Further evaluation of antihyperglycaemic activity of Hunteria umbellata (K. Schum) Hallier f. seed extract in experimental diabetes

Hunteriasines A - D, tryptamine-derived alkaloids from Hunteria umbellata

Four undescribed tryptamine-derived alkaloids, hunteriasines A - D, were isolated and identified from Hunteria umbellata (Apocynaceae), together with fifteen known indole alkaloids. The chemical structure and absolute configuration of hunteriasine A were determined by spectroscopic and X-ray crystallographic data analyses. Hunteriasine A, featuring with a unique scaffold comprised of tryptamine and an unprecedented "12-carbon unit" moiety, is a zwitterionic indole-derived and pyridinium-containing alkaloid. Hunteriasines B - D were identified by spectroscopic data analyses and theoretical calculations. A plausible biogenetic pathway for hunteriasines A and B was proposed. The lipopolysaccharide-stimulated mouse macrophage cell line J774A.1 cell-based bioactivity assays revealed that (+)-eburnamine, strictosidinic acid, and (S)-decarbomethoxydihydrogambirtannine enhance the release of interleukin-1β.

Antihyperglycemic Potential of Spondias mangifera Fruits via Inhibition of 11β-HSD Type 1 Enzyme: In Silico and In Vivo Approach

The 11 β- hydroxysteroid dehydrogenase 1 (11 β-HSD1) is hypothesized to play a role in the pathogenesis of type 2 diabetes and its related complications. Because high glucocorticoid levels are a risk factor for metabolic disorders, 11β-HSD1 might be a viable therapeutic target. In this investigation, docking experiments were performed on the main constituents of Spondias mangifera (SM) oleanolic acid, β-amyrin, and β-sitosterol to ascertain their affinity and binding interaction in the human 11β-hydroxysteroid dehydrogenase-1 enzyme’s active region. The results of in vitro 11β HSD1 inhibitory assay demonstrated that the extract of S. mangifera had a significant (p < 0.05) decrease in the 11-HSD1% inhibition (63.97%) in comparison to STZ (31.79%). Additionally, a non-insulin-dependent diabetic mice model was used to examine the sub-acute anti-hyperlipidemic and anti-diabetic effects of SM fruits. Results revealed that, in comparison to the diabetic control group, SM fruit extract (SMFE) extract at doses of 200 and 400 mg/kg body weight considerably (p < 0.05 and p < 0.01) lowered blood glucose levels at 21 and 28 days, as well as significantly decreased total cholesterol (TC) and triglycerides (TG) and enhanced the levels of high-density lipoprotein (HDL). After 120 and 180 s of receiving 200 and 400 mg/kg SMFE, respectively, disease control mice showed significantly poorer blood glucose tolerance (p < 0.05 and p < 0.01). SMFE extract 200 (p < 0.05), SMFE extract 400 (p < 0.01), and Glibenclamide at a dosage of 5 mg/kg body weight all resulted in statistically significant weight increase (p < 0.01) when compared to the diabetic control group after 28 days of treatment. According to in silico, in vitro, and in vivo validation, SMFE is a prospective medication with anti-diabetic and hypoglycemic effects.

In vivo antihyperglycaemic and antihyperlipidemic activities and chemical constituents of Solanum anomalum

Solanum anomalum is a plant used ethnomedically for the treatment of diabetes. The study was aimed to validate ethnomedical claims in rat model and identify the likely antidiabetic compounds. Leaf extract (70-210 mg/kg/day) and fractions (140 mg/kg/day) of S. anomalum were evaluated in hyperglycaemic rats induced using alloxan for effects on blood glucose, lipids and pancreas histology. Phytochemical characterisation of isolated compounds and their identification were performed using mass spectrometry and NMR spectroscopy. Bioinformatics tool was used to predict the possible protein targets of the identified bioactive compounds. The leaf extract/fractions on administration to diabetic rats caused significant lowering of fasting blood glucose of the diabetic rats during single dose study and on repeated administration of the extract. The hydroethanolic leaf extracts also enhanced glucose utilization capacity of the diabetic rats and caused significant lowering of glycosylated hemoglobin levels and elevation of insulin levels in the serum. Furthermore, triglycerides, LDL-cholesterol, and VLDL-cholesterol levels were lowered significantly, while HDL-cholesterol levels were also elevated in the treated diabetic rats. There was absence or few pathological signs in the treated hyperglycaemic rat pancreas compared to that present in the pancreas of control group. Diosgenin, 25(R)-diosgenin-3-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside, uracil, thymine, 1-octacosanol, and octacosane were isolated and identified. Protein phosphatases along with secreted proteins are predicted to be the major targets of diosgenin and the diosgenin glycoside. These results suggest that the leaf extract/fractions of S. anomalum possess antidiabetic and antihyperlipidemic properties, offer protection to the pancreas and stimulate insulin secretion, which can be attributable to the activities of its phytochemical constituents.

