Antihyperglycemic and antihyperlipidemic activity of ethyl acetate fraction of Rhododendron arboreum Smith flowers in streptozotocin induced diabetic rats and its role in regulating carbohydrate metabolism

Hypericum perforatum L. extract exerts insulinotropic effects and inhibits gluconeogenesis in diabetic rats by regulating AMPK expression and PKCε concentration

ETHNOPHARMACOLOGICAL RELEVANCE

Hypericum perforatum L., commonly known as St. John's Wort (SJW), represents one of the best-known and most thoroughly researched medicinal plant species. The ethnobotanical usage and bioactivities related to H. perforatum include treatment of skin diseases, wounds and burns, gastrointestinal problems, urogenital diseases and psychiatric disorders, particularly depression. In the last decade, many studies focused on the bioactive constituents responsible for the antihyperglycemic and antidiabetic activity of SJW extracts. However, the mechanism by which H. perforatum extract exhibits these properties is still unclear. Hence, the current study was designed to gain insight into the underlying biochemical and molecular mechanisms by which wildly growing H. perforatum exerts its antihyperglycemic and antidiabetic activities.

MATERIAL AND METHODS

Plant material of H. perforatum was harvested from a natural population in the Republic of North Macedonia during full flowering season. Methanol (80% v/v) was used to extract bioactive components from HH powder. The dissolved HH dry extract (in 0.3% CMC) was given daily as a single treatment (200 mg/kg bw) during 14 days both in healthy and streptozotocin-induced diabetic rats. As a positive control, we applied glibenclamide. The activity of key enzymes involved in carbohydrate methabolisam in the liver were assessed, along with substrate concentration, as well as AMPK mRNA levels, PKCε concentration, plasma insulin level and pancreatic PARP activity.

RESULTS

Compared to diabetic rats, treatment of diabetic rats with HH extract resulted with decreased activity of hepatic enzymes glucose-6-phospatase and fructose-1,6-bisphosphatase, increased liver glycogen and glucose-6-phosphate content, which resulted with reduced blood glucose concentration up to normoglycaemia. Non-significant changes were observed in the activity of hexokinase, glycogen phosphorylase and glucose-6-phospahte dehydrogenase. HH-treatment also caused an increase in plasma insulin concentration and increase in pancreatic PARP activity. Finally, HH treatment of diabetic rats showed significant increase in AMPK expression and decrease of PKCε concentration.

CONCLUSION

We present in vivo evidence that HH- extract exert insulinotropic effects and regulate endogenous glucose production mostly by suppressing liver gluconeogenesis. The HH-treatment did not effected glycogenolysys and glycolysis. Finally, we confirm the antihyperglycemic and antidiabetic effect of HH-extract and the mechanism of this effect involves amelioration of AMPK and PKCε changes in the liver.

Restorative Effect of Semecarpus Anacardium on Altered Energy Metabolism in Type-2 Diabetes Mellitus-Induced Cardiac Dysfunction in Rats

Semecarpus anacardium is an important herbal drug that has been used against various ailments. To evaluate the cardioprotective effect of the drug against altered cardiac energy metabolism in type-2 diabetes rats, type-2 diabetes was induced in rats by feeding them with a high-fat diet for 2 weeks followed by intraperitoneal injection of streptozotocin (STZ) 35 mg/kg body weight twice 24 h apart and left for 12 weeks to develop cardiovascular complication. The effects of the nut milk extract on the glucose metabolizing enzymes and mitochondrial complex enzymes were studied using biochemical assays. The drug effectively ameliorated the alteration in cardiac energy metabolism in diabetic rats. The cardioprotective effect may be mediated through the ability of the drug to enhance glucose utilization and control the oxidative stress under diabetic conditions.

Self microemulsifying formulation of Lagerstroemia speciosa against chemically induced hepatotoxicity

