Effects of ellagic acid and 2-(2,3,6-trihydroxy-4-carboxyphenyl)ellagic acid on sorbitol accumulation in vitro and in vivo

Function of selected natural antidiabetic compounds with potential against cancer via modulation of the PI3K/AKT/mTOR cascade

Diabetes mellitus (DM) is a metabolic disorder with growing global incidence, as 387 million people were diagnosed in 2014 with an expected projection of 642 million in 2040. Several complications are associated with DM including heart attack, stroke, kidney failure, blindness, and cancer. The latter is the second leading cause of death worldwide accounting for one in every six deaths, with liver, pancreas, and endometrium cancers are the most abundant among patients with diabetes. Phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway plays a vital role in developing a wide array of pathological disorders, among them diabetes and cancer. Natural secondary metabolites that counteract the deleterious effects of reactive oxygen species (ROS) and modulate PI3K/Akt/mTOR pathway could be a promising approach in cancer therapy. Here, 717 medicinal plants with antidiabetic activities were highlighted along with 357 bioactive compounds responsible for the antidiabetic activity. Also, 43 individual plant compounds with potential antidiabetic activities against cancer via the modulation of PI3K/Akt/mTOR cascade were identified. Taken together, the available data give an insight of the potential of repurposing medicinal plants and/or the individual secondary metabolites with antidiabetic activities for cancer therapy.

A review on phytochemistry and pharmacological uses of Tecoma stans (L.) Juss. ex Kunth

ETHNOPHARMACOLOGICAL RELEVANCE

Tecoma stans (L.) Juss. ex Kunth (Bignoniaceae) is an attractive evergreen plant known as kusi urakame, koyawari, Palo amarillo, tronadora, yellow-elder, yellow trumpet bush, trumpet-flower, yellow-bells, trumpet bush, ginger-Thomas, esperanza, and timboco. It is widely used in traditional Mexican medicine, to treat hyperglycemia, gastrointestinal and urinary tract disorders, jaundice, toothaches, headaches, colds, skin infections, and scorpion, snake, and rat bites. Current research focusses on evaluating its bioactive components and therapeutic potential.

AIM OF THE STUDY

The current article reviewed the information available on Tecoma stans ethnopharmacology, geographical distribution, chemical composition, phytochemistry, therapeutic effects, and toxicology.

MATERIAL AND METHODS

Information of botanical description, distribution, traditional uses, chemical composition, bioactive components, and therapeutic investigations was gathered from a comprehensive literature search of electronic databases such as Science Direct, PubMed, Web of Science, Wiley, ACS, Springer, Taylor and Francis, Google Scholar, and SCOPUS until 2020 for publications (peer-reviewed articles, eBooks, short communications, reports from international organizations, and case letters). Information was also included from books, conference proceedings, and thesis. Primary keywords for data collection were "Tecoma stans," and "Ethnopharmacology," followed by secondary keywords such as "Constituents," "Therapeutic effect," and "Toxicity."

RESULTS

An exhaustive comparative study of the accessible sources of Tecoma stans confirmed its origin, ethnopharmacological and therapeutic uses. More than 120 chemical compounds have been isolated, and the main active principles are alkaloids, phenolic acids, flavonoids, and fatty acids. The plant possesses vast therapeutic benefits, such as lowering elevated blood sugar levels, anti-inflammatory, anti-cancer, anti-bacterial, anti-fungal, anti-oxidant, hepatoprotective, and wound healing actions.

CONCLUSIONS

Comprehensive literature analysis exhibits that many populations have utilized Tecoma stans around the globe with specific reference to different parts of Mexico. The above information shows that the plant holds many hidden potentials and can, therefore, be studied extensively for its phytoconstituents and therapeutic effects. However, while going through the literature, it was observed that incomplete data is reported on in vivo trials, especially concerning its dosage, positive and negative control groups, intervention time, and toxicity studies. Additionally, there is a lack of information on its complete nutritional and phytochemical profiling. We trust that this review will help lay the groundwork for encouraging pharmacological and pharmaceutical studies. It will also direct us to understand the clinical relevance and applications of bioactive compounds from Tecoma stans in the prevention and treatment of diseases.

