alpha-Glucosidase inhibitory profile of catechins and theaflavins

Rhodiosin from Rhodiola crenulata effectively alleviate postprandial hyperglycemia by inhibiting both the activity and production of α‑glucosidase

BACKGROUND

Effective control of postprandial blood glucose (PBG) level is essential for the prevention and treatment of diabetes and its complications. Several flavonoids have attracted much attention due to their significant PBG-lowering effects. However, there is still a certain gap in the in vivo hypoglycemic activity of most flavonoids compared to first-line drugs available on the market, and are still lack of the PBG-lowering effects of 8-hydroxyflavones and their structure-activity relationship.

PURPOSE

Evaluate hypoglycemic effects of 8-hydroxyflavones from Rhodiola crenulata in vitro and in vivo, especially comparatively analyze the relationship between hypoglycemic effects and flavonoid configuration and reveal the possible mechanism of 8-hydroxyflavones in lowering hyperglycemia.

METHODS

Starch, maltose, sucrose, and glucose tolerance tests in both diabetic and normal mice were used to evaluate and compare the hypoglycemic effects of 8-hydroxyflavones rhodiosin (RHS), rhodionin (RHN), and herbacetin (HBT). Molecular docking, enzyme kinetics, and immunofluorescence analysis were used to research the possible hypoglycemic mechanisms of 8-hydroxyflavones.

RESULTS

RHS (5 and 10 mg/kg) could efficiently decrease PBG levels in both normal and diabetes mice. Moreover, RHS, RHN, and HBT all had significant PBG-lowering effects in transgenic diabetes mice, and the effects were equivalent to or stronger than acarbose. Further mechanism research indicated that 8-hydroxyflavones achieved PBG-lowering effects by inhibiting both the activity and production of glycosidase. Notably, we have innovatively discovered that inhibiting the expression of glycosidases rather than just their activities may be a new target for hypoglycemic drugs.

CONCLUSION

We have firstly comprehensively and systematically clarified PBG-lowering effects of 8-hydroxyflavones from Rhodiola crenulata, and revealed their structure-activity relationships and hypoglycemic mechanisms. The study demonstrated that the substitution of 8-hydroxy groups in flavonoids could significantly enhance their hypoglycemic effects, which were equivalent to or stronger than commercially available drug acarbose. 8-Hydroxyflavones could be used as therapeutic or health drugs with significant potential to reduce postprandial hyperglycemia.

Characterization of alkaloids and phenolics in Nitraria roborowskii Kom. fruit by UHPLC-triple-TOF-MS/MS and its sucrase and maltase inhibitory effects

Nitraria roborowskii Kom (NRK), with high economic and ecological value, is mainly distributed in the Qaidam Basin, China. However, research on its chemical components and bioactivities is still rare. In this study, its chemical constituents (52) including 10 β-carboline alkaloids, nine cyclic peptides, three indole alkaloids, five pyrrole alkaloids, eight phenolic acids and 17 flavonoids were identified tentatively using UPLC-triple-TOF-MS/MS. Notablely, one new β-carboline alkaloid and five new cyclic peptides were confirmed using MS/MS fragmentation pathways. In addition, experiments in vitro indicated that NRK-C had strong maltase and sucrase inhibitory activities (IC50 of 0.202 and 0.103 mg/mL, respectively). Polysaccharide tolerance experiments confirmed NRK-C (400 mg/kg) was associated with decreased postprandial blood glucose (PBG) in diabetic mice. These results suggested that NRK fruit might be used as a functional ingredient in food products.

Improvement of Theaflavins on Glucose and Lipid Metabolism in Diabetes Mellitus

In diabetes mellitus, disordered glucose and lipid metabolisms precipitate diverse complications, including nonalcoholic fatty liver disease, contributing to a rising global mortality rate. Theaflavins (TFs) can improve disorders of glycolipid metabolism in diabetic patients and reduce various types of damage, including glucotoxicity, lipotoxicity, and other associated secondary adverse effects. TFs exert effects to lower blood glucose and lipids levels, partly by regulating digestive enzyme activities, activation of OATP-MCT pathway and increasing secretion of incretins such as GIP. By the Ca2+-CaMKK ꞵ-AMPK and PI3K-AKT pathway, TFs promote glucose utilization and inhibit endogenous glucose production. Along with the regulation of energy metabolism by AMPK-SIRT1 pathway, TFs enhance fatty acids oxidation and reduce de novo lipogenesis. As such, the administration of TFs holds significant promise for both the prevention and amelioration of diabetes mellitus.

Antidiabetic Potential of Tea and Its Active Compounds: From Molecular Mechanism to Clinical Evidence

Diabetes mellitus (DM) is a chronic endocrine disorder that poses a long-term risk to human health accompanied by serious complications. Common antidiabetic drugs are usually accompanied by side effects such as hepatotoxicity and nephrotoxicity. There is an urgent need for natural dietary alternatives for diabetic treatment. Tea (Camellia sinensis) consumption has been widely investigated to lower the risk of diabetes and its complications through restoring glucose metabolism homeostasis, safeguarding pancreatic β-cells, ameliorating insulin resistance, ameliorating oxidative stresses, inhibiting inflammatory response, and regulating intestinal microbiota. It is indispensable to develop effective strategies to improve the absorption of tea active compounds and exert combinational effects with other natural compounds to broaden its hypoglycemic potential. The advances in clinical trials and population-based investigations are also discussed. This review primarily delves into the antidiabetic potential and underlying mechanisms of tea active compounds, providing a theoretical basis for the practical application of tea and its active compounds against diabetes.

