Hypoglycemic and hypocholesterolemic potential of Persea americana leaf extracts

Mexican Plants Involved in Glucose Homeostasis and Body Weight Control: Systematic Review

BACKGROUND

Obesity is defined as abnormal or excessive fat accumulation, provoking many different diseases, such as obesity and type 2 diabetes. Type 2 diabetes is a chronic-degenerative disease characterized by increased blood glucose levels. Obesity and type 2 diabetes are currently considered public health problems, and their prevalence has increased over the last few years. Because of the high cost involved in the treatment of both diseases, different alternatives have been sought. However, the general population uses medicinal plants, in the form of tea or infusions, to treat different diseases. Therefore, traditional medicine using medicinal plants has been investigated as a possible treatment for type 2 diabetes and body weight control.

AIM OF THE STUDY

The purpose of this review is to find medicinal plants used in Mexico that could exert their beneficial effect by regulating insulin secretion and body weight control.

MATERIAL AND METHOD

For the development of this review, Mexican plants used in traditional medicine to treat type 2 diabetes and body weight control were searched in PubMed, Google Scholar, and Scopus. The inclusion criteria include plants that presented a significant reduction in blood glucose levels and/or an increase in insulin secretion.

RESULTS

We found 306 Mexican plants with hypoglycemic effects. However, plants that did not show evidence of an increase in insulin secretion were eliminated. Finally, only five plants were included in this review: Momordica charantia L. (melón amargo), Cucurbita ficifolia bouché (chilacayote), Coriandrum sativum L. (cilantro), Persea americana Mill. (aguacate) Bidens pilosa (amor seco), including 39 articles in total. Here, we summarized the plant extracts (aqueous and organic) that have previously been reported to present hypoglycemic effects, body weight control, increased secretion and sensitivity of insulin, improvement of pancreatic β cells, and glucose tolerance. Additionally, these effects may be due to different bioactive compounds present in the plants' extracts.

CONCLUSION

Both in vivo and in vitro studies are required to understand the mechanism of action of these plant extracts regarding insulin secretion to be used as a possible treatment for type 2 diabetes and body weight control in the future.

Canagliflozin ameliorates aortic and hepatic dysfunction in dietary-induced hypercholesterolemia in the rabbit

AIMS

Canagliflozin is an antidiabetic agent which lowers blood glucose levels by inhibiting the glucose reabsorption machinery in the proximal tubules. There have not been conducted any study on its direct impact on hypercholesterolemia and associated vascular disorders independently of blood glucose lowering activity.

MATERIALS AND METHODS

Rabbits were arranged in 3 groups: Group 1 (Control): regular rabbit chow; Group 2 (HCD): 1% cholesterol-enriched chow was given to rabbits for 4 weeks; Group 3 (HCD-CANA): 1% cholesterol-enriched chow was fed to rabbits concurrently with canagliflozin (10 mg/kg/day, orally) for 4 weeks. At the end of experiment, blood and tissue samples were obtained for biochemical, histological, immunohistochemical, and vascular reactivity assessment.

KEY FINDINGS

When statistically compared to Control (P < 0.05), HCD showed a significant increase in the serum triglycerides, low-density lipoprotein, total cholesterol, C-reactive protein, alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase. Furthermore, a significant decrease was seen in both liver and aortic levels of glutathione peroxidase and superoxide dismutase concurrently with a significant elevation in malondialdehyde levels. Aortic levels of nitrate/nitrite ratio were significantly elevated. Acetylcholine-induced relaxation was impaired as the E_max decreased significantly in aortae. Moreover, a significant increase was seen in the level of aortic intima/media ratio. Canagliflozin treatment significantly improved vascular function, lipid profile and inflammation and reduced liver injury.

SIGNIFICANCE

Our data suggest that SGLT-2 inhibition via canagliflozin not only possesses an antihyperglycemic activity, but also improves hypercholesterolemia, vascular and liver function in dietary-induced hypercholesterolemia in the rabbit.

