Stevia rebaudiana Bertoni, source of a high-potency natural sweetener: A comprehensive review on the biochemical, nutritional and functional aspects

The Development and Consumer Acceptance of Functional Fruit-Herbal Beverages

The development of functional beverages often requires a compromise between the palatability and high content of bio-active compounds. The purpose of this study was to elaborate on the fruit-herbal beverages with defined pro-health functions and evaluate their consumer acceptance. The beverages contained 80% of juices obtained from the fruits of aronia, rugosa rose, acerola, sea buckthorn, and cranberry. Each beverage was supplemented with different plant extracts which enhanced the designed functions of the beverage. The beverages were sweetened with sugar or with steviol glycosides, and were preserved by thermal pasteurization. The main groups of bio-active compounds and antioxidant capacity using ABTS, DPPH, and ORAC methods were analysed before and after pasteurization. The sensory acceptance was tested by 60 adult consumers who assessed the desirability of taste, odour, colour, and overall quality. Each beverage contained substantial amounts of polyphenols, including anthocyanins; rosehip-acerola and sea buckthorn beverages were also sources of vitamin C and carotenoids. All these components were stable under thermal treatment. Rosehip-acerola beverages had the highest antioxidant capacity, which was measured using all three methods exhibited. The highest level of consumer acceptance and willingness to purchase went to aronia beverages, while the sea buckthorn gained the lowest. There was no significant difference between the acceptance of beverages sweetened with sugar and stevia. Women and the 25- to 34-year-old consumer group rated the overall acceptability of the beverages slightly higher, although this was not reflected in their inclination to buy them. Attitude toward proper body mass and health had no influence on overall acceptance and willingness to complete the purchases. The main motivation for purchasing the functional beverages was their sensory acceptance, even if the consumers were informed of their potential health benefits.

Ultrasound and deep eutectic solvents: An efficient combination to tune the mechanism of steviol glycosides extraction

Ultrasound-assisted extraction is widely recognized as an eco-friendly technique due to low solvent consumption and time extraction as well as enhanced extraction efficiency with respect to conventional methods. Nevertheless, it would be convenient to avoid the usually used organic solvents to reduce the environment pollution. In this regard, Deep Eutectic Solvents (DES) represent nowadays a green and sustainable alternative for the extraction of bioactive compounds from natural sources. In this study, an efficient extraction of stevioside and rebaudioside A from Stevia rebaudiana coupling ultrasound with DES was developed. A solvent screening was performed using the predictive approach COnductor-like Screening MOdel for Real Solvent (COSMO-RS). The effect of three independent variables, namely % of water, temperature, and sonication amplitude, were investigated by the response surface methodology (RSM). Comparing ultrasound-assisted extraction (UAE) with conventional extraction, it has been demonstrated that the amount of steviol glycosides through UAE is almost three times higher than that obtained by the conventional method. Possible physicochemical factors involved in the UAE mechanism were discussed.

Effect of stevia on the gut microbiota and glucose tolerance in a murine model of diet-induced obesity

Artificial sweeteners have been shown to induce glucose intolerance by altering the gut microbiota; however, little is known about the effect of stevia. Here, we investigate whether stevia supplementation induces glucose intolerance by altering the gut microbiota in mice, hypothesizing that stevia would correct high fat diet-induced glucose intolerance and alter the gut microbiota. Mice were split into four treatment groups: low fat, high fat, high fat + saccharin and high fat + stevia. After 10 weeks of treatment, mice consuming a high fat diet (60% kcal from fat) developed glucose intolerance and gained more weight than mice consuming a low fat diet. Stevia supplementation did not impact body weight or glucose intolerance. Differences in species richness and relative abundances of several phyla were observed in low fat groups compared to high fat, stevia and saccharin. We identified two operational taxonomic groups that contributed to differences in beta-diversity between the stevia and saccharin groups: Lactococcus and Akkermansia in females and Lactococcus in males. Our results demonstrate that stevia does not rescue high fat diet-induced changes in glucose tolerance or the microbiota, and that stevia results in similar alterations to the gut microbiota as saccharin when administered in concordance with a high fat diet.

Health-Promoting Compounds in Stevia: The Effect of Mycorrhizal Symbiosis, Phosphorus Supply and Harvest Time

This work aimed to establish the synergic role of arbuscular mycorrhizal fungi (AMF) symbiosis, phosphorus (P) fertilization and harvest time on the contents of stevia secondary metabolites. Consequently, steviol glycosides (SVglys) concentration and profile, total phenols and flavonoids as well as antioxidant assays, have been assessed in inoculated and no-inoculated plants, grown with or without P supply and collected at different growth stages(69, 89 and 123 days after transplanting).The obtained results suggest that the synthesis of stevia secondary metabolites is induced and/or modulated by all the investigated variability factors. In particular, AMF symbiosis promoted total SVglys content and positively influenced the concentration of some minor compounds (steviolbioside, dulcoside A and rebaudioside B), indicating a clear effect of mycorrhizal inoculation on SVglys biosynthetic pathway. Interestingly, only the mycorrhizal plants were able to synthesize rebaudioside B. In addition, P supply provided the highest levels of total phenols and flavonoids at leaf level, together with the maximum in vitro antioxidant activities (FRAP and ORAC). Finally, the harvest time carried out during the full vegetative phase enhanced the entire composition of the phytocomplex (steviolbioside, dulcoside A, stevioside, rebaudioside A, B, C. total phenols and flavonoids). Moreover, polyphenols and SVglys appeared to be the main contributors to the in vitro antioxidant capacity, while only total phenols mostly contributed to the cellular antioxidant activity (CAA). These findings provide original information about the role played by AMF in association with P supply, in modulating the accumulation of bioactive compounds during stevia growth. At the cultivation level, the control of these preharvest factors, together with the most appropriate harvest time, can be used as tools for improving the nutraceutical value of raw material, with particular attention to its exploitation as functional ingredient for food and dietary supplements and cosmetics.

