Exploring the anti-diabetic potential of Australian Aboriginal and Indian Ayurvedic plant extracts using cell-based assays

Comparative Studies of Palmatine with Metformin and Glimepiride on the Modulation of Insulin Dependent Signaling Pathway In Vitro, In Vivo & Ex Vivo

(1) Insulin resistance, a symptom of type 2 diabetes mellitus (T2DM), is caused by the inactivation of the insulin signaling pathway, which includes IRS-PI3K-IRS-1-PKC-AKT2 and GLUT4. Metformin (biguanide) and glimepiride (sulfonylurea) are both drugs that are derivatives of urea, and they are widely used as first-line drugs for the treatment of type 2 diabetes mellitus. Palmatine has been previously reported to possess antidiabetic and antioxidant properties. (2) The current study compared palmatine to metformin and glimepiride in a type 2 diabetes model for ADME and insulin resistance via the PI3K/Akt/GLUT4 signaling pathway: in vitro, in vivo, ex vivo, and in silico molecular docking. (3) Methods: Differentiated L6 skeletal muscle cells and soleus muscle tissue were incubated in standard tissue culture media supplemented with high insulin and high glucose as a cellular model of insulin resistance, whilst streptozotocin (STZ)-induced Sprague Dawley rats were used as the diabetic model. The cells/tissue/animals were treated with palmatine, while glimepiride and metformin were used as standard drugs. The differential gene expression of PI3K, IRS-1, PKC-α, AKT2, and GLUT4 was evaluated using qPCR. (4) Results: The results revealed that the genes IRS-PI3K-IRS-1-PKC-AKT2 were significantly down-regulated, whilst PKC-α was upregulated significantly in both insulin-resistant cells and tissue animals. Interestingly, palmatine-treated cells/tissue/animals were able to reverse these effects. (5) Conclusions: Palmatine appears to have rejuvenated the impaired insulin signaling pathway through upregulation of the gene expression of IRS-1, PI3K, AKT2, and GLUT4 and downregulation of PKC-expression, according to in vitro, in vivo, and ex vivo studies.

Heartwood Extract of Pterocarpus marsupium Roxb. Offers Defense against Oxyradicals and Improves Glucose Uptake in HepG2 Cells

Diabetes mellitus leads to cellular damage and causes apoptosis by oxidative stress. Heartwood extract of Pterocarpus marsupium has been used in Ayurveda to treat various diseases such as leprosy, diabetes, asthma, and bronchitis. In this study, we worked out the mechanism of the antidiabetic potential of methanolic heartwood extract of Pterocarpus marsupium (MPME). First, metabolic profiling of MPME was done using gas chromatography-mass spectrometry (GCMS), ultra-performance liquid chromatography-mass spectroscopy (UPLC-MS), and high-performance thin-layer chromatography (HPTLC) to identify phenols, flavonoids, and terpenoids in MPME. Biological studies were carried out in vitro using the HepG2 cell line. Many antidiabetic compounds were identified including Quercetin. Methanolic extract of MPME (23.43 µg/mL-93.75 µg/mL) was found to be safe and effective in reducing oxyradicals in HepG2 cells. A concentration of 93.75 µg/mL improved glucose uptake efficiently. A significant decrease in oxidative stress, cell damage, and apoptosis was found in MPME-treated HepG2 cells. The study suggests that the heartwood of Pterocarpus marsupium offers good defense in HepG2 cells against oxidative stress and improves glucose uptake. The results show the significant antidiabetic potential of MPME using a HepG2 cell model. The effect seems to occur by reducing oxidative stress and sensitizing the cells towards glucose uptake, hence lowering systemic glucose levels, as well as rescuing ROS generation.

