Oridonin protects the lung against hyperoxia-induced injury in a mouse model

Hyperoxic acute lung injury (HALI) is caused by prolonged exposure to high oxygen partial pressure. This study was undertaken to investigate the protective effects of oridonin on HALI in a mouse model. Mice were randomly divided into three groups: the control group, HALI group and oridonin (ORI) group. HALI was induced by exposing mice to pure oxygen at 2.5 atmospheres absolute (ATA) for six hours in the HALI and ORI groups. In the ORI group, mice were intraperitoneally injected with ORI at 10 mg/kg twice daily after hyperoxic exposure. Animals were sacrificed 24 hours after the hyperoxia exposure, followed by bronchoalveolar lavage fluid (BALF). Lungs were then collected. Each lung was processed for HE staining and detection of wet-to-dry weight ratio. The lactate dehydrogenase (LDH) activity and protein content of BALF were determined, and the contents of malonaldehyde (MDA), glutathione (GSH), tumor necrosis factor alpha (TNF-?) and interleukin-10 (IL-10) in the lung were measured. Our results showed prolonged exposure to hyperoxia significantly damaged the lung, caused lung edema, increased MDA and TNF-?, and reduced GSH and IL-10 in the lung. However, post-exposure treatment with oridonin was able to improve lung pathology, attenuate lung edema, reduce MDA and TNF-?, and increase GSH and IL-10 in the lung. These findings suggest that oridonin can protect the lung against hyperoxia-induced injury in mice.

Oridonin Attenuates Synaptic Loss and Cognitive Deficits in an Aβ1-42-Induced Mouse Model of Alzheimer's Disease

Synaptic loss induced by beta-amyloid (Aβ) plays a critical role in the pathophysiology of Alzheimer’s disease (AD), but the mechanisms underlying this process remain unknown. In this study, we found that oridonin (Ori) rescued synaptic loss induced by Aβ_1–42in vivo and in vitro and attenuated the alterations in dendritic structure and spine density observed in the hippocampus of AD mice. In addition, Ori increased the expression of PSD-95 and synaptophysin and promoted mitochondrial activity in the synaptosomes of AD mice. Ori also activated the BDNF/TrkB/CREB signaling pathway in the hippocampus of AD mice. Furthermore, in the Morris water maze test, Ori reduced latency and searching distance and increased the number of platform crosses in AD mice. These data suggest that Ori might prevent synaptic loss and improve behavioral symptoms in Aβ_1–42-induced AD mice.

[Chemical biology and novel molecular-targeted agents in cancer therapy]

Target-based screening and cell-based screening are major approaches to identify anticancer drug candidates. Cell-based screening often contributes to the discovery of first-in-class drugs, but identification of the cellular targets of obtained compounds is a time-consuming step. To overcome this problem, affinity purification with small-molecule probes, which is a classic, but still the most common approach, has become more sophisticated and diversified. In addition, recent advances in omics studies and imaging analyses have allowed us to profile the biological effects of small molecules globally and quantitatively. Consequently, new therapeutic targets/drug leads involved in cancer cell cycle, transcription and redox regulation have been discovered.

Stevioside plays an anti-inflammatory role by regulating the NF-κB and MAPK pathways in S. aureus-infected mouse mammary glands

Mastitis is an inflammatory disease caused by microbial infection. Staphylococcus aureus is one of the primary bacteria responsible for mastitis. Stevioside is isolated from Stevia rebaudiana and is known to have therapeutic functions. This study was designed to evaluate the effects of stevioside in a mouse model of S. aureus-induced mastitis. In this study, the mouse mammary gland was infected with S. aureus to induce the mastitis model. The stevioside was administered intraperitoneally after the S. aureus infection was established. Hematoxylin-eosin (HE) staining, ELISA, Western blot, and q-PCR methods were used. The results show that stevioside significantly reduced the inflammatory cell infiltration and the levels of TNF-α, IL-1β, and IL-6 and the respective expression of their messenger RNAs (mRNAs). Further studies revealed that stevioside downregulated the TLR2, NF-κB, and (mitogen-activated protein kinase) MAPK signaling pathways in the S. aureus-infected mouse mammary gland. Our results demonstrate that stevioside reduced the expression of TNF-α, IL-1β, and IL-6 by inhibiting the phosphorylation of proteins in the NF-κB and MAPK signaling pathways dose-dependently, but that their mRNA expression was not obviously changed.