Clinical applications and mechanism insights of natural flavonoids against type 2 diabetes mellitus

Diabetes is a complex disease that affects a large percentage of the world's population, and it is associated with several risk factors. Self-management poses a significant challenge, but natural sources have shown great potential in providing effective glucose reducing solutions. Flavonoids, a class of bioactive substances found in different natural sources including medicinal plants, have emerged as promising candidates in this regard. Indeed, several flavonoids, including apigenin, arbutin, catechins, and cyanidin, have demonstrated remarkable anti-diabetic properties. The clinical effectiveness of these flavonoids is linked to their potential to decrease blood glucose concentration and increase insulin concentration. Thus, the regulation of certain metabolic pathways such as glycolysis and neoglycogenesis has also been demonstrated. In vitro and in vivo investigations revealed different mechanisms of action related to flavonoid compounds at subcellular, cellular, and molecular levels. The main actions reside in the activation of glycolytic signaling pathways and the inhibition of signaling that promotes glucose synthesis and storage. In this review, we highlight the clinical efficiency of natural flavonoids as well as the molecular mechanisms underlying this effectiveness.

Phytochemical composition of Tibetan tea fermented by Eurotium cristatum and its effects on type 1 diabetes mice and gut microbiota

"Golden-flower" Tibetan tea (GTT) is an innovative dark tea fermented via fungus Eurotium cristatum. To study GTT effects on alleviating the symptoms of type 1 diabetes mellitus (T1DM), GTT's extract (GTTE) was prepared. GTTE chemical compositions were analyzed via HPLC, pyrolysis-gas chromatography-mass (Py-GC-MS) spectrometry analysis, and chemistry analyses. GTTE effects on T1DM were explored on T1DM mice model induced by streptozotocin (STZ). GTTE was composed mainly of tea pigment theabrownin (TB) (49.18%), with high percentages of polysaccharide (16.93%), protein (10.15%), polyphenols (13.90%), amino acids (5.89%), caffeine (1.83%), and flavonoids (0.67%). Py-GC-MS results exhibited that GTTE constituted of phenols, lipids, sugars, and proteins. GTTE attenuated T1DM conditions of mice, relieved their liver and pancreatic injury, restored damaged islet cells, decreased oxidative stress by increasing superoxide dismutase (SOD) and catalase (CAT) levels, modulated cytokine expression leading to the decreasing pro-inflammatory cytokines TNF-α and IL-6, increased anti-inflammatory cytokines IL-4 to improve inflammatory responses, and optimized gut microbiota composition and structure based on high-throughput 16S rDNA sequencing, suggesting multi-channel anti-diabetes mechanisms.

Effect of Justicia schimperiana (Acanthaceae) roots extract on blood glucose level and lipid profiles in streptozotocin-induced diabetic mice

Background

Justicia schimperiana has been used traditionally for the treatment of different diseases, including, diabetes. Yet, no in vivo study was conducted to substantiate these claims. This study aimed to evaluate the effect of Justicia schimperiana roots extract on blood glucose levels and lipid profiles in streptozotocin-induced diabetic mice.

Methods

Male Swiss albino mice weighing 25-35 g were induced diabetes with 150 mg/kg of STZ. Animals were randomly grouped into six groups of five each. Group I was a normal control, Group II was a Diabetic control, Group III-V were Diabetic Mice treated with the extract (100, 200, and 400 mg/kg) respectively, and Group VI was standard control. The treatments were followed for 14 days. The FBG measurements were done on 0, 7th, and 14th days of treatment. On the 15th day, the mice were anesthetized with diethyl ether; blood samples were collected for the assessment of serum lipid profiles. The antioxidant and α-amylase inhibitory activities of the extract were also investigated in vitro using the DPPH and DNSA assay methods, respectively. The data were entered into EPI DATA version 4.6, exported to IBM, SPSS version 26.0, and analyzed using a one-way ANOVA followed by Tukey's post hoc test. P < 0.05 was considered statistically significant.

Results

The hydromethanolic extract of J. schimperiana roots exhibited no toxicity up to a dose of 2000 mg/kg body weight. In the STZ-induced diabetic mice, the extract reduced blood glucose levels at all tested doses: 100, 200, and 400 mg/kg on the 14th day as compared to diabetic control. The higher dose showed maximum reduction (29.73 %, p < 0.001) on the 14th day of treatment compared to the baseline. There were significant reductions in serum TG, TC, LDL, and a significant increase in body weight and HDL compared to the diabetic control. Besides, good antioxidant and α-amylase inhibitory activity were obtained from the in vitro laboratory tests.

Conclusions

Evidence from our study revealed that the root extract of J. schimperiana has antihyperglycemic and antihyperlipidemic effects in STZ-induced diabetic mice.

In-silico, in-vitro and in-vivo Biological Activities of Flavonoids for the Management of Type 2 Diabetes

In spite of the fact that many medicinal plants have been truly utilized for the management of diabetes all through the world, very few of them have been reported scientifically. Recently, a diverse variety of animal models have been established to better understand the pathophysiology of diabetes mellitus, and new medications to treat the condition have been introduced in the market. Flavonoids are naturally occurring substances that can be found in plants and various foods and may have health benefits in the treatment of neuropathic pain. Flavonoids have also been shown to have an anti-inflammatory impact that is significant to neuropathic pain, as indicated by a decrease in several pro-inflammatory mediators such TNF-, NF-B IL-6, and IL-1. Flavonoids appear to be a viable novel therapy option for macrovasular complications in preclinical models; however, human clinical data is still inadequate. Recently, several in silico, in-vitro and in-vivo aproaches were made to evaluate mechanisms associated with the pathogenesis of diabetes in a better way. Screening of natural antidiabetic agents from plant sources can be analysed by utilizing advanced in-vitro techniques and animal models. Natural compounds, mostly derived from plants, have been studied in diabetes models generated by chemical agents in the majority of research. The aim of this work was to review the available in silico, in-vitro and animal models of diabetes for screening of natural antidiabetic agents. This review contributes to the scientist's design of new methodologies for the development of novel therapeutic agents having potential antihyperglycemic activity.