Constitutive expression of aldose reductase 1 from Zea mays exacerbates salt and drought sensitivity of transgenic Escherichia coli and Arabidopsis

Aldose reductases (ARs) have been considered to play important roles in sorbitol biosynthesis, cellular detoxification and stress response in some plants. ARs from maize are capable of catalyzing the oxidation of sorbitol to glucose. However, little is known how maize ARs response to abiotic stresses. In this work, we cloned one isoform of maize ARs (ZmAR1), and furthermore we analyzed the roles of ZmAR1 in response to salt and drought stresses at both prokaryotic and eukaryotic levels. ZmAR1 encodes a putative 35 kDa protein that contains 310 amino acids. Under normal growth conditions, ZmAR1 was expressed in maize seedlings, and the highest expression level was found in leaves. But when seedlings were subjected to drought or salt treatment, the expression levels of ZmAR1 were significantly reduced. The constitutive expression of ZmAR1 increased the sensitivity of recombinant E. coli cells to drought and salt stresses compared with the control. Under salt and drought stresses, transgenic Arabidopsis lines displayed lower seed germination rate, shorter seedling root length, lower chlorophyll content, lower survival rate and lower antioxidant enzyme activity than wild type (WT) plants, but transgenic Arabidopsis had higher relative conductivity, higher water loss rate, and more MDA content than WT. Meanwhile, the introduction of ZmAR1 into Arabidopsis changed the expression levels of some stress-related genes. Taken together, our results suggested that ZmAR1 might act as a negative regulator in response to salt and drought stresses in Arabidopsis by reducing the sorbitol content and modulating the expression levels of some stress-related genes.

Ellagic Acid Inhibits Neuroinflammation and Cognitive Impairment Induced by Lipopolysaccharides

Neuroinflammation is a predisposing factor for the development of cognitive impairment and dementia. Among the new molecules that are currently being studied, ellagic acid (EA) has stood out for its neuroprotective properties. The present study investigated the effects of ellagic acid in the object recognition test, oxidative stress, cholinergic neurotransmission, glial cell expression, and phosphorylated Tau protein expression. For this, 32 male Wistar rats received an intraperitoneal (IP) application of lipopolysaccharides (LPS) at a dose of 250 µg/kg or 0.9% saline solution (SAL) for 8 days. Two hours after the IP injections, the animals received 100 mg/kg of EA or SAL via intragastric gavage. Behavioral parameters (open field test and object recognition) were performed on days 5, 6, and 7 of the experimental periods. The results showed that the treatment with EA in the LPS group was able to inhibit cognitive impairment, modulate the immune system response by significantly reducing glial cell expression, attenuating phosphorylated Tau and oxidative damage with consequent improvement in the antioxidant system, as well as preventing the increase of acetylcholinesterase activity. Thus, the neuroprotective effects of EA and its therapeutic potential in cognitive disorders secondary to neuroinflammation were demonstrated.

Three new ester glycosides with cytotoxic activity from the seeds of Caesalpinia sappan

Three new ester glycosides, named as Caesateroside A (1), Caesateroside B (2) and Caesateroside C (3) were obtained from the seeds of Caesalpinia sappan. The new structures of compounds 1-3 were elucidated by analyzing their 1 D NMR, 2 D NMR and HR-ESI-MS spectra. Compounds 1-3 showed weak-moderate cytotoxicity against Hela and HepG-2 human cancer cell lines.

Antidiabetic phytoconstituents and their mode of action on metabolic pathways

Diabetes Mellitus, characterized by persistent hyperglycaemia, is a heterogeneous group of disorders of multiple aetiologies. It affects the human body at multiple organ levels thus making it difficult to follow a particular line of the treatment protocol and requires a multimodal approach. The increasing medical burden on patients with diabetes-related complications results in an enormous economic burden, which could severely impair global economic growth in the near future. This shows that today's healthcare system has conventionally been poorly equipped towards confronting the mounting impact of diabetes on a global scale and demands an urgent need for newer and better options. The overall challenge of this field of diabetes treatment is to identify the individualized factors that can lead to improved glycaemic control. Plants are traditionally used worldwide as remedies for diabetes healing. They synthesize a diverse array of biologically active compounds having antidiabetic properties. This review is an endeavour to document the present armamentarium of antidiabetic herbal drug discovery and developments, highlighting mechanism-based antidiabetic properties of over 300 different phytoconstituents of various chemical categories from about 100 different plants modulating different metabolic pathways such as glycolysis, Krebs cycle, gluconeogenesis, glycogen synthesis and degradation, cholesterol synthesis, carbohydrate metabolism as well as peroxisome proliferator activated receptor activation, dipeptidyl peptidase inhibition and free radical scavenging action. The aim is to provide a rich reservoir of pharmacologically established antidiabetic phytoconstituents with specific references to the novel, cost-effective interventions, which might be of relevance to other low-income and middle-income countries of the world.

Chemical and Biological Aspects of Extracts from Medicinal Plants with Antidiabetic Effects

Diabetes mellitus is a chronic disease and a leading cause of death in western countries. Despite advancements in the clinical management of the disease, it is not possible to control the late complications of diabetes. The main characteristic feature of diabetes is hyperglycemia, which reflects the deterioration in the use of glucose due to a faulty or poor response to insulin secretion. Alloxan and streptozotocin (STZ) are the chemical tools that are most commonly used to study the disease in rodents. Many plant species have been used in ethnopharmacology or to treat experimentally symptoms of this disease. When evaluated pharmacologically, most of the plants employed as antidiabetic substances have been shown to exhibit hypoglycemic and antihyperglycemic activities, and to contain chemical constituents that may be used as new antidiabetic agents. There are many substances extracted from plants that offer antidiabetic potential, whereas others may result in hypoglycemia as a side effect due to their toxicity, particularly their hepatotoxicity. In this article we present an updated overview of the studies on extracts from medicinal plants, relating the mechanisms of action by which these substances act and the natural principles of antidiabetic activity.