Oridonin inhibits tumor growth in glioma by inducing cell cycle arrest and apoptosis

Glioma is the most common malignant intracranial tumors. Despite newly developed therapies, these treatments mainly target oncogenic signals, and unfortunately, fail to provide enough survival benefit in both human patients and mouse xenograft models, especially the first-generation therapies. Oridonin is purified from the Chinese herb Rabdosia rubescens and considered to exert extensive anti-cancer effects on human tumorigenesis. In this study, we systemically investigated the role of Oridonin in tumor growth and the underlying mechanisms in human glioma. We found that Oridonin inhibited cell proliferations in a dose- and time-dependent manner in both glioma U87 and U251 cells. Moreover, these anti-cancer effects were also confirmed in a mouse model bearing glioma. Furthermore, cell cycle arrest in S phase was observed in Oridonin-mediated growth inhibition by flow cytometry. Cell cycle arrest in S phase led to eventual cell apoptosis, as revealed by Hoechst 33342 staining and annexin V/PI double-staining. The cell apoptosis might be accomplished through a mitochondrial manner. In all, we were the first to our knowledge to report that Oridonin could exert anti-cancer effects on tumor growth in human glioma by inducing cell cycle arrest and eventual cell apoptosis. The identification of Oridonin as a critical mediator of glioma growth may potentiate Oridonin as a novel therapeutic strategies in glioma treatments.

Oridonin attenuates Aβ1-42-induced neuroinflammation and inhibits NF-κB pathway

Neuroinflammation induced by beta-amyloid (Aβ) plays a critical role in the pathogenesis of Alzheimer’s disease (AD), and inhibiting Aβ-induced neuroinflammation serves as a potential strategy for the treatment of AD. Oridonin (Ori), a compound of Rabdosia rubescens, has been shown to exert anti-inflammatory effects. In this study, we demonstrated that Ori inhibited glial activation and decreased the release of inflammatory cytokines in the hippocampus of Aβ_1–42-induced AD mice. In addition, Ori inhibited the NF-κB pathway and Aβ_1–42-induced apoptosis. Furthermore, Ori could attenuate memory deficits in Aβ_1–42-induced AD mice. In conclusion, our study demonstrated that Ori inhibited the neuroinflammation and attenuated memory deficits induced by Aβ_1–42, suggesting that Ori might be a promising candidate for AD treatment.

Anti-rotavirus effects by combination therapy of stevioside and Sophora flavescens extract

Anti-rotaviral activities of Sophora flavescens extract (SFE) and stevioside (SV) from Stevia rebaudiana Bertoni either singly or in various combinations were examined in vitro and in vivo using a porcine rotavirus G5[P7] strain. Combination of SFE and SV inhibited in vitro virus replication more efficiently than each single treatment. In the piglet model, SV had no effect on rotavirus enteritis, whereas SFE improved but did not completely cure rotaviral enteritis. Interestingly, combination therapy of SFE and SV alleviated diarrhea, and markedly improved small intestinal lesion score and fecal virus shedding. Acute toxicity tests including the piglet lethal dose 50, and body weight, organ weight and pathological changes for the combination therapy did not show any adverse effect on the piglets. These preliminary data suggest that the combination therapy of SV and SFE is a potential curative medication for rotaviral diarrhea in pigs. Determination of the efficacy of this combination therapy in other species including humans needs to be addressed in the future.