Effect of Wild Strawberry Tree and Hawthorn Extracts Fortification on Functional, Physicochemical, Microbiological, and Sensory Properties of Yogurt

The composition analyses and health-promoting properties (antioxidant capacity, antidiabetic, and antihypertensive properties) of wild fruit extracts and the effect of the incorporation of strawberry tree (STE) and hawthorn (HTE) extracts on the physicochemical, instrumental textural, microbiological, and sensory parameters of yogurts were evaluated. The incorporation of wild fruit extracts in yogurt increased antioxidant and antidiabetic properties (inhibition of digestive α-amylase, α-glucosidase, and lipase enzymatic activities) compared to the control, without decreasing their sensory quality or acceptance by consumers. The hawthorn yogurt (YHTE) showed the highest total phenolic content (TPC) and antioxidant capacity (ABTS and ORAC methods). Yogurts containing wild fruit extracts and dietary fiber achieved high overall acceptance scores (6.16-7.04) and showed stable physicochemical, textural, and microbiological properties. Therefore, the use of wild fruit extracts and inulin-type fructans as ingredients in yogurt manufacture stands as a first step towards the development of non-added sugar dairy foods for sustainable health.

Antioxidant and Antidiabetic Properties of Phlorotannins from Ascophyllum nodosum Seaweed Extracts

Seaweeds have gained considerable attention in recent years due to their potential health benefits and high contents of bioactive compounds. This review focuses on the exploration of seaweed's health-promoting properties, with particular emphasis on phlorotannins, a class of bioactive compounds known for their antioxidant and antidiabetic properties. Various novel and ecofriendly extraction methods, including solid-liquid extraction, ultrasound-assisted extraction, and microwave-assisted extraction are examined for their effectiveness in isolating phlorotannins. The chemical structure and isolation of phlorotannins are discussed, along with methods for their characterization, such as spectrophotometry, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and chromatography. Special attention is given to the antioxidant activity of phlorotannins. The inhibitory capacities of polyphenols, specifically phlorotannins from Ascophyllum nodosum against digestive enzymes, such as α-amylase and α-glucosidase, are explored. The results suggest that polyphenols from Ascophyllum nodosum seaweed hold significant potential as enzyme inhibitors, although the inhibitory activity may vary depending on the extraction conditions and the specific enzyme involved. In conclusion, seaweed exhibits great potential as a functional food ingredient for promoting health and preventing chronic diseases. Overall, this review aims to condense a comprehensive collection of high-yield, low-cost, and ecofriendly extraction methods for obtaining phlorotannins with remarkable antioxidant and antidiabetic capacities.

Suppressive effect of black tea polyphenol theaflavins in a mouse model of ovalbumin-induced food allergy

Food allergy is recognized as a global medical problem with increasing prevalence in recent years. Currently, the treatment of food allergy mainly involves avoidance of allergens and allergen-specific immunotherapy. Barring the spontaneous resolution of food allergy during the growth process, this disease is difficult to treat fundamentally. In recent years, the use of functional food ingredients derived from natural products has been attracting attention for their prophylactic use in food allergy. Theaflavins, i.e., black tea polyphenols, are potent antioxidants that have inhibitory effects on a variety of diseases. However, little is known about the preventive effect of theaflavins on food allergy. In this study, we designed a mouse model of food allergy and examined the effect of theaflavins using the severity of diarrhea, a symptom of food allergy, as an indicator. The administration of a black tea extract rich in theaflavins or theaflavin 1 (subgroup of theaflavins) to mice reduced the severity of diarrhea when compared with a normal diet. A reduction in malondialdehyde levels, a key marker of lipid peroxidation, was also observed. Overall, these data suggest that theaflavins may potentially inhibit food allergy by alleviating oxidative stress in the colon and can be a potential food material for prevention of food allergy.

Supramolecular assembly of benzocaine bearing cyclodextrin cavity via host-guest complexes on polyacrylonitrile as an electrospun nanofiber

Nanofibers (NFs) can be encapsulated with cyclodextrins (CDs) based host-guest complexes (HCs) in order to enable many biological applications. Here, benzocaine (BNZ) forms HCs with β-cyclodextrin (β-CD) that are co-precipitated and further added to polyacrylonitrile (PAN) solution for making BNZ:β-CD-HCs/PAN NFs material with the aid of electrospinning technique. The marginal increase in absorbance and fluorescence intensity along with the shift in spectral maxima of BNZ in the presence of β-CD suggested the host-guest interaction between BNZ and β-CD. NFs showed a uniform and clean morphology in SEM images and interestingly, the ICs revealed that significantly thinner in terms of average fiber diameter (AFD) than those of free BNZ on PAN medium. BNZ molecule is completely included in the PAN surface as the result of NFs and thus, the original sharp peaks for the BNZ have vanished and the peaks are much broader for the BNZ and BNZ:β-CD-HCs. BNZ is also found to be a good candidate for anti-inflammatory, anti-oxidant, and anti-diabetic. The results showed an improved activity when it is in the form of HCs on a PAN medium. Making HCs of drugs could be significant in biological applications.

Identification of Phytochemicals in Bioactive Extracts of Acacia saligna Growing in Australia

Acacia saligna growing in Australia has not been fully investigated for its bioactive phytochemicals. Sequential polarity-based extraction was employed to provide four different extracts from individual parts of A. saligna. Bioactive extracts were determined using in vitro antioxidant and yeast α-glucosidase inhibitory assays. Methanolic extracts from barks, leaves, and flowers are the most active and have no toxicity against 3T3-L1 adipocytes. Compound isolation of bioactive extracts provided us with ten compounds. Among them are two novel natural products; naringenin-7-O-α-L-arabinopyranoside 2 and (3S*,5S*)-3-hydroxy-5-(2-aminoethyl) dihydrofuran-2(3H)-one 9. D-(+)-pinitol 5a (from barks and flowers), (-)-pinitol 5b (exclusively from leaf), and 2,4-di-t-butylphenol 7 are known natural products and new to A. saligna. (-)-Epicatechin 6, quercitrin 4, and myricitrin 8 showed potent antioxidant activities consistently in DPPH and ABTS assays. (-)-Epicatechin 6 (IC₅₀ = 63.58 μM),D-(+)-pinitol 5a (IC₅₀ = 74.69 μM), and naringenin 1 (IC₅₀ = 89.71 μM) are the strong inhibitors against the α-glucosidase enzyme. The presence of these compounds supports the activities exerted in our methanolic extracts. The presence of 2,4-di-t-butylphenol 7 may support the reported allelopathic and antifungal activities. The outcome of this study indicates the potential of Australian A. saligna as a rich source of bioactive compounds for drug discovery targeting type 2 diabetes.