Self microemulsifying formulation is an approach used for enhancing the bioavailability of poorly soluble molecules due to their lipidic nature and small particle size. The objective of the present study was to evaluate the hepatoprotective activity of poorly soluble hydroxy- and polyhydroxy-organic phytomolecules rich Lagerstroemia speciosa leaves extract in modern formulation i.e. "Self microemulsifying System". Different doses of SME (Self microemulsifying) formulation of L. speciosa leaves extract were evaluated for the hepatoprotective activity against carbon tetrachloride induced liver toxicity in rats. The parameters evaluated were (a) biochemical parameters like serum enzymes: aspartate aminotransferase (AST), serum glutamate pyruvate transaminase (ALT), serum alkaline phosphatase (ALP) and total bilirubin (b) liver antioxidant parameters as estimation of Lipid peroxidation (LPO), catalase (CAT), Superoxide dismutase (SOD) activity and concentration of reduced glutathione (GSH). Oral administration of SME formulation provided the significant protection in marker enzyme of treated group at 100 mg/kg, p.o. as AST (P < 0.001), ALT (P < 0.001), ALP (P < 0.001) and total bilirubin (P < 0.001) comparable to the group treated with silymarin. Treatment with SME formulation at the doses of 100 mg/kg, p.o. significantly prevented the rise in levels of LPO significantly (P < 0.001). The GSH, SOD and CAT contents had significantly (P < 0.001) increased in SME formulation treated groups whereas carbon tetrachloride intoxicated group had shown significant decrease in these parameters compared to control group. Formulation at the dose 100 mg/kg, p.o. has shown maximum protection which was almost comparable to those of the normal control and standard. The histological observations further uphold the results for hepatoprotective activity.

Pharmacodynamic evaluation of self micro-emulsifying formulation of standardized extract of Lagerstroemia speciosa for antidiabetic activity

BACKGROUND

Lagerstroemia speciosa (SEL) leaves are a popular folk medicine for diabetes treatment due to presence of corosolic acid. It has low water solubility resulting poor absorption after oral administration. Self micro-emulsified drug delivery system is the way by which we can improve the oral absorption of drug.

OBJECTIVE

The objective of this study was to develop the self micro-emulsifying formulation of standardized extract of SEL leaves and evaluate its pharmacodynamic performance for antidiabetic activity.

MATERIALS AND METHODS

The SME formulation was prepared by using sefsol-218 as oil, cremophor-EL as surfactant and transcutol-P as co-surfactant. The ratio of surfactant and co-surfactant was determined by pseudoternary phase diagram. SME formulations were characterized for dilution at different pH, self emulsification, optical clarity, globule size and thermodynamic stability. Pharmacodynamic evaluation of formulations was assessed in Wistar rats by using parameters viz. blood glucose level and serum lipid profile.

RESULTS

SEL loaded SME formulation was successfully developed by using sefsol-218, cremophor-EL and transcutol-P with a droplet size 23.53 nm. Pharmacodynamic results showed a higher reduction in blood glucose by SME formulation than SEL without SMES respectively at 50 mg/kg dose while reduction produced at dose of 100 mg/kg was found significant and better on 15th day of study. The percentage reduction produced by SME formulation on serum lipid profile was also significant and was more prominent than SEL.

CONCLUSION

This study confirms that the formulation elevates the pharmacodynamic performance of SEL approximately two fold.

Rhododendron oldhamii leaf extract improves fatty liver syndrome by increasing lipid oxidation and decreasing the lipogenesis pathway in mice

Some members of Rhododendron genus are traditionally used as medicinal plants for arthritis, acute and chronic bronchitis, asthma, pain, inflammation, rheumatism, hypertension and metabolic diseases. To the best of our knowledge, there is no report on the protective effects of R. oldhamii leaf extract on non-alcoholic fatty liver disease (NAFLD) in vivo and in vitro. In this study, the effects of R. oldhamii leaf extract on inhibiting the free fatty acid (FFA)-induced accumulation of fat in HepG2 cells and on improving fatty liver syndrome in mice with high fat diet (HFD)-induced NAFLD were investigated. For the in vitro assay, HepG2 cells were treated with FFAs (oleate/palmitate = 2:1) with or without treatment with R. oldhamii leaf ethyl acetate (EtOAc) fraction to observe lipid accumulation using Nile red and oil red O stains. For the in vivo assay, C57BL/6 mice were randomly assigned to three groups (n = 5), including the normal diet group, the HFD group and the HFD+EtOAc group. After 11 weeks, body weight, serum biochemical indices and the mRNA expressions of the liver tissue, as well as the outward appearance, weight and histopathological analysis of liver and adipose tissues were evaluated. Among the fractions derived from R. oldhamii leaf, the EtOAc fraction exhibited a strong fat-accumulation inhibitory activity. Following reverse-phase high-performance liquid chromatography (HPLC), four specific phytochemicals, including (2R, 3R)-astilbin (AS), hyposide (HY), guaijaverin (GU) and quercitrin (QU), were isolated and identified from the EtOAc fraction of R. oldhamii leaf extract. Among them, AS and HY showed excellent fat-accumulation inhibitory activity. Thus, the EtOAc fraction of R. oldhamii leaf and its derived phytochemicals have great potential in preventing FFA-induced fat accumulation. In addition, the EtOAc fraction of R. oldhamii leaf significantly improved fatty liver syndrome and reduced total cholesterol (TC) and triglyceride (TG) in HFD-induced NAFLD mice at a dosage of 200 mg/kg BW. These results demonstrated that the methanolic extracts from R. oldhamii leaf have excellent inhibitory activities against fat accumulation and anti-NAFLD activities and thus have great potential as a natural health product.