The Effects of Avocado Waste and Its Functional Compounds in Animal Models on Dyslipidemia Parameters

Ischemic heart disease and stroke are two main causes of death that have prevailed for more than 15 years. Dyslipidemia and its parameters like hypercholesterolemia, hypertriglyceridemia, increase in low-density cholesterol, and a reduction of high-density cholesterol have been related with heart disease and risk of stroke. Approaches to improve the health and specifically reduce the risk of heart disease, such as medications and dietary interventions have been effective, but there are other potential sources of biological compounds that could have an effect due to their antioxidant properties. Avocado is a commonly consumed fruit especially its pulp, while the peel, seed, and leaf are usually discarded as waste. Some researchers have reported antioxidant, hepatoprotective, gastroprotective, lipid-lowering, and hypoglycemic effects in these wastes. In this review article, we have summarized the current evidence on the effect of biological compounds from avocado waste on dyslipidemia parameters in preclinical models. Also, we have included the compound extracted and the extraction method from the selected articles.

Effects of aqueous leaf extract of avocado (Persea americana) on total cholesterol, triacylglycerols, protein and haematological parameters in CCl4-intoxicated rats

Background

Avocado (Persea americana) is one of the plants widely used in ethnomedicine in Nigeria. The present study was aimed at investigating effects of aqueous Avocado (Persea americana) leaf extract on total cholesterol, triacylglycerols, protein and haematological parameters in carbon tetrachloride (CCl4)-intoxicated rats.

Methods

We evaluated the possible effects of pre-treatment with aqueous extract of Persea americana (AEPA) on protein, total cholesterol (T-CHOL), triacylglycerols (TAGs) and haematological parameters in Wistar male albino rats intoxicated with CCl4. Group 1 was the healthy control; group 2 rats were pre-treated with Reducdyn® (100 mg/kg/day) as a standard drug, groups 4 and 5 rats were pre-treated with AEPA at a dose of 100 mg/kg and 200 mg/kg per day respectively, the treatments were administered orally for 7 days. On the seventh day, rats in the treatment groups were injected with a fresh mixture of CCl4 and olive oil (3 ml/kg, 1:1; sc).

Results

Pre-treatment of rats with AEPA resulted in marked increase (p < 0.05) in total protein and reduction in T-CHOL (19–34%) compared to CCl4 alone. Also, there was significant decrease (p < 0.05) in serum TAG concentration when rats were pre-treated with 100 mg and 200 mg kg− 1 b. wt. AEPA. Similarly, AEPA provoked (p < 0.05) a lowering of T-CHOL and TAG levels and an increase in liver protein concentration in the rats. Administration of AEPA at both concentrations restored (p < 0.05) WBC count and ameliorated neutropenia and lymphocytosis caused by CCl4 intoxication.

Conclusion

These results suggest that AEPA could be protective against the development of fatty liver and might also be exhibiting the potential to prevent alterations in haematological parameters caused by CCl4 intoxication in rats.

The potential effect of imatinib against hypercholesterolemia induced atherosclerosis, endothelial dysfunction and hepatic injury in rabbits

AIMS

Imatinib is an effective tyrosine kinase inhibitor which has different therapeutic actions. The recent work demonstrated the possible beneficial effects of imatinib on the progression of atherosclerosis, endothelial dysfunction, and hypercholesterolemia-associated liver damage in rabbits.

MAIN METHODS

Animals had been distributed in 4 groups: group 1 (non-treated): animals fed regular diet; group 2 high cholesterol [HC]: animals fed 1% cholesterol supplemented diet for 30 days; group 3 (HC-Imatinib): animals fed 1% cholesterol supplemented diet+imatinib (0.01 g/kg daily, p.o) for 30 days; group 4 (Imatinib): animals fed regular diet with imatinib (0.01 g/kg daily, p.o). After thirty days, tissue samples and blood were isolated to be detected biochemically, histologically, and for in vitro analysis.