The remarkable structural diversity achieved in ent-Kaurane Diterpenes by fungal biotransformations

The use of biotransformations in organic chemistry is widespread, with highlights of interesting applications in the functionalization of natural products containing unactivated carbons, like the kaurane diterpenes. A number of compounds with kaurane skeletons can be isolated in large amounts from several plant species and a myriad of biological activities has been related to these compounds. Studies on structure versus activity have showed that, in most cases, in kaurane diterpenes, activity increases with the increase of functionalization. Since naturally occurring kaurane diterpenes usually have limited functional groups to be used as targets for semi-synthetic modifications, production of more polar derivatives from kaurane diterpenes have been achieved mostly through the use of fungal biotransformations. In this review, selected examples the wonderful chemical diversity produced by fungi in kaurane diterpenes is presented. This diversity includes mainly hydroxylation of nearly all carbon atoms of the kaurane molecule, many of them carried out stereoselectively, as well as ring rearrangements, among other chemical modifications. Sources of starting materials, general biotransformation protocols employed, fungi with most consistent regioselectivity towards kaurane skeleton, as well as biological activities associated with starting materials and products are also described.

Anti-inflammatory and immunomodulatory activities of stevioside and steviol on colonic epithelial cells

BACKGROUND

Stevioside is a natural non-caloric sweetener isolated from Stevia rebaudiana Bertoni leaves. We have proposed its effect on attenuation of tumour necrosis factor α (TNF-α) and interleukin 1β (IL-1β) release in lipopolysaccharide (LPS)-stimulated monocytes. In this study, the anti-inflammatory and immunomodulatory activities of stevioside and its metabolite, steviol, on human colon carcinoma cell line (Caco-2) were evaluated.

RESULTS

Stevioside and steviol, in the doses used in this study, had no cytotoxicity on Caco-2 cells. Anti-inflammatory activities of these two compounds were observed by potentially suppressed LPS-mediated TNF-α, IL-1β and IL-6 release. In addition, stevioside and steviol showed immunomodulatory effects on IκBα activation and nuclear factor kappa B (NF-κB) suppression in western blotting.

CONCLUSION

Stevioside and steviol attenuate LPS-induced pro-inflammatory cytokine productions by affecting cytokine gene expression via IκBα/NF-κB signalling pathway.

Effect of Rebaudioside A, a diterpenoid on glucose homeostasis in STZ-induced diabetic rats

Rebaudioside A (Reb A), a major constituent of Stevia rebaudiana, was recently proposed as an insulinotropic agent. The aim of this investigation was to evaluate the antihyperglycemic effect of Reb A on the activities of hepatic enzymes of carbohydrate metabolism in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in adult male Albino Wistar rats, weighing 180-200 g, by a single intraperitoneal injection at a dose of STZ (40 mg/kg body weight). Diabetic rats showed significant (P<0.05) increase in the levels of plasma glucose and glycosylated hemoglobin and significant (P<0.05) decrease in the levels of plasma insulin and hemoglobin. Activities of gluconeogenic enzymes such as glucose-6-phosphatase and fructose-1,6-bisphosphatase were significantly (P<0.05) increased while hexokinase and glucose-6-phosphate dehydrogenase were significantly (P<0.05) decreased in the liver along with glycogen. Oral treatment with Reb A to diabetic rats significantly (P<0.05) decreased blood glucose and reversed these hepatic carbohydrate metabolizing enzymes in a significant manner. Histopathology changes of pancreas confirmed the protective effects of Reb A in diabetic rats. Thus, the results show that Reb A possesses an antihyperglycemic activity and provide evidence for its traditional usage in the control of diabetes.