Ethnopharmacological Study of Medicinal Plants Used for the Treatment of Cardiovascular Diseases and Their Associated Risk Factors in sub-Saharan Africa

Cardiovascular diseases (CVDs) are the leading cause of global mortality, including deaths arising from non-communicable diseases in sub-Saharan Africa (SSA). Consequently, this study aimed to provide details of medicinal plants (MPs) employed in SSA for the treatment of CVDs and their related risk factors to open new avenues for the discovery of novel drugs. The extensive ethnopharmacological literature survey of these MPs in 41 SSA countries was based on studies from 1982 to 2021. It revealed 1,085 MPs belonging to 218 botanical families, with Fabaceae (9.61%), Asteraceae (6.77%), Apocynaceae (3.93%), Lamiaceae (3.75%), and Rubiaceae (3.66%) being the most represented. Meanwhile, Allium sativum L., Persea americana Mill., Moringa oleifera Lam., Mangifera indica L., and Allium cepa L. are the five most utilised plant species. The preferred plant parts include the leaves (36%), roots (21%), barks (14%), fruits (7%), and seeds (5%), which are mostly prepared by decoction. Benin, Mauritius, Nigeria, South Africa, and Togo had the highest reported use while most of the investigations were on diabetes and hypertension. Despite the nutraceutical advantages of some of these MPs, their general toxicity potential calls for caution in their human long-term use. Overall, the study established the need for governments of SSA countries to validate the efficacy/safety of these MPs as well as provide affordable, accessible, and improved modern healthcare services.

Ethno-medicinal, phytochemistry, and pharmacological importance of Hunteria umbellate (K. Schum.) Hallier f. (Apocynaceae): a useful medicinal plant of sub-Saharan Africa

Background

Hunteria umbellate (K. Schum.) Hallier f. (Apocynaceae) is a tropical rainforest tree commonly found in sub-Saharan region of Africa. It is a useful and very popular plant among the locals due to the outstanding anti-diabetic activity of the seeds.

Methods

A comprehensive literature search on articles published on phytochemical analysis and various pharmacological activities of Hunteria umbellate was carried out using search engines such as Google Scholar, PubMed and Science Direct.

Results

In this review, it was deduced that H. umbellate is employed in folk medicine as an elixir for obesity, fever, leprosy sores, menstrual pain, infertility, yaws, intestinal worms, abdominal discomfort and stomach ache. Due to their durability and immunity against termites, the stems are coveted and desired as timbers in the construction of houses, while the bark has been reportedly exported to Europe for medicinal uses. Pharmacological activities such as fertility enhancing, aphrodisiac, hypoglycemic, anti-inflammatory, has been ascribed to the different morphological organs of H. umbellate. Moreover, compounds belonging to important classes of secondary metabolites with biological activities such as triterpenoids, flavonoids, tannins, alkaloids, quinic acids have been identified and characterized from the plant.

Conclusion

From this review, it can be inferred that, numerous and bioactive principles with known biological usefulness are present in the extracts of H. umbellate and might be responsible for the observed biological and pharmacological activities.

Gongronema latifolium leaf extract modulates hyperglycaemia, inhibits redox imbalance and inflammation in alloxan-induced diabetic nephropathy

Background

Gongronema latifolium leaf is used traditionally to treat diabetes and other diseases. The present study aimed to provide the modulatory effect of G. latifolium on hyperglycemia, inhibitory effect of redox imbalance and inflammation in alloxan-induced nephropathy in Wistar rats.

Methods

Alloxan monohydrate was used to induce diabetes by an intraperitoneal injection of (150 mg/kg). Three diabetic groups were administered aqueous leaf extract of G. latifolium at 6.36, 12.72 and 25.44 mg/kg bodyweight (BW) respectively; a group was administered with metformin (5 mg/kg BW), while the other two were served as positive and negative control. Thereafter, fasting blood glucose, antioxidant enzymes, malondialdehyde (MDA) level, interleukin 2 and 6 were determined.

