Influence of Extraction Methods on the Yield of Steviol Glycosides and Antioxidants in Stevia rebaudiana Extracts

Properties, extraction and purification technologies of Stevia rebaudiana steviol glycosides: A review

For health and safety reasons, the search for green, healthy, and low-calorie sweeteners with good taste has become the demand of many consumers. Furthermore, the need for sugar substitutes of natural origin has increased dramatically. In this review, we briefly discussed the safety and health benefits of stevia sweeteners and enumerated some examples of physiological functions of steviol glycosides (SGs), such as anti-inflammatory, anti-obesity, antihypertensive, anti-diabetes, and anticaries, citing various evidence related to their application in the food industry. The latest advances in emerging technologies for extracting and purifying SGs and the process variables and operational strategies were discussed. The impact of the extraction methods and their comparison against the conventional techniques have also been demonstrated. These technologies use minimal energy solvents and simplify subsequent purification stages, making viable alternatives suitable for a possible industrial application. Furthermore, we also elucidated the potential for advancing and applying the natural sweeteners SGs.

Integration of Antioxidant Activity Assays Data of Stevia Leaf Extracts: A Systematic Review and Meta-Analysis

Stevia rebaudiana Bertoni, a no-calorie natural sweetener, contains a plethora of polyphenols that exert antioxidant properties with potential medicinal significance. Due to the variety of functional groups, polyphenols exhibit varying solubility depending on the nature of the extraction solvents (water, organic, or their mixtures, defined further on as hydroalcoholic extracts). In the present study, we performed a systematic review, following PRISMA guidelines, and meta-analysis, synthesizing all available data from 45 articles encompassing 250 different studies. Our results showed that the total phenolic content (TPC) of hydroalcoholic and aqueous extracts presents higher values (64.77 and 63.73 mg GAE/g) compared to organic extracts (33.39). Total flavonoid content (TFC) was also higher in aqueous and hydroalcoholic extracts; meta-regression analysis revealed that outcomes in different measuring units (mg QE/g, mg CE/g, and mg RUE/g) do not present statistically significant differences and can be synthesized in meta-analysis. Using meta-regression analysis, we showed that outcomes from the chemical-based ABTS, FRAP, and ORAC antioxidant assays for the same extract type can be combined in meta-analysis because they do not differ statistically significantly. Meta-analysis of ABTS, FRAP, and ORAC assays outcomes revealed that the antioxidant activity profile of various extract types follows that of their phenolic and flavonoid content. Using regression meta-analysis, we also presented that outcomes from SOD, CAT, and POX enzymatic antioxidant assays are independent of the assay type (p-value = 0.905) and can be combined. Our study constitutes the first effort to quantitatively and statistically synthesize the research results of individual studies using all methods measuring the antioxidant activity of stevia leaf extracts. Our results, in light of evidence-based practice, uncover the need for a broadly accepted, unified, methodological strategy to perform antioxidant tests, and offer documentation that the use of ethanol:water 1:1 mixtures or pure water can more efficiently extract stevia antioxidant compounds.

In Vitro and In Silico Activities of E. radiata and E. cinerea as an Enhancer of Antibacterial, Antioxidant, and Anti-Inflammatory Agents

Eucalyptus, a therapeutic plant mentioned in the ancient Algerian pharmacopeia, specifically two species belonging to the Myrtaceae family, E. radiata and E. cinerea, were investigated in this study for their antibacterial, antioxidant, and anti-inflammatory properties. The study used aqueous extracts (AE) obtained from these plants, and the extraction yields were found to be different. The in vitro antibacterial activity was evaluated using a disc diffusion assay against three typical bacterial strains. The results showed that the two extracts were effective against all three strains. Both extracts displayed significant antioxidant activity compared to BHT. The anti-inflammatory impact was evaluated using a protein (BSA) inhibition denaturation test. The E. radiata extract was found to inhibit inflammation by 85% at a concentration of 250 µg/mL, significantly higher than the Aspirin. All phytoconstituents present good pharmacokinetic characteristics without toxicity except very slight toxicity of terpineol and cineol and a maximum binding energy of -7.53 kcal/mol for its anti-TyrRS activity in silico. The study suggests that the extracts and their primary phytochemicals could enhance the efficacy of antibiotics, antioxidants, and non-steroidal anti-inflammatory drugs (NSAIDs). As pharmaceutical engineering experts, we believe this research contributes to developing natural-based drugs with potential therapeutic benefits.