Greenhouse evaluation of branching, leaf yield and biochemical compositions of Stevia rebaudiana Bertoni to decapitation and foliar application of abscisic acid and fluridone

Stevia is a herbaceous plant containing non-sugar sweeteners that could be regarded as a successor to sugar for diabetics. However, there are some problems with the cultivation of stevia, especially in the greenhouse, including unbranching and low sweetening agents. To overcome this issue, an experiment was designed to increase not only the branching and leaf production but also the sweetness. Therefore, a novel strategy using abscisic acid (0, 50, 100, 150 μM), its inhibitor, i.e. fluridone (0, 50, 100, 150 μM) and decapitation of plant apical meristems was applied. Results showed that when stevia was decapitated, dormant buds responded to the application of abscisic acid and fluridone. Under these conditions, axillary buds were developed to branches. As well leaf, total dry weight, soluble sugars and steviol glycosides (SGs) were significantly increased. In addition, the interaction of abscisic acid (50 and 100 μM) and fluridone (50 μM) had the highest positive effects on plant growth and steviol glycosides production rather than their sole applications. Results also indicated that decapitation removed a terminal dominance over a limited period of time and the terminal dominance was re-established with the growth of the terminal branches, whereas the influence of 50 µM fluridone on stevia was long term and the number of shoots was greater. Since stevia is a costly sweetener, the results of this study could be used in greenhouses, where the cultivation of stevia seems to be reasonable in terms of economic aspects.

Photosynthetic performance and stevioside concentration are improved by the arbuscular mycorrhizal symbiosis in Stevia rebaudiana under different phosphate concentrations

In plants, phosphorus (P) uptake occurs via arbuscular mycorrhizal (AM) symbiosis and through plant roots. The phosphate concentration is known to affect colonization by AM fungi, and the effect depends on the plant species. Stevia rebaudiana plants are valuable sources of sweetener compounds called steviol glycosides (SGs), and the principal components of SGs are stevioside and rebaudioside A. However, a detailed analysis describing the effect of the phosphate concentration on the colonization of AM fungi in the roots and the relationship of these factors to the accumulation of SGs and photochemical performance has not been performed; such an analysis was the aim of this study. The results indicated that low phosphate concentrations (20 and 200 µM KH2PO4) induced a high percentage of colonization by Rhizophagus irregularis in the roots of S. rebaudiana, while high phosphate concentrations (500 and 1,000 µM KH2PO4) reduced colonization. The morphology of the colonization structure is a typical Arum-type mycorrhiza, and a mycorrhiza-specific phosphate transporter was identified. Colonization with low phosphate concentrations improved plant growth, chlorophyll and carotenoid concentration, and photochemical performance. The transcription of the genes that encode kaurene oxidase and glucosyltransferase (UGT74G1) was upregulated in colonized plants at 200 µM KH2PO4, which was consistent with the observed patterns of stevioside accumulation. In contrast, at 200 µM KH2PO4, the transcription of UGT76G1 and the accumulation of rebaudioside A were higher in noncolonized plants than in colonized plants. These results indicate that a low phosphate concentration improves mycorrhizal colonization and modulates the stevioside and rebaudioside A concentration by regulating the transcription of the genes that encode kaurene oxidase and glucosyltransferases, which are involved in stevioside and rebaudioside A synthesis in S. rebaudiana.

Bioconversion of Stevioside to Rebaudioside E Using Glycosyltransferase UGTSL2

Rebaudioside E, one of the minor components of steviol glycosides, was first isolated and identified from Stevia rebaudiana in 1977. It is a high-intensity sweetener that tastes about 150-200 times sweeter than sucrose and is also a precursor for biosynthesis of rebaudioside D and rebaudioside M, the next-generation Stevia sweeteners. In this work, new unknown steviol glycosides were enzymatically synthesized from stevioside by coupling UDP-glucosyltransferase UGTSL2 from Solanum lycopersicum and sucrose synthase StSUS1 from Solanum tuberosum. Rebaudioside E was speculated to be the main product of glucosylation of the Glc(β1→C-19) residue of stevioside along with the formation of a (β1→2) linkage based on the analysis of the regioselectivity and stereoselectivity of UGTSL2, and verified afterwards by LC-MS/MS with standard. In a 20-ml bioconversion reaction of 20 g/l stevioside by UGTSL2 and StSUS1, 15.92 g/l rebaudioside E was produced for 24 h.