In vitro and in vivo inhibitory activities of four Indian medicinal plant extracts and their major components on rat aldose reductase and generation of advanced glycation endproducts

The polyol enzyme aldose reductase (AR) and advanced glycation endproducts (AGEs) play an important role in diabetic complications such as cataracts. The purpose of this study was to investigate four standardized plant extracts used for the treatment of diabetes and related diseases, and their principal components for AR inhibitory activity and to find out their influence in diabetic complications. Thus, Boswellia serrata Triana & Planch. (Burseraceae), Lagerstroemia speciosa (L.) Pers. (Lythraceae), Ocimum gratissimum (L.) (Lamiaceae) and Syzygium cumin (L.) Skeels. (Myrthaceae) and their respective major constituents, boswellic acid, corosolic acid, ursolic acid and ellagic acid, were studied for their inhibitory activity against rat lens AR, rat kidney AR, human recombinant AR and generation of AGEs. In addition, in vivo inhibition of lens galactitol accumulation by the major constituents of the plants in galactose-fed rat has been studied. The results revealed that all the tested extracts and their active ingredients possess significant AR inhibitory actions in both in vitro and in vivo assays with urosolic acid showing the most potent effect. Furthermore, the study indicates the potential of the studied plants and their major constituents as possible protective agents against long-term diabetic complications.

Aldose reductase inhibitory activity and antioxidant capacity of pomegranate extracts

The pomegranate, Punica granatum L., has been the subject of current interest as a medicinal agent with wide-ranging therapeutic indications. In the present study, pomegranate ethanolic seed and hull extracts were tested, in comparison with a commercial sample, for the inhibition of aldose reductase, an enzyme involved in the etiology of diabetic complications. In vitro inhibition of rat lens aldose reductase was determined by a conventional method. Pomegranate ethanolic hull extract and commercial pomegranate hull extract exhibited similar aldose reductase inhibitory activity characterized by IC(50) values ranging from 3 to 33.3 μg/ml. They were more effective than pomegranate ethanolic seed extract with IC(50) ranging from 33.3 to 333 μg/ml. Antioxidant action of the novel compounds was documented in a DPPH test and in a liposomal membrane model, oxidatively stressed by peroxyl radicals. All the plant extracts showed considerable antioxidant potential in the DPPH assay. Pomegranate ethanolic hull extract and commercial pomegranate hull extract executed similar protective effects on peroxidatively damaged liposomal membranes characterized by 10<IC(50)<100 μg/ml. Pomegranate ethanolic seed extract showed significantly lower antioxidant activity compared to both hull extracts studied. Pomegranate extracts are thus presented as bifunctional agents combining aldose reductase inhibitory action with antioxidant activity and with potential therapeutic use in prevention of diabetic complications.

Hypoglycaemic activity and molecular mechanisms of Caesalpinia ferrea Martius bark extract on streptozotocin-induced diabetes in Wistar rats

ETHNOPHARMACOLOGICAL RELEVANCE

The tea from the stem bark of Caesalpinia ferrea Martius (Leguminosae) has been popularly used in the treatment of diabetes in Brazil.

AIM OF THE STUDY

To investigate the hypoglycaemic properties and to elucidate the mechanisms by which the aqueous extract of the stem bark of Caesalpinia ferrea reduces blood glucose levels in streptozotocin-induced diabetic rats via the enzymatic pathways of protein kinase B (PKB/Akt), AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC).

MATERIALS AND METHODS

The aqueous extract of the stem bark of Caesalpinia ferrea (300 and 450 mg/kg/day), vehicle and metformin (500 mg/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 (P) and the expression of Akt, AMPK and ACC in the liver and skeletal muscle were determined using Western blot.

RESULTS

The aqueous extract of the stem bark of Caesalpinia ferrea reduced blood glucose levels and improved the metabolic state of the animals. P-Akt was increased in the liver and skeletal muscle of the treated animals, P-AMPK was reduced only in the skeletal muscle of these animals and P-ACC was reduced in both when compared with untreated rats.

CONCLUSION

The results indicate that the aqueous extract of the stem bark of Caesalpinia ferrea has hypoglycaemic properties and possibly acts to regulate glucose uptake in liver and muscles by way of Akt activation, restoring the intracellular energy balance confirmed by inhibition of AMPK activation.