Optimization of ultrasound-assisted extraction method for phytochemical compounds and antioxidant activities of sour jujube extracts

Ultrasonic-assisted extraction is a rapid and effective extraction method that uses ultrasound energy and solvents to extract target compounds from various plant matrices. In this study, the ultrasonic-assisted extraction conditions of sour jujube were optimized. A five-level central composite design (CCD) with four variables was used to evaluate ultrasonic treatment variables influencing the total saponin content (TSC), total flavonoid content (TFC), and total phenolic content (TPC) extracted from sour jujube. The solvent concentration, extraction time, ultrasonic power, and solid-to-liquid (S/L) ratio were optimized using aqueous ethanol and methanol solutions as extraction solvents. A central composite design (CCD) was used for an in-depth study, and then the optimal value that could produce the maximum TPC, TFC, TSC, and four in vitro antioxidant activities (scavenging activity of hydroxyl free radicals, ferric-reducing antioxidant power (FRAP), phosphomolybdic acid reduction method, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity) was determined. Hydrogen peroxide-induced oxidative stress experiment confirmed that the Jujube extract could have an antioxidant role in vivo. The relationship between the contents of three compounds and the antioxidant activity in vitro and in vivo was further studied. The results showed that optimizing methanol and ethanol extraction process parameters could improve target components' extraction efficiency. Under the optimum conditions, the TFC and TPC yields of sour jujube by ethanol are better than methanol, while the yield of TSC by methanol is better than ethanol. In vivo data showed that Jujube extract protects against the adverse effects of oxidative stress and improves the life span of female and male Drosophila. This study provides a valuable reference for the full use of Ziziphus jujube, as well as a new direction in food development.

A Hybrid RSM-ANN-GA Approach on Optimization of Ultrasound-Assisted Extraction Conditions for Bioactive Component-Rich Stevia rebaudiana (Bertoni) Leaves Extract

Stevia rebaudiana (Bertoni) leaves consist of dietetically important diterpene steviol glycosides (SGs): stevioside (ST) and rebaudioside-A (Reb-A). ST and Reb-A are key sweetening compounds exhibiting a sweetening potential of 100 to 300 times more intense than that of table sucrose. Ultrasound-assisted extraction (UAE) of SGs was optimized by effective process optimization techniques, such as response surface methodology (RSM) and artificial neural network (ANN) modeling coupled with genetic algorithm (GA) as a function of ethanol concentration (X₁: 0–100%), sonication time (X₂: 10–54 min), and leaf–solvent ratio (X₃: 0.148–0.313 g·mL⁻¹). The maximum target responses were obtained at optimum UAE conditions of 75% (X₁), 43 min (X₂), and 0.28 g·mL⁻¹ (X₃). ANN-GA as a potential alternative indicated superiority to RSM. UAE as a green technology proved superior to conventional maceration extraction (CME) with reduced resource consumption. Moreover, UAE resulted in a higher total extract yield (TEY) and SGs including Reb-A and ST yields as compared to those that were obtained by CME with a marked reduction in resource consumption and CO₂ emission. The findings of the present study evidenced the significance of UAE as an ecofriendly extraction method for extracting SGs, and UAE scale-up could be employed for effectiveness on an industrial scale. These findings evidenced that the UAE is a high-efficiency extraction method with an improved statistical approach.

Infusions prepared with Stevia rebaudiana: application of a simplex centroid mixture design for the study of natural sweeteners and phenolic compounds

Three mixture designs were used to characterize herbal formulations for infusions prepared with cedron, boldo, and yerba mate in addition to stevia. This study aimed to investigate if the inclusion of stevia in infusions could affect the recovery of phenolic compounds with antioxidant activity. Infusions with higher phenolic content and higher antioxidant activity were obtained when yerba mate or boldo predominated in the infusion. The highest tannin content was found in mixtures containing yerba mate, boldo, and stevia, while the minimum tannin contents were found in some cedron infusions. The content of steviol glycosides increased as the proportion of stevia increased in the infusions. In general, the recovery of natural sweeteners or phenolic compounds with antioxidant activity exhibited different patterns, depending on the components of the infusions. The presence of stevia and steviol glycosides did not influence the recovery of phenolic compounds with antioxidant activity.

SUPPLEMENTARY INFORMATION

The online version of this article (10.1007/s13197-021-04979-9).

A comparison of the effects of Stevia extract and metformin on metabolic syndrome indices in rats fed with a high-fat, high-sucrose diet

The beneficial effects of Stevia on metabolic indices have been studied in recent years. However, controversial results emphasize the need for further investigation. We aimed to examine and compare the effects of Stevia's hydroalcoholic extract with two dosages (200, 400 mg/kg) with those of metformin (100 mg/kg) on metabolic syndrome (MetS) indices of rats fed with a high-fat, high-sucrose diet (HFHS). It was found that both Stevia extract and metformin could prevent the adverse effects of a HFHS on lipid profile, liver enzymes, total antioxidant capacity (TAC), and histopathologic factors. Except for the finding that metformin showed a greater potential to alleviate insulin resistance than did Stevia extract, no significant difference was observed between the rats receiving metformin or Stevia extract. In addition, using a high treatment dosage of Stevia extract did not lead to better results than a low dosage. Collectively, the efficacy of Stevia extracts to modify metabolic, oxidative, and histopathological indices in a MetS model was comparable to that of the metformin. PRACTICAL APPLICATIONS: This study was aimed to compare the efficiency of Stevia hydroalcoholic extract with metformin in attenuating MetS abnormalities of rats induced by a high-fat, high-sucrose diet. The results showed the beneficial changes caused due to the administration of Stevia extract on lipid profile, antioxidant capacity, liver enzyme, and liver histopathological indices. The changes were comparable with the results of metformin group. Despite some promising results, further investigation is suggested to evaluate the effectiveness of Stevia extract on human subjects.

