Cucurbitane triterpenoids from Momordica charantia L. and their inhibitory activity against α-glucosidase, α-amylase and protein tyrosine phosphatase 1B (PTP1B)

Momordica charantia Bioactive Components: Hypoglycemic and Hypolipidemic Benefits Through Gut Health Modulation

Momordica charantia (MC), a member of the Cucurbitaceae family, is well known for its pharmacological activities that exhibit hypoglycemic and hypolipidemic properties. These properties are largely because of its abundant bioactive compounds and phytochemicals. Over the years, numerous studies have confirmed the regulatory effects of MC extract on glycolipid metabolism. However, there is a lack of comprehensive reviews on newly discovered MC-related components, such as insulin receptor-binding protein-19, adMc1, and MC protein-30 and triterpenoids 3β,7β,25-trihydroxycucurbita-5,23(E)-dien-19-al, and the role of MC in gut microbiota and bitter taste receptors. This review offers an up-to-date overview of the recently reported chemical compositions of MC, including polysaccharides, saponins, polyphenolics, peptides, and their beneficial effects. It also provides the latest updates on the role of MC in the regulation of gut microbiota and bitter taste receptor signaling pathways. As a result, this review will serve as a theoretical basis for potential applications in the creation or modification of MC-based nutrient supplements.

Effects of Momordica charantia L. supplementation on glycemic control and lipid profile in type 2 diabetes mellitus patients: A systematic review and meta-analysis of randomized controlled trials

Background and aims

Momordica charantia L. (M. charantia) has been traditionally utilized as a medicinal intervention for managing type 2 diabetes mellitus (T2DM). The current study was designed to offer a GRADE-assessed systematic review and meta-analysis of randomized controlled trials (RCTs) examining the impact of M. Charantia intake on glycemic indexes and the lipid profile of patients with T2DM.

Methods

A comprehensive search was conducted across several databases, including PubMed, EMBASE, Web of Science, and Cochrane Library, from the inception of each database until April 22, 2023. The Hartung-Knapp adjustment was applied to ensure conservative summary estimates with broad confidence intervals.

Results

A total of eight trials involving 423 patients with T2DM were included in this study. Compared to the control group, the intake of M. charantia supplementation resulted in significant reductions in fasting blood glucose (FBG) (WMD: -0.85 mmol/L; 95%CI: -1.44, -0.26; p = 0.005; I2 = 73.4 %), postprandial glucose (PPG) (WMD: -2.28 mmol/L; 95%CI: -3.35, -1.21; p = 0.000; I2 = 66.9 %), glycosylated hemoglobin A1c (HbA1c) (WMD: -0.38 %; 95%CI: -0.53, -0.23; p = 0.000; I2 = 37.6 %), and total cholesterol (TC) (WMD: -0.38 mmol/L; 95%CI: -0.70, -0.07; p = 0.017; I2 = 63.6 %). These results remained statistically significant even after applying the Hartung-Knapp adjustment. However, no significant differences were observed in terms of triglyceride (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL).

Conclusions

The findings of this study suggest that M. charantia could serve as a potential alternative for individuals with T2DM, particularly those with elevated total cholesterol levels. However, further high-quality studies are necessary to validate these results.

Pharmacological properties of Ensete glaucum seed extract: Novel insights for antidiabetic effects via modulation of oxidative stress, inflammation, apoptosis and MAPK signaling pathways

ETHNOPHAMACOLOGICAL RELEVANCE

Medicinal plants are increasingly making important contributions to diabetic treatment. Ensete glaucum seeds have been widely used in folk medicine to treat diabetes.

AIM OF THE STUDY

The study was aimed to investigate the protective effect and active mechanisms of E. glaucum seed extract (EGSE) against streptozotocin (STZ)-induced hyperglycemia.

MATERIALS AND METHODS

Hyperglycemic mice were treated with EGSE (25 and 50 mg/kg) or glibenclamide (5 mg/kg) once daily for 7 d. The effects of these treatments on changes in blood biochemical parameters, pancreatic, liver, and kidney histopathology, oxidative stress and inflammatory marker levels in pancreatic, hepatic, and renal tissues were assessed. Expression of several proteins in MAPK signaling pathway related to apoptosis in pancreatic tissue were investigated. Furthermore, ex vivo, in vitro, and in silico biological activities of EGSE and its compounds were also examined.

RESULTS

EGSE and glibenclamide increased notably insulin, reduced significantly glucose, AST, ALT, BUN and creatinine levels in blood. Pancreatic islets, hepatic and renal tissue structure were restored by EGSE or glibenclamide. EGSE showed significant anti-oxidative stress and anti-inflammatory effects by enhancing GSH level and dropping MDA, NF-κB, TNF-α and IL-6 levels in these tissues. Particularly, EGSE exhibited pancreatic protective effect against STZ-induced apoptosis through the MAPK signaling pathway by down-regulation of p-p38 MAPK, ERK1/2, JNK1, p-AMPK, Bax, Bax/Bcl-2, cytochrome c, cleaved-caspase 3 and PARP expression, and slight up-regulation of Bcl-2 expression. Moreover, EGSE inhibited intestinal glucose absorption, PTP1B, α-amylase, and α-glucosidase activities. Its isolated compounds (Afzelechin and coniferaldehyde) showed PTP1B and α-glucosidase inhibitory activities, and potent structure-activity relationships.

CONCLUSION

These findings indicated the hypoglycemic and protective effects of E. glaucum seed extract against the STZ diabetogenic action. E. glaucum seed is a potential candidate for further studies to confirm its activities as a therapeutic agent for diabetic patients.

