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.
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.
BACKGROUNDStevia 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.RESULTSThe 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 18F‐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.CONCLUSIONSThe 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.
Stevia leaves have been claimed to possess the highest antioxidant capacity among botanic foods, yet the antioxidant activity has been attributed to the polyphenols from Stevia leaves (PPS). However, most studies about the PPS were based on Stevia extracts that contain abundant polyphenols and flavonoids. The PPS excluded flavonoids were found to possess antioxidant activity similar to that of epigallocatechin gallate, demonstrating stronger hydrophilic antioxidant activity and stability than that of ascorbic acid (VC), vitamin E, or chlorogenic acid under the assayed circumstances. Both of the PPS and their antioxidant activity are very stable in various physical environments, but less stable in the presence of potassium sorbate or sucrose. Moreover the combination of PPS and VC could increase the antioxidant stability of either VC or PPS. Therefore, the PPS have the potential to be a natural, inexpensive, and abundant antioxidant that can be utilized in the pharmaceutical and cosmetics.
Practical applications
The PPS excluded flavonoids were found to possess antioxidant activity similar to that of epigallocatechin gallate, demonstrating stronger hydrophilic antioxidant activity and stability than that of ascorbic acid (VC), vitamin E, or chlorogenic acid under the assayed circumstances. Both of the PPS and their antioxidant activity are very stable in various physical environments, but less stable in the presence of potassium sorbate or sucrose. Moreover the combination of PPS and VC could increase the antioxidant stability of either VC or PPS. Therefore, the PPS have the potential to be a new natural, inexpensive, and abundant antioxidant that can be utilized in the pharmaceutical and cosmetics.
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