The role of dietary antioxidants in type 2 diabetes and neurodegenerative disorders: An assessment of the benefit profile

Healthy diet is vital to cellular health. The human body succumbs to numerous diseases which afflict severe economic and psychological burdens on the patient and family. Oxidative stress is a possible crucial regulator of various pathologies, including type 2 diabetes and neurodegenerative diseases. It generates reactive oxygen species (ROS) that trigger the dysregulation of essential cellular functions, ultimately affecting cellular health and homeostasis. However, lower levels of ROS can be advantageous and are implicated in a variety of signaling pathways. Due to this dichotomy, the terms oxidative "eustress," which refers to a good oxidative event, and "distress," which can be hazardous, have developed. ROS affects multiple signaling pathways, leading to compromised insulin secretion, insulin resistance, and β-cell dysfunction in diabetes. ROS is also associated with increased mitochondrial dysfunction and neuroinflammation, aggravating neurodegenerative conditions in the body, particularly with age. Treatment includes drugs/therapies often associated with dependence, side effects including non-selectivity, and possible toxicity, particularly in the long run. It is imperative to explore alternative medicines as an adjunct therapy, utilizing natural remedies/resources to avoid all the possible harms. Antioxidants are vital components of our body that fight disease by reducing oxidative stress or nullifying the excess toxic free radicals produced under various pathological conditions. In this review, we focus on the antioxidant effects of components of dietary foods such as tea, coffee, wine, oils, and honey and the role and mechanism of action of these antioxidants in alleviating type 2 diabetes and neurodegenerative disorders. We aim to provide information about possible alternatives to drug treatments used alone or combined to reduce drug intake and encourage the consumption of natural ingredients at doses adequate to promote health and combat pathologies while reducing unwanted risks and side effects.

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.

Critical Assessment of In Vitro Screening of α-Glucosidase Inhibitors from Plants with Acarbose as a Reference Standard

Postprandial hyperglycemia is treated with the oral antidiabetic drug acarbose, an intestinal α-glucosidase inhibitor. Side effects of acarbose motivated a growing number of screening studies to identify novel α-glucosidase inhibitors derived from plant extracts and other natural sources. As "gold standard", acarbose is frequently included as the reference standard to assess the potency of these candidate α-glucosidase inhibitors, with many outperforming acarbose by several orders of magnitude. The results are subsequently used to identify suitable compounds/products with strong potential for in vivo efficacy. However, most α-glucosidase inhibitor screening studies use enzyme preparations obtained from nonmammalian sources (typically Saccharomyces cerevisiae), despite strong evidence that inhibition data obtained using nonmammalian α-glucosidase may hold limited value in terms of identifying α-glucosidase inhibitors with actual in vivo hypoglycemic potential. The aim was to critically discuss the screening of novel α-glucosidase inhibitors from plant sources, emphasizing inconsistencies and pitfalls, specifically where acarbose was included as the reference standard. An assessment of the available literature emphasized the cruciality of stating the biological source of α-glucosidase in such screening studies to allow for unambiguous and rational interpretation of the data. The review also highlights the lack of a universally adopted screening assay for novel α-glucosidase inhibitors and the commercial availability of a standardized preparation of mammalian α-glucosidase.

New glucogenesis inhibition model based on complete α-glucosidases from rat intestinal tissues validated with various types of natural and pharmaceutical inhibitors

BACKGROUND

Inhibition of intestinal α-glucosidases from rat intestinal acetone powder (RIAP) has been widely used in research focused on regulating glucogenesis to be applied as a strategy to control obesity and type II diabetes. However, the crude extract has different compositions of α-glucosidases than a complete RIAP suspension due to enzymes anchored on the intestinal tissues after the extraction. Here, the inhibitory effects of different pharmaceutical and food-grade inhibitors on the enzymes in the RIAP suspension were investigated.

RESULTS

Instead of crude extracts from RIAP, the RIAP suspension without the extraction process was applied to optimize the α-glucosidase inhibitory model by pharmaceutical/natural inhibitors. The results clearly showed that the half-maximal inhibitory concentration ratios of four individual α-glucosidases by various inhibitors were different between the RIAP suspension and the crude extract. In particular, isomaltase from the RIAP suspension required more inhibitors than the crude extraction did, as this enzyme is still anchored to the remaining intestinal tissue from the extraction process.

CONCLUSION

The crude extract from RIAP contains only a portion of the enzymes, which poses limitations for determining the precise inhibitory properties by various types of enzyme inhibitors. On the contrary, an in vitro assay with RIAP suspension that has all the α-glucosidases is a more suitable method for determining digestibility of glycemic carbohydrates. This new approach can be applied to the development of natural/synthetic α-glucosidase inhibitors to attenuate the postprandial glycemic response more accurately. © 2022 Society of Chemical Industry.

Phytochemical Profiling, In Vitro Biological Activities, and In-Silico Studies of Ficus vasta Forssk.: An Unexplored Plant

Ficus vasta Forssk. (Moraceae family) is an important medicinal plant that has not been previously investigated for its phytochemical and biological potential. Phytochemical screening, total bioactive content, and GCMS analysis were used to determine its phytoconstituents profile. Antioxidant, antibacterial, antifungal, anti-viral, cytotoxicity, thrombolytic, and enzyme inhibition activities were examined for biological evaluation. The plant extract exhibited the maximum total phenolic (89.47 ± 3.21 mg GAE/g) and total flavonoid contents (129.2 ± 4.14 mg QE/g), which may be related to the higher antioxidant potential of the extract. The extract showed strong α-amylase (IC₅₀ 5 ± 0.21 µg/mL) and α-glucosidase inhibition activity (IC₅₀ 5 ± 0.32 µg/mL). Significant results were observed in the case of antibacterial, antifungal, and anti-viral activities. The F. vasta extract inhibited the growth of HepG2 cells in a dose-dependent manner. The GCMS analysis of the extract provided the preliminary identification of 28 phytocompounds. In addition, the compounds identified by GCMS were subjected to in silico molecular docking analysis in order to identify any interactions between the compounds and enzymes (α-amylase and α-glucosidase). After that, the best-docked compounds were subjected to ADMET studies which provide information on pharmacokinetics, drug-likeness, physicochemical properties, and toxicity. The present study highlighted that the ethanol extract of F. vasta has antidiabetic, antimicrobial, anti-viral, and anti-cancer potentials that can be further explored for novel drug development.

