Polyopes lancifolia Extract, a Potent α-Glucosidase Inhibitor, Alleviates Postprandial Hyperglycemia in Diabetic Mice

Changes in antinutrients, phenolics, antioxidant activities and in vitro α-glucosidase inhibitory activity in pumpkin leaves (Cucurbita moschata) during different domestic cooking methods

Pumpkin leaves (Cucurbita moschata) were subjected to different household cooking methods (boiling, microwaving, steaming, and stir-frying) to evaluate their effect on antinutrients, phenolic compounds, antioxidant properties (ABTS, and DPPH) and in vitro α-glucosidase activity. All cooking methods studied significantly reduced the antinutrients and antioxidant activities, whilst phenolic compounds p-coumaric and ferulic acids significantly increased. The cooking methods reduced the oxalates by more than 50%, tannins by 47% and phytates by 79.22%. Steaming and boiling resulted in highest concentrations of p-coumaric (195.40 mg kg^-1) and ferulic acids (103.90 mg kg^-1) compared to other methods. Overall, boiled leaves retained the highest total phenolic compounds, whilst steamed leaves retained the highest antioxidant capacity. Raw pumpkin leaf extracts showed higher in vitro α-glucosidase inhibitory effects than the cooked leaves. Thus, cooking affected the inhibitory effect of in vitro α-glucosidase activity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-00916-w.

Insight into Gentisic Acid Antidiabetic Potential Using In Vitro and In Silico Approaches

Numerous scientific studies have confirmed the beneficial therapeutic effects of phenolic acids. Among them gentisic acid (GA), a phenolic acid extensively found in many fruit and vegetables has been associated with an enormous confirmed health benefit. The present study aims to evaluate the antidiabetic potential of gentisic acid and highlight its mechanisms of action following in silico and in vitro approaches. The in silico study was intended to predict the interaction of GA with eight different receptors highly involved in the management and complications of diabetes (dipeptidyl-peptidase 4 (DPP4), protein tyrosine phosphatase 1B (PTP1B), free fatty acid receptor 1 (FFAR1), aldose reductase (AldR), glycogen phosphorylase (GP), α-amylase, peroxisome proliferator-activated receptor gamma (PPAR-γ) and α-glucosidase), while the in vitro study studied the potential inhibitory effect of GA against α-amylase and α-glucosidase. The results indicate that GA interacted moderately with most of the receptors and had a moderate inhibitory activity during the in vitro tests. The study therefore encourages further in vivo studies to confirm the given results.

Impact of Household Cooking Techniques on African Nightshade and Chinese Cabbage on Phenolic Compounds, Antinutrients, in vitro Antioxidant, and β-Glucosidase Activity

Different household cooking techniques (boiling, steaming, stir frying, and microwave) were tested on the changes of targeted phenolic compounds, antioxidant property (ferric reducing-antioxidant power (FRAP) activity), α-glucosidase activity, antinutritive compounds, and sensory properties in commonly consumed traditional leafy vegetables in Southern Africa, the non-heading Chinese cabbage (Brassica rapa L. subsp. chinensis) and African nightshade (Solanum retroflexum Dun). Stir frying increased kaempferol-3-O-hydroxyferuloyl-trihexoside, kaempferol-dihexoside, sinapoyl malate, rutin, and isorhamnetin-O-dihexoside in Chinese cabbage leaves, followed by steaming. Similarly, stir frying increased kaempferol-3-O-rutinoside, chlorogenic acid, caffeoylmalic acid, and quercetin-3-O-xylosyl-rutinoside in nightshade, followed by steaming. Biomarkers, sinapoyl malate (Chinese cabbage) and caffeoylmalic acid (nightshade), separated the stir frying from the other cooking techniques. Steaming and stir-frying techniques significantly increased the FRAP activity; whereas boiling and microwaving reduced the tannin, oxalate, and phytate contents in both leafy vegetables and steroidal saponins in nightshade. Stir-fried nightshade leaf extract showed the most effective inhibition against α-glucosidase activity, with an IC₅₀ of 26.4 μg ml^-1, which was higher than acarbose, a synthetic compound (positive control; IC₅₀ 69.83 μg ml^-1). Sensory panelists preferred the stir-fried Chinese cabbage and nightshade leaves, followed by steamed, microwaved, and boiled vegetables.