Prophylactic effect of aquatic extract of stevia on acetic acid induced-ulcerative colitis in male rats: a possible role of Nrf2 and PPARγ

Objectives Ulcerative colitis (UC) is a non-specific intestinal inflammatory disease. Several studies demonstrated that inflammation and oxidative stress play significant role in the pathogenesis of this disease. This study aimed to determine the protective effect and possible mechanism by which stevia affects the course of experimentally induced colitis. Methods Male rats were received stevia 20, 40, 80 mg/kg/day before induction of colitis by intra-rectal administration of 2 mL of 4% acetic acid, AA. Macroscopic and histopathological examination of the colon were done. Colonic content of catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH), myeloperoxidase (MPO) and thiobarbituric acid reactive substances (TBARS) activities and serum levels of interleukin (IL)1- β and tumor necrosis factor (TNF)-α were assessed. Real time-PCR (RT-PCR) was done to determine the expression of NF-κB, Nrf2 and PPARγ genes. Spontaneous contraction and effects of increasing concentrations of acetylcholine and stevia have been studied on the isolated colonic segments. Results Stevia ameliorated colitis not only histopathologically but also it decreased the level of TNF-α, IL-1β, TBARS, MPO and the expression of NF-κB which were significantly increased in the AA group. The concentration of GSH, SOD, CAT and expression of Nrf2 and PPARγ were significantly increased with stevia. Moreover, stevia showed a relaxant effect on the colonic contractility which was increased in AA group. These all effects of stevia were more prominent with its highest dose. Conclusion Our results explored that, stevia acts protectively against UC by its anti-inflammatory and antioxidant properties which mediated by up-regulation of Nrf2 and PPARγ with downregulation of NF-κB. We suggest that stevia has the potential for treatment of chronic inflammatory diseases, such as UC.

Sugar Reduction in Dairy Food: An Overview with Flavoured Milk as an Example

Owing to the public health concern associated with the consumption of added sugar, the World Health Organization recommends cutting down sugar in processed foods. Furthermore, due to the growing concern of increased calorie intake from added sugar in sweetened dairy foods, the present review provides an overview of different types and functions of sugar, various sugar reduction strategies, and current trends in the use of sweeteners for sugar reduction in dairy food, taking flavoured milk as a central theme where possible to explore the aforementioned aspects. The strength and uniqueness of this review are that it brings together all the information on the available types of sugar and sugar reduction strategies and explores the current trends that could be applied for reducing sugar in dairy foods without much impact on consumer acceptance. Among different strategies for sugar reduction, the use of natural non-nutritive sweeteners (NNSs), has received much attention due to consumer demand for natural ingredients. Sweetness imparted by sugar can be replaced by natural NNSs, however, sugar provides more than just sweetness to flavoured milk. Sugar reduction involves multiple technical challenges to maintain the sensory properties of the product, as well as to maintain consumer acceptance. Because no single sugar has a sensory profile that matches sucrose, the use of two or more natural NNSs could be an option for food industries to reduce sugar using a holistic approach rather than a single sugar reduction strategy. Therefore, achieving even a small sugar reduction can significantly improve the diet and health of an individual.

Rapid and Economic Determination of 13 Steviol Glycosides in Market-Available Food, Dietary Supplements, and Ingredients: Single-Laboratory Validation of an HPLC Method

Steviol glycosides, obtained from leaves of Stevia rebaudiana Bertoni (stevia) or produced via bioconversion and biosynthesis, are diterpenes used by the food/dietary supplement industry as zero-calorie sweeteners derived from natural sources. JECFA 2017 is the most updated international standardized method but it runs for 80 min per sample with suboptimal separations on several critical pairs for its high-performance liquid chromatography-ultraviolet (HPLC-UV) determination. We developed and validated a rapid and economic HPLC-UV method using the superficially porous particle column to determine 13 steviol glycosides (stevioside, dulcoside A, rubusoside, steviobioside, and rebaudioside A-F, I, M, and N). Baseline separation with a minimum resolution of 1.5 for 13 steviol glycosides was achieved within only 14 min of separation time. The hydrocarbon stationary phase with additional steric interactions from the isobutyl side chains on the C18 ligand was shown to be an important contributor to chromatographic selectivity of several critical pairs of steviol glycosides. The method was proven to perform suitably on columns from three different manufacturers and two HPLC instruments. The method was further used to perform a single-lab validation on eight food and supplement products with multiple matrices. The results ranged from 0.05% w/w rebaudioside A for a hard-candy finished product to 100.8% w/w purity for a rebaudioside M raw ingredient. The validation test results showed that the method was linear, suitable, specific, accurate, and precise. The method is therefore suitable to be considered as a new industrial standard for quality control analysis for stevia products.

ISSR markers to assess genetic diversity of cultivated populations from artificial selection of Stevia rebaudiana (Bert.) Bertoni

Artificial selection related with important agronomic characteristics of Stevia rebaudiana may cause genetic divergence and formation of genetically structured populations with genetic uniformity or diversity within cultivars. Current study employed inter simple sequence repeats of DNA (ISSR markers) to assess genetic diversity within and among a single cultivated population maintained through sexual propagation (SR1) and four cultivated populations generated by artificial selection and maintained by vegetative propagation (SR2-SR5). Highest polymorphism rate was reported in SR1 (89.24%), whilst the lowest rate of polymorphism occurred in SR2 (60.13%). ISSR markers revealed that selection of plants with traits of vegetative-propagated interest may lead towards the generation of genetically more uniform DNA-level populations, while plants maintained by sexual propagation have high genetic variability. High estimated genetic divergence level indicated that the five areas of stevia form genetically structured populations. SR2 and SR4 are constituted by plants more homogeneous at DNA level for the selected characteristics than plants of SR3 and SR5 populations. Predominant and homogeneous genotypes selected at SR2 and SR4 areas could be valuable for tracing strategies to obtain stevia plants with the desirable agronomic characteristics through crosses between contrasting individuals in future breeding programs.