Proteomic identification of proteins involved in the anticancer activities of oridonin in HepG2 cells

Oridonin is the main bioactive constituent of the Chinese medicinal herb Isodon rubescens and has been shown to have anti-neoplastic effects against a number of cancers in vitro and in vivo. Here we report the proteomic identification of proteins involved in the anticancer properties of oridonin in hepatocarcinoma HepG2 cells. Cell viability assay showed that oridonin dose-dependently inhibited cell growth with an IC(50) of 41.77μM. Treatment with oridonin at 44μM for 24h induced apoptosis and G2/M cell cycle arrest, which were associated with nine differentially expressed proteins identified by proteomic analysis. The proteomic expression patterns of Hsp70.1, Sti1 and hnRNP-E1 were confirmed by quantitative real-time PCR and/or immunoblotting. Eight of the nine identified proteins are shown, for the first time, to be involved in the anticancer activities of oridonin. Up-regulation of Hsp70.1, STRAP, TCTP, Sti1 and PPase, as well as the down-regulation of hnRNP-E1 could be responsible for the apoptotic and G2/M-arresting effects of oridonin observed in this study. Up-regulation of HP1 beta and GlyRS might contribute to inhibitory effects of oridonin on telomerase and tyrosine kinase, respectively. These findings shed new insights into the molecular mechanisms underlying the anticancer properties of oridonin in liver cancer cells.

Anxiolytic and sedative-hypnotic activities of polygalasaponins from Polygala tenuifolia in mice

In the present study, the anxiolytic and sedative-hypnotic activities of polygalasaponins extracted from Polygala tenuifolia Willdenow (Polygalaceae) were determined in mice using hole-board, elevated plus maze, open field, and sodium pentobarbital-induced hypnosis tests. Moreover, the acute toxicity of polygalasaponins was also estimated in mice. Sixty minutes after p.o. administration of polygalasaponins (40, 80, 160 mg/kg) in mice, the central crossing counts and percentage of central/total ambulation significantly increased and the number of rearings and defecations was evidently inhibited in the open field test. Polygalasaponins also increased the head-dips of mice in the hole-board test and the time spent by mice in the open arms of the X-maze, prolonged sleep duration and shortened sleep latency in the test of synergetic effect on sodium pentobarbital (45 and 25 mg/kg, respectively). Acute toxic study showed the oral median lethal dose (LD(50)) of polygalasaponins was 3.95 g/kg and 0% lethal dose 2.6 g/kg. These results suggest that polygalasaponin possesses evident anxiolytic and sedative-hypnotic activities and has a relatively safe dose range, which supports the use of Polygala tenuifolia root as an anxiolytic and sedative-hypnotic drug in folk medicine.

Ent-kaurane diterpenoids from Rabdosia rubescens and their cytotoxic effects on human cancer cell lines

Two new ent-kaurane diterpenoids, 16,17-exo-epoxide-oridonin ( 1) and 11,15- O,O-diacetyl-rabdoternins D ( 2), together with thirteen known ones, were isolated from the aerial parts of Rabdosia rubescens. Their structures were established on the basis of high-field 1D and 2D NMR methods supported by HRMS. All diterpenoids were tested for cytotoxicity against human Hep G2, COLO 205, MCF-7, and HL-60 cancer cells. The compounds oridonin ( 3), 14- O-acetyl-oridonin ( 4), 1,14- O,O-diacetyl-oridonin ( 5), rosthorin ( 6), effusanin E ( 7), and ponicidin ( 8), as well as six alpha-methylene gamma-ketone bearing diterpenoids, were modestly active in these assays.

Cytotoxic ent-kaurane diterpenoids from Isodon sinuolata

Five (1-5) ent-kaurane diterpenoids and 17 other known ones, were isolated from the leaves and stems of Isodon sinuolata. Their structures were determined on the basis of spectroscopic methods including 1D and 2D NMR spectroscopic analysis. All compounds were evaluated for cytotoxicity against a small panel of cell lines. Some compounds exhibited significant cytotoxicity.