Phytochemical Analysis and Antioxidant and Antidiabetic Activities of Extracts from Bergenia ciliata, Mimosa pudica, and Phyllanthus emblica

Diabetes is a metabolic disorder of high blood sugar levels which leads to various chronic health-related complications. The digestive enzymes α-amylase and α-glucosidase play a major role in the hydrolysis of starch to glucose; hence, inhibiting these enzymes is considered an important strategy for the treatment of diabetes. Medicinal plants such as Bergenia ciliata, Mimosa pudica, and Phyllanthus emblica are commonly used in traditional remedies due to their numerous health benefits. This study aimed to determine the phytochemicals as well as TPC and TFC contents in these plant extracts along with their antioxidant and enzyme inhibitory activity against α-glucosidase and α-amylase. The ethyl acetate extracts of selected plants have shown higher TPC and TFC contents. The aqueous extract of B. ciliata (IC₅₀: 16.99 ± 2.56 μg/mL) and ethyl acetate extract of P. emblica (IC₅₀: 11.98 ± 0.36 μg/mL) and M. pudica (IC₅₀: 21.39 ± 3.76 μg/mL) showed effective antioxidant activities. Furthermore, ethyl acetate extract of B. ciliata showed significant inhibitory activity against α-amylase and α-glucosidase with IC₅₀ values of 38.50 ± 1.32 μg/mL and 3.41 ± 0.04 μg/mL, respectively. Thus, secondary metabolites of these medicinal plants can be repurposed as effective inhibitors of digestive enzymes.

Preparation of Spice Extracts: Evaluation of Their Phytochemical, Antioxidant, Antityrosinase, and Anti-α-Glucosidase Properties Exploring Their Mechanism of Enzyme Inhibition with Antibrowning and Antidiabetic Studies In Vivo

Tyrosinase and α-glucosidase enzymes are known as promising target candidates for inhibitors to control unwanted pigmentation and type II diabetics mellitus. Therefore, twenty extracts as enzyme inhibitors were prepared from edible spices: nutmeg, mace, star anise, fenugreek, and coriander aiming to explore their antioxidant, antibrowning, and antidiabetic potential. Results confirmed that all extracts showed potent antioxidant activity ranging from IC₅₀ = 0.14 ± 0.03 to 3.69 ± 0.37 μg/mL. In addition, all extracts exhibited excellent antityrosinase (IC₅₀ = 1.16 ± 0.06 to 71.32 ± 4.63 μg/mL) and anti-α-glucosidase (IC₅₀4.76 ± 0.71 to 42.57 ± 2.13 μg/mL) activities outperforming the corresponding standards, hydroquinone, and acarbose, respectively. Among all extracts, star anise ethyl acetate (Star anise ETAC) was found most potent inhibitor for both tyrosinase and α-glucosidase enzymes and was further studied to explore the mechanism of enzyme inhibition. Kinetic analysis revealed its irreversible but mixed-type tyrosinase inhibition with preferentially competitive mode of action. However, it binds reversibly with α-glucosidase through competitive mode of action. Further, star anise ETAC extract showed concentration dependent and posttreatment time-dependent antibrowning effect on potato slices and antidiabetic effect on diabetic rabbits in vivo proposing it promising candidate for tyrosinase-rooted antibrowning and α-glucosidase-associated diabetes management for future studies.

Comparative studies on the physicochemical profile and potential hypoglycemic activity of different tea extracts: Effect on sucrase-isomaltase activity and glucose transport in Caco-2 cells

Tea is one of the most popular beverages in the world and is believed to be beneficial for health. The main components in tea change greatly depending on different processes, and thus, the effects of different teas on human health may differ. In this study, we compared the effect of green, oolong, black, and dark tea extracts on sucrase-isomaltase (SI) activity and glucose transport, which are two intervention options for postprandial blood glucose control, using Caco-2 cells as a model. Theaflavin-rich black tea extracts showed the highest inhibition of SI activity and retardation of the hydrolysis of sucrose, maltose, and isomaltose, with IC₅₀ values of 8.34 μg/mL, 16.10 μg/mL, and 21.63 μg/mL, respectively. All four kinds of tea extracts caused a dose-dependent inhibition of glucose transport, which were closely related to the catechin content. Green tea extracts showed the highest inhibition of glucose transport and was more effective against sodium-dependent glucose cotransporter 1 (SGLT1) than glucose transporter 2 (GLUT2) in the management of glucose transport. Black tea extracts also inhibited glucose transport despite low level of catechins. The reason could partly lie in the suppression of Na⁺/K⁺-ATPase, which reduced the energy needed for SGLT1 to actively transport glucose. Furthermore, the mRNA level of SI, SGLT1, GLUT2, and Na⁺/K⁺-ATPase in Caco-2 cells were significantly reduced after treatment with tea extracts for 2 h. These in vitro studies suggested that tea could be used as a functional food in the diet to modulate postprandial hyperglycaemia for diabetic patients.