KEY FINDINGS

HC exhibited significant elevations in serum lipid parameters, CRP, ALT, AST and ALP. Additionally, HC induced significant increases for aortic and hepatic MDA, aortic NO and hepatic PDGFR-β, while significantly exhibited reductions in aortic and hepatic GSH, SOD and hepatic PPARγ1. Moreover, HC produced impairment in ACh-enhanced aortic relaxation and aortic pathological changes. Histopathological examination of HC-fed rabbits revealed hepatic steatosis compared with non-treated group. Imatinib administration exhibited significant decreases in serum lipid parameters, CRP, ALT, AST and ALP. Additionally, imatinib induced significant decreases for aortic and hepatic MDA, aortic NO and hepatic PDGFR-β, while significantly exhibited elevations in aortic and hepatic GSH, SOD and hepatic PPARγ1 compared with HC animals. Furthermore, imatinib significantly protected against HC produced attenuation in ACh-induced aortic relaxation and pathological changes in aortic and hepatic tissues. Interestingly, imatinib could return serum CRP, ALP, hepatic SOD and PDGFR-β to basal values.

SIGNIFICANCE

The recent observation reports that imatinib could have beneficial effect against atherosclerosis progression, vascular malfunction, and liver damage in high cholesterol diet (HCD)-fed rabbits.

Comparative Antidiabetic Activity of Aqueous, Ethanol, and Methanol Leaf Extracts of Persea americana and Their Effectiveness in Type 2 Diabetic Rats

Native to Mexico, Persea americana Mill. (avocado) is a fruit tree whose different parts (leaf, bark, roots, and stone) are used in traditional medicine especially against diabetes mellitus. The aim of this study was to investigate the beneficial effects of 28-day treatment with aqueous, ethanolic, and methanolic leaf extracts on glucose homeostasis in type 2 diabetic mellitus using Wistar rats. Type 2 diabetes was induced with nicotinamide (120 mg/kg, i.p.) and streptozotocin (65 mg/kg, i.p.). After 28 days of treatment, histopathological examination of the pancreas, kidneys, liver, and muscle (tibialis anterior) were realized. Biochemical markers were determined and an intestinal absorption test of D-glucose was performed. All extracts (100 mg/kg/day, p.o.) significantly (p < 0.001) reduced blood glucose level at the 28^th day of treatment with a more pronounced effect for methanolic extract. The treatments were well tolerated and induced a restoration of T-CHOL and HDL-C levels compared to the control group. Methanolic extract reduced the AIP (atherogenic index of plasma) by 45%. Histopathological analyzes of the pancreas showed regeneration of islets of Langerhans. Methanolic extract was the most effective in preventing intestinal glucose uptake up to 60.90% in relation to metformin. These results justify the use of this plant in traditional medicine against type 2 diabetes. However, other complementary studies should be done to identify the molecules responsible for this activity and their signaling voice.

Anticlastogenic, radiation antagonistic, and anti-inflammatory activities of Persea americana in albino Wistar rat model

The present study was undertaken to evaluate the anti-inflammatory activity and antigenotoxic effect of hydroalcoholic leaf extract of Persea americana (P. americana) in albino Wistar rats against whole body X-ray irradiation. Rats were orally administered with (25, 50, 100, 200, and 400 mg/kg body weight) of P. americana leaf extract for five days. On the fifth day after last administration, animals were exposed to whole body X-rays of 8 Gy. Based on Kaplan Meier's survival analysis, 100 mg/kg body weight was selected as an optimum dose for radioprotection. The radioprotective potential was analysed by bone marrow micronucleus test and comet assay in peripheral blood lymphocytes. Biochemical estimations were performed in liver tissue homogenates. DNA damage indicators analysed through comet assay displayed significant reduction in olive tail movement (P < 0.01), percentage DNA in tail (P < 0.05) and tail length (P < 0.001) in pretreated group when compared to radiation group. P. americana leaf extract restored the levels of reduced glutathione, catalase, and reduced the levels of lipid peroxidation, protein carbonyls, and cyclooxygenase-2 levels in liver homogenates of pre-treated group. Decrease in micronucleated polychromatic erythrocytes (P < 0.05) was witnessed in P. americana pretreated group when compared to radiation control. Pretreatment also resulted in the increase of animal survival with dose reduction factor of 1.28. Our findings for the first time demonstrated that P. americana offers significant protection to rats from whole body exposure to X-rays and helps in antagonising the radiation effects, thereby combating acute radiation induced damage in living systems.