Structural dependence of antidiabetic effect of steviol glycosides and their metabolites on streptozotocin-induced diabetic mice

BACKGROUND

Stevia has been proposed as a potential antidiabetic sweetener, mainly based on inconsistent results from stevioside or the plant extract, yet lacking relative experimental evidence from individual steviol glycosides (SGs) and their metabolites.

RESULTS

The results systematically revealed that the typical SGs and their final metabolite (steviol) presented an antidiabetic effect on streptozotocin (STZ) diabetic mice in all assayed antidiabetic aspects. In general, the performance strength of the samples followed the sequence steviol > steviol glucosyl ester > steviolbioside > rubusoside > stevioside > rebaudioside A, which is opposite to their sweetness strength order, and generally in accordance with the glucosyl group numbers in their molecules. This may imply that the antidiabetic effect of the SGs might be achieved through steviol, which presented antidiabetic performance similar to that of metformin with a dose of 1/20 that of metformin. Moreover, the ¹⁸ F-fluorodeoxyglucose traced micro-PET experiment revealed that stevioside and steviol could increase the uptake of glucose in the myocardium and brain of the diabetic mice within 60 min, and decrease the accumulation of glucose in the liver and kidney.

CONCLUSIONS

The SGs and steviol presented an antidiabetic effect on STZ diabetic mice in all assayed aspects, with an induction time to start the effect of the SGs. Stevioside and steviol could increase uptake of glucose in the myocardium and brain of the diabetic mice, and decrease accumulation of glucose in the liver and kidney. The performance strength of the SGs is generally in accordance with glucosyl group numbers in their molecules.

Challenges in confectionery industry: Development and storage stability of innovative white tea-based candies

The aim of this study was the development of innovative candies formulations accordant with the present trends in the confectionery industry. Steviol glycosides, sorbitol, and agave syrup were used as sucrose alternatives, while agar and pectin were included instead of gelatin for the formulation of vegan candies. Additionally, white tea extract was used as a candy base and source of bioactive compounds. Bioactive quality (total phenolic content, antioxidant capacity, epigallocatechin gallate, and caffeine content) and physicochemical (dry matter, springiness, hardness, color) parameters of candies were monitored during 4 months of storage at 4 and 22 °C. Pectin candies with the highest content of dry matter (79.8%) showed the longest shelf life, while those with agar (52.0% and 66.2%) were the most susceptible to spoilage. Candies prepared with agar were less hard (0.4 and 0.6 N) and with less elastic texture (1.5 and 3.4 mm) and showed the highest stability of physicochemical parameters during storage, while those with pectin were also less hard (0.5 N) but with more elastic texture (10.7 mm) than gelatin candies (3.6 and 4.4 mm; 2.4 and 4.1 N). Although gelatin samples were characterized with the greatest bioactive quality parameters immediately after production, they showed a higher instability of the same parameters during storage compared to the agar and pectin candies. PRACTICAL APPLICATION: According to the consumers' demands for healthier confectionery products, formulations of candies with sucrose alternatives, non-animal hydrocolloids, and natural bioactive compounds were developed. Giving a deeper insight into their physicochemical and bioactive properties, this paper could contribute to confectionery industry in development and optimization of formulations in order to obtain candies with desirable and attractive properties.

Chemical, biological and in silico assessment of Ocimum viride essential oil

AIMS

Ocimum viride Willd. (family: Lamiaceae) is a member of the genus Ocimum, an aromatic annual and perennial herb with numerous culinary, horticultural and ethno-medicinal benefits. This study aims to explore the chemical properties of leaf essential oil (EO) from Ocimum viride and to evaluate its antimicrobial and anticancer potential.

MAIN METHODS

Characterization of essential oil was done by GCMS, antimicrobial by agar well diffusion methods, in vitro cytotoxicity evaluation by MTT assay, cell death analysis was done by DNA fragmentation, cell cycle analysis, nuclear morphology analysis and molecular docking studies were also conducted.

KEY FINDINGS

Essential oil from aerial parts (leaf) of Ocimum viride revealed high content of oxygenated monoterpenes, notably thymol (~50%) and γ-terpinene (~18%). Further, antibacterial analysis showed that among all the evaluated bacterial species EO showed highest sensitivity against the Bacillus subtilis and was also found most effective against HT-29 colon cancer cell line with IC50 value of ~0.034 ± 0.001μL/mL. Mechanistic studies revealed that EO inhibits the growth of HT-29 colon cancer cells probably through induction of irreparable DNA damage leading to subsequent cell death in apoptotic manner. Molecular docking analysis also supports the in vitro studies conducted by indicating the interaction of thymol with Sec A protein of Bacillus subtilis cell wall as well as with Beclin protein responsible for apoptotic corpse clearance.

SIGNIFICANCE

Taken together, our results indicate that EO possesses potent antimicrobial and anticancer properties, and may find applications as effective antibacterial and in cancer therapeutics.

An aqueous extract of Stevia rebaudiana variety Morita II prevents liver damage in a rat model of cirrhosis that mimics the human disease

INTRODUCTION AND AIM

Stevia has exhibited antioxidant, antihyperglycemic, antihypertensive and anti-inflammatory properties in several in vivo and in vitro models. The objective of this study was to investigate the ability of an aqueous extract of stevia (AES) to prevent experimental cirrhosis in rats and to explore its mechanism of action.

MATERIALS AND METHODS

Liver cirrhosis was induced by administering carbon tetrachloride (CCl₄) (400mg/kg by i.p. injection 3 times a week for 12 weeks); AES was administered (100mg/kg by gavage daily) during the CCl₄ treatment. Fibrosis was evaluated with histological, biochemical and molecular approaches, and liver damage was assessed with standardized procedures. The profibrotic pathways were analyzed by western blotting, qRT-PCR and immunohistochemistry.