Personal Glucose Meter for α-Glucosidase Inhibitor Screening Based on the Hydrolysis of Maltose

As a key enzyme regulating postprandial blood glucose, α-Glucosidase is considered to be an effective target for the treatment of diabetes mellitus. In this study, a simple, rapid, and effective method for enzyme inhibitors screening assay was established based on α-glucosidase catalyzes reactions in a personal glucose meter (PGM). α-glucosidase catalyzes the hydrolysis of maltose to produce glucose, which triggers the reduction of ferricyanide (K₃[Fe(CN)₆]) to ferrocyanide (K₄[Fe(CN)₆]) and generates the PGM detectable signals. When the α-glucosidase inhibitor (such as acarbose) is added, the yield of glucose and the readout of PGM decreased accordingly. This method can achieve the direct determination of α-glucosidase activity by the PGM as simple as the blood glucose tests. Under the optimal experimental conditions, the developed method was applied to evaluate the inhibitory activity of thirty-four small-molecule compounds and eighteen medicinal plants extracts on α-glucosidase. The results exhibit that lithospermic acid (52.5 ± 3.0%) and protocatechualdehyde (36.8 ± 2.8%) have higher inhibitory activity than that of positive control acarbose (31.5 ± 2.5%) at the same final concentration of 5.0 mM. Besides, the lemon extract has a good inhibitory effect on α-glucosidase with a percentage of inhibition of 43.3 ± 3.5%. Finally, the binding sites and modes of four active small-molecule compounds to α-glucosidase were investigated by molecular docking analysis. These results indicate that the PGM method is feasible to screening inhibitors from natural products with simple and rapid operations.

Therapeutic Potential of Polyphenols in the Management of Diabetic Neuropathy

Diabetic neuropathy (DN) is a common and serious diabetes-associated complication that primarily takes place because of neuronal dysfunction in patients with diabetes. Use of current therapeutic agents in DN treatment is quite challenging because of their severe adverse effects. Therefore, there is an increased need of identifying new safe and effective therapeutic agents. DN complications are associated with poor glycemic control and metabolic imbalances, primarily oxidative stress (OS) and inflammation. Various mediators and signaling pathways such as glutamate pathway, activation of channels, trophic factors, inflammation, OS, advanced glycation end products, and polyol pathway have a significant contribution to the progression and pathogenesis of DN. It has been indicated that polyphenols have the potential to affect DN pathogenesis and could be used as potential alternative therapy. Several polyphenols including kolaviron, resveratrol, naringenin, quercetin, kaempferol, and curcumin have been administered in patients with DN. Furthermore, chlorogenic acid can provide protection against glutamate neurotoxicity via its hydrolysate, caffeoyl acid group, and caffeic acid through regulating the entry of calcium into neurons. Epigallocatechin-3-gallate treatment can protect motor neurons by regulating the glutamate level. It has been demonstrated that these polyphenols can be promising in combating DN-associated damaging pathways. In this article, we have summarized DN-associated metabolic pathways and clinical manifestations. Finally, we have also focused on the roles of polyphenols in the treatment of DN.

Chitosan Activated with Genipin: A Nontoxic Natural Carrier for Tannase Immobilization and Its Application in Enhancing Biological Activities of Tea Extract

In this work, a non-toxic chitosan-based carrier was constructed via genipin activation and applied for the immobilization of tannase. The immobilization carriers and immobilized tannase were characterized using Fourier transform infrared spectroscopy and thermogravimetric analysis. Activation conditions (genipin concentration, activation temperature, activation pH and activation time) and immobilizations conditions (enzyme amount, immobilization time, immobilization temperature, immobilization pH, and shaking speed) were optimized. The activity and activity recovery rate of the immobilized tannase prepared using optimal activation and immobilization conditions reached 29.2 U/g and 53.6%, respectively. The immobilized tannase exhibited better environmental adaptability and stability. The immobilized tannase retained 20.1% of the initial activity after 12 cycles and retained 81.12% of residual activity after 30 days storage. The catechins composition analysis of tea extract indicated that the concentration of non-ester-type catechins, EGC and EC, were increased by 1758% and 807% after enzymatic treatment. Biological activity studies of tea extract revealed that tea extract treated with the immobilized tannase possessed higher antioxidant activity, higher inhibitory effect on α-amylase, and lower inhibitory effect on α-glucosidase. Our results demonstrate that chitosan activated with genipin could be an effective non-toxic carrier for tannase immobilization and enhancing biological activities of tea extract.

Gene set enrichment analysis of α-amylase and α-glucosidase inhibitors of Cassia glauca

Background

The present study aimed to evaluate in vitro α-amylase and α-glucosidase inhibitory activity of various extracts of Cassia glauca, predict the binding affinity of multiple phytoconstituents with both enzymes via in silico molecular docking and identify the probably modulated pathways by the lead hit.

Methods

Different extracts of Cassia glauca i.e. acetone, ethanol, and aqueous extracts were evaluated for α-amylase and α-glucosidase inhibitory activity using in vitro method in which starch and 4-Nitrophenyl β-D-glucopyranoside were used as substrate respectively. Similarly, the docking study was performed using autodock4 to predict the binding affinity of phytoconstituents with α-amylase and α-glucosidase. After docking, ten different poses were obtained for the ligand molecule. Among them, the pose of ligand molecule with the lowest binding energy was visualized in Discovery Studio 2019.

Results and conclusion

Among the multiple extracts, the aqueous extract showed the highest α-amylase (IC₅₀:652.10 ± 20.09) and α-glucosidase (IC₅₀:482.46 ± 8.70) inhibitory activity. Similarly, cassiaoccidentalin B was predicted to have the highest binding affinity with both enzymes. The potency of aqueous extract to inhibit α-amylase and α-glucosidase could be due to multiple water-soluble compounds like saponins, flavonoids, and glycosides.

A Review on Natural Products and Herbs Used in the Management of Diabetes

AIM

We aimed to review the importance of the natural products and herbs used in the management of diabetes mellitus (DM) as medicinal agents.

BACKGROUND

Naturally occuring phytoactive compounds and herbs are very important because they are found to be effective against several diseases. DM is a commonly occurring endocrinological disorder, with the incidences increased four times in the last 34 years. There are several oral hypoglycemic agents available in the market, which in the long term, may lead to a high risk of secondary failure rate.