Results

G. latifolium leaf significantly (p < 0.05) reduced the alloxan-induced increases in blood glucose, MDA, interleukin 2 and interleukin 6 level and increased the alloxan-induced decreases in superoxide dismutase, catalase, glutathione peroxidase, glutathione reduced and glutathione transferase activity. All these changes compared with those of metformin-treated diabetic rats.

Conclusion

The data from this study suggest that G. latifolium modulates glucose homeostasis as well as inhibiting redox imbalance and inflammation in diabetic rats, which may be attributed to the effects of its phytochemical constituents such as saponins, flavonoids and alkaloids. It also indicated that inhibition of inflammatory cytokines and redox imbalance are likely mechanisms by which G. latifolium leaf exert its antidiabetic action.

Aqueous seed extract of Hunteria umbellata (K. Schum.) Hallier f. (Apocynaceae) palliates hyperglycemia, insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Hunteria umbellata is used in the management and treatment of diabetes and obesity in Nigeria. This study evaluates the effect of aqueous seed extract of Hunteria umbellata on insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome MATERIALS AND METHODS: Rats were randomized into seven groups (A-G). Control (group A) and group C rats received control diet for nine weeks while rats in groups B, D - G were placed on high-fructose diet for 9 weeks. In addition to the diets, groups C - F rats orally received 400, 100, 200 and 400mg/kg body weight aqueous seed extract of Hunteria umbellata for 3 weeks starting from 6th - 9th week.

RESULTS

High-fructose diet (when compared to control rats) mediated a significant (p<0.05) increase in body weight, body mass index and abdominal circumference. Similarly, levels of blood glucose, insulin, leptin, adiponectin and insulin resistance were increased. It also caused a significant increase in the levels of cholesterol, triglycerides, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, atherogenic index, cardiac index and coronary artery index while high-density lipoprotein cholesterol was decreased significantly. Levels of proinflammatory factor, tumour necrosis factor-α, interleukin-6 and 8 were also increased by the high fructose diet. Moreover, it mediated decrease in activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose 6-phosphate dehydrogenase and level of glutathione reduced. Conversely, levels of malondialdehyde, conjugated dienes, lipid hydroperoxides, protein carbonyl and fragmented DNA were elevated. Aqueous seed extract of Hunteria umbellata significantly ameliorated the high fructose diet-mediated alterations.

CONCLUSIONS

From this study, it is concluded that aqueous seed extract of Hunteria umbellata possesses hypoglycemic, hypolipidemic and antioxidants abilities as evident from its capability to extenuate insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome rats.

Popular edible seaweed, Gelidium amansii prevents against diet-induced obesity

The popular edible seaweed, Gelidium amansii is broadly used as food worldwide. To determine whether G. amansii extract (GAE) has protective effects on obesity, mice fed a high-fat diet (HFD) treated with GAE (1 and 3 %) were studied. After 12 weeks of GAE treatment, body weight was greatly decreased in mice fed a high-fat diet. This effect could be due to decreased adipogenesis, as evidenced by the fact that GAE suppressed adipogenic gene expression in adipocytes. In addition, blood glucose and serum insulin levels were reduced by GAE treatment in mice fed a high-fat diet, suggesting improvement in glucose metabolism. GAE supplementation also led to a significant decrease in total cholesterol and triglyceride levels. These data are further confirmed by H&E staining. Our findings indicate that Gelidium amansii prevents against the development of diet-induced obesity, and further implicate that GAE supplementation could be the therapeutical option for treatment of metabolic disorder such as obesity.

High-calorie diet inflates steatogenic effects of valproic acid in mice

Valproic acid (VPA) is an anti-epileptic drug used in patients with convulsive seizures and psychic disorders. Despite its therapeutic use, VPA administration is associated with several side effects of which hepatosteatosis (lipid deposition in liver >10% of organ weight) is of concern. Recently, the consumption of western-type diet rich in fat and simple sugar has increased, the pathological consequences of which has been linked to the escalating incidence of metabolic disorders. The hypothesis of the study is that the metabolic stress induced by high-calorie diet may potentiate VPA-induced hepatosteatosis. Two groups of Swiss Mus musculus male mice weighing 25-35 g were fed either normal chow or high fat and high fructose diet (HFFD) and maintained for 30 days. On the 16th day of the experiment, VPA (100 mg/kg bw) administration was initiated in one set of animals from each group and the other set was left without VPA treatment. Assays were done in the hemolysate, plasma and liver tissue of mice after the experimental period. Deregulated lipid metabolism, loss of insulin sensitivity, enhanced CYP2E1 activity and oxidative damage, and diminution of cellular antioxidants were observed in animals that received HFFD and VPA. HFFD-fed mice are sensitized to VPA toxicity than the normal chow-fed counterparts. The results of this study show that preformed metabolic derangements due to high-energy diet may infuriate VPA-induced hepatosteatosis and insulin resistance.