Effects of Avocado (Persea americana) on Metabolic Syndrome: A Comprehensive Systematic Review

Metabolic syndrome (MetS) is a clustering of risk factors including high blood glucose, dyslipidemia, hypertension, and obesity that lead to the increased risk of type 2 diabetes mellitus and cardiovascular diseases (CVDs), which are among leading causes of death in the world. Metabolic syndrome increases the risk of type 2 diabetes mellitus and CVDs by approximately five and three folds, respectively. Therefore, it is of vital importance to manage such conditions with herbal options which have less undesirable adverse effects and may be more efficacious in comparison with synthetic options. Avocado is a well-known source of carotenoids, minerals, phenolics, vitamins, and fatty acids. The lipid-lowering, antihypertensive, antidiabetic, anti-obesity, antithrombotic, antiatherosclerotic, and cardioprotective effects of avocado have been demonstrated in several studies. In this review, we aimed to find out avocado's pharmacological effects on different components of MetS. Moreover, this review report is performed on the MetS effects of peel, seed, flesh, and leaves of avocado. Copyright © 2017 John Wiley & Sons, Ltd.

Bio-efficacy of medicinal plants used for the management of diabetes mellitus in Gabon: An ethnopharmacological approach

BACKGROUND/AIM

People suffering of diabetes increased significantly worldwide. Population, in Sub-Saharan Africa and mainly in Gabon, rely on medicinal plants to manage diabetes, as well in rural as in urban areas. This study aimed to survey a wide range of Gabonese plants for their antidiabetic activity.

MATERIALS AND METHODS

This study focused on the identification of medicinal plants used in the local treatment of diabetes mellitus. Ethnobotanical investigations were carried out in rural and urban areas of three provinces of Gabon using a semi-structured interview.

RESULTS

About 50 plant species belonging to 31 families and 50 genera were recorded, a majority of which have been documented previously to have medicinal properties. Most have documented antidiabetic properties with characterized therapeutic chemical compounds. Of the plant parts used for treatment, stem barks were employed most frequently (50%), followed by leaves (26%); the remaining 24% comprised roots, fibers, fruit, bulbs, flowers, rhizom, skin, and stem. Regarding the mode of preparation, decoction was the most widely used (58%), followed by maceration (18%) and infusion (14%). Almost all the plant products were administered orally (98%).

CONCLUSIONS

Taken in concert, this study highlights the possibility of exploiting traditional knowledge of specific medicinal plants for the inexpensive treatment and management of diabetes.

Isolation, characterization and hypolipidemic activity of ferulic acid in high-fat-diet-induced hyperlipidemia in laboratory rats

Prosopis cineraria (L.) Druce (Leguminosae) (syn. Prosopis spicigera L.) has antidiabetic and antioxidant potential. Earlier we reported its hypolipidemic activity obtained from ethanol extract (ET-PCF). Object of this work was to isolate ferulic acid (FA) from ET-PCF and evaluate hypolipidemic activity against high-fat diet (HFD)-induced hyperlipidemic laboratory rats. ET-PCF was subjected to flash column chromatography to isolate FA. The chemical structure of the isolated compound was elucidated by UV, IR, ¹H NMR,¹³C NMR and LC-MS. Further, the antihyperlipidemic effect of FA (10, 20 and 40 mg/kg, p.o.) in HFD-induced hyperlipidemic rats was investigated. Hyperlipidemia was induced in male Sprague-Dawley rats by feeding with HFD for 60 days. Lipid parameters such as total cholesterol (TC), Low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) levels were measured in serum and hepatic tissue. Hepatic oxido-nitrosative stress (SOD, GSH, MDA and NO) were also determined. Histological evaluation of liver tissue was carried out. The structure of the isolated compound was characterized based on spectral data and confirmed as FA. HFD induced an alteration in serum, and hepatic lipid profile (triglyceride, cholesterol, HDL, and LDL) was significantly restored (p < 0.001) by administration of FA (20 and 40 mg/kg, p.o.). The elevated level of oxido-nitrosative stress in liver was significantly reduced (p < 0.001) by FA (20 and 40 mg/kg, p.o.). Histological aberration induced in the liver after HFD ingestion were restored by FA administration. Ferulic acid isolated from ET-PCF showed hypolipidemic effects in HFD-induced hyperlipidemic rats via modulation of elevated oxido-nitrosative stress.

