• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.2
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• pp.313-318
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• 2010

This study was carried out to evaluate the antioxidant activity of stevia extracts from Stevia rebaudiana Bertoni leaves. Stevia extracts were prepared by three different methods including hot water extraction (HWE) at $120^{\circ}C$ for 4 hr, vacuum extraction (VE) at $65^{\circ}C$ for 4 hr under 0.08 MPa, and fermentation of hot water extract (FHWE) using Lactobacillus buchneri. The antioxidant activities measured by radical scavenging activity, ferric-reducing antioxidant potential ability, and thiobarbituric acid reactive substance showed the highest values in vacuum extract. Also, the antioxidant activities of all extracts were higher than those of stevioside and rebaudioside at the same concentrations, known as the major active components in stevia. To define the antioxidative compound in stevia extracts, the total phenol content was measured, and it was shown that the highest contents of total phenolic compounds were in vacuum extract. These results suggest that the antioxidant activity of stevia extract was due to the phenolic compound components. In addition, vacuum extraction was the proper method to prepare stevia extract with higher antioxidant activity.

• Korean Journal of Pharmacognosy
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• v.9 no.3
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• pp.149-156
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• 1978

The result of the study about the cultivation, the constituents, the sweetenity, and the development of preparations of Stevia and Hydrangea are as follows: 1. Hydrangea thrived at $200{\sim}1,400m$ above the sea-level, and the good ones were brought up at $600{\sim}1,200m$. 2. The good ones which belonged to the genera of Hydrangea were produced in the damp, dark and cold place. 3. The growth and cultivated yield of Stevia was not significantly influenced by the acidity of the soil. 4. The best season was May and June for propagation of Stevia by cutting method. 5. The growth rate of Stevia and Hydrangea was really good in the sandy fertile soil, but in the mucotic soil it was not suitable. 6. The extraction and separation of phyllodulcin by solvent had many difficulties, because it was very soluble in water, ethanol, ether, petroleum ether, acetone and benzene, etc. 7. The solubility of stevioside on the solvent was as follows: It was very soluble in water and methanol, slightly soluble in ethanol and acetone, and insoluble in ether, petroleum ether and chloroform. 8. The alkaloid reaction by Mayer reagent in Hydrangea extract was positive. 9. The ashification rate of Stevia was 8.66% to 8.72% and that of Hydrangea 17.02% to 17.04%. 10. The tannin of Stevia leaf was 7.80% to 7.88% and its of Hydrangea decreased 9.46% to 6.08% by fermentation. 11. The percent rates in minimum concentration-occurring sweetness in sugar, glycyrrhiza methanol extract, Hydrangea water extract, Stevia leaf water extract, decoction of Stevia's leaf, decoction of Stevia's stem were as follows: 1.2, 0.1, 0.1, 0.2, 0.4, 0.01, 0.1, 0.6. and sweetenity ratios of those were 1, 12, 12, 6, 3, 64, 12, 2, 12. It was very meaningful to develop preparations of stevia as stevioside, micronized powder, water extract, methanol extract and compound teas and in Hydrangea, water extract, methanol extract, single tea, and compound teas were less meaningful. 13. The genera of Hydrangea which is natural species in Korea was positive in phyllodulcin-identification test, but it was not available to make the sweet tea because of having a little content.

• Korean Journal of Human Ecology
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• v.9 no.1
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• pp.71-80
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• 2006

To investigate the effects of the supplementation of Stevia. Rebaudian Bertoni on serum and hepatic lipid levels and enzyme activities in rat administered with ethanol chronically. Sprague-Dawley male rats were orally treated with either an AIN-76 diet(C, control), a control diet plus ethanol(E, 4g/kg bw), E plus stevia extract-1(ES1, 1ml/kg bw), or E plus stevia extract-2(ES2, 2ml/kg bw) for 7 weeks. Serum triglyceride levels were increased in the E group and were decreased in the ES 1 group. Liver triglyceride levels were decreased significantly in the ES2 groups and Total-cholesterol were decreased in the ES1, ES2 groups compared with the E group. Liver $\gamma-GTP$ levels were decreased significantly in the ES1, ES2 groups compared with the E group. In addition, we have evaluated the serum or liver carnitine levels in those groups. Liver TCNE levels were increased significantly in the ES1, ES2 compared with the E group. These results may suggest that supplementation of Stevia. Rebaudian Bertoni has effects on the recovery of chronic ethanol-related diseases.