Synergistic effects of Momordica charantia, Nigella sativa, and Anethum graveolens on metabolic syndrome targets: In vitro enzyme inhibition and in silico analyses

Momordica charantia, Nigella sativa, and Anethum graveolens are established medicinal plants possessing noted anti-diabetic and anti-obesity properties. However, the molecular mechanisms underscoring their inhibitory effects on pancreatic lipase, α-glucosidase, and HMG-CoA reductase remain unexplored. This study aimed to elucidate the efficacy of various NS, MC, and AG blends in modulating the enzymatic activity of pancreatic lipase, HMG-CoA reductase, and a-glucosidase, utilizing an integrative approach combining in vitro assessments and molecular modeling techniques. A factorial design matrix generated eight distinct concentration combinations of NS, MC, and AG, subsequently subjected to in vitro enzyme inhibition assays. Molecular docking analyses using AutoDock Vina, molecular dynamics simulations, MMPBSA calculations, and principal component analysis, were executed with Gromacs to discern the interaction dynamics between the compounds and target enzymes. A formulation comprising NS:MC:AG at a 215:50:35 μg/mL ratio yielded significant inhibition of pancreatic lipase (IC50: 74.26 ± 4.27 μg/mL). Moreover, a concentration combination of 215:80:35 μg/mL effectively inhibited both α-glucosidase (IC50: 66.09 ± 3.98 μg/mL) and HMGCR (IC50: 129.03 μg/mL). Notably, MC-derived compounds exhibited superior binding affinity towards all three enzymes, compared to their reference molecules, with diosgenin, Momordicoside I, and diosgenin displaying binding affinities of -11.0, -8.8, and -7.9 kcal/mol with active site residues of pancreatic lipase, α-glucosidase, and HMGCR, respectively. Further, 100 ns molecular dynamics simulations revealed the formation and stabilization of non-bonded interactions between the compounds and the enzymes' active site residues. Through a synergistic application of in vitro and molecular modeling methodologies, this study substantiated the potent inhibitory activity of the NS:MC:AG blend (at a ratio of 215:80:35 μg/mL) and specific MC compounds against pancreatic lipase, α-glucosidase, and HMGCR. These findings provide invaluable insights into the molecular underpinnings of these medicinal plants' anti-diabetic and anti-obesity effects and may guide future therapeutic development.

New insights into anti-diabetes effects and molecular mechanisms of dietary saponins

Diabetes mellitus (DM) is a long-term metabolic disorder that manifests as chronic hyperglycemia and impaired insulin, bringing a heavy load on the global health care system. Considering the inevitable side effects of conventional anti-diabetic drugs, saponins-rich natural products exert promising therapeutic properties to serve as safer and more cost-effective alternatives for DM management. Herein, this review systematically summarized the research progress on the anti-diabetic properties of dietary saponins and their underlying molecular mechanisms in the past 20 years. Dietary saponins possessed the multidirectional anti-diabetic capabilities by concurrent regulation of various signaling pathways, such as IRS-1/PI3K/Akt, AMPK, Nrf2/ARE, NF-κB-NLRP3, SREBP-1c, and PPARγ, in liver, pancreas, gut, and skeletal muscle. However, the industrialization and commercialization of dietary saponin-based drugs are confronted with a significant challenge due to the low bioavailability and lack of the standardization. Hence, in-depth evaluations in pharmacological profile, function-structure interaction, drug-signal pathway interrelation are essential for developing dietary saponins-based anti-diabetic treatments in the future.

Exploring plant-based alpha-glucosidase inhibitors: promising contenders for combatting type-2 diabetes

Objective: This systematic review aimed to provide comprehensive details on the α-G inhibitory potential of various bioactive compounds derived from natural sources.Methods: A comprehensive literature search was conducted using various databases and search engines, including Science Direct, Google Scholar, SciFinder, Web of Science, and PubMed until May, 2023.Results and conclusions: The enzyme alpha-glucosidase (α-G) is found in the brush border epithelium of the small intestine and consists of duplicated glycoside hydrolase (GH31) domain. It involves the conversion of disaccharides and oligosaccharides into monosaccharides by acting on alpha (1 → 4) and (1 → 6) linked glucose residue. Once absorbed, glucose enters the bloodstream and elevates postprandial glucose, which is associated with the development of type 2 Diabetes (T2D). Epidemic obesity, cardiovascular disease, and nephropathy are linked to T2D. Traditional medicinal plants with α-G inhibitory potential are commonly used to treat T2D due to the adverse effects of currently used α-G inhibitors miglitol, acarbose, and voglibose. Various bioactive compounds derived from natural sources, including lupenone, Wilforlide A, Baicalein, Betulinic acid, Ursolic acid, Oleanolic acid, Katononic acid, Carnosol, Hypericin, Astilbin, lupeol, betulonic acid, Fagomine, Lactucaxanthin, Erythritol, GP90-1B, Procyanidins, Galangin, and vomifoliol retain α-G inhibitory potential for regulating hyperglycaemia.

Modulation of Insulin Resistance by Silybum marianum Leaves, and its Synergistic Efficacy with Gymnema sylvestre, Momordica charantia, Trigonella-foenum graecum Against Protein Tyrosine Phosphatase 1B

Prolonged insulin resistance is considered one of the reasons for Type 2 Diabetes Mellitus. Upregulation of Protein tyrosine phosphatase 1B (PTP1B), a negative regulator of insulin signalling, has been well studied as a key regulator in prognosis to insulin resistance. It has been widely studied as a desirable molecular therapeutic target. The study aimed to evaluate the efficacy of leaf extract of the medicinal plants Silybum marianum on the inhibition of PTP1B activity. It also explored the synergistic effect with extracts of Gymnema sylvestre (leaves), Momordica charantia (seeds), and Trigonella foenum graecum (seeds). The S. marianum leaves showed dose-dependent inhibition of PTP1B ranging from 9.48-47.95% (25-1000 μg mL-1). Assay with individual plant extracts showed comparatively lesser inhibition of PTP1B as compared to metformin as a control (38% inhibition). However, a synergistic effect showed nearly 45% PTP1B inhibition (higher than metformin) after the assay was done with selected four plant extracts in combination. The effect of leaf extracts of S. marianum was studied for glucose uptake efficiency in yeast cell lines which was found to be increased by 23% as compared to the control (without extract). Metformin improves glucose upake by yeast cells by ~15-31%. GC-MS analysis revealed 23 phytochemicals, some of which possessed anti-diabetic properties. A dose-dependent increase in antioxidant activity of S. marianum leaves extracts was observed (40-53%). The findings of the study highlighted the presence of various phytochemicals in leaves extracts that are effective against PTP1B inhibition and may help in reinvigorating drug development.