Medicinal plants used in the traditional management of diabetes and its sequelae in Central America: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Globally 387 million people currently have diabetes and it is projected that this condition will be the 7th leading cause of death worldwide by 2030. As of 2012, its total prevalence in Central America (8.5%) was greater than the prevalence in most Latin American countries and the population of this region widely use herbal medicine. The aim of this study is to review the medicinal plants used to treat diabetes and its sequelae in seven Central American countries: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and Panama.

MATERIALS AND METHODS

We conducted a literature review and extracted from primary sources the plant use reports in traditional remedies that matched one of the following disease categories: diabetes mellitus, kidney disease, urinary problems, skin diseases and infections, cardiovascular disease, sexual dysfunctions, visual loss, and nerve damage. Use reports were entered in a database and data were analysed in terms of the highest number of use reports for diabetes management and for the different sequelae. We also examined the scientific evidence that might support the local uses of the most reported species.

RESULTS

Out of 535 identified species used to manage diabetes and its sequelae, 104 species are used to manage diabetes and we found in vitro and in vivo preclinical experimental evidence of hypoglycaemic effect for 16 of the 20 species reported by at least two sources. However, only seven of these species are reported in more than 3 studies: Momordica charantia L., Neurolaena lobata (L.) R. Br. ex Cass., Tecoma stans (L.) Juss. ex Kunth, Persea americana Mill., Psidium guajava L., Anacardium occidentale L. and Hamelia patens Jacq. Several of the species that are used to manage diabetes in Central America are also used to treat conditions that may arise as its consequence such as kidney disease, urinary problems and skin conditions.

CONCLUSION

This review provides an overview of the medicinal plants used to manage diabetes and its sequelae in Central America and of the current scientific knowledge that might explain their traditional use. In Central America a large number of medicinal plants are used to treat this condition and its sequelae, although relatively few species are widely used across the region. For the species used to manage diabetes, there is variation in the availability and quality of pharmacological, chemical and clinical studies to explain traditional use.

A Soxhlet Extract of Gongronema latifolium Retains Moderate Blood Glucose Lowering Effect and Produces Structural Recovery in the Pancreas of STZ-Induced Diabetic Rats

BACKGROUND

Gongronema latifolium Benth. (GL) possesses considerable glucose lowering effects able to be utilized on a large-scale. This paper investigates the effects of a Soxhlet extract on hyperglycemia, Langerhans islets and glucose uptake by abdominal muscles.

METHODS

Ethanol and a Soxhlet apparatus were used to obtain GL ethanolic Soxhlet extract (GLES). It was then administered to randomly-segregated male Sprague-Dawley, normal and STZ-induced diabetic rats, using oral gavage to evaluate blood glucose levels (BGLs), serum lipid profile, insulin levels and the pancreas post-treatment.

RESULTS

GLES significantly (p < 0.05) decreased BGLs of normal rats in glucose tolerance testing at a dose of 2 g/kg b.w. but failed to do so in diabetic rats undergoing acute 7-h treatment. Given twice-daily, 1 g/kg b.w. of GLES moderately controlled diabetic BGLs starting from day 10. After 14 days of treatment, 1 g/kg and 0.5 g/kg b.w. of GLES caused 44% and 50% respective increases in the average area of Langerhans islets compared to DC. Using isolated rat abdominal muscle, GLES was found to be a mild insulin-sensitizer. GC-MS analysis revealed the presence of the known glucose-lowering phytosterol, Sitostenone.

CONCLUSION

Despite retaining moderate antidiabetic activity, Soxhlet extraction of Gongronema latifolium probably leads to the destruction of active heat-liable compounds.

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.