Stevioside and related compounds: therapeutic benefits beyond sweetness

Stevioside, an abundant component of Stevia rebaudiana leaf, has become well-known for its intense sweetness (250-300 times sweeter than sucrose) and is used as a non-caloric sweetener in several countries. A number of studies have suggested that, beside sweetness, stevioside along with related compounds, which include rebaudioside A (second most abundant component of S. rebaudiana leaf), steviol and isosteviol (metabolic components of stevioside) may also offer therapeutic benefits, as they have anti-hyperglycemic, anti-hypertensive, anti-inflammatory, anti-tumor, anti-diarrheal, diuretic, and immunomodulatory actions. It is of interest to note that their effects on plasma glucose level and blood pressure are only observed when these parameters are higher than normal. As steviol can interact with drug transporters, its role as a drug modulator is proposed. This review summarizes the current knowledge of the pharmacological actions, therapeutic applications, pharmacokinetics and safety of stevioside and related compounds. Although much progress has been made concerning their biological and pharmacological effects, questions regarding chemical purity and safety remain unsolved. These issues are discussed to help guide future research directions.

Isosteviol increases insulin sensitivity and changes gene expression of key insulin regulatory genes and transcription factors in islets of the diabetic KKAy mouse

AIMS

Isosteviol (ISV), a diterpene molecule, is an isomer of the backbone structure of a group of substances with recently proven antidiabetic capabilities in both man and rodents. The aim of this study was to investigate if ISV possesses beneficial effects on the metabolism in the diabetic KKAy mouse and to establish the long-term in vivo effects of ISV on the gene expression profile of key insulin regulatory genes in islets.

METHODS

Twenty KKAy mice, aged 5 weeks, were divided into two groups and treated for 9 weeks with either (i) standard chow diet (control) or (ii) chow + 20 mg/kg body weight of ISV. Blood samples were collected before and after intervention and were subsequently analysed. As a non-diabetic control group, 10 normal C57BL mice were fed with standard chow diet. Gene expression was determined in islets by quantitative real-time RT-PCR and Affymetrix microarray.

RESULTS

We demonstrated that long-term treatment with ISV improves glucose homeostasis, increases insulin sensitivity, lowers plasma triglycerides and lowers weight in the diabetic KKAy mice. Furthermore, ISV markedly changes the gene expression profile of key insulin regulatory genes GLUT2, Ins1, Ins2, Pdx1/Ipf1, Beta2/Neurod1, Pax6 and 11-beta-HSD-1 and beta-cell transcription factors Nkx2-2, Nkx6-1, C/EBPalpha and FoxA2 in isolated islets of the KKAy mice.

CONCLUSIONS

The results indicate that ISV improves glucose and insulin sensitivity as well as improving the lipid profile and upregulates the gene expression of key beta-cell genes, including insulin regulatory transcription factors.

The neuroprotective effects of isosteviol against focal cerebral ischemia injury induced by middle cerebral artery occlusion in rats

Occlusion of a cerebral artery impairs blood flow leading to neuronal death. Reperfusion of the tissue is associated with inflammation, increased reactive oxygen species, necrosis and apoptosis. Hence, damage to the brain will continue even after the blood flow is restored. Isosteviol has been demonstrated to have protective effects against ischemia-reperfusion (IR) injury in the rat heart and the current study was undertaken to determine whether it is also effective in preventing IR injury in the brain. Rats were divided into six groups: a sham-operation control group and 5 IR groups that were pre-treated with either isosteviol 5 mg.kg (-1), 10 mg.kg (-1), 20 mg.kg (-1), nimodipine 5 mg.kg (-1), or saline. Cerebral ischemia was induced for 2 hours. Twenty-two hours after re-perfusion the rats were assessed for neurobehavioral deficit, infarct volume, histological changes, and malondialdehyde, superoxide dismutase (SOD), Bcl-2 and NF-kappaB levels in brain tissue. Pre-treatment with isosteviol reduced infarct volume, ameliorated cell death and infiltration of neutrocytes, improved neuro-locomotor activity, increased SOD activity, induced Bcl-2, suppressed lipid superoxidation and the expression of NF-kappaB, and therefore retarded necrosis and apoptosis of neurons and inflammation. These positive effects were dose-dependent with an isosteviol dose of 20 mg.kg (-1), thus being as effective as nimodipine.