Status of research on natural protein tyrosine phosphatase 1B inhibitors as potential antidiabetic agents: Update

Protein tyrosine phosphatase 1B (PTP1B) is a crucial therapeutic target for multiple human diseases comprising type 2 diabetes (T2DM) and obesity because it is a seminal part of a negative regulator in both insulin and leptin signaling pathways. PTP1B inhibitors increase insulin receptor sensitivity and have the ability to cure insulin resistance-related diseases. However, the few PTP1B inhibitors that entered the clinic (Ertiprotafib, ISIS-113715, Trodusquemine, and JTT-551) were discontinued due to side effects or low selectivity. Molecules with broad chemical diversity extracted from natural products have been reported to be potent PTP1B inhibitors with few side effects. This article summarizes the recent PTP1B inhibitors extracted from natural products, clarifying the current research progress, and providing new options for designing new and effective PTP1B inhibitors.

Phenolic profile, alpha-amylase inhibitory activity, and in vitro glycemic index of adzuki beans

Regular consumption of low-glycemic index (GI) foods is a common strategy for type 2 diabetes patients. To evaluate the potential application of adzuki beans in low-GI foods, the phenolic profile and alpha-amylase inhibitor (α-AI) activity of four varieties of adzuki beans (G24, Te Xiao Li No. 1, Gui Nong No. 1, and Qian Xiao Hei) were determined. The starch digestibility properties and in vitro glycemic index (IVGI) of these beans were also evaluated using the in vitro digestion model coupled with 3,5-dinitrosalicylic acid colorimetry. The results indicated that these adzuki beans, containing numerous phenolics, showed inhibitory activities to alpha-amylase with the α-AI activities between 1.760 ± 0.044 and 3.411 ± 0.186 U/g. The resistant starch (RS) contributed predominantly to the total starch with proportions between (69.78 ± 2.45%) and (81.03 ± 0.06%); Te Xiao Li No. 1 was the highest compared with the other varieties. The adzuki beans were categorized into low- or medium-GI foods, and the IVGI ranged from (39.00 ± 0.36) to (56.76 ± 4.21). These results suggested that adzuki beans can be used as a component of low-GI foods.

Silviridoside: A New Triterpene Glycoside from Silene viridiflora with Promising Antioxidant and Enzyme Inhibitory Potential

A new triterpene glycoside, silviridoside, was isolated from the aerial parts of Silene viridiflora (Caryophyllaceae) using different chromatographic techniques. The structure of silviridoside was comprehensively elucidated as 3-O-β-D-galacturonopyranosyl-quillaic acid 28-O-β-D-glucopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→3)]-β-D-fucopyranosyl ester by one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HR-MS). Silviridoside showed promising antioxidant activity in different antioxidant assays such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) (2.32 mg TE/g), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (1.24 mg TE/g), cupric-reducing antioxidant capacity (CUPRAC) (9.59 mg TE/g), ferric-reducing antioxidant power (FRAP) (5.13 mg TE/g), phosphomolybdenum (PHD) (0.28 mmol TE/g), and metal-chelating (MCA) (6.62 mg EDTA/g) assays. It exhibited a good inhibitory potential on acetylcholinesterase (AChE) (2.52 mg GALAE/g), butyrylcholinesterase (BChE) (7.16 mg GALAE/g), α-amylase (0.19 mmol ACAE/g), α-glucosidase (1.21 mmol ACAE/g), and tyrosinase (38.83 mg KAE/g). An in silico evaluation of the pharmacodynamic, pharmacokinetic, and toxicity properties of silviridoside showed that the new compound exhibited reasonable pharmacodynamic and pharmacokinetic properties without any mutagenic effect, but slight toxicity. Thus, it could be concluded that silviridoside could act as a promising lead drug for pharmaceutical and nutraceutical developments to combat oxidative stress and various disorders, but a future optimization is necessary.

Hypoglycemic Activity of Self-Assembled Gellan Gum-Soybean Isolate Composite Hydrogel-Embedded Active Substance-Saponin

In order to avoid hemolysis caused by direct dietary of kidney tea saponin, complex gels based on gellan gum (GG) and soybean isolate protein (SPI) loaded with saponin were created in the present study by using a self-assembly technique. Studies were conducted on the rheological characteristics, encapsulation effectiveness, molecular structure, microstructure, and hypoglycemic activity of GG/SPI-saponin gels. Increasing the concentration of SPI helped to enhance the strength and energy storage modulus (G') of the gels, and the incorporation of high acylated saponin allowed the whole gel to undergo sol-gel interconversion. The encapsulation efficiency showed that GG/SPI-saponin was 84.52 ± 0.78% for saponin. Microstructural analysis results suggested that GG and SPI were bound by hydrogen bonds. The in vitro digestion results also indicated that saponin could be well retained in the stomach and subsequently released slowly in the intestine. In addition, the in vitro hypoglycemic activity results showed that the IC₅₀ of encapsulated saponin against α-glucosidase and α-amylase were at 2.4790 mg/mL and 1.4317 mg/mL, respectively, and may be used to replace acarbose for hypoglycemia.

