Stevia Polyphenols, Their Antimicrobial and Anti-Inflammatory Properties, and Inhibitory Effect on Digestive Enzymes.

Polyphenols from stevia leaves (PPSs) are abundant byproducts from steviol glycoside production, which have been often studied as raw extracts from stevia extracts for their bioactivities. Herein, the PPSs rich in isochlorogenic acids were studied for their antimicrobial and anti-inflammatory properties, as well as their inhibitory effects on digestive enzymes. The PPSs presented stronger antibacterial activity against E. coli, S. aureus, P. aeruginosa, and B. subtilis than their antifungal activity against M. furfur and A. niger. Meanwhile, the PPSs inhibited four cancer cells by more than 60% based on their viability, in a dose-dependent manner. The PPSs presented similar IC50 values on the inhibition of digestive enzyme activities compared to epigallocatechin gallate (EGCG), but had weaker anti-inflammatory activity. Therefore, PPSs could be a potential natural alternative to antimicrobial agents. This is the first report on the bioactivity of polyphenols from stevia rebaudiana (Bertoni) leaves excluding flavonoids, and will be of benefit for understanding the role of PPSs and their application.

A comparative study on physicochemical and micellar solubilization performance between monoglucosyl rebaudioside A and rebaudioside A.

BACKGROUND: Rebaudioside A (RA) and its monoglucosyl derivative, as like rebaudioside D (RD) are the most popular stevia glycosides but possess poor solubility in water, which limited their application as edible surfactants, the applications as in micellar solubilization and drug delivery. Meanwhile, effect of the monoglucosyl attached to RA moiety remains unclear. RESULTS: Monoglucosyl rebaudioside A (RAG1) was synthesized via hydrolyzing the transglycosylation product of RA with 95% of RA converted. RAG1 content in raw reaction mixture was as high as 69.5% of total glycosides, and harvested with a content of 88.2% by simple filtration. The RAG1 exhibited an aqueous solubility of 87 folds of RA or 391 folds of RD at 25 °C. The surface activity of RAG1 solution was higher than RA and invincible to RD. The RAG1 micelles promoted aqueous solubility of idebenone (IDE) up to 500 folds higher at 25 °C. The cumulative release rate of IDE encapsulated in RAG1 micelles was 777.5% or 456.7% higher of that of free IDE in simulated gastric/intestinal fluids in 14 h, respectively. The RAG1-IDE remained the same in 98 days at 25 °C. CONCLUSION: The α-linked glucosyl to RA induced higher hydrophilicity and surface activity than that resulted by ß-linked glucosyl, making RAG1 not only dramatically raise the aqueous solubility of RA, but also endow IDE folds higher in bioaccessibility, yet making the capsule stable at storage. The results would provide a new edible delivery nanocarrier for encapsulation of hydrophobic bioactive components. © 2021 Society of Chemical Industry.

Bioavailability and antioxidant activity of nanotechnology-based botanic antioxidants.

Botanic bioactive substances have issues with their solubility, stability, and oral bioavailability in the application, which could be improved by nanotechnologies. In another hands, green synthesis of nanoparticles (NPs) with plant extract is also a promising technology for preparation of NPs due to its safety advantage, yet the bioactive botanic substances that could be more than the assistant of the green synthesis of NPs. Based on the above concerns, this review summarized the preparation of botanic NPs with various plant extract, their solubility, stability, and oral bioavailability; specific attention has been paid to the botanic Ag/Au NPs, their capacity of antioxidant, bioavailability, antimicrobial, anti-inflammatory, and anticancer.

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.

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.