RESULTS AND CONCLUSIONS

Chronic CCl₄ administration increased nuclear factor kappa B (NF-κB) and proinflammatory cytokine production as well as oxidative parameters such as lipid peroxidation and 4-hydroxynonenal levels, whereas GSH and nuclear factor-E2-related factor 2 (Nrf2) levels were decreased. CCl₄ induced profibrogenic mediator expression, hepatic stellate cell (HSC) activation and, consequently, extracellular matrix production. AES exhibited antioxidant, anti-inflammatory and antifibrotic properties, probably because of its capacity to induce Nrf2 expression, reduce NF-κB expression and block several profibrogenic signaling pathways, subsequently inhibiting HSC activation and preventing fibrosis induced by chronic CCl₄ administration.

Efficient Biocatalytic Preparation of Rebaudioside KA: Highly Selective Glycosylation Coupled with UDPG Regeneration

Rebaudioside KA is a diterpene natural sweetener isolated in a trace amount from the leaves of Stevia rebaudiana. Selective glycosylation of rubusoside, a natural product abundantly presented in various plants, is a feasible approach for the biosynthesis of rebaudioside KA. In this study, bacterial glycosyltransferase OleD was identified to selectively transfer glucose from UDPG to 2′-hydroxyl group with a β-1,2 linkage at 19-COO-β-D-glucosyl moiety of rubusoside for the biosynthesis of rebaudioside KA. To eliminate the use of UDPG and improve the productivity, a UDPG regeneration system was constructed as an engineered Escherichia coli strain to couple with the glycosyltransferase. Finally, rubusoside at 22.5 g/L (35.0 mM) was completely converted to rebaudioside KA by the whole cells without exogenous addition of UDPG. This study provides an efficient and scalable method for highly selective biosynthesis of rebaudioside KA.

Effect of Sugar Substitution with Steviol Glycosides on Sensory Quality and Physicochemical Composition of Low-Sugar Apple Preserves

The purpose of this study was to determine the sensory profile and consumer response, as well as physicochemical properties of low-sugar apple preserves (with or without gelling agent or acidity regulator), in which sugar was replaced with varying amounts of steviol glycosides (SGs). According to the analytical assessment and consumer tests’ results, the reduction of sugar by SGs use in the apple preserves without food additives was possible at a substitution level of 10% (0–0.05 g/100 g). Consumers’ degree of liking for sugar substitution with SGs was high, up to 40% (0.20 g/100 g) in the preserves, with the use of pectin and citric acid. Higher levels of sugar substitution with the SGs resulted in flavor and odor deterioration, such as a metallic flavor and odor, a bitter taste, an astringent oral sensation, and a sharp odor. The use of food additives (pectin, citric acid) in apple preserves, allowed the SGs substitution level to be increased. The preserves (Experiment I, II, III) with higher sensory ratings were subjected to physicochemical tests. Physical and chemical analysis of low-sugar products with sucrose substitution by SGs at the level of 10%, 30%, 40% showed their good technological quality. The results demonstrated the possibility of substituting sugar with steviol glycosides to produce energy-reduced apple preserves, with acceptable sensory quality and good physicochemical properties.

The SrWRKY71 transcription factor negatively regulates SrUGT76G1 expression in Stevia rebaudiana

SrUGT76G1 is vital for the biosynthesis of rebaudioside A, D and M in Stevia rebaudiana Bertoni; however, its transcriptional regulatory mechanism remains unknown. In this study, the 2050-bp promoter region of SrUGT76G1 was isolated by the TAIL-PCR method, and sequence analysis revealed the presence of several W-box cis-elements, which are the recognition motifs of WRKY transcription factors. Furthermore, SrWRKY71, characterized by a typical WRKY domain and a C2H2 zinc finger-like motif, was identified as a putative transcriptional regulator of SrUGT76G1. The transcript of SrWRKY71 predominantly accumulated in leaves and was present at a lower level in stems, roots and flowers. The SrWRKY71-GFP fusion protein was specifically localized to the nucleus in tobacco epidermal cells. In addition, the N and C terminal regions of SrWRKY71 contributed to its transactivation activity. Y1H and EMSA assays validated that SrWRKY71 binds directly to W-box1 and W-box2 in the proximal promoter region of SrUGT76G1. Moreover, SrWRKY71 represses the expression level of SrUGT76G1 in both tobacco leaves and stevia callus. Taken together, the data in this study represent the first identification of an essential upstream transcription factor of SrUGT76G1 and provides new insight into the regulatory network of steviol glycoside biosynthesis in Stevia rebaudiana.