Inhibitory effect of plant essential oils on α-glucosidase

Diabetes mellitus, associated with α-glucosidase, has been considered as a chronic metabolic disorder, seriously affecting human health. Thus, searching natural α-glucosidase inhibitors and investigating their inhibition mechanism are urgently important. In this study, sixty-two essential oils (EOs), derived from aromatic plants, were found to exert different inhibition on α-glucosidase. The further study revealed that the most potent EOs against α-glucosidase were chuan-xiong, fructus cnidii, sacha inchi, aloe, ganoderma lucidum spore and ginger with IC50 values of 3.02, 2.88, 7.37, 5.06, 5.32 and 7.40 μg/mL. Moreover, the inhibitory mechanism and kinetics studies found that chuan-xiong and sacha inchi were reversible and mixed-type inhibitors. Fructus cnidii, aloe, ganoderma lucidum spore and ginger were reversible and uncompetitive-type inhibitors. It is suggested that EOs, being of natural origin, would be promising anti-α-glucosidase agents.

Therapeutic potential of non-starch polysaccharides on type 2 diabetes: from hypoglycemic mechanism to clinical trials

Non-starch polysaccharides (NSPs) have been reported to exert therapeutic potential on managing type 2 diabetes mellitus (T2DM). Various mechanisms have been proposed; however, several studies have not considered the correlations between the anti-T2DM activity of NSPs and their molecular structure. Moreover, the current understanding of the role of NSPs in T2DM treatment is mainly based on in vitro and in vivo data, and more human clinical trials are required to verify the actual efficacy in treating T2DM. The related anti-T2DM mechanisms of NSPs, including regulating insulin action, promoting glucose metabolism and regulating postprandial blood glucose level, anti-inflammatory and regulating gut microbiota (GM), are reviewed. The structure-function relationships are summarized, and the relationships between NSPs structure and anti-T2DM activity from clinical trials are highlighted. The development of anti-T2DM medication or dietary supplements of NSPs could be promoted with an in-depth understanding of the multiple regulatory effects in the treatment/intervention of T2DM.

D-optimal mixture design optimized solid formulation containing fruits extracts of Momordica charantia and Abelmoschus esculentus

Fruit extracts of Momordica charantia L. (Cucurbitaceae) and Abelmoschus esculentus (L.) Moench (Malvaceae) have shown promising antidiabetic activities in clinical trials. However, they remain underutilized due to insufficient standardization and lack of formulation containing their mixture. This study’s overall purpose was to develop and optimize a capsule dosage form containing dried fruit extracts of M. charantia and A. esculentus. The design of the experiment involved two steps; first, response surface methodology (RSM) with a five-level two-factor central composite rotatable design (CCRD) was employed to determine the optimal dose of a mixture of extracts for adequate glycemic control. The extract of M. charantia and A. esculentus were the independent variables while fasting plasma glucose (FPG) was the dependent factor. In the second step, a D-optimal mixture design was applied to study the interaction effect of the optimal dose and selected excipients on granules flowability and capsules’ disintegration time. Moreover, a second-order quadratic model determined the interrelationship of excipients and the desired capsules’ quality attributes. The validity of the predicted models was confirmed. The findings indicated that a combined dose of 175 A. esculentus and 281 M. charantia (mg/kg) significantly reduced the FPG level compared to vehicle at day 14 (mean difference -2.7 ± 0.21, p < 0.001). This dose was used to make a 600 mg capsule (DM083) with 76% drug loading. The DM083 had 40.4 ± 0.62 mg GAE/gDW total polyphenols, 12 peaks HPLC fingerprint, and 26.6 ± 4.75 min average disintegration time. Together, these findings showed that a mixture of M. charantia and A. esculentus fruit extracts could be formulated in a stable capsule dosage form with acceptable quality standards. Further biological studies such as toxicity assays and long-term efficacy studies of the developed capsules could be carried out before large-scale commercial production.

Bioactives of Momordica charantia as Potential Anti-Diabetic/Hypoglycemic Agents

Momordica charantia L., a member of the Curcubitaceae family, has traditionally been used as herbal medicine and as a vegetable. Functional ingredients of M. charantia play important roles in body health and human nutrition, which can be used directly or indirectly in treating or preventing hyperglycemia-related chronic diseases in humans. The hypoglycemic effects of M. charantia have been known for years. In this paper, the research progress of M. charantia phytobioactives and their hypoglycemic effects and related mechanisms, especially relating to diabetes mellitus, has been reviewed. Moreover, the clinical application of M. charantia in treating diabetes mellitus is also discussed, hoping to broaden the application of M. charantia as functional food.

Structure determination, bitterness evaluation and hepatic gluconeogenesis inhibitory activity of triterpenoids from the Momordica charantia fruit

Triterpenoids are hypoglycemic substances and flavor components of Momordica charantia L., whether their bitterness correlated with hypoglycemic potential remain unknown. Thus, triterpenoids in M. charantia were isolated by phytochemical methods and identified by spectroscopic analysis. The bitterness levels and hypoglycaemic activity of isolated triterpenoids were evaluated by electronic tongue and hepatic gluconeogenesis assay. Eighteen triterpenoids including two new ones, Momordicoside Y and Z, were identified. Among the six identified bitter triterpenoids, karaviloside III, goyaglycoside C, and momordicoside F2 were bitterer than caffeine (P < 0.05), with caffeine equivalent (CE) values of 289.19, 4.32, and 41.24 mg CE/mg, respectively. Momordicoside Y, charantoside C, momordicoside F1, and momordicoside G could inhibit hepatic gluconeogenesis by 23.9%, 36.2%, 33.4%, 34.4% at 40 μM, respectively. These four compounds could interact with active site of phosphoenolpyruvate carboxykinase in molecular docking simulation. No correlation was observed between hepatic gluconeogenesis inhibitory activity and bitterness of triterpenoids.

