New derivatives of steviol 1, the aglycone of the glycosides of Stevia rebaudiana, including a novel class of semisynthetic diterpenoids, namely macrocyclic ent-kauranes were synthesized. These compounds possess antituberculosis activity inhibiting the in vitro growth of Mycobacterium Tuberculosis (H37R(V) strain) with MIC 5-20μg/ml that is close to MIC 1μg/ml demonstrated by antituberculosis drug isoniazid in control experiment. For the first time it was found that the change of ent-kaurane geometry (as in steviol 1) of tetracyclic diterpenoid skeleton to ent-beyerane one (as in isosteviol 2) influences on antituberculosis activity.
Five new phenolic glycosides, hedyotosides A-E (1-5), including a new cyanogenic glycoside (1), along with 10 known compounds (6-15) were isolated from the whole plants of Hedyotis scandens. The structures of compounds 1-5 were established by extensive spectroscopic analyses and acid hydrolysis. All the isolated compounds were evaluated for their in vitro antiviral activity against respiratory syncytial virus (RSV) with cytopathic effect (CPE) reduction assay. Compounds 6 and 15 showed anti-RSV effects with IC(50) values of 20 and 25μg/mL, respectively.
Five new chlorophenolic glucosides, Curculigine E (1), Curculigine F (2), Curculigine G (3), Curculigine H (5), Curculigine I (6) and one new phenolic glycoside, Orcinoside H (4), together with eight known phenolic glycosides (7-14) were isolated from the Curculigo orchioides Gaertn.. Their structures were established by spectroscopic techniques (IR, UV, MS, 1D and 2D NMR). The isolated phenolic glycosides were evaluated for antiosteoporotic activity against MC3T3-E1 cell line using MTT assays. Compounds 1, 2, 3, 5 showed moderate antiosteoporotic activity with the proliferation rate of 10.1-14.1%.
In vitro Inhibitory Effect of Gymnema sylvestre Extracts and Total Gymnemic Acids Fraction on Select Cytochrome P450 Activities in Rat Liver Microsomes
- European journal of drug metabolism and pharmacokinetics
- Published over 2 years ago
Gymnema sylvestre R. Br. is a well-known Indian medicinal herb. Gymnemic acids are pentacyclic triterpenes saponins and active phytoconstituents of Gymnema sylvestre. The study aimed at evaluation of the in vitro rat liver cytochrome P450 (CYP) inhibition potential of extracts and total gymnemic acid (TA)-enriched fractions from G. sylvestre.
Stevia rebaudiana (SR) is often used by the food industry due to its steviol glycoside content, which is a suitable calorie-free sweetener. Further, both in vitro and in vivo studies indicate that these glycosides and the extracts from SR have pharmacological and therapeutic properties, including antioxidant, antimicrobial, antihypertensive, antidiabetic, and anticancer. This work reviews the antiobesity, antihyperglycemic, antihypertensive, and antihyperlipidemic effects of the majority of glycosides and aqueous/alcoholic extracts from the leaves, flowers, and roots of the SR. These compounds can serve as a natural and alternative treatment for diseases that are associated with metabolic syndrome, thus contributing to health promotion.
Steviol glycosides (SGs), such as stevioside and rebaudioside A, are natural, non-caloric sweet-tasting organic molecules, present in extracts of the scrub plant Stevia rebaudiana, which are widely used as sweeteners in consumer foods and beverages. TRPM5 is a Ca(2+)-activated cation channel expressed in type II taste receptor cells and pancreatic β-cells. Here we show that stevioside, rebaudioside A and their aglycon steviol potentiate the activity of TRPM5. We find that SGs potentiate perception of bitter, sweet and umami taste, and enhance glucose-induced insulin secretion in a Trpm5-dependent manner. Daily consumption of stevioside prevents development of high-fat-diet-induced diabetic hyperglycaemia in wild-type mice, but not in Trpm5(-/-) mice. These results elucidate a molecular mechanism of action of SGs and identify TRPM5 as a potential target to prevent and treat type 2 diabetes.