In Silico Approaches to Identify Polyphenol Compounds as α-Glucosidase and α-Amylase Inhibitors against Type-II Diabetes

Type-II diabetes mellitus (T2DM) results from a combination of genetic and lifestyle factors, and the prevalence of T2DM is increasing worldwide. Clinically, both α-glucosidase and α-amylase enzymes inhibitors can suppress peaks of postprandial glucose with surplus adverse effects, leading to efforts devoted to urgently seeking new anti-diabetes drugs from natural sources for delayed starch digestion. This review attempts to explore 10 families e.g., Bignoniaceae, Ericaceae, Dryopteridaceae, Campanulaceae, Geraniaceae, Euphorbiaceae, Rubiaceae, Acanthaceae, Rutaceae, and Moraceae as medicinal plants, and folk and herb medicines for lowering blood glucose level, or alternative anti-diabetic natural products. Many natural products have been studied in silico, in vitro, and in vivo assays to restrain hyperglycemia. In addition, natural products, and particularly polyphenols, possess diverse structures for exploring them as inhibitors of α-glucosidase and α-amylase. Interestingly, an in silico discovery approach using natural compounds via virtual screening could directly target α-glucosidase and α-amylase enzymes through Monte Carto molecular modeling. Autodock, MOE-Dock, Biovia Discovery Studio, PyMOL, and Accelrys have been used to discover new candidates as inhibitors or activators. While docking score, binding energy (Kcal/mol), the number of hydrogen bonds, or interactions with critical amino acid residues have been taken into concerning the reliability of software for validation of enzymatic analysis, in vitro cell assay and in vivo animal tests are required to obtain leads, hits, and candidates in drug discovery and development.

Phytochemistry and Pharmacological Activity of Plants of Genus Curculigo: An Updated Review Since 2013

The genus Curculigo, as a folk herbal medicine, has been used for many years in China, treating impotence, limb limpness, and arthritis of the lumbar and knee joints. The last systematic review of the genus Curculigo was written in 2013, scientifically categorizing the phytochemistry and biological activities. Hitherto, the original compounds and their pharmacological activities were presented as the development of this genus, but there is not an updated review. To conclude the progression of the genus Curculigo, we collected the new literature published from 2013 to 2021 in PubMed, Web of Science, Google Scholar databases, and the Chinese National Knowledge Infrastructure. The novel chlorophenolic glucosides, curculigine, phenolic glycosides, orcinosides and polysaccharides were isolated from Curculigo. The new analyzing methods were established to control the quality of Curculigo as a herbal medicine. In addition, the pharmacological effects of Curculigo focused on anti-diabetes, antibacterial, anti-inflammatory, osteoporosis, antioxidation, etc. The antitumor and neuroprotective activities were newly explored in recent years. The application of herbal medicine was gradually developed in scientific methods. The medicinal value of the genus Curculigo needs to further investigate its pharmacological mechanisms. This new review offers more insights into the exploitation of the pharmacological value of the genus Curculigo.

Anil Kumar N, Sharopov F, Ramírez-Alarcón K, Ruiz-Ortega A, Abdulmajid Ayatollahi S, Valere Tsouh Fokou P, Kobarfard F, Amiruddin Zakaria Z, Iriti M, Taheri Y, Martorell M, Sureda A, N. Setzer W, Durazzo A, Lucarini M, Santini A, Capasso R, Adrian Ostrander E, -ur-Rahman A, Iqbal Choudhary M, C. Cho W, Sharifi-Rad J. Antidiabetic Potential of Medicinal Plants and Their Active Components

Diabetes mellitus is one of the major health problems in the world, the incidence and associated mortality are increasing. Inadequate regulation of the blood sugar imposes serious consequences for health. Conventional antidiabetic drugs are effective, however, also with unavoidable side effects. On the other hand, medicinal plants may act as an alternative source of antidiabetic agents. Examples of medicinal plants with antidiabetic potential are described, with focuses on preclinical and clinical studies. The beneficial potential of each plant matrix is given by the combined and concerted action of their profile of biologically active compounds.