Novel ent-Beyeran-19-oic acids from biotransformations of isosteviol metabolites by Mortierella isabellina

Biotransformations of ENT-16beta-hydroxybeyeran-19-oic acid ( 1) by Mortierella isabellina produced hydroxylated metabolites. The isolated metabolites included three new compounds, ent-14beta,16beta-dihydroxybeyeran-19-oic acid ( 3), ent-12beta-hydroxy-16-oxobeyeran-19-oic acid ( 4), and ent-7alpha,12beta-dihydroxy-16-oxobeyeran-19-oic acid ( 5), and one known compound, ent-7alpha,16beta-dihydroxybeyeran-19-oic acid ( 2). The structural elucidation was achieved by detailed analysis of LC-MS chromatograms, and MS and NMR spectroscopic data. In this study, M. isabellina hydroxylated the basic skeleton beyeran-19-oic acid at the 7beta-, 12alpha-, and 14alpha-positions, and oxidized the skeleton at the 16-position. All compounds were evaluated with the cell viability assay. The results of the bioassay indicated that MTT formazan exocytosis occurs upon treatment of the cells with 1.

THE EFFECTS OF ISOSTEVIOL AGAINST MYOCARDIUM INJURY INDUCED BY ISCHAEMIA?REPERFUSION IN THE ISOLATED GUINEA PIG HEART

1. This study aimed to investigate the protective effects of isosteviol against myocardial ischaemia-reperfusion (IR) injury and its effects on mitochondrial adenosine triphosphate (ATP)-sensitive potassium channel (mitoK(ATP)) activity in vitro. 2. Groups of eight guinea pigs were treated as follows: constant perfusion control (PC), IR control, ischaemic preconditioning (IPC) + IR, isosteviol (50, 250 or 500 nmol) + IR, 5-hydroxydecanoate acid (5-HD) (5 micromol) + isosteviol (500 nmol) + IR. The guinea pig heart was isolated and perfused in Langendorff mode with modified Tyrode solution at a flow rate of 10 mL/min. Ischaemia was introduced for 30 min followed by reperfusion for 20 min. Cardiac function, coronary arterial flow rate, lactate dehydrogenase (LDH) and creatine kinase (CK) activities in the perfusate were measured prior to ischaemia and at the end of reperfusion. 3. There were no significant (P > 0.05) changes in cardiac function or markers of cell damage (i.e. activities of LDH and CK) in the PC group. In contrast, cardiac function was adversely affected in the IR group, with significant (P < 0.05) decreases in left ventricular developing pressure (LVDevP), dP/dt(max) and dP/dt(min) compared with baseline and the PC group. In addition, there were increases in activity of LDH (20%) and CK (67%) compared with baseline and the PC group. 4. Ischaemic preconditioning and pretreatment with isosteviol, at all dose levels, resulted in a significant (P < 0.05) attenuation of IR injury. Lactate dehydrogenase and CK activities were not significantly (P < 0.05) different compared with baseline. Isosteviol did not increase coronary flow, suggesting that the protective effect of isosteviol on the myocardium was not mediated by dilation of the coronary blood vessels. 5. Pretreatment with the mitoK(ATP) blocker 5-HD partially antagonized the effects of 500 nmol isosteviol, with a statistically significant attenuation of its protective effects on HR, LVDevP, dP/dt(max) and dP/dt(min) compared with isosteviol alone pretreatment. 6. The IR injury on the Langendorff perfused guinea pig heart was alleviated by isosteviol, which appears to mediate its effects through mitoK(ATP) channels. Future research might aim to investigate the interaction of isosteviol with mitoK(ATP) channels in order to clarify its mechanism of action.