OBJECTIVES

This review focuses on natural products and herbs application for effective management of diabetic conditions, and natural products that can be utilized as alternative therapy.

METHODS

We searched the various online databases (PubMed, Bentham, ScienceDirect) and scientific publications from the library using a qualitative systematic review. The criteria of the review were based on natural products and herbs application for possessing medicinal value against diabetes and the literature of previous thirty years has been searched. The inclusion criteria of materials were based on the quality and relevancy with our aim.

RESULTS

We observed that owing to the potential of natural products and herbs, different research groups are searching for the potent natural antidiabetic agents with minimal side effects. Recent research showed that there is a decline in a number of new molecules that fail in clinical trials because of toxicity thus, natural products and herbs are considered as the alternative. Currently, some of the natural products and herbs like coixol, andrographolide, Tinospora cordifolia, polypeptide p, charantin, Annona squamosa, and Nigella are being explored for their potential to be used successfully for the management of type 2 diabetes.

CONCLUSION

The significance of natural products and herbs in the anticipation of diabetes and allied complications are being described herein. We observed that a huge amount of work is being done to explore the natural products and herbs to manage the diabetes and this review gives the highlights of them.

In vitro antidiabetic potentials, antioxidant activities and phytochemical profile of african black pepper (Piper guineense)

Background

Diabetes mellitus is a metabolic disorder of glucose metabolism and management of blood glucose level is the hallmark in the treatment of this disease. The present study investigated chemical composition, in vitro antioxidant and antidiabetic activity of different fractions of 80% methanol Piper guineense leaves extract.

Materials and methods

The crude methanolic extract of P. guineense was obtained following 80% methanol cold extraction and was successively partitioned with dichloromethane (DCM), ethyl acetate (EtOAc), n-butanol (nBuOH) and aqueous solvents to give four fractions. The chemical composition of the fractions from P. guineense was determined using gas chromatography coupled with mass spectrometry (GC-MS) and their potentials as antioxidant and anti-diabetes were evaluated.

Results

The percentage yields were 3.16, 2.22, 0.68 and 0.66% (w/w) in n-butanol, DCM, aqueous and ethyl acetate fractions of P. guineense methanolic extract, respectively. The GC-MS analyses identified a total of 71 and 34 phytochemicals in n-butanol and ethyl acetate fractions respectively. Tributyl acetylcitrate (10.95%) and phytol (9.11%) were the major components in the n-butanol fraction while ethyl piperonyl cyanoacetate (27.35%) and phytol (15.17%) were the major constituents in the ethyl acetate fraction. Ethyl acetate fraction had the highest ferric reducing antioxidant power with a value of 53.96 ± 0.40 mgAAE/g while n-butanol fraction possessed highest total antioxidant power (9.98 ± 0.15) followed by aqueous fraction (9.72 ± 0.02). The ethyl acetate and n-butanol fractions with IC50 value of 0.24 ± 0.07 and 0.83 ± 0.15 μg/mL respectively elicited significant inhibitory activities against α-glucosidase while only n-butanol fraction (IC50 = 0.33 ± 0.09 μg/ml) exhibited appreciable inhibition against α-amylase activity. However, none of the four fractions showed significant inhibitory activity towards dipeptidyl-peptidase-IV.

Conclusion

n-butanol and ethyl acetate fractions of 80% methanol P. guineense leaves extract can be a potential source of bioactive compounds of pharmacological importance in the management of diabetes.

Insight into interaction mechanism between theaflavin-3-gallate and α-glucosidase using spectroscopy and molecular docking analysis

To elucidate the α-glucosidase (α-GC) inhibitory mechanism of theaflavin-3-gallate (TF-3-G), their interaction mechanism was investigated using spectroscopy and molecular docking analysis. The inhibition ratio of TF-3-G against α-GC was determined to be 92.3%. Steady fluorescence spectroscopy showed that TF-3-G effectively quenched the intrinsic fluorescence of α-GC through static quenching, forming a stable complex through hydrophobic interactions. Formation of the TF-3-G/α-GC complex was also confirmed by resonance light scattering spectroscopy. Synchronous fluorescence spectroscopy and circular dichroism spectroscopy indicated that the secondary structure of α-GC was changed by TF-3-G. Molecular docking was used to simulate TF-3-G/α-GC complex formation, showing that TF-3-G might be inserted into the hydrophobic region around the active site of ɑ-GC, and bind with the catalytic Asp215 and Asp352 residues. The ɑ-GC inhibitory mechanism of TF-3-G was mainly attributed to the change in ɑ-GC secondary structure caused by the complex formation. PRACTICAL APPLICATIONS: α-Glucosidase (α-GC) can hydrolyze the glycosidic bonds of starch and oligosaccharides in food and release glucose. Therefore, the inhibition of α-GC activity has been used to treat postprandial hyperglycemia and type 2 diabetes mellitus. Theaflavin-3-gallate (TF-3-G), a flavonoid found in the fermentation products of black tea, exhibits strong inhibition of α-GC activity. However, the α-GC inhibitory mechanism of TF-3-G is unclear. This study aids understanding of this mechanism, and proposed a possibly basic theory for improving the medicinal value of TF-3-G in diabetes therapy.

Maltoheptaoside hydrolysis with chromatographic detection and starch hydrolysis with reducing sugar analysis: Comparison of assays allows assessment of the roles of direct α-amylase inhibition and starch complexation

The aim was to determine inhibition of human α-amylase activity by (poly)phenols using maltoheptaoside as substrate with direct chromatographic product quantification, compared to hydrolysis of amylose and amylopectin estimated using 3,5-dinitrosalicylic acid. Acarbose exhibited similar IC₅₀ values (50% inhibition) with maltoheptaoside, amylopectin or amylose as substrates (2.37 ± 0.11, 3.71 ± 0.12 and 2.08 ± 0.01 µM respectively). Epigallocatechin gallate, quercetagetin and punicalagin were weaker inhibitors of hydrolysis of maltoheptaoside (<50% inhibition) than amylose (IC₅₀: epigallocatechin gallate = 20.41 ± 0.25 µM, quercetagetin = 30.15 ± 2.05 µM) or amylopectin. Interference using 3,5-dinitrosalicylic acid was in the order punicalagin > epigallocatechin gallate > quercetagetin, with minimal interference using maltoheptaoside as substrate. The main inhibition mechanism of epigallocatechin gallate and punicalagin was through complexation with starch, especially amylose, whereas only quercetagetin additionally binds to the α-amylase active site. Interference is minimised using maltoheptaoside as substrate with product detection by chromatography, potentially allowing assessment of direct enzyme inhibition by almost any compound.