Stevia vs. Sucrose: Influence on the Phytochemical Content of a Citrus-Maqui Beverage-A Shelf Life Study

The consumption of sugar-sweetened beverages has been related with the risk of cardiovascular diseases and other pathophysiological situations, such as obesity or diabetes mellitus. Given the increasing awareness on this fact, food industries are developing new products to reduce the amount of added sugar in development of food products development. Accordingly, in the present work, new functional beverages, constituting a dietary source of bioactive phenolics and supplemented with stevia or sucrose, were designed in order to study the influence of the sweetener during processing and shelf-life. This study is of critical for the informed selection of the sweetener based on its effect on the final phytochemical profile of beverages, especially taking into consideration that there are no previous studies on Stevia rebaudiana. Physicochemical features and phytochemical composition, as well as stability of the different beverages concerning these parameters, were evaluated for 90 days during storage under different conditions (refrigeration (4 °C) and room temperature (25 °C) under light or darkness conditions). Physicochemical parameters (pH, titratable acidity, total soluble solids, and color) did not display statistically significant differences between beverages. Storage temperature was the greatest determinant affecting the stability of all the analyzed bioactive compounds (vitamin C, anthocyanins, and flavanones). The main difference between sweeteners was observed in flavanones, which exhibited a higher loss during storage under day light conditions when stevia was added instead of sucrose. In addition, the juices’ colors were rather stable, keeping a reddish coloration and natural appearance throughout the shelf life. Hence, stevia could be considered as an alternative sweetener by the beverage industry.

Interaction of Organic Anion Transporter 3-Mediated Uptake of Steviol Acyl Glucuronide, a Major Metabolite of Rebaudioside A, with Selected Drugs

Organic anion transporter 3 (OAT3) plays a critical role in the renal excretion of many xenobiotics. Because steviol acyl glucuronide (SVAG), an OAT3 substrate, is the major circulating metabolite after oral ingestion of steviol glycosides and is excreted into the urine, inhibition of OAT3 activity may alter pharmacokinetic profiles of SVAG. The present study showed that drugs such as probenecid and glimepiride displayed potent inhibition toward the OAT3-mediated SVAG transport, with IC₅₀ values of 4.9 and 0.8 μM, respectively. No species differences were observed. Probenecid and glimepiride could significantly elevate plasma concentrations of SVAG after oral administration of rebaudioside A, with significant increases in plasma maximum (C_max) and area under the plasma time-concentration curve values. The inhibitory effect on the OAT3-mediated SVAG transport exemplified a unique case between drugs and the metabolite of a food additive. Our data suggest that caution should be exercised when giving steviol glycoside products to human subjects with compromised renal function.

Development of Bacillus safensis-based liquid bioformulation to augment growth, stevioside content, and nutrient uptake in Stevia rebaudiana

The application of chemical fertilizers to enhance crop production is a major concern due to associated environmental pollution and health hazards. Hence, there is an urgent need to develop an eco-friendly solution to improve crop production and promote sustainable agriculture simultaneously. Stevia rebaudiana is an important medicinal crop being substitute for sugar, superior flavor outline, extensive medicinal properties, and also of agronomic interest. In the present study, bacterium STJP isolated from the rhizospheric soil of S. rebaudiana and identified as Bacillus safensis on the basis of 16S rRNA gene sequencing, showed good amount of zinc (4.4 mg/L) and potassium (5.4 mg/L) solubilization. Paneer-whey (a dairy waste) based bioformulation (P-WBF) was developed utilizing isolate B. safensis STJP (accession number NAIMCC TB-2833) and inspected for the quality and ability to enhance the growth, nutrients uptake, and stevioside content in S. rebaudiana. The application of P-WBF displayed a significantly higher concentration (153.12%) of stevioside in S. rebaudiana as compared to control. P-WBF treated Stevia plants showed significantly higher fresh and dry weight as well (as compared to control). Further, enhancement of phosphorous, nitrogen, potassium, and zinc uptake in plant tissue was also recorded by application of P-WBF. This study suggests the use of P-WBF based biofertilizer using B. safensis STJP to increase stevioside content in Stevia plant by a nutrient(s) linked mechanism. This novel approach can also be beneficial for utilization of a dairy waste in preparation of bioformulation and, for enhancement of crop yield by an ecofriendly manner leading to sustainable agriculture.

Stevia residue extract alone and combination with allopurinol attenuate hyperuricemia in fructose-PO-induced hyperuricemic mice

The current project was designed to utilize flavonoids and chlorogenic acids enriched stevia residue extract (STVRE) against hyperuricemia (HU). The in vitro results showed that STVRE potently and synergistically inhibits Xanthine oxidase (XO) with allopurinol. The AFM results predicted that STVRE compounds bind with XO and alter its structure which further prevents the entrance of substrate with XO. These in vitro results were further confirmed in fructose-PO-induced hyperuricemic mice model. The results showed that supplementation of STVRE with allopurinol significantly attenuated HU, oxidative stress, and inflammation caused by UA via inhibiting the production of uric acid and lowering cyclooxygenase-2, tumor necrosis factor-alpha, prostaglandin E2, interleukin-6, and interleukin 1-beta levels in serum and renal tissues. Moreover, STVRE and allopurinol treatment attenuated, tubular dilation, infiltration of inflammatory cells, improved structure disorder of podocyte, and foot process fusion, and decreased glomerular basement membrane thickness. These findings suggested that STVRE can be used as an antihyperuricemic agent along with allopurinol. PRACTICAL APPLICATIONS: The results of present study showed that STVRE has a beneficial effect against fructose-PO-induced hyperuricemia by decreasing uric acid level, xanthine oxidase activity, improving oxidative stress and inflammation. These findings suggested that by-product of stevia (STVRE) enriched with polyphenolic compounds can be used as a functional ingredient against hyperuricemia and related diseases.