Medicinal Plants Used for the Traditional Management of Diabetes in the Eastern Cape, South Africa: Pharmacology and Toxicology

The use of medicinal plants for the management of diabetes mellitus is on the rise in the developing countries, including South Africa. There is increasing scientific evidence that supports the claims by the traditional healers. In this review, we compare the families of previously reported anti-diabetic plants in the Eastern Cape by rating the anti-diabetic activity, mode of action and also highlight their therapeutic potentials based on the available evidence on their pharmacology and toxicity. Forty-five plants mentioned in ethnobotanical surveys were subjected to a comprehensive literature search in the available electronic databases such as PubMed, ScienceDirect, Google Scholar and Elsevier, by using “plant name” and “family” as the keywords for the primary searches to determine the plants that have been scientifically investigated for anti-diabetic activity. The search returned 25 families with Asteraceae highly reported, followed by Asphodelaceae and Alliaceae. Most of the plants have been studied for their anti-diabetic potentials in vivo and/or in vitro, with most of the plants having a higher percentage of insulin release and inhibition against carbohydrate digesting enzymes as compared with insulin mimetic and peripheral glucose uptake. Almost all the investigated plants also inhibit oxidative stress as part of their hypoglycemic activity with less toxicity. However, the isolation of their bioactive molecules is still lacking. This review provides a resource to enable thorough assessments of the therapeutic profiles of available medicinal plants used for the management of diabetes in the Eastern Cape, South Africa. Further studies such as the identification of the active ingredients of potent plants still need to be carried out; this may lead to new molecules in drug discovery and development.

In Vitro Antidiabetic Effects and Antioxidant Potential of Cassia nemophila Pods

The antidiabetic and antioxidant potential of ethanolic extract of Cassia nemophila pod (EECNP) was evaluated by three in vitro assays, including yeast glucose uptake assay, glucose adsorption assay, and DPPH radical scavenging activity. The result revealed that the extracts have enhanced the uptake of glucose through the plasma membrane of yeast cells. A linear increase in glucose uptake by yeast cells was noticed with gradual increase in the concentration of the test samples. Moreover, the adsorption capacity of the EECNP was directly proportional to the molar concentration of glucose. Also, the DPPH radical scavenging capacity of the extract was increased to a maximum value of 43.3% at 80 μg/ml, which was then decreased to 41.9% at 100 μg/ml. From the results, it was concluded that EECNP possess good antidiabetic and antioxidant properties as shown by in vitro assays.

Plants used to treat diabetes in Sri Lankan Siddha Medicine - An ethnopharmacological review of historical and modern sources

INTRODUCTION AND BACKGROUND

In recent decades diabetes mellitus has become a considerable health problem in countries like Sri Lanka and results in an increasing economic burden hampering the social and economic development of these countries. About 60% to 70% of the rural population in Sri Lanka rely on indigenous medicinal systems as their main source for primary health care. Siddha (Tamil) Medicine is one of the four Sri Lankan traditional medicinal systems and it is practised mostly in the eastern and northern provinces of Sri Lanka where the majority of Tamils reside.

AIM

The foundation of this study is a documentation of plant species recorded in historical and modern Sri Lankan Siddha Medical documents used to treat diabetes. Based on the systematic documentation and analysis of Siddha concepts about diabetes and its signs and preparations used to treat diabetes in Sri Lankan Siddha Medicine, the plant species included in these preparations (excluding globally or very widely used, very well studied species) were evaluated in terms of the current state-of-the-art about these species' pharmacology and effectiveness in order to lay a foundation for their further development.

METHOD

Historic and modern Sri Lankan university texts books in Tamil were used as sources for information on diabetes Siddha concepts and antidiabetic Sri Lankan Siddha Medicine preparations. Information on the known antidiabetic effects of extracts and compounds obtained from these species were used in order to assess the current state of the art of these species.