Phenolic Acids from Lycium barbarum Leaves: In Vitro and In Silico Studies of the Inhibitory Activity against Porcine Pancreatic α-Amylase

Nowadays, bioactive compounds from vegetable food and waste are of great interest for their inhibitory potential against digestive enzymes. In the present study, the inhibitory activity of methanolic extract from Lycium barbarum leaves on porcine pancreas α-amylase has been studied. The α-amylase inhibitory activity of the constituent phenolic acids was also investigated. The leaves were extracted by ultrasound-assisted method, one of the most efficient techniques for bioactive extraction from plant materials, and then the phenolic acids were identified by Accurate-Mass Quadrupole Time-of-Flight (Q-TOF) Liquid Chromatography/Mass Spectrometry (LC/MS). Chlorogenic and salicylic acids were the most abundant phenolic acids in L. barbarum leaf extract. The inhibitory effect against α-amylase, determined for individual compounds by in vitro assay, was higher for chlorogenic, salicylic, and caffeic acids. L. barbarum leaf extract showed an appreciable α-amylase inhibitory effect in a concentration-dependent manner. Docking studies of the considered phenolic acids into the active site of α-amylase suggested a conserved binding mode that is mainly stabilized through H-bonds and π-π stacking interactions.

Ginseng Extracts, GS-KG9 and GS-E3D, Prevent Blood-Brain Barrier Disruption and Thereby Inhibit Apoptotic Cell Death of Hippocampal Neurons in Streptozotocin-Induced Diabetic Rats

Type 1 diabetes mellitus is known to be linked to the impairment of blood–brain barrier (BBB) integrity following neuronal cell death. Here, we investigated whether GS-KG9 and GS-E3D, bioactive ginseng extracts from Korean ginseng (Panax ginseng Meyer), inhibit BBB disruption following neuronal death in the hippocampus in streptozotocin-induced diabetic rats showing type 1-like diabetes mellitus. GS-KG9 and GS-E3D (50, 150, or 300 mg/kg, twice a day for 4 weeks) administered orally showed antihyperglycemic activity in a dose-dependent manner and significantly attenuated the increase in BBB permeability and loss of tight junction proteins. GS-KG9 and GS-E3D also inhibited the expression and activation of matrix metalloproteinase-9 and the infiltration of macrophages into the brain parenchyma, especially into the hippocampal region. In addition, microglia and astrocyte activation in the hippocampus and the expression of proinflammatory mediators such as tnf-α, Il-1β, IL-6, cox-2, and inos were markedly alleviated in GS-KG9 and GS-E3D-treated group. Furthermore, apoptotic cell death of hippocampal neurons, especially in CA1 region, was significantly reduced in GS-KG9 and GS-E3D-treated groups as compared to vehicle control. These results suggest that GS-KG9 and GS-E3D effectively prevent apoptotic cell death of hippocampal neurons by inhibiting BBB disruption and may be a potential therapy for the treatment of diabetic patients.

Gene ontology enrichment analysis of α-amylase inhibitors from Duranta repens in diabetes mellitus

Background

Although α-amylase is the choice of target to manage postprandial hyperglycemia, inhibitors of this enzyme may get absorbed into the systemic circulation and modulate proteins involved in the pathogenesis of diabetes mellitus. Hence, the present study aimed to identify α-amylase inhibitors from Duranta repens via in silico and in vitro and predict their role in the modulation of multiple pathways involved in diabetes mellitus.

Methods

α-amylase inhibitory activity of hydroalcoholic extract/fractions (s) and pure compounds from D. repens was performed using in vitro enzyme inhibitory assay. Multiple open-source databases and published literature were used to retrieve reported phytoconstituents present in D. repens and their targets. The network was constructed between α-amylase inhibitors, modulated proteins, and expressed pathways. Further, hit molecules were also confirmed for their potency to inhibit α-amylase using in silico molecular docking and in vitro enzyme inhibitory assay. The glucose uptake assay was performed to assess the effect of hydrolcoholic extract/fraction(s) using rat hemidiaphragm.

Results

Fraction rich in flavonoids showed the highest α-amylase inhibitory activity with a IC₅₀ of 644.29 ± 4.36 µg/ml compared to other fractions. PI3K-Akt signaling pathway and p53 signaling pathway were predicted to be primarily modulated in the compound-protein-pathway network. Similarly, scutellarein was predicted as lead hit based on α-amylase inhibitory action, binding affinity, and regulated pathways. Further, α-amylase inhibitors were also predicted to modulate the pathways involved in diabetes complications like AGE-RAGE and FoxO signaling pathway. Fraction rich in flavonoids showed the highest glucose uptake in rat hemidiaphragm with an effective concentration of 534.73 ± 0.79 µg/ml.

Conclusions

The α-amylase inhibitors from D. repens may not be limited within the gastrointestinal tract to inhibit α-amylase but may get absorbed into the systemic circulation and modulate multiple pathways involved in the pathogenesis of diabetes mellitus to produce synergistic/additive effect.