Ellagic acid attenuates oxidative stress on brain and sciatic nerve and improves histopathology of brain in streptozotocin-induced diabetic rats

The aim of this study was to investigate the possible effects of ellagic acid in brain and sciatic nerve tissues of diabetic rats. Also, the impact of ellagic acid on catalase and paraoxonase (PON-1) activities, total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), malondialdehyde (MDA) and nitric oxide (NO) were examined. The rats were randomly divided into four groups, with eight rats each: Normal controls (not diabetic), only ellagic acid treated (ellagic acid controls, not diabetic), Diabetic controls (streptozotocin, diabetic), ellagic acid-treated diabetic (streptozotocin + ellagic acid). After a 4 week experiment, rats were sacrificed, and biomarkers for oxidative stress in the brain and sciatic nerve tissues of the rats were measured. There was significant depletion in the PON-1, catalase, and TAS levels in the brain and sciatic nerve tissues compared to the control groups (for both parameters, p<0.05). The values of catalase, PON-1 and TAS reversed back to normal levels in ellagic acid-treated diabetic rats compared to untreated diabetic rats (for both parameters, p<0.05). The levels of MDA, TOS, NO and, OSI in the brain and sciatic nerve tissues were higher in untreated diabetic rats compared to control group (for both parameters p<0.05). However, MDA, TOS, OSI, and NO levels were found to be significantly reduced in the ellagic acid-treated diabetic group compared to the untreated diabetic group in these tissues (for both parameters, p<0.05). In conclusion, the results of the present study suggested that ellagic acid exhibits neuroprotective effects against oxidative damage in diabetic rats.

Prevention effect in selenite-induced cataract in vivo and antioxidative effects in vitro of Crataegus pinnatifida leaves

Cataract is the leading cause of blindness worldwide. It is a multifactorial disease primarily associated with oxidative stress produced by free radicals. The present study was undertaken to evaluate the anticataract potential of Crataegus pinnatifida (hawthorn tree) leaves extract in selenite-induced cataract in vivo and antioxidant effects in vitro. In vitro antioxidant assay of C. pinnatifida leaves extract on NO production inhibition, aldose reductase inhibition, and O(2)(-) radical scavenging activities gave the IC(50) of 98.3, 89.7, and 5.98 μg/mL, respectively. To characterize some major compounds in C. pinnatifida leaves extract, nine flavonoids were identified via LC-MS/MS qualitative analysis. Based on in vitro screening results, C. pinnatifida leaves extract eye drops in 0.1% hydroxypropyl methyl cellulose solution were prepared to evaluate the anticataract potential in vivo. Administration of C. pinnatifida leaves extract eye drops alternately three times a day in rat pups with selenite-induced oxidative stress significantly increased serum SOD and CAT activities, and tended to reduce MDA level compared with control group. The antioxidant enzyme SOD, CAT, and GSH activities in lens showed a significant increase. These results may be applied in the future for the prevention and treatment of cataracts.

Aldose-reductase- and protein-glycation-inhibitory principles from the whole plant of Duchesnea chrysantha

Ellagic acid (1), 3,3'-di-O-methylellagic acid (2), 3,3',4-tri-O-methylellagic acid (3), isovitexin (4), kaempferol 3-O-beta-D-glucuronide methyl ester (5), quercetin 3-O-alpha-L-arabinopyranosyl-(1-->6)-beta-D-galactopyranoside (6), ursolic acid, pomolic acid, tormentic acid, euscaphic acid, euscaphic acid 28-O-beta-D-glucopyranoside, and maslinic acid were isolated from the AcOEt- and BuOH-soluble MeOH extract of Duchesnea chrysantha (whole plant). The isolates were subjected to in vitro bioassays to evaluate their inhibitory activity on rat-lens aldose reductase (RLAR) and formation of advanced glycation end products (AGEs). The ellagic acids and flavonoids, compounds 1-6, exhibited moderate inhibitory effects on RLAR. However, compounds 1 and 4-6 showed excellent inhibitory activities towards the formation of AGEs. This is the first report that 4 and 6 exhibit inhibitory activity towards AR and AGEs formation.

Crystallization and preliminary X-ray diffraction analysis of maize aldose reductase

Maize aldose reductase (AR) is a member of the aldo-keto reductase superfamily. In contrast to human AR, maize AR seems to prefer the conversion of sorbitol into glucose. The apoenzyme was crystallized in space group P2(1)2(1)2(1), with unit-cell parameters a = 47.2, b = 54.5, c = 100.6 A and one molecule in the asymmetric unit. Synchrotron X-ray diffraction data were collected and a final resolution limit of 2.0 A was obtained after data reduction. Phasing was carried out by an automated molecular-replacement procedure and structural refinement is currently in progress. The refined structure is expected to shed light on the functional/enzymatic mechanism and the unusual activities of maize AR.