RESULTS AND DISCUSSION

Information of ingredients, preparation methods, amount of ingredients used, and dosages of 60 antidiabetic Sri Lankan Siddha Medicine preparations were obtained. Animal parts including marine organisms, inorganic substances, and plants are the three types of ingredients used. Overall 171 plant species in 73 families were documented. Senna auriculata (L.) Roxb. (Fabaceae) was identified as the most frequently cited species. Globally distributed and very well studied plants were excluded in the pharmacological and clinical literature review which includes 123 plant species. The majority (48%) of the plant species reviewed were studied up to in vivo level as the current maximum level of scientific evidence available. Followed by 41% of species have not been studied for antidiabetic activities or did not show antidiabetic activity. Moreover, 6% and 5% were studied up to in vitro and in clinical levels, respectively. The majority of the species were studied only in the models that represent type 1 diabetes.

CONCLUSION

This is the first study systematically assessing the importance of preparations and plants used in antidiabetic Sri Lankan Siddha Medicine preparations. Antidiabetic plants are a crucial health care resource in Sri Lankan Siddha Medicine. This study also identified a wide range of methodological problems in the studies conducted so far. More and better type 2 diabetes models should be employed in future studies. This comprehensive review creates the basis for a more systematic study of these local resources.

In vitro inhibitory activities of selected Australian medicinal plant extracts against protein glycation, angiotensin converting enzyme (ACE) and digestive enzymes linked to type II diabetes

Background

There is a need to develop potential new therapies for the management of diabetes and hypertension. Australian medicinal plants collected from the Kuuku I’yu (Northern Kaanju) homelands, Cape York Peninsula, Queensland, Australia were investigated to determine their therapeutic potential. Extracts were tested for inhibition of protein glycation and key enzymes relevant to the management of hyperglycaemia and hypertension. The inhibitory activities were further correlated with the antioxidant activities.

Methods

Extracts of five selected plant species were investigated: Petalostigma pubescens, Petalostigma banksii, Memecylon pauciflorum, Millettia pinnata and Grewia mesomischa. Enzyme inhibitory activity of the plant extracts was assessed against α-amylase, α-glucosidase and angiotensin converting enzyme (ACE). Antiglycation activity was determined using glucose-induced protein glycation models and formation of protein-bound fluorescent advanced glycation endproducts (AGEs). Antioxidant activity was determined by measuring the scavenging effect of plant extracts against 1, 1-diphenyl-2-picryl hydrazyl (DPPH) and using the ferric reducing anti-oxidant potential assay (FRAP). Total phenolic and flavonoid contents were also determined.

Results

Extracts of the leaves of Petalostigma banksii and P. pubescens showed the strongest inhibition of α-amylase with IC₅₀ values of 166.50 ± 5.50 μg/mL and 160.20 ± 27.92 μg/mL, respectively. The P. pubescens leaf extract was also the strongest inhibitor of α-glucosidase with an IC₅₀ of 167.83 ± 23.82 μg/mL. Testing for the antiglycation potential of the extracts, measured as inhibition of formation of protein-bound fluorescent AGEs, showed that P. banksii root and fruit extracts had IC₅₀ values of 34.49 ± 4.31 μg/mL and 47.72 ± 1.65 μg/mL, respectively, which were significantly lower (p < 0.05) than other extracts. The inhibitory effect on α-amylase, α-glucosidase and the antiglycation potential of the extracts did not correlate with the total phenolic, total flavonoid, FRAP or DPPH. For ACE inhibition, IC₅₀ values ranged between 266.27 ± 6.91 to 695.17 ± 15.38 μg/mL.

Conclusions

The tested Australian medicinal plant extracts inhibit glucose-induced fluorescent AGEs, α-amylase, α-glucosidase and ACE with extracts of Petalostigma species showing the most promising activity. These medicinal plants could potentially be further developed as therapeutic agents in the treatment of hyperglycaemia and hypertension.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1421-5) contains supplementary material, which is available to authorized users.