Anti‐hyperglycaemic effects of Burdock ( Arctium lappa L .) leaf flavonoids through inhibiting α‐amylase and α‐glucosidase

Shiitake polysaccharides acted as a non-competitive inhibitor to α-glucosidase and inhibited glucose transport of digested starch from Caco-2 cells monolayer

The inhibition mechanism of shitake mushroom polysaccharides (Lentinula edodes polysaccharides, LEP) against α-glucosidase was studied by enzyme kinetic assay, fluorescence quenching and molecular docking. The effect of LEP on glucose transport of digested starch was investigated via an in vitro digestion/Caco-2 transwell model. LEP exhibited a stronger inhibiting effect (IC50 = 0.66 mg/mL) than acarbose and presented a non-competitive inhibition mechanism. The interaction between LEP and α-glucosidase primarily involved electrostatic interaction and hydrogen bonding. Molecular docking modelling showed that the four structures of LEP were bound to the allosteric tunnel or adjacent pocket of α-glucosidase via electrostatic force and hydrogen bonds. The (1 → 6)-linkages in LEP structures favoured its binding affinity to the α-glucosidase. The α-glucosidase inhibiting activity of LEP was also found to emanate from the reduction in glucose transport of digested starch as deducted from the in vitro digestion/Caco-2 transwell data. The release of glucose from digested starch cooked with LEP was significantly reduced (33.7%) compared to the digested starch without LEP. The findings from the current study suggest that LEP could be a promising ingredient to inhibit α-glucosidase activity as well as control the level of postprandial blood glucose when incorporated into starchy foods.

Alpha-glucosidase inhibitory activities of astilbin contained in Bauhinia strychnifolia Craib. stems: an investigation by in silico and in vitro studies

INTRODUCTION

Bioactive compounds from traditional medicines are good alternatives to standard diabetes therapies and may lead to new therapeutic discoveries. The stems of Bauhinia strychnifolia Craib. (BC) have a possible antihyperglycemic effect; However, the extraction of astilbin from BC has never been recorded in alpha-glucosidase inhibitory activities.

METHODS

Using liquid chromatography-mass spectrometry (LC-MS/MS), 32 compounds were detected in the BC extract. The screening was based on peak area. Seven compounds found. PASS recognized all seven compounds as potential alpha-glucosidase (AG) inhibitors. Astilbin and quercetin 3-rhamnoside were the most likely inhibitors of AG. Arguslab, AutoDock, and AutoDock Vina investigated the binding of the two compounds and AG. The binding stability was confirmed by molecular dynamics (MD). In addition, the optimum solvent extraction was studied via CosmoQuick, and extracts were examined with ¹H-NMR prior to testing with AG.

RESULTS

All three software programs demonstrated that both compounds inhibit AG more effectively than acarbose. According to the sigma profile, THF is recommended for astilbin extraction. The BC extract with THF showed outstanding AG inhibitory action with an IC₅₀ of 158 ± 1.30 µg mL-1, which was much lower than that of the positive control acarbose (IC₅₀ = 190 ± 6.97 µg mL-1). In addition, astilbin from BC was found to inhibit AG strongly, IC50 = 22.51 ± 0.70 µg mL-1 through the extraction method of large-scale astilbin with THF has the best extraction capacity compared to other solvents, hence the initial stage of extraction employs THF to extract and precipitate them with ethyl acetate and water.

CONCLUSION

In silico and in vitro studies reveal that astilbin inhibits AG and is superior to acarbose, validating its promise as an AG inhibitor. Overall, astilbin was the most bioactive component of BC for antidiabetic action.