Flavonoids, alkaloids and terpenoids: a new hope for the treatment of diabetes mellitus

Diabetes mellitus is a metabolic syndrome characterized by a hyperglycemic state and multi-organ failure. Millions of people worldwide are suffering from this deadly disease taking a hit on their pocket and mental health in the name of its treatment. Modern medical practices with new technological advancements and discoveries have made revolutionary changes in the treatment. But, unfortunately, Glucose-lowering drugs used have many accompanying effects such as chronic vascular disease, renal malfunction, liver disease and, many skin problems. These complications have made us think about alternative treatments for diabetes with minimum or no side effects. Nowadays, in addition to modern medicine, herbal treatment has been suggested to treat diabetes mellitus. These herbal medicines contain biological macromolecules such as flavonoids, Terpenoids, glycosides, and alkaloids, which show versatile anti-diabetic effects. These phytochemicals are generally considered safe, and naturally occurring compounds have a potential role in preventing or controlling diabetes mellitus. The underlying mechanism of their anti-diabetic effects includes improvement in insulin secretion, decrease in insulin resistance, enhanced liver glycogen synthesis, antioxidant and anti-inflammatory activities. In this review, we have focused on the mechanism of various phytochemicals targeting hyperglycemia and its underlying pathogenesis.

Charantoside L, A New Cucurbitane-Type Glycoside from Momordica charantia L. with α-Glucosidase Inhibitory Activities

A new cucurbitane-type glycoside (1) and two known compounds (2-3) were isolated from the ethanol extract of the fruits of Momordica charantia L. Their chemical structures were determined as (19 S,23 E)-5 β­,19-epoxy-19-methoxycucurbita-6,23-diene-3 β,25-diol 3 -O-β-D-allopyranoside (1), goyaglycoside d (2), and (19 S,23 E)-5 β,19-epoxy-19-methoxycucurbita-6,23-diene-3 β,25-diol (3) on the basis of the extensive spectroscopic methods, including 1D, 2D NMR, HRESIMS, and in comparison with the reported data. Compounds 1 to 3 were evaluated for α-glucosidase inhibitory effects. Compounds 1 and 2 showed anti α-glucosidase activity with IC50 values of 134.12 ± 11.20 and 163.17 ± 13.71 µM, respectively, compared with the positive control, acarbose, IC50 160.99 ± 14.30 μM. Compounds 2 and 3 were first isolated from plant M. charantia growing in Vietnam.

Approaches to Decrease Hyperglycemia by Targeting Impaired Hepatic Glucose Homeostasis Using Medicinal Plants

Liver plays a pivotal role in maintaining blood glucose levels through complex processes which involve the disposal, storage, and endogenous production of this carbohydrate. Insulin is the hormone responsible for regulating hepatic glucose production and glucose storage as glycogen, thus abnormalities in its function lead to hyperglycemia in obese or diabetic patients because of higher production rates and lower capacity to store glucose. In this context, two different but complementary therapeutic approaches can be highlighted to avoid the hyperglycemia generated by the hepatic insulin resistance: 1) enhancing insulin function by inhibiting the protein tyrosine phosphatase 1B, one of the main enzymes that disrupt the insulin signal, and 2) direct regulation of key enzymes involved in hepatic glucose production and glycogen synthesis/breakdown. It is recognized that medicinal plants are a valuable source of molecules with special properties and a wide range of scaffolds that can improve hepatic glucose metabolism. Some molecules, especially phenolic compounds and terpenoids, exhibit a powerful inhibitory capacity on protein tyrosine phosphatase 1B and decrease the expression or activity of the key enzymes involved in the gluconeogenic pathway, such as phosphoenolpyruvate carboxykinase or glucose 6-phosphatase. This review shed light on the progress made in the past 7 years in medicinal plants capable of improving hepatic glucose homeostasis through the two proposed approaches. We suggest that Coreopsis tinctoria, Lithocarpus polystachyus, and Panax ginseng can be good candidates for developing herbal medicines or phytomedicines that target inhibition of hepatic glucose output as they can modulate the activity of PTP-1B, the expression of gluconeogenic enzymes, and the glycogen content.

Antidiabetic Medicinal Plants Used in Democratic Republic of Congo: A Critical Review of Ethnopharmacology and Bioactivity Data

Several studies have been conducted and published on medicinal plants used to manage Diabetes Mellitus worldwide. It is of great interest to review available studies from a country or a region to resort to similarities/discrepancies and data quality. Here, we examined data related to ethnopharmacology and bioactivity of antidiabetic plants used in the Democratic Republic of Congo. Data were extracted from Google Scholar, Medline/PubMed, Scopus, ScienceDirect, the Wiley Online Library, Web of Science, and other documents focusing on ethnopharmacology, pharmacology, and phytochemistry antidiabetic plants used in the Democratic Republic of Congo from 2005 to September 2021. The Kew Botanic Royal Garden and Plants of the World Online web databases were consulted to verify the taxonomic information. CAMARADES checklist was used to assess the quality of animal studies and Jadad scores for clinical trials. In total, 213 plant species belonging to 72 botanical families were reported. Only one plant, Droogmansia munamensis, is typically native to the DRC flora; 117 species are growing in the DRC and neighboring countries; 31 species are either introduced from other regions, and 64 are not specified. Alongside the treatment of Diabetes, about 78.13% of plants have multiple therapeutic uses, depending on the study sites. Experimental studies explored the antidiabetic activity of 133 plants, mainly in mice, rats, guinea pigs, and rabbits. Several chemical classes of antidiabetic compounds isolated from 67 plant species have been documented. Rare phase II clinical trials have been conducted. Critical issues included poor quality methodological protocols, author name incorrectly written (16.16%) or absent (14.25%) or confused with a synonym (4.69%), family name revised (17.26%) or missing (1.10%), voucher number not available 336(92.05%), ecological information not reported (49.59%). Most plant species have been identified and authenticated (89.32%). Hundreds of plants are used to treat Diabetes by traditional healers in DRC. However, most plants are not exclusively native to the local flora and have multiple therapeutic uses. The analysis showed the scarcity or absence of high-quality, in-depth pharmacological studies. There is a need to conduct further studies of locally specific species to fill the gap before their introduction into the national pharmacopeia.