Comprehensive bioactivity and chemical characterization of the endemic plant Scorzonera hieraciifolia Hayek extracts: A promising source of bioactive compounds

Members of Scorzonera genus are known for their potential application in both food and pharmaceutical industries. The present study reports the chemical component and bioactivity of the dichloromethane, ethyl acetate, hexane, methanol and infused extracts of Scorzonera hieraciifolia Hayek aerial parts and roots. The methanolic extracts of both aerial parts and roots were good sources of total phenolic and flavonoid content. For the aerial parts, the infused and methanolic extracts showed highest (p < 0.05) free radical scavenging (2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS)), reducing (cupric reducing antioxidant capacity (CUPRAC))and ferric reducing antioxidant power (FRAP)) and metal chelating capacities. Whilst, for the root extracts, overall most remarkable free scavenging and reducing activity was observed for the methanolic extracts (p < 0.05) while the hexane extracts showed highest metal chelating activity. The inhibitory activity of the extracts was evaluated against key enzymes. Overall, the hexane extracts of both aerial parts (acetylcholinesterase (AChE): 2.27 ± 0.04 and butyrlcholinesterase (BChE): 5.75 ± 0.48 mg galantamine equivalent (GALAE)/g) and roots (AChE: 2.44 ± 0.35 and BChE: 53.17 ± 0.22 mg GALAE/g) were most potent against AChE and BChE, suggesting a role for the more lipophilic compounds in this regard. The highest inhibitory activity against tyrosinase was displayed by methanolic extracts of aerial parts (64.70 ± 0.26 mg kojic acid equivalent (KAE)/g) and roots (63.63 ± 0.20 mg KAE/g). Modest activity was observed against α-amylase and α-glucosidase, two major enzymes implicated in the pathology of diabetes. Liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) analysis showed the presence of 40 compounds such as caffeic, ursolic, betulinic and oleanolic acid and their derivatives in the studied extracts. Multivariate analysis showed that the biological activities were dependent on the plant parts used as well as on the type of solvent used. Overall, the results showed that S. hieraciifolia is a valuable source of phytochemicals for both the nutraceutical and pharmaceutical sectors.

Innovative perspectives on Pulicaria dysenterica extracts: phyto-pharmaceutical properties, chemical characterization and multivariate analysis

BACKGROUND

In this study, we aimed to evaluate the influence of different extraction procedures [decoction, homogenizer-assisted extraction (HAE), infusion, maceration, Soxhlet and ultrasound-assisted extraction (UAE)] on the chemical profiling and biological properties of methanol and water extracts of Pulicaria dysenterica (L.) Bernh. The chemical profiles of the extracts were evaluated by high-performance liquid chromatography coupled to electrospray ionization and time-of-flight mass spectrometry (HPLC-ESI-TOF-MS). The antioxidant properties and enzymes (lipase, α-amylase, α-glucosidase, tyrosinase and cholinesterases) inhibitory potential of the extracts were evaluated.

RESULTS

The chemical profiles were dependent on the type of extraction methods as well as on the type of solvent. The methanolic extracts showed higher levels of total phenolic, flavonoid, and phenolic acid content, while the highest total flavonol content was observed in the HAE-water extract. Forty different compounds were identified from P. dysenterica. In relation to the potential in vitro anti-diabetic effects, the highest activity against the studied key enzymes was observed for the macerated extract (α-amylase: 0.58 ± 0.03 and α- glucosidase: 1.65 ± 0.03 mmol ACAE g^-1 ). The HAE-methanol extract was the most potent inhibitor of cholisterases, whereas the highest activities against tyrosinase were observed for UAE-methanol extract, followed by macerated and Soxhlet. The inhibitory activity of the studied extracts against lipase were in the order: soxhlet > macerated> HAE-methanol > UAE-methanol.

CONCLUSION

This study has established scientific baseline data on the therapeutic properties of P. dysentrica, thereby advocating the need for further investigations in an endeavour to develop novel pharmaceuticals from this plant. © 2019 Society of Chemical Industry.

Sargassum sagamianum Extract Alleviates Postprandial Hyperglycemia in Diabetic Mice

In this study, we investigated the postprandial hypoglycemic effect of Sargassum sagamianum extract (SSE) in streptozotocin-induced diabetic mice. Freeze-dried S. sagamianum was extracted with 80% ethanol and concentrated. The inhibition of postprandial hyperglycemia was determined by the inhibitory activity against α-glucosidase and α-amylase as well as the measurement of postprandial blood glucose levels. SSE demonstrated a high inhibitory activity against α-glucosidase and α-amylase. The IC50 value of SSE against α-glucosidase and α-amylase was 0.095 mg/mL and 0.199 mg/mL, respectively, and thus it was significantly more efficacious than the pharmaceutical acarbose (0.115 mg/mL and 0.229 mg/mL, respectively). The postprandial blood glucose levels in the SSE-administered group were significantly lower than those in the control group. Furthermore, the area under the curve significantly decreased following the administration of SSE. These results indicate that SSE can be used as an α-glucosidase and α-amylase inhibitor and can delay the absorption of dietary carbohydrates.