• Korean Journal of Plant Resources
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• v.32 no.3
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• pp.220-227
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• 2019

Stevia rebaudiana (Asteraceae), a perennial plant, has been used as a low-calorie sweetener and is being developed as a therapeutic agent for diabetes, hypertension, myocardial diseases, and microbial infections. Despite the common use of its leaves and stem, the bioavailability of the components present in S. rebaudiana flowers, when used as ingredients of cosmetics, has not been well investigated. Herein, we investigated the antioxidative and antimelanogenic effects of an aqueous extract of S. rebaudiana flowers (Stevia-F). Total flavonoid and phenolic content in Stevia-F were determined to be $8.64{\pm}0.23mg$ of quercetin equivalents/100 g and $631.5{\pm}2.01mg$ of gallic acid equivalents/100 g, respectively. The $IC_{50}$ values of Stevia-F for reducing power, and 2,2-diphenyl-1-picryl-hydrazyl-hydrate radical, hydrogen peroxide, and nitric oxide scavenging activities were 5541.96, 131.39, 466.34, and $10.44{\mu}g/mL$, respectively. Stevia-F showed inhibitory effects on the tyrosinase ($IC_{50}=134.74{\mu}g/mL$) and ${\alpha}$-glucosidase ($IC_{50}=114.81{\mu}g/mL$) activities. No significant cytotoxicity of Stevia-F was observed in B16F10 cells, treated with up to $100{\mu}g/mL$ of the extract for 24 and 48 h (p > 0.05). Stevia-F ($1-100{\mu}g/mL$) suppressed ${\alpha}$-melanocyte stimulating hormone-induced melanin production in B16F10 cells (p < 0.05) and also inhibited the cellular tyrosinase activity (p < 0.05). Overall, our results show that Stevia-F possesses potential for inhibiting tyrosinase and ${\alpha}$-glucosidase activities and has significant antioxidant capacity. The antimelanogenic potential of Stevia-F should extend the usage of S. rebaudiana flowers in the development of skin-whitening products.

• Journal of Life Science
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• v.16 no.6
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• pp.994-1000
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• 2006

Stevia rebaudiana Bertoni is a sweet herb of the Asteraceae family originally derived from South America. Twenty three bacterial strains and ten yeast strains were isolated from fermented Stevia extract and identified by general taxonomic methods and molecular genetic method. Isolated strains from fermented Stevia extract include ten species of bacteria which belong to five genus and one species of yeast. Based on 16S and 18S rDNA sequence analysis, phylogenetic trees were constructed. Antimicrobial activity of the isolated strains was examined against various bacteria and plant-pathogenic fungi. Among them, Lactobacillus paracasei SB13 showed strong antibacterial activity towards a wide range of bacteria. These results may be useful to develop environmentally friendly microbial agent for soil improvement.

• Journal of Dairy Science and Biotechnology
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• v.34 no.1
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• pp.51-57
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• 2016

In this study, the fermentation and quality characteristics of Greek-style yogurt supplemented with stevia leaf extract during storage were examined. Stevia leaf extract was extracted from dried leaves with hot water and 70% ethanol. The pH decreased significantly in all samples over time during fermentation (p<0.05). In particular, the sharpest decrease was detected in the group in which the hot water extract of stevia was added. Acidity increased significantly over time during fermentation (p<0.05). Lactic acid bacteria counts increased in all samples up to 9 h after the start of fermentation, but decreased after 12 h. The sugar content decreased over time, and there were no major differences between samples. Based on the results of a sensory evaluation, the group treated with stevia extract was rated high in sweetness, but was rated somewhat low in color and flavor. Accordingly, it was rated low in overall acceptability. In a storability experiment, as the days of storage increased, the pH gradually decreased, and acidity showed a tendency to increase. The sugar content showed a tendency to decrease and then increase.

