of elicitors such as hydrogen peroxide (H₂O₂) and methyl jasmonate (MeJA), is shown in the present study. Stevioside, rebaudioside A, and the isomers steviol/isosteviol were identified through DFI-ESI-IT-MSⁿ and UPLC-TOFMS spectrometric systems, in combination with solid-phase extraction. The accumulation of steviol glycosides increased by 2.4 times (compared to the control value of 22.35 μgSG per gDW), with the addition of 250 μM H₂O₂. The non-enzymatic antioxidant response, which resulted from production of phenolic and flavonoid compounds, was modified based on the elicitor and the dose used. The maximum accumulation of flavonoids was induced on the third day with the addition of H₂O₂ (250 or 500 μM), and with MeJA (250 or 500 μM); the increase was observed on the fifth day. The enzymatic antioxidant response of the catalase and peroxidase from the roots under elicitation confirmed the stress conditions.

     

Effect of two plant growth retardants on steviol glycosides content and antioxidant capacity in Stevia (Stevia rebaudiana Bertoni)

Two greenhouse experiments were conducted to study the effect of two plant growth retardants, Chlorocholine chloride (CCC) and Paclobutrazol (PBZ), on growth, Steviol glycosides (SVglys) content and antioxidant capacity in Stevia (Stevia rebaudiana Bertoni). Five concentrations of CCC (0, 250, 500, 750 and 1,000 ppm) and PBZ (0, 6, 12, 18 and 24 ppm) with three replications were applied to Stevia plants as treatments based on completely randomized design. CCC was sprayed on Stevia shoots, but PBZ was applied as a drench. The obtained results showed that CCC reduced plant height but improved leaf and stem dry weight, especially with 750 ppm concentration. Total SVgly content and consequently SVglys yield were significantly reduced by CCC application, and 1,000 ppm of CCC concentration was more effective than other treatments. PBZ had no effect on Stevia height while it significantly enhanced stem and dry weight at 12 ppm. Moreover, PBZ remarkably increased total SVglys contents, SVglys yield, and Rebaudioside A/Stevioside ratio. Total antioxidant capacity significantly varied with CCC and PBZ and the highest activity was obtained with 1,000 and 12 ppm of CCC and PBZ, respectively. The results of these experiments indicated that, although CCC and PBZ are plant growth retardants and act as anti-gibberellins, only CCC reduced plant height and SVglys production in Stevia. On the contrary, PBZ at 12 ppm concentration, improved Stevia growth, SVglys production, and antioxidant capacity.     

Impact of nitrogen supply on growth,steviol glycosides and photosynthesis in Stevia rebaudiana Bertoni

This work investigated the agronomic, physiological and biochemical response of Stevia rebaudiana Bertoni grown under different nitrogen (N) rates. A pot trial in open air conditions was set up in 2012 with the aim to evaluate the effect of four N rates on the biometric and productive characteristics, steviol glycoside (SG) content as well as on leaf gas exchanges, chlorophyll fluorescence, photosynthetic pigments, Rubisco activity and N use efficiency. N deficiency caused a decrease in leaf N content, chlorophylls and photosynthetic CO₂ assimilation, resulting in a lower dry matter accumulation as well as in reduced SG production. The application of 150 kg N ha^? 1 seems to be the most effective treatment to improve rebaudioside A (Reb A) content, Reb A/stevioside ratio, photosynthetic CO₂ assimilation, stomatal conductance, N use efficiency, ribulose-1,5-bis-phosphate carboxylase/oxygenase (Rubisco) and PSII efficiency. The results demonstrate that by using an appropriate N rate it is possible to modulate the SG biosynthesis, with a significant increase in the Reb A content and in the ratio between Reb A and stevioside. This finding is of great relevance in order to obtain a raw material designed to meet consumer needs and bio-industry requirements for high-quality, Reb A content, and safe and environmentally friendly products.     

Bisabolene derivatives from Stevia salicifolia

The aerial parts of Stevia salicifolia afforded two new bisabolene type sesquiterpenes. The structures were elucidated by spectroscopic, chemical transformations and correlation with 15-acetoxy bisabol-1-one.     

Novelties in Stevia (Compositae: Eupatorieae)

Twenty-four new taxa (16 species, 8 varieties) are described in the genusStevia from North and Central America. Three new combinations are made. Brief discussions concerning the relationships of the new taxa are provided.     

甜叶菊RAPD反应体系的优化

以甜叶菊为试材,对影响其RAPD反应体系的7个因子进行优化.结果表明,20 μL的优化体系包括:双蒸水13.6 μL,10×Buffer(含15 mmol/L MgCI2)溶液3μL,2.5 mmol/L的dNTPS 1.2 μL,10 μmol/L的引物1μL,20 ng的模板DNA 1μL,1UTaq聚合酶;热循环...     

Sesquiterpene lactones and other constituents from Stevia jorullensis

A chemical study of the aerial parts of Stevia jorullensis was carried out as a contribution to the knowledge of the chemistry of the genus Stevia. In this investigation the sesquiterpene lactones 11β,13-dihydrocostunolide (1), 11,13-dihydroreynosin (4), and 1β-hydroxycolartin (5) were isolated for the first time in the genus. Additionally, chlorogenic acid (8), the steroidal compounds β-sitosterol (2), stigmasterol (3), β-sitosteryl glucopyranoside (6), and stigmasteryl glucopyranoside (7) were also isolated. This is the third report of the presence of a 11,13-dihydrogermacranolide and the second of 11,13-dihydroeudesmanolides in the genus Stevia.     

Kaurenic acid derivatives from Stevia eupatoria

Two kaurene type diterpenes were isolated from the aerial part of Stevia euphoria. Their structures and stereochemistry were established by carbon and ¹H NMR, chemical transformation and correlation with known compounds.     

Beyerene derivatives and other terpenoids from Stevia aristata

The aerial parts of Stevia aristata afforded in addition to known compounds two new germacranolides, a melampolide, a 4Z-melampolide and two beyerene derivatives. From the roots a new dihydrolongipinene derivative was isolated while the aerial parts of Stevia andina gave the E/Z-isomers of austroinulin and 6-desoxyaustroinulin. The absolute configuration of these typical diterpenes is discussed.