DIA-DB: A Database and Web Server for the Prediction of Diabetes Drugs

The DIA-DB is a web server for the prediction of diabetes drugs that uses two different and complementary approaches: (a) comparison by shape similarity against a curated database of approved antidiabetic drugs and experimental small molecules and (b) inverse virtual screening of the input molecules chosen by the users against a set of therapeutic protein targets identified as key elements in diabetes. As a proof of concept DIA-DB was successfully applied in an integral workflow for the identification of the antidiabetic chemical profile in a complex crude plant extract. To this end, we conducted the extraction and LC-MS based chemical profile analysis of Sclerocarya birrea and subsequently utilized this data as input for our server. The server is open to all users, registration is not necessary, and a detailed report with the results of the prediction is sent to the user by email once calculations are completed. This is a novel public domain database and web server specific for diabetes drugs and can be accessed online through http://bio-hpc.eu/software/dia-db/.

α-Glucosidase Inhibitory Activity of Tannat Grape Phenolic Extracts in Relation to Their Ripening Stages

The present study aimed to screen grape extracts as novel α-glucosidase inhibitors to prevent type-2 diabetes and hyperglycemia. The total polyphenol content (TPC) was measured by Folin-Ciocalteu assay and the stilbene, anthocyanin and flavan-3-ol compounds were measured by Ultra High-Performance Liquid Chromatography coupled to Mass Spectrometry (UHPLC-MS). The α-glucosidase inhibitory of seed and skin Tannat grape extracts at four ripening stages were investigated. The highest TPC values were measured in seeds at the “veraison stage” (65.29 ± 5.33 g of Gallic Acid Equivalent (GAE) per kilogram of Fresh Weight (FW)). This was in accordance with the high flavan-3-ol contents measured for these two extracts (43.22 ± 2.59 and 45.45 ± 6.48 g/kg of seeds FW, respectively). The skin and seed extracts at the first stage of ripening exerted strong α-glucosidase inhibition, exceeding 95% (p < 0.05). A high linear correlation (R = 0.723, p ≤ 0.05) was observed between flavan-3-ol contents and the α-glucosidase inhibitory activity. The stilbene contents and this activity were moderately to strongly anti-correlated (R = –0.828, p ≤ 0.05 for trans-resveratrol). The enzyme kinetic studies revealed a mixed type of inhibition. This study brings promising results for the therapeutic potential of seed and skin Tannat grape extracts as a functional food product with anti-diabetic activity.

Bergenia pacumbis from Nepal, an astonishing enzymes inhibitor

BACKGROUND

The Bergenia species are perennial herbs native to central Asia, and one of the most promising medicinal plants of the family Saxifragaceae which are popularly known as 'Pashanbheda'. The aim of this study was to evaluate antioxidant and α-amylase, α-glucosidase, lipase, tyrosinase, elastase, and cholinesterases inhibition potential of Bergenia pacumbis of Nepali origin collected from the Karnali region of Nepal.

METHODS

The sequential crude extracts were made in hexane, ethyl acetate, methanol, and water. Antioxidant activities were analyzed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. The α-amylase, α-glucosidase, lipase, tyrosinase, elastase, acetylcholinesterase, and butyrylcholinesterase inhibition were analyzed by the 3,5-Dinitrosalicylic acid (DNSA), p-Nitrophenyl-α-D-glucopyranoside (p-NPG), 4-nitrophenyl butyrate (p-NPB), l-3,4-dihydroxyphenylalanine (L-DOPA), N-Succinyl-Ala-Ala-p-nitroanilide (AAAPVN), acetylthiocholine, and butyrylcholine as a respective substrate. The major metabolites were identified by high performance liquid chromatography with electron spray ionization- quadrupole time-of-flight mass spectrometry (HPLC-ESI-QTOF-MS) profiling.

RESULTS

Our results revealed the great antioxidant ability of crude extract of B. pacumbis in ethyl acetate extract against both DPPH (IC50 = 30.14 ± 0.14 μg/mL) and ABTS (IC50 = 17.38 ± 1.12 μg/mL). However, the crude methanol extract of B. pacumbis showed the comparable enzymes inhibitions with standard drugs; α-amylase (IC50 = 14.03 ± 0.04 μg/mL), α-glucosidase (IC50 = 0.29 ± 0.00 μg/mL), lipase (IC50 = 67.26 ± 0.17 μg/mL), tyrosinase (IC50 = 58.25 ± 1.63 μg/mL), elastase (IC50 = 74.00 ± 3.03 μg/mL), acetylcholinesterase (IC50 = 31.52 ± 0.58 μg/mL), and butyrylcholinesterase (IC50 = 11.69 ± 0.14 μg/mL). On the basis of HPLC-ESI-QTOF-MS profiling of metabolites, we identified major compounds such as Bergenin, Catechin, Arbutin, Gallic acid, Protocatechuic acid, Syringic acid, Hyperoside, Afzelechin, Methyl gallate, Paashaanolactone, Astilbin, Quercetin, Kaempferol-7-O-glucoside, Diosmetin, Phloretin, and Morin in methanol extract which has reported beneficial bioactivities.

CONCLUSION

Our study provides a plethora of scientific evidence that the crude extracts of B. pacumbis from Nepalese origin in different extracting solvents have shown significant potential on inhibiting free radicals as well as enzymes involved in digestion, skin related problems, and neurological disorders compared with the commercially available drugs.