• Korean Journal of Food Science and Technology
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• v.11 no.4
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• pp.224-231
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• 1979

The safety of the sweetening component of stevia was studied by administrating it to the rats. The $LD_{50}$ determined by intraperitoneal injection was 3,400 mg/Kg as the stevia extract containing 50 % stevioside, i.e. $LD_{50}$ of stevioside was more than 1,700 mg/Kg. Oral administration of large quantities of the stevia extract for 56 days resulted in no effect on the growth of rats. The analyses of total blood (RBC, WBC, Hb and Hct), 17 blood serum components including total protein, glucose, cholesterol, GOT, and 11 items of findings on the liver tissues including nuclear deterioration of liver cells, proliferation of Kupffer cells, fibrosis of portal area showed no significant differences between control and treatments except lactate dehydrogenase activity after 56 day-oral administration of the extract. From the results obtained, it was supposed that the stevia extract/stevioside revealed no acute or sub-acute toxic effects on rats.

• Journal of Dairy Science and Biotechnology
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• v.34 no.4
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• pp.263-270
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• 2016

This study was carried out to evaluate the antioxidant activity and total polyphnol content of Greek-style yogurt in 12% solid content with added stevia leaf extracts. Stevia leaf extracts used as sweetener in preparing Greek-style yogurt were prepared in hot water ($100^{\circ}C$ for 6 h 3 times, and by 70% fermented ethanol for 24 h at room temperature 3 times). The antioxidant activities were measured by assessing the radical scavenging effect through DPPH, ABTS, and FRAP assays. To identify the compounds present, total polyphenol content was evaluated using a Folin-Dennis assay. The capability to scavenge free radicals and total polyphenolic content were the highest in Greek-style yogurt containing 1% stevia extract and fermented in 70% ethanol. According to the results, antioxidant activities significantly increased when high concentration of stevia extracts were added to the yogurt (p<0.05). Therefore, these results suggest that stevia leaf extracts can be used as a source of functional compounds in Greek-style yogurt. We also suggest that fermented ethanol extraction can be used to obtain stevia leaf extracts.

• Korean Journal of Food Science and Technology
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• v.37 no.6
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• pp.893-897
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• 2005

Effect of foliar application of stevia extract on strawberry quality was investigated. Soluble solid and free sugar contents of strawberry (SS) cultivated with foliar application of stevia extract were higher, and acidity and organic acid contents were lower than those of control. Free sugars were composed of fructose, glucose, and sucrose. Organic acids were composed of citric, malic, oxalic, succinic, and fumaric acids. Sensory evaluation revealed score of sweetness, sourness, and overall acceptability for SS were higher than those of control.

• Journal of Physiology & Pathology in Korean Medicine
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• v.27 no.6
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• pp.764-770
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• 2013

Stevia rebaudiana is a traditional herb used as a sweetener in Brazil and Paraguay as well as Korea and China. This study investigated the efficacy of Stevia rebaudiana methanol extract (SRE) to protect cells against the mitochondrial dysfunction and apoptosis in hepatocyte. To determine the effects of SRE on oxidative stress, we used the human derived hepatocyte cell line, HepG2 cell. Treatment of arachidonic acid (AA)+iron in HepG2 cells synergistically amplified cytotoxicity, as indicated by the excess reactive oxygen species (ROS) and mitochondrial permeability transition by fluorescence activated cell sorter (FACS) and immunoblot analysis. Treatment with SRE protected hepatocytes from AA+iron-induced cellular toxicity, as shown by alterations in the protein levels related with cell viability such as procaspase-3. SRE also prevented the mitochondrial dysfunction induced by AA+iron, and showed anti-oxidant effects as inhibition of $H_2O_2$ production and GSH depletion. Moreover, we measured the effects of SRE on AMP-activated protein kinase (AMPK), a key regulator in determining cell survival or death. Acetyl-CoA Carboxylase (ACC), a direct downstream target of AMPK. SRE increased phosphorylation of ACC, and prevented the inhibition of ACC phosphorylation by AA+iron. These results indicated that SRE has the ability to protect cells against AA+iron-induced $H_2O_2$ production and mitochondrial impairment, which may be mediated with AMPK-ACC pathway.