Review of the scientific evidence and technical opinion on noncaloric sweetener consumption in gastrointestinal diseases

The present review of noncaloric sweeteners (NCSs) by the Asociación Mexicana de Gastroenterología was carried out to analyze and answer some of the most frequent questions and concerns about NCS consumption in patients with gastrointestinal disorders, through a thorough review of the medical literature. A group of gastroenterologists and experts on nutrition, toxicology, microbiology, and endocrinology reviewed and analyzed the published literature on the topic. The working group formulated conclusions, based on the scientific evidence published, to give an opinion with respect to NCS ingestion. Current evidence does not confirm the carcinogenic potential of NCSs. However, the studies analyzed showed that saccharin could have a proinflammatory effect and that polyols can cause gastrointestinal symptoms and manifestations, depending on the dose and type of compound. The ingestion of xylitol, erythritol, sucralose, aspartame, acesulfame K, and saccharin could increase the secretion of the gastrointestinal hormones that regulate intestinal motility, and stevia and its derivatives could have a favorable effect on the percentage of liver fat. Caution should be taken in recommending aspartame consumption in patients with chronic liver disease because it reduces the ratio of branched-chain amino acids to aromatic amino acids. In addition, NCS ingestion could modify the composition of the intestinal microbiota, having an effect on gastrointestinal symptoms and manifestations. It is important to continue conducting causality studies on humans to be able to establish recommendations on NSC consumption.

Whey protein sweetened with Stevia rebaudiana Bertoni (Bert.) increases mitochondrial biogenesis markers in the skeletal muscle of resistance-trained rats

Background

A combination of resistance training and whey protein supplementation is a common practice among athletes and recreational exercisers to enhance muscle growth and strength. Although their safety as food additives is controversial, artificial sweeteners are present in whey protein supplements. Thus, natural sweeteners extracted from the leaves of Stevia rebaudiana are a potential alternative, due to their safety and health benefits. Here, we investigated the effects of whey protein sweetened with S. rebaudiana on physical performance and mitochondrial biogenesis markers in the skeletal muscle of resistance-trained rats.

Methods

Forty male Wistar rats were distributed into four groups: sedentary rats, trained rats, trained rats receiving whey protein and trained rats receiving whey protein sweetened with S. rebaudiana leaf extracts. Resistance training was performed by climbing a ladder 5 days per week, during 8-weeks. The training sessions consisted of four climbs carrying a load of 50, 75, 90, and 100% of the maximum load-carrying capacity which we determined before by performing a maximum load-carrying test for each animal. After this period, we collected plasma and tissues samples to evaluate biochemical, histological and molecular (western blot) parameters in these rats.

Results

Dietary supplementation with whey protein sweetened with S. rebaudiana significantly enhanced the maximum load-carrying capacity of resistance-trained rats, compared with non-sweetened whey protein supplementation. This enhanced physical performance was accompanied by an increase in the weight of the gastrocnemius and soleus muscle pads. Although the muscle pad of the biceps brachii was not altered, we observed a significant increase in PGC-1α expression, which was followed by a similar pattern in TFAM protein expression, two important mitochondrial biogenesis markers. In addition, a higher level of AMPK phosphorylation was observed in these resistance-trained rats. Finally, supplementation with whey protein sweetened with S. rebaudiana also induced a significant decrease in retroperitoneal adipocyte diameter and an increase in the weight of brown adipose tissue pads in resistance-trained rats.

Conclusion

The addition of Stevia rebaudiana leaf extracts to whey protein appears to be a potential strategy for those who want to increase muscular mass and strength and also improve mitochondrial function. This strategy may be useful for both athletes and patients with metabolic disorders, such as obesity and type 2 diabetes.

Simple and Efficient Green Extraction of Steviol Glycosides from Stevia rebaudiana Leaves

The food industry has currently shown great interest in alternative sweeteners to sugars with the aim of producing healthier products. In light of this, steviol glycosides are natural low-caloric sweeteners present in Stevia rebaudiana, which have additionally been described as bioactive components with potential therapeutic properties. In this work, a green method for the extraction of steviol glycosides from stevia leaves was optimized by applying a factorial screening design of five variables (time, temperature, agitation, grinding, and sample-solvent ratio) and the subsequent response surface design of Box-Behnken. The optimized extraction method allows for the recovery of stevia sweeteners in a simple and efficient manner by using tap water as the extractant, without the application of an auxiliary energy source to reduce costs, thus representing an interesting strategy for their industrial-scale production.

Stevia rebaudiana Bertoni bioactive effects: From in vivo to clinical trials towards future therapeutic approaches

Stevia rebaudiana Bertoni, a plant from South America and indigenous of Paraguay, has shown several biological effects and healthy properties, although it is especially used in South America and some Asiatic regions. In addition, it is a natural sweetener, almost 300 times sweeter than sucrose, being attributed to its phytoconstituents prominent antioxidant, antimicrobial, antidiabetic (antihyperglycemic, insulinotropic, and glucagonostatic), antiplatelet, anticariogenic, and antitumor effects. In this sense, this work aims to provide an extensive overview on the historical practices of stevia and its effects in human health based on its chemical composition and applications for both food and pharmaceutical industries.

Nitrogen drives plant growth to the detriment of leaf sugar and steviol glycosides metabolisms in Stevia (Stevia rebaudiana Bertoni)

Steviol glycosides (SGs) in Stevia (Stevia rebaudiana Bertoni) leaves are important due to their high sweetness and low calorific value. The yield of SGs is dependent on fertilization regimes, but the relationship between nitrogen (N) administration and SGs synthesis is still unclear. In this study, we investigate the effects of N rates on SGs production through hydroponic and plot experiments. The SGs yield was not significantly changed by N fertilization, but leaf SGs concentrations were significantly reduced due to the "dilution effect". Additionally, N addition decreased leaf carbon (C)/N ratio and soluble sugar concentration, accompanied with the inhibited phosphoenolpyruvate carboxylase and L-phenylalanine ammonia_lyase activities. A significant positive correlation between leaf SGs concentrations, C/N ratio and soluble sugar concentration was observed. Overall, we suggest that N-driven Stevia growth negatively affects SGs concentrations. The leaf C/N ratio and soluble sugar changes indicated the occurrence of metabolic reprogramming.

