A Structure—Activity Relationship Study of the Inhibition of α-Amylase by Benzoic Acid and Its Derivatives

Valorization of grape pomace extracts against cranberry, elderberry, rose hip berry, goji berry and raisin extracts: Phytochemical profile and in vitro biological activity

The circular economy is gaining attention around the world as a sustainable approach to tackling environmental problems, promoting more responsible management of resources. The aim of this work is the valorization of grape pomace as a waste product of agrifood chain. We prepared decoction (DC), ultrasound-assisted and microwave-assisted extracts (UAE and MAE respectively) of grape pomace, determining their phytochemical profile (using HPLC-ESI-Q-TOF-MS), antioxidant activity and enzyme inhibitory effects. Then, the results were compared with those of raisins and several edible berries already present in the market. Grape pomace extracts presented the highest total phenolic content (62-68 mg gallic acid equivalents/g; mg GAE/g), whereas the concentrations in the other berries were 4-43 mg GAE/g. These results were in agreement with the higher antioxidant activity and tyrosinase inhibition observed in grape pomace compared with the other berries, except for the metal chelating activity. The main compounds in grape pomace extracts were flavonoids (particularly quercetin glycosides), followed by organic acids (citric, isocitric and gallic acids). These results open new perspectives in the development of food supplements and nutraceuticals based on grape pomace extracts.

Mechanistic in vitro study of the effect of Cucurbita moschata (Cucurbitaceae) on carbohydrate digestive enzymes

Diabetes is marked by postprandial hyperglycemia (PHG), an abnormal rise in blood glucose after meals. A key therapeutic goal to reduce PHG is the inhibition of α-amylase (αAM) and α-glucosidase (αGL), enzymes that break down carbohydrates into sugars. Cucurbita moschata has been shown to inhibit both enzymes. However, its inhibition mechanism has not been explored. This study investigated the in vitro inhibition mechanisms of αAM and αGL and conducted a metabolomic analysis of C. moschata (edible part) water-extract (CME), aiming to preliminarily identify its bioactive compounds (BCs). The inhibitory mechanisms were determined using Lineweaver-Burk plots. The BCs were identified and quantified using HPLC-QTOF-MS, employing both targeted and untargeted metabolomic approaches. CME had a significant higher effect (p < 0.05) on αAM activity than against αGL with IC50 of 28.99 and 698.42 mg/mL, respectively. The extract showed mixed and uncompetitive type inhibitions on αAM and αGL, respectively. The lowest inhibition constant (Ki) was 47.68 mg/mL on αAM activity at 20 mg/mL. Untargeted metabolic profiling by UPLC-MS-ESI-QTOF putatively identified 30 compounds in CME, such as amino acids, vitamins, phytohormones, fatty acids, cucurbitacins and phenolic acids, and flavonoids. Functional analysis of CME identified significant pathways, including pantothenate and CoA biosynthesis and phenylpropanoids, among others. The targeted analysis by UPLC-MS-ESI-QqQ allowed us to identify 12 compounds, with l-phenylalanine, p-hydroxybenzoic, and p-coumaric acid as majors. This study demonstrated the inhibitory potential of CME on αAM and αGL activities, which may be attributed to its metabolites. Thus, this plant represents a valuable source of BC against PHG. Practical Application: The research highlights that Cucurbita moschata has significant potential in managing postprandial hyperglycemia in diabetic patients by inhibiting enzymes like α-amylase and α-glucosidase. In addition, the identification of its compounds emphasizes its importance as a source of bioactive compounds. Therefore, C. moschata could be effectively utilized in the development of nutraceuticals or as an ingredient in functional foods specifically designed for postprandial hyperglycemia management. Thus, integrating C. moschata as part of the daily diet could offer patients with diabetes a natural alternative to control their blood glucose levels after eating.

Research Progress on the Mechanism for Improving Glucose and Lipid Metabolism Disorders Using Phenolic Acid Components from Medicinal and Edible Homologous Plants

Glucose and lipid metabolism disorders are the core pathological mechanism of a variety of metabolic diseases, and the incidence of related diseases is increasing year by year, which seriously threatens human life and health. Traditional Chinese medicine with medicinal and edible properties refers to Chinese medicinal resources that have both medicinal and edible characteristics. Due to its safety and its health-promoting and medicinal functions, traditional Chinese medicine has received increasing attention in the development of functional health foods. Phenolic acids are important secondary metabolites that are ubiquitous in medicinal and edible homologous plants, and the regulation of glycolipid metabolism is an important activity and plays a key role in many diseases. In this paper, we focus on the alleviation of glycolipid disorders using MEHH phenolic acids, which regulate glucose metabolism and lipid metabolism, improve insulin resistance, inhibit inflammatory responses, alleviate oxidative stress, and regulate intestinal flora; additionally, we summarize the mechanism in order to provide a reference for MEHH phenolic acids in the treatment of glycolipid metabolism diseases.