The cardioprotective effect of isosteviol on rats with heart ischemia-reperfusion injury

This study was designed to assess the cardioprotective effect of isosteviol on rats with heart ischemia-reperfusion (IR) injury and to explore the mechanism of action of the compound. Sprague Dawley rats were divided into 8 groups (n=10-12): a sham-operated control and 7 ischemia-reperfusion groups (IR control, 3 isosteviol pre-treated (0.5, 1.0 and 2.0 mg kg(-1)), ligustrazine pre-treated, 5-hydroxydecanoate (5-HD) pre-treated and 5-HD+ isosteviol pre-treated groups). IR was produced by occluding the left coronary artery for 30 min followed by re-opening the artery for 90 min. The compounds under investigation were administered intravenously 10 min prior to occluding the artery. Hemodynamic parameters (+/-dp/dt(max), LVSP, LVDevP, MAP), heart rate, ventricular tachycardia (VT) and ventricular fibrillation (VF) were determined during the IR period. The myocardial infarct size, activities of serum lactate dehydrogenase and creatine kinase were determined at the end of the experiment. In the isosteviol pre-treated groups, the hemodynamic parameters were improved and the myocardial infarct size, the activities of serum enzymes, and the incidences of VT and VF were all decreased when compared to the control group. These effects of isosteviol were similar to that of a traditional cardioprotective agent, ligustrazine. The 5-HD+ isosteviol group displayed parameters that were between those in the equivalent isosteviol pre-treated group and the IR control group. In conclusion, damage due to a standard rat heart IR injury was reduced by pretreatment with intravenous isosteviol, and this effect was partly attenuated by a mitochondrial ATP-sensitive potassium channel blocker, 5-HD.

Antiproliferative ent-Kauranoids from Isodon parvifolius

Nine new 7alpha,20-epoxy- ENT-kaurane diterpenoids, parvifolines O - W (1 - 9), together with five known analogues, lasiocarpanin (10), rosthorin A (11), longikaurin E (12), adenolin D (13) and longikaurin B (14), were isolated from the leaves of Isodon parvifolius. Their structures were determined by means of spectroscopic analysis. Selected diterpenoids (1 - 10) were tested for their antiproliferative activity against A549, HT-29 and K562 cells. Compounds 3, 7, 8 and 10 showed moderate inhibitory activity against all three cell lines.

Comparative effects of Stevia rebaudiana leaves and stevioside on glycaemia and hepatic gluconeogenesis

The purpose of the present study was to compare the effect of the oral treatment (gavage) with Stevia rebaudiana (Bert.) Bertoni (SRB) and stevioside (STV) on glycaemia and gluconeogenesis of 15-h fasted rats. For this purpose, the rats received SRB (20 mg/kg x day), STV (5.5 mg/kg x day) or an equal volume of water (controls) during 15 days. To measure hepatic gluconeogenesis, liver perfusion and isolated hepatocytes were used. Glycaemia and gluconeogenesis from L-alanine (5 mM), L-glutamine (5 mM) and L-lactate (2 mM) were decreased (P < 0.05) after pre-treatment with SRB. However, the treatment with STV did not influence glycaemia and gluconeogenesis. Moreover, to get further information about the mechanism by which SRB leaves inhibit gluconeogenesis their potential role as a PPARgamma agonist was investigated. The data showed absence of activation of PPARgamma receptors. In summary, our results showed that the reduction of glycaemia promoted by the treatment with SRB leaves was mediated, at least in part, by an inhibition of hepatic gluconeogenesis. However, this effect did not involve stevioside and the activation of PPARgamma receptors.

An anti-inflammatory ent-kaurane from the stems of Annona squamosa that inhibits various human neutrophil functions