The effect of the elicitors on the steviol glycosides biosynthesis pathway in Stevia rebaudiana

Stevia rebaudiana Bertoni has been promoted for having sweet leaves as well as pharmaceutical and industrial properties. The sweet taste of Stevia leaves is due to the presence of steviol glycosides (a group of diterpene glycosides) found in a small number of plants. In the biosynthetic pathway of steviol glycosides (SGs), 15 enzymes that express the genes are associated with these enzymes under the influence of the elicitors. Due to the individuality of the stevia and few studies on the biosynthesis pathway of SGs, this paper attempted to investigate the effects of some of the elicitors, including methyl jasmonate (MeJA), salicylic acid (SA), auxins (Aux), cytokinins (CKs), gibberellins (GAs) and its inhibitors including paclobutrazol (BPZ) and chloroquate (CCC)), on the responsible genes for the biosynthesis of SGs. Some of these elicitors, including MeJA, SA and GA have great potential in increasing secondary metabolites. Moreover, the biosynthetic pathway of GAs and SGs are shared till ent-kaurenoic acid (ent-KA) biosynthesis, which raises the question of whether this hormone and its inhibitors are effective in the SGs biosynthesis.

Expression and characterization of a recombinant stevioside hydrolyzing β-glycosidase from Enterococcus casseliflavus

The demand for steviol glycosides, non-caloric sweet components of Stevia rebaudiana Bertoni (stevia) leaves, has increased considerably as a benefit to enhance human health. However, the supply has remained challenging due to limited production, with the lack of a specific steviol glycoside hydrolyzing enzyme. In this study, a novel β-glucosidase (EcBgl) from Enterococcus casseliflavus was cloned and expressed in Escherichia coli. An EcBgl consists of 721 amino acids corresponding to a molecular mass of 79.37 kDa. The EcBgl was purified to homogeneity, followed by enzyme characterization. The enzyme showed optimum pH and temperature at 6.0 and 37 °C, and exhibited the kinetic constants k_cat/K_m for pNPG and k_cat/K_m for stevioside of 8583 mM^-1s^-1 and 95.41 mM^-1s^-1, respectively. When compared to the stevioside hydrolyzing β-glycosidases previously reported, EcBgl was found to be the most efficient enzyme. EcBgl also rendered hydrolysis of the stevioside to produce rubusoside, a rare steviol glycoside with a pharmaceutical solubilizing property, by cleaving at the glucose moiety. In addition, the enzyme demonstrated substantial resistance against amygdalin, so it served as a potential enzyme in agricultural and pharmaceutical applications.

Five New Ent-Atisene Glycosides From Stevia rebaudiana

Five new ent-atisene diterpene glycosides (1-5) have been isolated from Stevia rebaudiana Bertoni. This adds to a list of only 2 new ent-atisene diterpene glycosides isolated previously from S. rebaudiana. Diterpene glycosides isolated from S. rebaudiana, such as the rebaudiosides, are typically associated with the ent-kaurene core and glycosylation at the C-13 and C-19 positions. Extensive application of nuclear magnetic resonance spectroscopy techniques (1H, 13C, 1D-TOCSY, COSY, HSQC-DEPT, HMBC, and ROESY) as well as high-resolution mass spectrometry demonstrated that the ent-atisenes 1 to 5 had glycosylation patterns identical to rebaudiosides J, N, O, K, and T, respectively. We have named these compounds stevatisene J, N, O, K, and T, respectively.

Overexpression of SrUGT76G1 in Stevia alters major steviol glycosides composition towards improved quality

Steviol glycosides (SGs) are extracted from Stevia leaves for use as a natural sweetener. Among SGs, stevioside is most abundant in leaf extracts followed by rebaudioside A (Reb A). However, Reb A is of particular interest because of its sweeter and more pleasant taste compared to stevioside. Therefore, the development of new Stevia varieties with a higher Reb A to stevioside ratio would be desirable for the production of higher quality natural sweeteners. Here, we generated transgenic Stevia plants overexpressing Stevia UDP-glycosyltransferase 76G1 (SrUGT76G1) that is known to convert stevioside to Reb A through 1,3-β-d-glucosylation in vitro. Interestingly, by overexpressing SrUGT76G1, the Reb A to stevioside ratio was drastically increased from 0.30 in wild-type (WT) plants up to 1.55 in transgenic lines without any significant changes in total SGs content. This was contributed by a concurrent increase in Reb A content and a decrease in stevioside content. Additionally, we were able to find an increase in the Reb C to dulcoside A ratio in transgenic lines. Using the glutathione S-transferase-tagged SrUGT76G1 recombinant protein for an in vitro glucosyltransferase assay, we further demonstrated that Reb C can be produced from the glucosylation of dulcoside A by SrUGT76G1. Transgenic Stevia plants having higher Reb A to stevioside ratio were visually indistinguishable from WT plants. Taken together, our results demonstrate that the overexpression of SrUGT76G1 in Stevia is an effective way to generate new Stevia varieties with higher proportion of the more preferred Reb A without compromising on plant development.