The glucosyltransferase UGT76G1 from Stevia rebaudiana is a chameleon enzyme in the targeted biosynthesis of the next-generation premium stevia sweeteners, rebaudioside D (Reb D) and rebaudioside M (Reb M). These steviol glucosides carry five and six glucose units, respectively, and have low sweetness thresholds, high maximum sweet intensities and exhibit a greatly reduced lingering bitter taste compared to stevioside and rebaudioside A, the most abundant steviol glucosides in the leaves of Stevia rebaudiana.
The food industry is moving towards the use of natural sweeteners such as those produced by Stevia rebaudiana due to the number of health and safety concerns surrounding artificial sweeteners. Despite the fact that these sweeteners are natural; they cannot be assumed safe. Steviol glycosides have a steroidal structure and therefore may have the potential to act as an endocrine disruptor in the body. Reporter gene assays (RGAs), H295R steroidogenesis assay and Ca(2+) fluorimetry based assays using human sperm cells have been used to assess the endocrine disrupting potential of two steviol glycosides: stevioside and rebaudioside A, and their metabolite steviol. A decrease in transcriptional activity of the progestagen receptor was seen following treatment with 25,000 ng/ml steviol in the presence of progesterone (157 ng/ml) resulting in a 31% decrease in progestagen response (p= <0.01). At the level of steroidogenesis, the metabolite steviol (500-25,000 ng/ml) increased progesterone production significantly by 2.3 fold when exposed to 10,000 ng/ml (p= <0.05) and 5 fold when exposed to 25,000 ng/ml (p=<0.001). Additionally, steviol was found to induce an agonistic response on CatSper, a progesterone receptor of sperm, causing a rapid influx of Ca(2+). The response was fully inhibited using a specific CatSper inhibitor. These findings highlight the potential for steviol to act as a potential endocrine disruptor.
In addition to their widely recognized use as dietary supplement ingredients, plant-derived compounds are increasingly used as natural sweeteners. The search for nonnutritive sweeteners has been stimulated over the last 20-30 years by concern over demonstrated or suspected relationships between consumption of sucrose and high-fructose corn syrups and a variety of health-related conditions. In the USA, there is increased use of plant extracts known to contain highly sweet terpenoids. Purified extracts of Stevia rebaudiana (Bertoni) containing the diterpene glycosides stevioside and rebaudioside A are popular as sweeteners and are also used as dietary supplements, and soft drinks and nutritional and energy shakes incorporating extracts of Siraitia grosvenorii (Swingle) fruits containing sweet triterpene glycosides such as mogroside V are also on the market. Here, we review recent studies on these two important sources of noncaloric natural sweeteners, including analytical methods used to identify and quantify specific constituents and structural features relating to their sweetness. We also review the generally recognized as safe status of specific components and their status with respect to review by the Joint FAO/WHO Expert Committee on Food Additives.
Acteoside and salidroside are major phenylethanoid glycosides (PhGs) in Osmanthus fragrans Lour. flowers with extensive pharmacological activities and poor oral bioavailability. The absorption mechanisms of these two compounds remain unclear. This study aimed to investigate the bioaccessibility of these compounds using an in vitro gastro-intestinal digestion model, and to examine the absorption and transport mechanisms of PhGs using the Caco-2 cell model. The in vitro digestion model revealed that the bioaccessibility of salidroside (98.7±1.35%) was higher than that of acteoside (50.1±3.04%), and the superior bioaccessibility of salidroside can be attributed to its stability. The absorption percentages of total phenylethanoid glycoside, salidroside and acteoside were 1.42-1.54%, 2.10-2.68% and 0.461-0.698% in the Caco-2 model, respectively. Salidroside permeated Caco-2 cell monolayers through passive diffusion. At the concentration of 200 μg/mL, the apparent permeability ( Papp) of salidroside in the basolateral (BL)-to-apical (AP) direction was 23.7±1.33 × 10-7 cm/s, which was 1.09-fold of that in the AP-to-BL direction (21.7±1.38 × 10 -7 cm/s). Acteoside was poorly absorbed with low Papp (AP to BL) (4.75±0.251 × 10 -7 cm/s), and its permeation mechanism was passive diffusion with active efflux mediated by P-glycoprotein (P-gp). This study clarified the bioaccessibility, absorption and transport mechanisms of PhGs. It also demonstrated that the low bioavailability of acteoside might be attributed to its poor bioaccessibility, low absorption and P-gp efflux transporter.