Persea declinata (Bl.) Kosterm Bark Crude Extract Induces Apoptosis in MCF-7 Cells via G0/G1 Cell Cycle Arrest, Bcl-2/Bax/Bcl-xl Signaling Pathways, and ROS Generation

Persea declinata (Bl.) Kosterm is a member of the Lauraceae family, widely distributed in Southeast Asia. It is from the same genus with avocado (Persea americana Mill), which is widely consumed as food and for medicinal purposes. In the present study, we examined the anticancer properties of Persea declinata (Bl.) Kosterm bark methanolic crude extract (PDM). PDM exhibited a potent antiproliferative effect in MCF-7 human breast cancer cells, with an IC₅₀ value of 16.68 µg/mL after 48 h of treatment. We observed that PDM caused cell cycle arrest and subsequent apoptosis in MCF-7 cells, as exhibited by increased population at G₀/G₁ phase, higher lactate dehydrogenase (LDH) release, and DNA fragmentation. Mechanistic studies showed that PDM caused significant elevation in ROS production, leading to perturbation of mitochondrial membrane potential, cell permeability, and activation of caspases-3/7. On the other hand, real-time PCR and Western blot analysis showed that PDM treatment increased the expression of the proapoptotic molecule, Bax, but decreased the expression of prosurvival proteins, Bcl-2 and Bcl-xL, in a dose-dependent manner. These findings imply that PDM could inhibit proliferation in MCF-7 cells via cell cycle arrest and apoptosis induction, indicating its potential as a therapeutic agent worthy of further development.

Agmatine ameliorates atherosclerosis progression and endothelial dysfunction in high cholesterol-fed rabbits

OBJECTIVES

The aim of this work was to explore possible effects of agmatine, an endogenous inhibitor of inducible nitric oxide synthase (iNOS), against hypercholesterolemia-induced lipid profile changes and endothelial dysfunction.

METHODS

Hypercholesterolemia was induced by feeding rabbits with a high-cholesterol diet (HCD, 0.5%) for 8 weeks. Another HCD-fed group was orally administered agmatine (10 mg/kg/day) during weeks 5 through 8. Serum lipid profile, malondialdehyde (MDA), nitric oxide (NO) and lactate dehydrogenase (LDH) were determined. Aorta was isolated to analyse vascular reactivity, atherosclerotic lesions and intima/media (I/M) ratio.

KEY FINDINGS

HCD induced a significant increase in serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides and high-density lipoprotein cholesterol (HDL-C). Agmatine administration significantly decreased HCD-induced elevations in serum TC and LDL-C, MDA, LDH and NO while significantly increased HDL-C levels. Additionally, agmatine significantly protected against HCD-induced attenuation of rabbit aortic endothelium-dependent relaxation to acetylcholine. HCD and agmatine did not significantly influence aortic endothelium-independent relaxation to sodium nitroprusside. Moreover, agmatine significantly reduced the elevation in aortic atherosclerotic lesion area and I/M ratio.

CONCLUSIONS

This study is the first to reveal that agmatine has the ability to ameliorate hypercholesterolemia-induced lipemic-oxidative and endothelial function injuries possibly by its antioxidant potential and/or iNOS inhibition.

Anti-diabetic activity of extract from Persea americana Mill. leaf via the activation of protein kinase B (PKB/Akt) in streptozotocin-induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Persea americana Mill. (Lauraceae) have been popularly used in the treatment of diabetes in countries in Latin America and Africa.

AIM OF THE STUDY

To investigate the hypoglycaemic properties and to determine the molecular mechanism by which the hydroalcoholic extract of the leaves of Persea americana reduce blood glucose levels in streptozotocin (STZ)-induced diabetes in rats via the enzymatic pathway of protein kinase B (PKB/Akt).

METHODS

The hydroalcoholic extract of the leaves of Persea americana (0.15 and 0.3g/kg/day), vehicle and metformin (0.5g/kg/day) were administered orally to STZ-diabetic rats (n=7/group) for 4 weeks. Changes in body weight, food and water intake, fasting glucose levels and oral glucose tolerance were evaluated. Phosphorylation and the expression of PKB in the liver and soleus muscle were determined by Western blot.

RESULTS

The hydroalcoholic extract of the leaves of Persea americana reduced blood glucose levels and improved the metabolic state of the animals. Additionally, PKB activation was observed in the liver and skeletal muscle of treated rats when compared with untreated rats.