Characteristics of the interaction mechanisms of procyanidin B1 and procyanidin B2 with protein tyrosine phosphatase-1B: Analysis by kinetics, spectroscopy methods and molecular docking

Protein tyrosine phosphatase-1B (PTP1B) is a novel and indispensable drug target for the treatment of type 2 diabetes mellitus (T2DM). Procyanidins are flavonoids that exhibit a significant hypoglycemic function. However, the potential inhibitory effects of procyanidins on PTP1B are unclear. In this study, the interaction mechanisms of PTP1B with procyanidin B1 (PB1) and procyanidin B2 (PB2) were investigated through kinetics analysis, UV-visible spectroscopy, fluorescence spectroscopy, circular dichroism spectroscopy and molecular docking. The results showed that PB1 and PB2 could inhibit the activity of PTP1B in a mixed inhibition mode, which was one of the reversible inhibition types. Multi-spectral analysis showed that PB1/PB2 formed complexes with PTP1B, which effectively quenched the intrinsic fluorescence of PTP1B based on the static mechanism. The values of the binding constants were K_S(PTP1B-PB1) = 4.06 × 10² L·mol^-1 and K_S(PTP1B-PB2) = 2.53 × 10² L·mol^-1, indicating that the binding affinity of PTP1B to PB1 was higher than that for PB2. PB1 and PB2 both changed the secondary structure of the enzyme, thereby decreasing the PTP1B activity. Thermodynamic investigations revealed that the binding of procyanidin B1 and B2 to PTP1B was spontaneous in both cases, and highlighted the key role of hydrophobic interactions. Molecular docking analysis provided further information regarding the interactions between PB1 or PB2 and the amino acid residues of PTP1B. Moreover, PB1 and PB2 were found to down-regulate the expression level of PTP1B in insulin-resistant HepG2 cells. These findings are the first to elucidate the inhibitory effects of PB1 and PB2 on PTP1B, and highlight the role of procyanidins as dietary supplements in regulating T2DM.

Pharmacological reflection of plants traditionally used to manage diabetes mellitus in Tanzania

ETHNOPHARMACOLOGICAL RELEVANCE

The increasing national prevalence of diabetes mellitus (DM) and its complications have overstretched the health care system in Tanzania and influenced patients to use herbal medicines as alternative therapeutic strategies. Therefore, an urgent need exists to validate the safety and efficacy of plants used locally.

AIM OF THE STUDY

To identify plants used for the management of DM in Tanzania and analyses their pharmacological, phytochemistry, and safety evidence with a special focus on the mechanism of action.

METHODS

Researchers searched Medline, web of science, and Scopus for published articles. Also, specialized herbarium documents of Muhimbili Institute of traditional medicine were reviewed. Articles were assessed for relevance, quality, and taxonomical accuracy before being critically reviewed.

RESULTS

We identified 62 plant species used locally for DM management. Moringa oleifera Lam. and Cymbopogon citratus (D.C) stapf were the most mentioned. Fifty-four phytochemicals from 13 species had DM activities. These were mainly; polyphenolics, phytosterols, and triterpenoids. Extracts, fractions, and pure compounds from 18 species had in vitro antidiabetic activities of which 14 had α-glucosidase and α-amylase inhibition effects. The most studied -Momordica charantia L. increased; glucose uptake and adiponectin release in 3T3-L1 adipocytes, insulin secretion, insulin receptor substrate-1 (IRS-1), GLUT-4 translocation, and GLP-1 secretion; and inhibited protein tyrosine phosphatase 1 B (PTP1B). Preclinical studies reported 30 species that lower plasma glucose with molecular targets in the liver, skeletal muscles, adipose tissues, pancreases, and stomach. While three species; Aspilia mossambiscensis (Oliv.) Willd, Caesalpinia bonduc (L.) Roxb, and Phyllanthus amarus Schumach. & Thonn. had mild toxicity in animals, 33 had no report of their efficacy in DM management or toxicity.

CONCLUSION

Local communities in Tanzania use herbal medicine for the management of DM. However, only a fraction of such species has scientific evidence. A. mossambiscensis, C. bonduc., and P. amarus had mild toxicity in animals. Together, our findings call for future researches to focus on in vitro, in vivo, and phytochemical investigation of plant species for which their use in DM among the local communities in Tanzania have not been validated.

Jayaprakasha G, S. Patil B. Anti-Inflammatory, Antidiabetic Properties and In Silico Modeling of Cucurbitane-Type Triterpene Glycosides from Fruits of an Indian Cultivar of Momordica charantia L

Diabetes mellitus is a chronic disease and one of the fastest-growing health challenges of the last decades. Studies have shown that chronic low-grade inflammation and activation of the innate immune system are intimately involved in type 2 diabetes pathogenesis. Momordica charantia L. fruits are used in traditional medicine to manage diabetes. Herein, we report the purification of a new 23-O-β-d-allopyranosyl-5β,19-epoxycucurbitane-6,24-diene triterpene (charantoside XV, 6) along with 25ξ-isopropenylchole-5(6)-ene-3-O-β-d-glucopyranoside (1), karaviloside VI (2), karaviloside VIII (3), momordicoside L (4), momordicoside A (5) and kuguaglycoside C (7) from an Indian cultivar of Momordica charantia. At 50 µM compounds, 2–6 differentially affected the expression of pro-inflammatory markers IL-6, TNF-α, and iNOS, and mitochondrial marker COX-2. Compounds tested for the inhibition of α-amylase and α-glucosidase enzymes at 0.87 mM and 1.33 mM, respectively. Compounds showed similar α-amylase inhibitory activity than acarbose (0.13 mM) of control (68.0–76.6%). Karaviloside VIII (56.5%) was the most active compound in the α-glucosidase assay, followed by karaviloside VI (40.3%), while momordicoside L (23.7%), A (33.5%), and charantoside XV (23.9%) were the least active compounds. To better understand the mode of binding of cucurbitane-triterpenes to these enzymes, in silico docking of the isolated compounds was evaluated with α-amylase and α-glucosidase.