Antinociceptive and anti-inflammatory potential of Rhododendron arboreum bark

Rhododendron arboreum Smith. (Ericaceae), an evergreen small tree, is one of the 1000 species that belongs to genus Rhododendron distributed worldwide. In folk medicine, as various parts of this plant exhibit medicinal properties, it is used in the treatment of different ailments.The present study was designed to evaluate the potential anti-inflammatory and antinociceptive effects of methanolic extract of R. arboreum bark, followed by activity-guided fractionation of n-hexane, n-butanol, chloroform, ethyl acetate and aqueous fractions.The ethyl acetate fraction (200 mg/kg i.p.) showed the maximum analgesic effect (82%) in acetic acid-induced writhing, followed, to a less extent, by crude extract and chloroform fraction both at a dose of 200 mg/kg i.p. (65.09% and 67.89%, respectively). In carrageenan-induced mouse paw oedema, the crude extract and its related fractions displayed in a dose-dependent manner (50-200 mg/kg i.p.) an anti-inflammatory activity for all time-courses (1-5 hrs). For the active extract/fractions (200 mg/kg i.p.), the maximum effect was observed 5 h after carrageenan injection. These evidences were also supported by in vitro lipoxygenase inhibitory properties. In conclusion, R. arboreum crude methanolic extract and its fractions exhibited anti-inflammatory and antinociceptive effects. For these reasons, this plant could be a promising source of new compounds for the management of pain and inflammatory diseases.

The genus Rhododendron: an ethnopharmacological and toxicological review

ETHNOPHARMACOLOGICAL RELEVANCE

The vast genus Rhododendron includes species that have been used in traditional medicine for the treatment of inflammatory conditions, pain, gastro-intestinal disorders, common cold, asthma, skin disease, etc. Rhododendrons are also well known for their toxicity and some species have been traditionally used as poison.

AIM OF THE REVIEW

The work reviews and analyses the traditional use, biological activities with the corresponding chemical constituents, and toxicological data on Rhododendron species. The review aims at characterizing the ethnopharmacology of the genus in relation to its toxicity in order to identify the therapeutic potential of Rhododendron species and future directions for research.

METHODS

Data regarding Rhododendron spp. was collected using electronic databases (SciFinder, PubMed, Google Scholar) and library search for selected peer-reviewed articles. Plant taxonomy was validated by the databases The Plant List, Tropicos, eFloras, Flora Iberica and Flora Europaea (RBGE). Additional information on traditional use and botany was obtained from published books. The review encompasses literature, mainly regarding biological activity and toxicological data, from 1898 to the end of December 2012.

RESULTS

Rhododendrons have been used in Asian, North American and European traditional medicine mainly against inflammation, pain, skin ailments, common cold and gastro-intestinal disorders. In vivo and in vitro testing of plant extracts and isolated compounds determined diverse biological activities including anti-inflammatory, analgesic, anti-microbial, anti-diabetic, insecticidal and cytotoxic activity. Rhododendron spp. can cause intoxications in humans following intake of rhododendron honey or medicinal preparations. The toxicity is due to grayanotoxins, diterpenes which activate voltage-gated sodium channels and lead to gastro-intestinal, cardiac and central nervous system symptoms.

CONCLUSION

Rhododendron species are useful traditional remedies for the treatment of inflammation, pain, skin ailments, common cold and gastro-intestinal disorders. Pharmacological data has validated most indications of rhododendrons in ethnomedicine and toxicology studies have confirmed the toxicity observed by traditional use. Ethnopharmacological data point to the therapeutic potential of the genus Rhododendron for the treatment of inflammatory conditions and pain and, thus, research should focus on identification of active compounds and related mechanistic studies. Prolonged and high dose intake of traditional formulations containing rhododendrons should be avoided until more in depth toxicity studies become available.