Comparative study of phenolic compounds reveals a positive relationship between astringency and the phenolic composition in table grape varieties

Phenolic compounds and their derivatives play a major role in the intensity and characteristics of grape (Vitis vinifera) astringency. The present study investigated the relationship between phenolic composition and astringency of six commercial table grape varieties (two of each white-, red-, and black-skinned). Qualitative and quantitative liquid chromatography-mass spectrometry analysis was used to identify the variety-specific phenolic profiles in the skins and total astringency intensity was assessed and described by a trained sensory panel. Thirty phenolic compounds were identified among the six varieties. Principal component analysis of the phenolic profiles revealed that the intensity of astringency of grape skin was positively correlated with catechin, epicatechin, epicatechin-3-O-gallate, and proanthocyanidin dimers B1, B2, and B3. A further orthogonal partial least-squares discrimination analysis of these compounds showed that catechin was the substance most strongly and positively correlated (R = 0.904) with grape skin astringency. PRACTICAL APPLICATION: This study provided a better understanding of the relationships between phenolic composition and table grape astringency and highlighted a potential metabolic marker that could be used as a predictor for the complex astringency sensory attributes of table grape berries.

Phytochemical Composition and Biological Activities of Arctium minus (Hill) Bernh.: A Potential Candidate as Antioxidant, Enzyme Inhibitor, and Cytotoxic Agent

Arctium minus (Hill) Bernh. (Asteraceae), which has a wide distribution area in Turkey, is a medicinally important plant. Eighty percent methanol extracts of the leaf, flower head, and root parts of A. minus were prepared and their sub-fractions were obtained. Spectrophotometric and chromatographic (high-performance liquid chromatography) techniques were used to assess the phytochemical composition. The extracts were evaluated for antioxidant activity by diphenyl-2-picrylhydrazil radical (DPPH^●), 2,2′-Azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS^●+) radical scavenging, and β-carotene linoleic acid bleaching assays. Furthermore, the extracts were subjected to α-amylase, α-glucosidase, lipoxygenase, and tyrosinase enzyme inhibition tests. The cytotoxic effects of extracts were investigated on MCF-7 and MDA-MB-231 breast cancer cell lines. The richest extract in terms of phenolic compounds was identified as the ethyl acetate sub-fraction of the root extract (364.37 ± 7.18 mg_GAE/g_extact). Furthermore, chlorogenic acid (8.855 ± 0.175%) and rutin (8.359 ± 0.125%) were identified as the primary components in the leaves’ ethyl acetate sub-fraction. According to all methods, it was observed that the extracts with the highest antioxidant activity were the flower and leaf ethyl acetate fractions. Additionally, ABTS radical scavenging activity of roots’ ethyl acetate sub-fraction (2.51 ± 0.09 mmol/L Trolox) was observed to be as effective as that of flower and leaf ethyl acetate fractions at 0.5 mg/mL. In the β-carotene linoleic acid bleaching assay, leaves’ methanol extract showed the highest antioxidant capacity (1422.47 ± 76.85) at 30 min. The enzyme activity data showed that α-glucosidase enzyme inhibition of leaf dichloromethane extract was moderately high, with an 87.12 ± 8.06% inhibition value. Lipoxygenase enzyme inhibition was weakly detected in all sub-fractions. Leaf methanol extract, leaf butanol, and root ethyl acetate sub-fractions showed 99% tyrosinase enzyme inhibition. Finally, it was discovered that dichloromethane extracts of leaves, roots, and flowers had high cytotoxic effects on the MDA-MB-231 cell line, with IC50 values of 21.39 ± 2.43, 13.41 ± 2.37, and 10.80 ± 1.26 µg/mL, respectively. The evaluation of the plant extracts in terms of several bioactivity tests revealed extremely positive outcomes. The data of this study, in which all parts of the plant were investigated in detail for the first time, offer promising results for future research.

Burdock (Arctium lappa L.) leaf flavonoids rich in morin and quercetin 3-O-rhamnoside ameliorate lipopolysaccharide-induced inflammation and oxidative stress in RAW264.7 cells