Antioxidant plants and diabetes mellitus

The incidence of diabetes mellitus (DM) is increasing rapidly and it is expected to increase by 2030. Other than currently available therapeutic options, there are a lot of herbal medicines, which have been recommended for its treatment. Herbal medicines have long been used for the treatment of DM because of the advantage usually having no or less side-effects. Most of these plants have antioxidant activities and hence, prevent or treat hard curable diseases, other than having the property of combating the toxicity of toxic or other drugs. In this review other than presenting new findings of DM, the plants, which are used and have been evaluated scientifically for the treatment of DM are introduced.

The use of plants in the traditional management of diabetes in Nigeria: pharmacological and toxicological considerations

ETHNOPHARMACOLOGICAL RELEVANCE

The prevalence of diabetes is on a steady increase worldwide and it is now identified as one of the main threats to human health in the 21st century. In Nigeria, the use of herbal medicine alone or alongside prescription drugs for its management is quite common. We hereby carry out a review of medicinal plants traditionally used for diabetes management in Nigeria. Based on the available evidence on the species׳ pharmacology and safety, we highlight ways in which their therapeutic potential can be properly harnessed for possible integration into the country׳s healthcare system.

MATERIALS AND METHODS

Ethnobotanical information was obtained from a literature search of electronic databases such as Google Scholar, Pubmed and Scopus up to 2013 for publications on medicinal plants used in diabetes management, in which the place of use and/or sample collection was identified as Nigeria. 'Diabetes' and 'Nigeria' were used as keywords for the primary searches; and then 'Plant name - accepted or synonyms', 'Constituents', 'Drug interaction' and/or 'Toxicity' for the secondary searches.

RESULTS

The hypoglycemic effect of over a hundred out of the 115 plants reviewed in this paper is backed by preclinical experimental evidence, either in vivo or in vitro. One-third of the plants have been studied for their mechanism of action, while isolation of the bioactive constituent(s) has been accomplished for twenty three plants. Some plants showed specific organ toxicity, mostly nephrotoxic or hepatotoxic, with direct effects on the levels of some liver function enzymes. Twenty eight plants have been identified as in vitro modulators of P-glycoprotein and/or one or more of the cytochrome P450 enzymes, while eleven plants altered the levels of phase 2 metabolic enzymes, chiefly glutathione, with the potential to alter the pharmacokinetics of co-administered drugs.

CONCLUSION

This review, therefore, provides a useful resource to enable a thorough assessment of the profile of plants used in diabetes management so as to ensure a more rational use. By anticipating potential toxicities or possible herb-drug interactions, significant risks which would otherwise represent a burden on the country׳s healthcare system can be avoided.

Cytoprotective and anti-diabetic effects of Derris reticulata aqueous extract

The current study was aimed to investigate pancreatic protective and anti-diabetic activities of the aqueous extract of Derris reticulata stem. First, we evaluated a cytoprotective potential of D. reticulata extract on alloxan-induced damage in vitro. Treatment with D. reticulata extract at the doses of 250 and 500 μg/ml significantly increased cell viability of the pancreatic β-cell line RINm5F after exposure of alloxan. The anti-hyperglycemic activity of D. reticulata extract was further studied in alloxan-induced diabetic rats. A significant reduction in blood glucose level along with an increase in body weight was observed in diabetic rats treated with D. reticulata extract at 250 mg/kg body weight for 15 days. Serum aspartate transaminase and alanine transaminase levels were also significantly decreased compared to diabetic control rats. In accordance with in vitro cytoprotective effect, histopathological examination revealed that pancreatic islet cells of the extract-treated diabetic rat were less damage than those of the untreated diabetic group. In order to find another possible mechanism of action underling hypoglycemic activity, the effect on glucose absorption was examined using everted sac jejunum. The results showed that D. reticulata extract suppressed glucose absorption from small intestine. To corroborate safety use of D. reticulata extract, acute oral toxicity was also conducted in rats. Our results showed that none of the tested doses (250, 500, 1,000, and 2,000 mg/kg) induced signs of toxicity or mortality after administration of the extract. The results suggested that D. reticulata extract possess anti-diabetic activity, which resulting from its pancreatic cytoprotective effect and inhibition of intestinal glucose absorption.