We have previously shown that 11 ent-kauranes isolated from the stems of Annona squamosa exhibited immunomodulating effects in leukocytes. In this study, a cellular model using isolated human neutrophils, which are important in the pathogenesis of rheumatoid arthritis, ischemia-reperfusion injury, chronic obstructive pulmonary disease, asthma and other inflammatory diseases, was established in order to elucidate the anti-inflammatory functions of 16beta,17-dihydroxy-ent-kauran-19-oic acid (1). Reactive oxygen species (ROS) and granule proteases produced by neutrophils contribute to the pathogenesis of inflammatory diseases. Compound 1 inhibited the generation of superoxide anion, the formation of ROS, and the release of elastase in formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP)-activated human neutrophils in a concentration-dependent manner with IC (50) values of 3.95 +/- 0.68, 12.20 +/- 2.16, and 12.52 +/- 2.26 microM, respectively. The anti-inflammatory actions were not attributable to cytotoxicity because incubation of the neutrophils with 1 did not result in lactate dehydrogenase release. Compound 1 did not display antioxidant or superoxide anion-scavenging activity. Furthermore, neither subcellular NADPH oxidase activity nor cAMP-dependent pathways were altered by 1. Compound 1 significantly inhibited rapid calcium release from internal calcium stores induced by FMLP but not by thapsigargin. In summary, the presented results indicate that the inhibitory effects of 1 on respiratory burst and degranulation of human neutrophils are through the inhibition of cytosolic calcium mobilization, but not via the cAMP-dependent pathways.

Increase of insulin sensitivity by stevioside in fructose-rich chow-fed rats

The intake of dietary fructose has undergone a marked increase around the world, especially the developed countries, in recent times. Stevioside, a glycoside contained in the leaves of Stevia rebaudiana Bertoni (Compositae), was used to screen the effect induced by a diet containing 60% fructose on insulin resistance in rats. Single oral administration of stevioside for 90 min decreased plasma glucose concentrations in a dose-dependent manner in rats receiving fructose-rich chow for four weeks. In addition, insulin action on glucose disposal rate was measured using the glucose-insulin index, the product of the areas under the curve of glucose, and insulin during the intraperitoneal glucose tolerance test. Oral administration of stevioside (5.0 mg/kg) in rats given four weeks of fructose-rich chow for 90 min reversed the value of glucose-insulin index, indicating that stevioside has the ability to improve insulin sensitivity in this insulin-resistant animal model. Time for the loss of plasma glucose lowering response to tolbutamide (10.0 mg/kg, i. p.) in fructose-rich chow fed rats was also markedly delayed by repeated stevioside treatment three times daily compared to the vehicle-treated group. The plasma glucose-lowering activity of tolbutamide was introduced to account for varying levels of endogenous insulin secretion, and is widely used as the indicator of insulin resistance development. Thus, it provided the supportive data that repeated oral administration of stevioside delayed the development of insulin resistance in rats on a high-fructose diet. Increased insulin sensitivity by stevioside administration was further identified using the plasma glucose-lowering action of exogenous insulin in streptozotocin-induced diabetic rats (STZ-diabetic rats). Oral administration of stevioside at 0.2 mg/kg three times daily into STZ-diabetic rats for ten days increased the response to exogenous insulin. Taken together, this demonstrated that oral administration of stevioside improves insulin sensitivity, and seems suitable as an adjuvant for diabetic patients and/or those that consume large amounts of fructose.

Two novel ent-kauranoid diterpenoids from Isodon japonica leaves

Two novel ent-kaurane diterpenoids, taihangjaponicain A (1), and taihangjaponicain B ( 2), and nine known diterpenoids, epinodosin (3), oridonin (4), epinodosinol (5), lasiokaurin ( 6), 1alpha- O-beta- D-glucopyranosylenmenol (7), lasiodonin (8), rabdosichuanin D ( 9), shikokianin (10) and rabdoternin A (11) were isolated from I. japonica leaves. The structures of the two new compounds were elucidated using 1-D and 2-D NMR spectroscopy. Compounds 1 and 3 - 11 were tested against HL-60, HO-8910 and A-549 human tumor cells. Compounds 4, 6 and 10 showed significant cytotoxicity against HL-60 cells with IC (50) values of 4.6, 2.0 and 3.4 microM, respectively, and against A-549 cells with IC (50) values of 17.5, 11.4 and 18.8 microM, respectively. Compound 6 exhibited moderate cytotoxicity against HO-8910 cells with an IC (50) value of 17.9 microM.