Polyphenols in foods: a potential strategy for preventing and managing the postprandial hyperglycemic response

Type 2 diabetes mellitus (T2DM) is a significant health risk worldwide, and effective management strategies are needed. Polyphenols exhibit diverse biological functions, are abundant in various plants, and influence carbohydrate digestion and absorption. This review provides a comprehensive overview of clinical evidence regarding the relationship between dietary polyphenols and the postprandial hyperglycemic response. Human intervention studies have demonstrated the benefits of polyphenol-rich foods in improving glucose and insulin metabolism, underscoring their role in preventing T2DM. These findings highlight the potential of polyphenol-rich foods for managing hyperglycemia and mitigating T2DM risk and provide insight into effective dietary strategies for glycemic control and overall health.

Phenolic content of Thai Bao mango peel and its in-vitro antioxidant, anti-cholinesterase, and antidiabetic activities

Plant phenolics have been known for various biological activities. This study aims to extract and examine the presence of phenolics in Bao mango (Mangifera indica L. var.) peel ethanolic extract (MPE). Further, antioxidant, anti-diabetic (α-amylase, and α-glucosidase inhibitory activity), and anti- Alzheimer's disease (AD) (acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase (BACE-1) inhibitory activity) efficacy of MPE were determined. The results indicated that mangiferin (8755.89 mg/ 100 g extract) was the major phenolic compound in MPE. An antioxidant mechanism revealed that MPE had a higher radical scavenging ability (4266.70 µmol TE/g extract) compared to reducing power (FRAP) or oxygen radical absorption capacity (ORAC). Further in-vitro enzyme inhibitory assay against diabetic and AD involved enzymes showed that MPE had stronger inhibitory action against an enzyme involved in diabetes compared to their standard drug (Acarbose) (P < 0.05). While a lower IC50 value was observed against AD-involved enzymes compared to their standard drug (donepezil) (P < 0.05). The results show that Thai Bao mango peel byproduct can be a potential source of nutraceuticals to lower diabetes and improve cognitive health.

Structure-function relationships in (poly)phenol-enzyme binding: Direct inhibition of human salivary and pancreatic α-amylases

(Poly)phenols inhibit α-amylase by directly binding to the enzyme and/or by forming starch-polyphenol complexes. Conventional methods using starch as the substrate measure inhibition from both mechanisms, whereas the use of shorter oligosaccharides as substrates exclusively measures the direct interaction of (poly)phenols with the enzyme. In this study, using a chromatography-based method and a short oligosaccharide as the substrate, we investigated the detailed structural prerequisites for the direct inhibition of human salivary and pancreatic α-amylases by over 50 (poly)phenols from the (poly)phenol groups: flavonols, flavones, flavanones, flavan-3-ols, polymethoxyflavones, isoflavones, anthocyanidins and phenolic acids. Despite being structurally very similar (97% sequence homology), human salivary and pancreatic α-amylases were inhibited to different extents by the tested (poly)phenols. The most potent human salivary α-amylase inhibitors were luteolin and pelargonidin, while the methoxylated anthocyanidins, peonidin and petunidin, significantly blocked pancreatic enzyme activity. B-ring methoxylation of anthocyanidins increased inhibition against both human α-amylases while hydroxyl groups at C3 and B3' acted antagonistically in human salivary inhibition. C4 carbonyl reduction, or the positive charge on the flavonoid structure, was the key structural feature for human pancreatic inhibition. B-ring glycosylation did not affect salivary enzyme inhibition, but increased pancreatic enzyme inhibition when compared to its corresponding aglycone. Overall, our findings indicate that the efficacy of interaction with human α-amylase is mainly influenced by the type and placement of functional groups rather than the number of hydroxyl groups and molecular weight.

Potential anti-obesity effect of saponin metabolites from adzuki beans: A computational approach

In contrast to its widespread traditional and popular culinary use to reduce weight, Vigna angularis (adzuki beans) was not subjected to sufficient scientific scrutiny. Particularly, its saponins whose role was never investigated before to unveil the beans' antidiabetic and anti-obesity effects. Four vital pancreatic and intestinal carbohydrate enzymes were selected to assess the potency of the triterpenoidal saponins of V. angularis to bind and activate these proteins through high-precision molecular modeling and dynamics mechanisms with accurate molecular mechanics Generalized Born Surface Area (MMGBSA) energy calculations; thus, recognizing their anti-obesity potential. Our results showed that adzukisaponin VI and adzukisaponin IV were the best compounds in the α-amylase and α-glucosidase enzymatic grooves, respectively. Adzukisaponin VI and angulasaponin C were the best fitting in the N-termini of sucrase-isomaltose (SI) enzyme, and angulasaponin C was the best scoring compound in maltase-glucoamylase C-termini. All of them outperformed the standard drug acarbose. These compounds in their protein complexes were selected to undergo molecular simulations of the drug-bound protein compared to the apo-protein through 100 ns, which confirmed the consistency of binding to the key amino acid residues in the four enzyme pockets with the least propensity of unfolding. Detailed analysis is given of the different polar and hydrophobic binding interactions of docked compounds. While maltase-adzukisaponin VI complex scored the lowest MMGBSA free energy of -67.77 Kcal/mol, α-amylase complex with angulasaponin B revealed the free binding energy of -74.18 Kcal/mol with a dominance of van der Waals energy (ΔEVDW) and the least change from the start to the end of the simulation time. This study will direct researchers to the significance of isolating the pure adzuki saponin components to conduct future in vitro and in vivo experimental works and even clinical trials.