Antihyperglycemic profile of erinidine isolated from Hunteria umbellata seed

Water decoction made from the seed of Hunteria umbellata is widely used in the traditional management of diabetes mellitus by Nigerian herbalists, particularly, in the southwest region of the country. Recently, a new bisindole alkaloid, erinidine, was isolated but its antihyperglycemic profile remains largely un-investigated scientifically. This forms the basis for the current study which is primarily designed at investigating the antihyperglycemic profile of erinidine and other fractions in both in vitro and in vivo models of diabetes mellitus. In the present study, erinidine was isolated and purified using the earlier described methods and its antihyperglycemic potentials tested in in vitro models such as dipeptidylpeptidase (IV), glycogen phosphorylase, HIT-T15 cell insulin secretion, glucose uptake activity, aldose reductase assays and α-glucosidase inhibition assay testings. In addition, 50 mg/kg of erinidine and that of other fractions were evaluated in in vivo models of normal and chemically-induced hyperglycemic rats. Results showed that erinidine was a light yellow, amorphous solid with UV (CHCl3) λ max 256 nm, HRESIMS m/z 382.1881 [(M+H)(+)] (calculated for C22H26N4O2, 382.1876) and melting point of 230 °C. The in vitro study showed the antihyperglycemic action of erinidine to be weakly mediated via α-glucosidase inhibition mechanism as the results for other in vitro tests such as dipeptidylpeptidase (IV), glycogen phosphorylase, HIT-T15 cell insulin secretion, glucose uptake activity and aldose reductase assays were all negative. However, the in vivo results showed 50 mg/kg erinidine given per os to normal and alloxan-induced hyperglycemic rats to significantly (p<0.05, p<0.001) attenuate an increase in their post-absorptive blood glucose concentrations after 3 g/kg glucose loading in the rats, suggesting its antihyperglycemic mechanism to be via α-glucosidase inhibition. This result, although, further corroborated the in vitro findings but also suggests that erinidine needs to be biotransformed in vivo for its inhibitory activity on intestinal glucose absorption to become evident. Thus, the present study suggests erinidine to be the possible antihyperglycemic agent in Hunteria umbellata seed extract mediating its antihyperglycemic action via intestinal glucose uptake inhibition.

Ethnobotanical study of plants used in treating hypertension in Edo State of Nigeria

A study was undertaken in 12 local government areas (LGAs) of Edo State located in central southern Nigeria, representing 66.6% coverage, in order to obtain an inventory of the major medicinal plants used in folk medicine to treat arterial hypertension. One hundred and eighty nine respondents who were mainly traditional medical practitioners and were knowledgeable in the medicinal plants for treating hypertension were interviewed using semi-structured questionnaire administered by trained interviewers. The inventory of medicinal plants is summarized in a synoptic table, which contains the scientific, vernacular and common names of the plants/frequency of citation, the part of the plant and method of preparation of recipes. The study indicated 70 plants belonging to 67 genera in 43 families are commonly prescribed. Of these plants, 39 species are cultivated, 29 species grow in the wild, while only 2 both grow wild and also cultivated. Ninety three herbal antihypertensive recipes are recognized and are mainly prepared as decoctions, infusions, powders and juice. The leaf (43%) represented the dominant morphological part often included in recipes. Plants frequently included in antihypertensive recipes were Allium species, Persea americana, Acalypha godseffiana, Zingiber officinale, Sida acuta, Hunteria umbellata, Rauwolfia vomitoria, Viscum album and Aframomum melegueta.