Polyphenols from Stevia rebaudiana (Bertoni) leaves and their functional properties

The major polyphenol components from Stevia rebaudiana (Bertoni) leaves (PPS) are chlorogenic acids, a polyphenol family of esters, including hydroxycinnamic acids with quinic acid, which possesses excellent hydrophilic antioxidant activity and other therapeutic properties. As an abundant byproduct during production of steviol glycosides, the PPS would be a new antioxidantive food resource or additives applied in foods and drugs with antidiabetic function. Extracting PPS from S. rebaudiana (Bertoni) leaves together with steviol glycosides would be an economic process, which will change most operation process in current Stevia factories. The quantification of PPS needs to be unified for regulation. In view of the current regulation status of polyphenols and extracts from Stevia, the PPS would be ready to go to the market with few regulation barriers in the near future. This review will summarize the analysis, extraction, and some functional properties of PPS, such as antioxidant, antidiabetic, antimicrobial, anti-inflammatory, and anticancer.

New seminal variety of Stevia rebaudiana: Obtaining fractions with high antioxidant potential of leaves

The aim of this study was to determine the composition and antioxidant potential of leaves of a new variety of Stevia rebaudiana (Stevia UEM-13). Stevia leaves of UEM-13 contain rebaudioside A as the main glycoside, while most wild Stevia plants contain stevioside. Furthermore can be multiplied by seed, which reduces the cost of plant culture techniques as other clonal varieties are multiplied by buds, requiring sophisticated and expensive seedling production systems. Ethanol and methanol were used in the extraction to determine the bioactive compounds. The methanolic extract was fractionated sequentially with hexane, chloroform, ethyl acetate and isobutanol, and the highest concentration of phenolic compounds and flavonoids was obtained in the ethyl acetate fraction (524.20 mg galic acid equivalent/g; 380.62 µg quercetin equivalent/g). The glycoside content varied greatly among the fractions (0.5% - 65.3%). Higher antioxidant potential was found in the methanol extract and the ethyl acetate fraction with 93.5% and 97.32%, respectively. In addition to being an excellent source for obtaining of extracts rich in glycoside, this new variety can also be used as raw material for the production of extracts or fractions with a significant amount of antioxidant activity and potential to be used as additives in food.

Rapid Solid-Liquid Dynamic Extraction (RSLDE): a New Rapid and Greener Method for Extracting Two Steviol Glycosides (Stevioside and Rebaudioside A) from Stevia Leaves

Stevioside and rebaudioside A are the main diterpene glycosides present in the leaves of the Stevia rebaudiana plant, which is used in the production of foods and low-calorie beverages. The difficulties associated with their extraction and purification are currently a problem for the food processing industries. The objective of this study was to develop an effective and economically viable method to obtain a high-quality product while trying to overcome the disadvantages derived from the conventional transformation processes. For this reason, extractions were carried out using a conventional maceration (CM) and a cyclically pressurized extraction known as rapid solid-liquid dynamic extraction (RSLDE) by the Naviglio extractor (NE). After only 20 min of extraction using the NE, a quantity of rebaudioside A and stevioside equal to 1197.8 and 413.6 mg/L was obtained, respectively, while for the CM, the optimum time was 90 min. From the results, it can be stated that the extraction process by NE and its subsequent purification developed in this study is a simple, economical, environmentally friendly method for producing steviol glycosides. Therefore, this method constitutes a valid alternative to conventional extraction by reducing the extraction time and the consumption of toxic solvents and favouring the use of the extracted metabolites as food additives and/or nutraceuticals. As an added value and of local interest, the experiment was carried out on stevia leaves from the Benevento area (Italy), where a high content of rebaudioside A was observed, which exhibits a sweet taste compared to stevioside, which has a significant bitter aftertaste.

Stevia Glycosides: Chemical and Enzymatic Modifications of Their Carbohydrate Moieties to Improve the Sweet-Tasting Quality

Stevia glycosides, extracted from the leaves of the plant Stevia rebaudiana Bertoni, display an amazing high degree of sweetness. As processed plant products, they are considered as excellent bio-alternatives for sucrose and artificial sweeteners. Being noncaloric and having beneficial properties for human health, they are the subject of an increasing number of studies for applications in food and pharmacy. However, one of the main obstacles for the successful commercialization of Stevia sweeteners, especially in food, is their slight bitter aftertaste and astringency. These undesirable properties may be reduced or eliminated by modifying the carbohydrate moieties of the steviol glycosides. A promising procedure is to subject steviol glycosides to enzymatic glycosylation, thereby introducing additional monosaccharide residues into the molecules. Depending on the number and positions of the monosaccharide units, the taste quality and sweetness potency of the compounds will vary. Many studies have been performed already, and this review summarizes the structures of native steviol glycosides and the recent data of modifications of the carbohydrate moieties that have been published to provide an overview of the current progress.