In this study, the anti-inflammatory and antioxidant activities and mechanism of burdock leaf flavonoids (BLF) on LPS-stimulated inflammation in RAW264.7 macrophage cells were explored. We have observed that BLF and main effective components morin and quercetin 3-O-rhamnoside pretreatment significantly inhibited LPS-stimulated inflammatory activation of RAW264.7 cells by lowering the levels of NO, PGE2, TNF-α, and IL-6 production (p < .05). At the same time, BLF not only had potent free radical scavenging ability in vitro (DPPH: 2025.33 ± 84.15 μmol Trolox/g, ABTS: 159.14 ± 5.28 μmol Trolox/g, and ORAC: 248.72 ± 9.74 μmol Trolox/g) but also effectively ameliorated cellular oxidative stress status by restoring the decreased activity of antioxidant enzymes (SOD, CAT, and GSH-Px) and decreasing the elevated levels of ROS and TBARS in LPS-stimulated macrophages (p < .05). The western blot analysis indicated that BLF and main components morin and quercetin 3-O-rhamnoside mainly inhibited LPS-stimulated inflammation by reducing the iNOS and COX-2 protein expression, decreasing cellular ROS, and blocking the activation of NF-κB signaling pathway in macrophages. Our results collectively imply that BLF could be used as a new type of functional factor for the development of antioxidant and anti-inflammatory foods.

Mechanistic insights on burdock (Arctium lappa L.) extract effects on diabetes mellitus

Diabetes mellitus (DM) type 2 is amongst the most common chronic diseases, being responsible for various problems in humans and contributing to increased mortality rates worldwide. Fructooligosaccharide, which can be produced from the roots of burdock (Arctium lappa L.), has been shown to have a wide range of pharmacological proprieties, including antiviral, anti-inflammatory, hypolipidemic, and antidiabetic effects. Moreover, burdock also contains chlorogenic acid, which has been used in traditional medicine as an antioxidant. Considering its natural origin and minimal toxicity, burdock fructooligosaccharides (BFO) has gained considerable attention from researchers owing its wide, efficient, and beneficial action against DM. Although the effectiveness of fructooligosaccharide and chlorogenic acid has been extensively discussed, limited information is available on the application of burdock for DM treatment. In this review, we discuss the beneficial contributions, and the recent in vitro and in vivo analytical findings on A. lappa extract as DM therapy.

LC-ESI-QTOF/MS characterization of antimicrobial compounds with their action mode extracted from vine tea (Ampelopsis grossedentata) leaves

Vine tea (Ampelopsis grossedentata) is a tea plant cultivated south of the Chinese Yangtze River. It has anti-inflammatory properties and is used to normalize blood circulation and detoxification. The leaves of vine tea are the most abundant source of flavonoids, such as dihydromyricetin and myricetin. However, as the main bioactive flavonoid in vine tea, dihydromyricetin was the main focus of previous research. This study aimed to explore the antibacterial activities of vine tea against selected foodborne pathogens. The antimicrobial activity of vine tea extract was evaluated by the agar well diffusion method. Cell membrane integrity and bactericidal kinetics, along with physical damage to the cell membrane, were also observed. The extract was analyzed using a high-performance liquid chromatography-diode array detector (HPLC-DAD), and the results were confirmed using a modified version of a previously published method that combined liquid chromatography and electrospray-ionized quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF/MS). Cell membrane integrity and bactericidal kinetics were determined by releasing intracellular material in suspension and monitoring it at 260 nm using an ultraviolet (UV) spectrophotometer. A scanning electron microscope (SEM) was used to detect morphological alterations and physical damage to the cell membrane. Six compounds were isolated successfully: (1) myricetin (C15H10O8), (2) myricetin 3-O-rhamnoside (C21H20O12), (3) 5,7,8,3,4-pentahydroxyisoflavone (C15H10O7), (4) dihydroquercetin (C15H12O7), (5) 6,8-dihydroxykaempferol (C15H10O8), and (6) ellagic acid glucoside (C20H16O13). Among these bioactive compounds, C15H10O7 was found to have vigorous antimicrobial activity against Bacillus cereus (AS11846) and Staphylococcus aureus (CMCCB26003). A dose-dependent bactericidal kinetics with a higher degree of absorbance at optical density 260 (OD260) was observed when the bacterial suspension was incubated with C15H10O7 for 8 h. Furthermore, a scanning electron microscope study revealed physical damage to the cell membrane. In addition, the action mode of C15H10O7 was on the cell wall of the target microorganism. Together, these results suggest that C15H10O7 has vigorous antimicrobial activity and can be used as a potent antimicrobial agent in the food processing industry.