The novel antihyperglycaemic action of Hunteria umbellata seed fractions mediated via intestinal glucose uptake inhibition

The present study evaluated the antihyperglycaemic effect and mechanism of action of fractions of the aqueous seed extract of Hunteria umbellata (K. Schum.) Hallier f. (HU) in normal and alloxan-induced hyperglycaemic rats. HU was partitioned in chloroform, acetyl acetate and butan-1-ol to give chloroform fraction (HU c), ethyl acetate fraction (HU e), butanol fraction (HU b) and the "residue" (HU m), respectively. 200 mg/kg of each of these fraction dissolved in 5% Tween 20 in distilled water was investigated for its acute oral hypoglycaemic effects in normal rats over 6 hours while its repeated dose antihyperglycaemic effect was evaluated in alloxan-induced hyperglycaemic rats over 5 days. In addition, 50 mg/kg of the crude alkaloid fraction (HU Af) extracted from HU was evaluated for its possible antihyperglycaemic activity in alloxaninduced hyperglycaemic rats using oral glucose tolerance test (OGTT) over 6 hours. Using the solvent system, distilled water-butanol-ammonium hydroxide (2:15:1, v/v/v), HU b was chromatographed and stained with Dragendorff's reagent for confirmatory qualitative analysis for alkaloids. Results showed that oral pre-treatment with 200 mg/kg of HU e, HU b and HU m resulted in a significant (p<0.05, p<0.001) time dependent hypoglycaemic effect, with the butan-1-ol fraction HU causing the most significant (p<0.001) hypoglycaemic effect. In the alloxan-induced hyperglycaemic rats, repeated oral treatment with 200 mg/kg of same HU fractions for 5 days resulted in significant (p<0.05) decreases in the fasting blood glucose concentrations with the most significant (p<0.01) antihyperglycaemic effect also recorded for HU b. Similarly, oral pretreatment with 50 mg/kg of HU Af significantly (p<0.05, p<0.01 and p<0.001) attenuated an increase in the post-absorptive glucose concentration at 1(st) - 6(th) h in the alloxan-induced hyperglycaemic OGTT model. In addition, alkaloid was present in most of the separated spots on the TLC plate. In conclusion, results of this study showed that HU contains a relative high amount of alkaloids which could have accounted for the antihyperglycaemic action of HU that was mediated via intestinal glucose uptake inhibition.

Evaluation of glycemic and lipid profile of offspring of diabetic Wistar rats treated with Malpighia emarginata juice

Knowing that maternal diabetes is related to hyperglycemia and fetal hyperinsulinemia, which affect the lipid metabolism, the aim of this study was to evaluate the effects of Malpighia emarginata (acerola) juice on the glycemic and lipid profile of offspring of diabetic and nondiabetic Wistar rats. The adult offspring of non-diabetic dams and of dams with severe streptozotocin-induced diabetes were divided into groups: G1, offspring (of control dams) treated with water, G2, offspring (of diabetic dams) treated with water, G3, male offspring (of control dams) treated with acerola juice, and G4, male offspring (of diabetic dams) treated with acerola juice. The offspring of diabetic dams treated with acerola juice showed significantly decreased levels of glucose, cholesterol, triglycerides, and increased HDL-c. The use of acerola juice is a potential strategy to aid in the prevention of DM and dyslipidemia and its complications or to act as an auxiliary in the treatment of these diseases.

Suppression of hepatic oxidative events and regulation of eNOS expression in the liver by naringenin in fructose-administered rats

Previous studies show that naringenin promotes insulin sensitivity in fructose-fed rats. This study investigates whether naringenin prevents oxidative events and apoptotic changes triggered in the rat liver by a high fructose diet. Male Wistar rats of body weight 150-180 g were fed either diet containing starch (60% carbohydrate) or fructose (60% fructose diet). From the 16th day of feeding, rats in each dietary group were divided into two, and treated or not with naringenin (50mg/kg b.w/day). After 60 days, oxidative and nitrosative damage and endothelial nitric oxide synthase (eNOS) expression and hepatocyte apoptosis were determined. To evaluate whether nitric oxide (NO) plays a role in naringenin action, insulin sensitivity indices, fasting plasma glucose and insulin were assessed in response to co-administration of L-nitro-arginine methyl ester (L-NAME), a NOS inhibitor. Fructose feeding caused oxidative damage to proteins and lipids and resulted in reduced antioxidant status, eNOS expression and nitrite level. Increased formation of 4-hydroxy nonenal (4-HNE), 2, 4-dinitrophenol (2, 4-DNP) and 3-nitrotyrosine (3-NT)-modified proteins and the presence of apoptotic nuclei were observed in the liver. Treatment with naringenin attenuated all these parameters to levels not significantly different from control. Treatment with naringenin improved insulin sensitivity. However, L-NAME plus naringenin administration abolished the insulin-sensitizing effects of naringenin in fructose-fed rats. Reduced oxidative events with simultaneous increase in NO bioavailability may be involved in the insulin-sensitizing and cytoprotective effects of naringenin in fructose-fed rats.