Rapid qualitative profiling and quantitative analysis of phenolics in Ribes meyeri leaves and their antioxidant and antidiabetic activities by HPLC-QTOF-MS/MS and UHPLC-MS/MS

Ribes meyeri leaves are used as traditional Kazakh medicine in China. However, no study on the characterization of the phenolic compounds in R. meyeri leaves has been reported, resulting in the lack of quality control measures and poor standardization. This study was conducted to identify the phenolic compounds in R. meyeri leaves and evaluate their antioxidant and antidiabetic activities. A total of 77 phenolics were tentatively identified by liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry. Ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry was applied to simultaneously quantify 12 phenolics in R. meyeri leaves. Rutin, epigallocatechin, isoquercitrin, epicatechin, protocatechuic acid, and kaempferol-3-O-rutinoside were abundant in the R. meyeri leaves. The methanol extract and four different extracts enhanced the glucose uptake in 3T3-L1 adipocytes. The ethyl acetate extracts showed a total phenolic content of 966.89 ± 3.59 mg gallic acid equivalents/g, a total flavonoid content of 263.58 ± 17.09 mg catechin equivalents/g, and good protein-tyrosine phosphatase-1B inhibitory activities (IC₅₀ : 0.60 ± 0.03 μg/mL). To our knowledge, this work is the first to identify and quantify the major phenolics in R. meyeri leaves.

Fruit, vegetables, and mushrooms for the preparation of extracts with α-amylase and α-glucosidase inhibition properties: A review

The inhibition of the α-amylase and α-glucosidase activity facilitates the maintenance of circulating glucose levels by decreasing the rate of blood sugar absorption. Existing enzyme inhibitors such as acarbose, miglitol, and voglibose are used for inhibiting the activity of these enzymes, however, alternative solutions are required to avoid the side-effects of using these drugs. The current study aims to review recent evidence regarding the in vitro α-amylase and α-glucosidase inhibition activities of extracts derived from selected fruit, vegetables, and mushrooms. The mechanisms of action of the extracts involved in the inhibition of both enzymes are also presented and discussed. Compounds including flavonoids, phenolic acids, anthocyanins, saponins, carotenoids, terpenes, sugars, proteins, capsaicinoids, fatty acids, alkaloids have been shown to have α-amylase and α-glucosidase inhibition activities. Harvesting period, maturity stage, sample preparation, extraction technique, and solvent type are parameters that affect the α-amylase and α-glucosidase inhibition activities of the extracts.

The safety and efficacy of Momordica charantia L. in animal models of type 2 diabetes mellitus: A systematic review and meta-analysis

Type 2 diabetes mellitus is a chronic hyperglycemic condition due to progressively impaired glucose regulation. Momordica charantia L. could potentially improve hyperglycemia because its fruit extracts can alleviate insulin resistance, beta-cell dysfunction, and increase serum insulin level. We evaluated the effect of M. charantia L. in comparison with a vehicle on glycemic control in animal models of type 2 diabetes mellitus. MEDLINE, Web of Science, Scopus, and CINAHL databases were searched without language restriction through April 2019. About 66 studies involving 1861 animals that examined the effect of M. charantia L. on type 2 diabetes mellitus were included. Fruits and seed extracts reduced fasting plasma glucose (FPG) and glycosylated hemoglobin A1c in comparison to vehicle control: (42 studies, 815 animals; SMD, -6.86 [95% CI; -7.95, -5.77], 3 studies, 59 animals; SMD; -7.76 [95% CI; -12.50, -3.01]) respectively. Also, the extracts have hepato-renal protective effects at varying doses and duration of administration. Despite the observed significant glycemic control effect, poor methodological quality calls for future researches to focus on standardizing extract based on chemical markers and adopt measures to improve the quality of preclinical studies such as sample size calculation, randomization, and blinding.

Systematic review and meta-analysis protocol for efficacy and safety of Momordica charantia L. on animal models of type 2 diabetes mellitus

BACKGROUND

Studies on several preclinical models of type 2 diabetes mellitus have been conducted to establish the hypoglycemic activity of Momordica charantia L. Concerned with appropriateness of these models, we designed a systematic review to establish the efficacy and safety of M. charantia L. in preclinical models of type 2 diabetes mellitus.

METHODS

Review authors will search without language restriction in MEDLINE/PubMed, Web of Science, Embase, Scopus, and CINAHL databases through April 2019. Search filters will be applied to enhance search efficiency. The authors will search for gray literature in Google and Google Scholar, OpenGrey, and ProQuest Dissertations & Theses. Two authors will evaluate full texts, extract data, and asses risk of bias independently. The review will include randomized or non-randomized studies that assessed the efficacy or safety of M. charantia L. with vehicle control group. The primary endpoint will be fasting blood glucose level. We will use Egger's test to assess publication biases. Chi-square test and I2 will be used to assess heterogeneity in effect size of the primary outcome. Using RevMan software version 5.3, the authors will perform a meta-analysis of quantitative data.

DISCUSSION

The strength of evidence will be rated as high, moderate, low, or very low using GRADE framework for animal studies. This systematic review will potentially improve research practice by identifying risks of bias and design features that compromise translatability and contribute to evidence-based clinical trial design.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019119181.