CONCLUSION

The results indicate that the hydroalcoholic extract of the leaves of Persea americana has anti-diabetic properties and possibly acts to regulate glucose uptake in liver and muscles by way of PKB/Akt activation, restoring the intracellular energy balance.

A pharmacological appraisal of medicinal plants with antidiabetic potential

Diabetes mellitus is a complicated metabolic disorder that has gravely troubled the human health and quality of life. Conventional agents are being used to control diabetes along with lifestyle management. However, they are not entirely effective and no one has ever been reported to have fully recovered from diabetes. Numerous medicinal plants have been used for the management of diabetes mellitus in various traditional systems of medicine worldwide as they are a great source of biological constituents and many of them are known to be effective against diabetes. Medicinal plants with antihyperglycemic activities are being more desired, owing to lesser side-effects and low cost. This review focuses on the various plants that have been reported to be effective in diabetes. A record of various medicinal plants with their established antidiabetic and other health benefits has been reported. These include Allium sativa, Eugenia jambolana, Panax ginseng, Gymnema sylvestre, Momrodica charantia, Ocimum sanctum, Phyllanthus amarus, Pterocarpus marsupium, Trigonella foenum graecum and Tinospora cordifolia. All of them have shown a certain degree of antidiabetic activity by different mechanisms of action.

In vitro evaluation of genotoxicity of avocado (Persea americana) fruit and leaf extracts in human peripheral lymphocytes

Persea americana is much sought after both for the nutritional value of its fruit and the medicinal values of its various plant parts. A chromosomal aberration assay was undertaken to evaluate the potential genotoxicity of crude extracts from avocado fruits and leaves. Chromosomal aberrations were observed in cultured human peripheral lymphocytes exposed to separately increasing concentrations of 50% methanolic extracts of Persea americana fruit and leaves. The groups exposed to leaf and fruit extracts, respectively, showed a concentration-dependent increase in chromosomal aberrations as compared to that in a control group. The mean percentage total aberrant metaphases at 100 mg/kg, 200 mg/kg, and 300 mg/kg concentrations of leaf extract were found respectively to be 58 ± 7.05, 72 ± 6.41, and 78 ± 5.98, which were significantly higher (p < 0.0001 each) than that in the control group (6 ± 3.39). The mean percentage total aberrant metaphases at 100 mg/kg, 200 mg/kg, and 300 mg/kg concentrations of fruit extract were found to be 18 ± 5.49, 40 ± 10.00, and 52 ± 10.20, respectively, which were significantly higher (p = 0.033, p < 0.0001, and p < 0.0001, respectively) than that for control (6 ± 3.39). Acrocentric associations and premature centromeric separation were the two most common abnormalities observed in both the exposed groups. The group exposed to leaf extracts also showed a significant number of a variety of other structural aberrations, including breaks, fragments, dicentrics, terminal deletion, minutes, and Robertsonian translocations. The group exposed to leaf extract showed higher frequency of all types of aberrations at equal concentrations as compared to the group exposed to fruit extract.

Acute and sub-acute toxicological assessment of the aqueous seed extract of Persea americana mill (Lauraceae) in rats

The aqueous seed extract of Persea americana Mill (Lauraceae) is used by herbalists in Nigeria for the management of hypertension. As part of our on-going scientific evaluation of the extract, we designed the present study to assess its acute and sub-acute toxicity profiles in rats. Experiments were conducted to determine the oral median lethal dose (LD(50)) and other gross toxicological manifestations on acute basis. In the sub-acute experiments, the animals were administered 2.5 g/kg (p.o) per day of the extract for 28 consecutive days. Animal weight and fluid intake were recorded during the 28 days period. Terminally, kidneys, hearts, blood/sera were obtained for weight, haematological and biochemical markers of toxicity. Results show that the LD(50) could not be determined after a maximum dose of 10 g/kg. Sub-acute treatment with the extract neither affected whole body weight nor organ-to-body weight ratios but significantly increased the fluid intake (P < 0.0001). Haematological parameters and the levels of ALT, AST, albumin and creatinine were not significantly altered. However, the concentration of total proteins was significantly increased in the treated group. In conclusion, the aqueous seed extract of P. americana is safe on sub-acute basis but extremely high doses may not be advisable.