Anti-obesity and antihyperlipidaemic effect of Hunteria umbellata seed extract in experimental hyperlipidaemia

AIM OF THE STUDY

In Nigerian folk medicine, water infusion of the dried seeds of Hunteria umbellata (K. Schum.) Hallier f. has a reputation for the local management of obesity and hyperlipidaemia. The present study is aimed at evaluating the anti-obesity and antihyperlipidaemic activities as well as the underlying mechanisms of action of the aqueous seed extract of Hunteria umbellata (HU) in normal, triton-induced, and olive oil-induced hyperlipidaemic rats.

MATERIALS AND METHODS

Normal and olive oil-induced hyperlipidaemic, and triton-induced hyperlipidaemic rats were pre-treated with single, daily oral administration of 10 ml/kg of distilled water, 20 mg/kg of simvastatin, 50 mg/kg, 100 mg/kg and 200 mg/kg of HU in 10 ml/kg of distilled water for 28 days and 24 h. The effects of these drugs on % body weight change, feeding pattern, serum lipids, coronary artery risk index (CRI) and atherogenic index (AI) and Lee's index (LI) were investigated.

RESULTS

Oral pre-treatment with simvastatin and graded oral doses of HU significantly (p<0.05) reduced the weight gain pattern and caused dose related (p<0.05, p<0.01 and p<0.001) reductions in the serum lipids, CRI, AI and LI. Also, HU pre-treatment significantly improved triton-induced hepatic histological lesions.

CONCLUSIONS

Results of this study showed that HU has both anti-obesity and antihyperlipidaemic effects which may partly be mediated via inhibition of intestinal lipid absorption and de novo biosynthesis of cholesterol. Thus, the results justify the ethnopharmacological use of the extract in the management of obesity and hyperlipidaemia.

Evaluation of the toxicity and reversibility profile of the aqueous seed extract of Hunteria umbellata (K. Schum.) Hallier f. in rodents

Hunteria umbellata (K. Schum.) Hallier f. (family: Apocynaceae) is reputed for the folkloric management of labour, pain and swellings, stomach ulcers, diabetes, obesity, and anaemia, with no scientific report of its toxicity and reversibility profile. The present study was, therefore, aimed at investigating the in vivo toxicity and reversibility profile of the aqueous seed extract of Hunteria umbellata (HU). The acute oral and intraperitoneal toxicity studies of HU were determined in Swiss albino mice while its 90-day oral toxicity and toxicity reversibility profile on anthropometric, biochemical, haematological and histopathological parameters were also assessed using standard procedures. Results showed that the LD50 values for the acute oral and intraperitoneal toxicity studies for HU were estimated to be 1000 mg/kg and 459.3 mg/kg, respectively. Visible signs of immediate and delayed toxicities including starry hair coat, respiratory distress, and dyskinesia were observed. For the chronic oral toxicity study, HU administered for 90 days produced significant (p < 0.001) reductions in the weight gain pattern and significant (p < 0.001) and dose related increases in the relative weights of liver, stomach, spleen, testis, lungs and heart, at the 100 and 500 mg/kg of HU. Chronic HU treatment also produced significant (p < 0.05, p < 0.001) dose related reductions in the serum levels of fasting blood glucose, bicarbonate, urea and creatinine while causing non-significant (p > 0.05) alterations in the serum levels of sodium, potassium, alaninine transaminase, aspartate transaminase, alkaline phosphatase, total and conjugated bilirubin, total protein and albumin. Also, chronic oral treatment with HU produced significant (p < 0.05, p < 0.01, p < 0.001) and dose-related increases in the red cell count, packed cell volume, haemoglobin concentration, platelet count, total leucocyte count and lymphocyte differential while producing significant (p < 0.05) reductions in neutrophil and granulocyte differentials. HU also produced histological features of proliferations of the stomach epithelia, lung tissues, splenic white and red pulps, and testicular spermatogenic series. Following 14 days of oral toxicity reversibility test, there was no significant (p>0.05) reversal in the serum levels of the biochemical and haematological parameters investigated, including the HU-induced histological lesions. Overall, results of this study showed that HU has a relatively low oral toxicity profile but its prolonged use, particularly, at high doses should be with great caution.