Purification, characterization, and bioactivity of two new polysaccharide fractions from Thelephora ganbajun mushroom

Two new polysaccharide fractions (TZP1-1 and TZP2-1) were obtained from the fruiting bodies of Thelephora ganbajun using DEAE-52 cellulose and Superdex 200 columns chromatography. The physiochemical characterization and biological activities of TZP1-1 and TZP2-1 were investigated. The relative molecular weight of TZP1-1 and TZP2-1 were 2.07 × 10⁶ and 4,886 Da, respectively. TZP1-1 included mannose, rhamnose, galactose, and xylose (4:1:83.9:7.5), while TZP2-1 included mannose, glucose, galactose, and xylose (5.4:1:79.0:8.1). The Congo red experiment results confirmed that TZP2-1 had triple helix conformation. Furthermore, both TZP1-1 and TZP2-1 showed a certain cytotoxicity on HeLa and SH-SY5Y cells, while they exhibited a stronger inhibitory effect on HeLa than SH-SY5Y. Besides, the cytotoxicity of TZP1-1 was better than that of TZP2-1. Moreover, both of them exhibited a moderate inhibitory effect on α-amylase and α-glucosidase. These findings could promote the application of polysaccharides from T. ganbajun. PRACTICAL APPLICATIONS: Thelephora ganbajun is an edible fungus widely distributed in Southwestern China. T. ganbajun polysaccharides as important active ingredients have not been reported. In this current study, two polysaccharides fractions (TZP1-1 and TZP2-1) were characterized, and their cytotoxicities and antidiabetic effect were also assayed. These findings could promote polysaccharides from T. ganbajun to be better application.

Four new cucurbitane-type triterpenes from Momordica charantia L. with their cytotoxic activities and protective effects on H2O2-damaged pancreatic cells

Four new cucurbitane-type triterpenes were isolated from the fruit of Momordica charantia L. The structures of the new compounds were identified based on HR-ESI-MS and 1D- and 2D-NMR spectroscopic methods. The cytotoxicity of the isolated compounds was evaluated using three human cancer cell lines, HeLa, Caco2, and U87. Compound 3 exhibited significant cytotoxic activity against HeLa cells with an IC₅₀ value of 11.18 μM. Additionally, the cytoprotective activity of these compounds was determined in vitro against H₂O₂-induced pancreatic injury. The results revealed that all the compounds obtained possess cytoprotective effects against H₂O₂-induced injury in MIN6 β-cells at a concentration of 10 μM.

Effects of phytochemicals against diabetes

Diabetes mellitus, a chronic metabolic disease, characterized by elevated levels of blood glucose and insufficiency in production and action of insulin is the seventh leading cause of death worldwide. Numerous studies have shown that diabetes mellitus is associated with increased formation of free radicals and decrease in antioxidant potential. In the patients with diabetes mellitus, the levels of antioxidant parameters are found to decrease, hence in many studies phytochemicals which can exert antioxidant and free radical scavenging activities, are suggested to improve the insulin sensitivity. Several phytoactive compounds such as flavonoids, lignans, prophenylphenols, are also found to combat the complications of diabetes. This chapter mainly focuses on the relationship between diabetes mellitus and preventive roles of various phytochemicals on diabetes via their antioxidant properties.

Momordica charantia L. lowers elevated glycaemia in type 2 diabetes mellitus patients: Systematic review and meta-analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Momordica charantia Linnaeus (Cucurbitaceae) has been extensively used traditionally as food and herbal medicine for type 2 diabetes mellitus in Asia, Brazil, and east Africa. In vitro and in vivo studies suggest its glycemic control potential; however, clinical studies produced conflicting results.

AIM OF THE STUDY

To evaluate the efficacy of M. charantia preparations in lowering elevated plasma glucose level in prediabetes and type 2 diabetes mellitus patients.

METHODS

Electronic search of the Cochrane library, PubMed®, CINAHL, and SCOPUS databases was done from 1st January 1960-30th April 2018 without language restriction. Two independent reviewers extracted data and assessed risk of bias of articles. Revman var. 5.3 software was used for data synthesis in meta-analysis. Heterogeneity was assessed using Chi-square and I² tests. Treatment effect was estimated using mean difference at follow up in outcome measures between M. charantia preparations and placebo or oral hypoglycemic agents control group. The protocol of this study has a registration number PROSPERO CRD42018083653.

RESULTS

Ten studies of type 2 diabetes mellitus (n = 1045) were included in the meta-analysis. They had 4-16 weeks follow up and overall moderate to high risk of bias. Compared to placebo, M. charantia monoherbal formulation significantly reduces FPG, PPG and HBA_1c with mean difference of - 0.72 mmol/L, (95% CI: -1.33, -0.12), I² = 14%, - 1.43 mmol/L, (95% CI: -2.18, -0.67), I² = 0, - 0.26%, (95% CI: -0.49, -0.03), I² = 0 respectively. M. charantia also lowered FPG in prediabetes (mean difference -0.31 mmol/L, n = 52); the evidence was downgraded to low quality because the study had unclear risk of bias and inadequate sample size. No serious adverse effects were reported.

CONCLUSION

M. charantia adjunct preparations improved glycemic control in T2DM patients. However, this conclusion is based on low to very low quality evidences for the primary outcomes and sparse data for several safety outcomes, thus, warrant further research. Particularly needed are the researches that focus on standardizing M. charantia formulation and determine its efficacy and safety in clinical trials with adequate sample size, designed with random sequence generation, allocation concealment of intervention and blinding of both research personnel and participants.

Cucurbitane triterpenoids from the fruit of Momordica charantia L. and their anti-hepatic fibrosis and anti-hepatoma activities

Momordica charantia L. (Cucurbitaceae) is a popular vegetable and traditional folk medicine, that has been used for hundreds of years. In this study, three undescribed cucurbitane-type triterpene glycosides furpyronecucurbitane A, goyaglycoside I and charantagenin F along with nine known compounds were isolated from the immature fruit of Momordica charantia L. Their structures were identified on the basis of extensive 1D, 2D NMR and HRESIMS spectroscopy analysis. All isolated compounds were examined for their anti-hepatic fibrosis activity against murine hepatic stellate cells (t-HSC/Cl-6) and anti-hepatoma activity against two kinds of liver cancer cell lines (HepG2 and Hep3B). Among them, karaviloside III exhibited excellent inhibitory activity against activated t-HSC/Cl-6 cells and cytotoxic activity against Hep3B and HepG2 cell lines with IC₅₀ values of 3.74 ± 0.13, 16.68 ± 2.07 and 4.12 ± 0.36 μM, respectively, which may potential to be developed as a chemotherapy agent for treatment hepatic fibrosis or carcinoma and protection against both diseases.