Phenolic profiles and in vitro biochemical properties of Thai herb ingredients for chronic diseases prevention

Traditional remedies using natural ingredients have been handed down over generations, providing collective information for the development of modern therapeutics. These natural products have a long history of safe consumption with curative effects but lack of scientific-based evidence hinders the mass production of new remedies containing active ingredients with particular medicinal properties. This research investigated the phenolic profiles and biochemical properties of 29 herbal ingredients identified in two traditional Thai remedies, Prasachandaeng (PSCD) and Chantaharuethai (CHRT), and their effectiveness in combating chronic diseases. These two traditional remedies are used to reduce fever but some ingredients have been previously reported to possess other health-related properties. Statistical analysis by TOPSIS indicated that Biancaea sappan (L.) Tod. extract exhibited the highest overall closeness coefficient (C) score analyzed from all variables including total phenolic contents, antioxidant potentials, and enzyme inhibitions. Bouea macrophylla Griff. extract showed potential as an effective agent against diabetes through inhibition of two carbohydrate degrading enzymes, α-glucosidase and α-amylase, while Dischidia major (Vahl) Merr. showed strong properties as an anti-angiotensin-converting enzyme, leading to the control of hypertension. Dracaena cochinchinensis (Lour.) S.C. Chen effectively controlled the progression of Alzheimer's disease through the inhibition of cholinergic and β-amyloid formation enzymes. These results can be used as preliminary data for the development of new remedies to prevent or treat particular chronic diseases.

Graphene oxide exposure alters gut microbial community composition and metabolism in an in vitro human model

Graphene oxide (GO) nanomaterials have unique physicochemical properties that make them highly promising for biomedical, environmental, and agricultural applications. There is growing interest in the use of GO and extensive in vitro and in vivo studies have been conducted to assess its nanotoxicity. Although it is known that GO can alter the composition of the gut microbiota in mice and zebrafish, studies on the potential impacts of GO on the human gut microbiome are largely lacking. This study addresses an important knowledge gap by investigating the impact of GO exposure- at low (25 mg/L) and high (250 mg/L) doses under both fed (nutrient rich) and fasted (nutrient deplete) conditions- on the gut microbial communitys' structure and function, using an in vitro model. This model includes simulated oral, gastric, small intestinal phase digestion of GO followed by incubation in a colon bioreactor. 16S rRNA amplicon sequencing revealed that GO exposure resulted in a restructuring of community composition. 25 mg/L GO induced a marked decrease in the Bacteroidota phylum and increased the ratio of Firmicutes to Bacteroidota (F/B). Untargeted metabolomics on the supernatants indicated that 25 mg/L GO impaired microbial utilization and metabolism of substrates (amino acids, carbohydrate metabolites) and reduced production of beneficial microbial metabolites such as 5-hydroxyindole-3-acetic acid and GABA. Exposure to 250 mg/L GO resulted in community composition and metabolome profiles that were very similar to the controls that lacked both GO and digestive enzymes. Differential abundance analyses revealed that 3 genera from the phylum Bacteroidota (Bacteroides, Dysgonomonas, and Parabacteroides) were more abundant after 250 mg/L GO exposure, irrespective of feed state. Integrative correlation network analysis indicated that the phylum Bacteroidota showed strong positive correlations to multiple microbial metabolites including GABA and 3-indoleacetic acid, are much larger number of correlations compared to other phyla. These results show that GO exposure has a significant impact on gut microbial community composition and metabolism at both low and high GO concentrations.

Identification and Structure–Activity Relationship of Recovered Phenolics with Antioxidant and Antihyperglycemic Potential from Sugarcane Molasses Vinasse

Sugarcane molasses vinasse is the residue of the fermentation of molasses and the water and soil environmental pollutants from distilleries. However, its recycling value has been neglected. The chemical analysis of the molasses vinasse led to the isolation of a new benzoyl chloride called 2,3,4-trihydroxy-5-methoxy benzoyl chloride, as well as thirteen known compounds, including six benzoic acids. The structure of the new benzoyl chloride was elucidated on the basis of extensive spectroscopic analysis. The antioxidant activity of all isolated compounds was measured using the ORAC assay. Moreover, we compared the cellular antioxidant activity (CAA) and inhibitory activity against α-amylase and α-glucosidase for structure–activity analysis. The results showed that only vanillic acid had CAA (8.64 μmol QE/100 μmol in the no PBS wash protocol and 6.18 μmol QE/100 μmol in the PBS wash protocol), although other benzoic acid derivatives had high ORAC values ranging between 1879.9 and 32,648.1 μmol TE/g. Additional methoxy groups at the ortho-positions of the p-hydroxy group of benzoic acids enhanced the inhibition of α-glucosidase but reduced the ORAC activity unless at the para-position. This work indicated that phenolics, especially phenolic acids in the sugarcane molasses vinasse, possessed potential antioxidant and antihyperglycemic activity, which improved the utilization rate of resources and reduced the discharge of pollutants.