Α-glucosidase Inhibitory Activity Research Articles

Microspheres as carriers of sea buckthorn carotenoids and tocols with antidiabetic potential: Effect of biopolymers, cross-linking and storage

The bioactivity of carotenoids and tocols is limited by their instability, hydrophobicity, and low bioavailability. Hence, the study aimed to design microspheres from sea buckthorn juice by ionotropic gelation to increase stability, ensure high content of carotenes, xanthophylls, tocopherols and tocotrienols and their antidiabetic activity. The effects of biopolymers, cross-linking and storage on the carotenoid and tocol profile of microspheres (identified and quantified by LC-PDA-QTOF-ESI-MS and UPLC-FL methods) and their in vitroα-amylase and α-glucosidase inhibitory activity were investigated. Microspheres containing sodium alginate/κ-carrageenan (4:1) had significantly high content of carotenoids and tocols, and antihyperglycemic activity (p < 0.05). The two-step cross-linking (1-calcium chloride, 2-chitosan) provided a 17% higher carotenoid content. Cross-linking with CaCl2 promoted high content of tocopherols but stability protection was provided by sodium alginate and CaCl2/chitosan (9:1) cross-linking (1.7-fold decrease in instability). The encapsulation using newly designed combinations of biopolymers and cross-linking could be an effective strategy to increase the stability and bioactivities of microspheres as nutraceuticals and smart food.

Ellagitannins from pomegranate (Punica granatum L.) flower with xanthine oxidase and α-glucosidase inhibitory activities

In the course of our research on utilizing edible flower resources to promote health, five ellagitannins (1–5) were isolated from pomegranate (Punica granatum L.) flower by bioassay-guided fractionation. Among them, mallotusinin (1) and tercatain (2) were first isolated from pomegranate flower, and punicatannin D (4) was an unprecedented compound. Compounds 1–3 exhibited significant xanthine oxidase (XO) inhibitory activity compared with allopurinol, and a potent inhibition on α-glucosidase that was superior to acarbose was observed for compounds 1–4. The XO inhibitory activity is positively correlated with the amount of galloyl moiety (3 > 2 > 1). Presenting tetrahydroxydibenzofuranoyl substituent or increasing the number of galloyl group enhanced the inhibition capacity of α-glucosidase (1 > 3 > 2). The inhibitory mechanism was further clarified in terms of kinetic studies and molecular docking. This study revealed that the ellagitannins present in pomegranate flower might be promising functional food ingredients with anti-hyperuricemia and anti-hyperglycemia properties.

Polyphenols from Tropical Almond Leaves (Terminalia catappa L.): Optimized Extraction Conditions and α-Glucosidase Inhibitory Activity

The purpose of this study was to find the optimal conditions for extracting polyphenols from Vietnamese tropical almond leaves (Terminalia catappa L.) and to assess the anti-diabetic activities of the resulting extract. The polyphenol extraction from Vietnamese tropical almond leaves was optimized using the response surface methodology. A rotatable central composite design (RCCD) with three variables (ethanol concentration, temperature, and extraction time), consisting of 21 experimental runs with three replicates at the center, minimal, and maximal factorial points was applied to describe the experimental data. The experimental results properly confirmed the constructed model (R2 = 0.8337). The optimized conditions were as follows: ethanol concentration of 62.76%, a temperature of 62.2°C, and an extraction time of 70 minutes. Five extractions were performed in parallel at the optimized conditions to validate the model. The experimental values highly agreed with the predicted value. The extract powder has powerful effects against the α-glucosidase activity and can develop as a novel natural anti-diabetic agent.

Biological Activity Evaluation of Olive, Grape, and Fig at Various Mixing Ratios

Purpose: This study aimed to evaluate the antioxidation and enzymatic activity-related qualities of four mixtures prepared with different mixing ratios of olives (O), grapes (V), and figs (F), which are representative ingredients of the Mediterranean diet. Methods: Following mixtures were prepared: olives–figs (OF), grapes–figs (VF), and olives–grapes–figs (OVF). For mixture preparation, the ingredients were mixed in following ratios: olives-to-grapes, olives-to-figs, and grapes-to-figs at ratios of 1:1 (30 g of each) as well as olives-to-grapes-to-figs at a ratio of 1:1:1 (20 g of each). The antioxidant (total polyphenol and flavonoid contents along with 2,2-diphenyl-1-picrylhydrazyl [DPPH] and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) [ABTS] radical scavenging) and enzymatic (α-glucosidase inhibitory and angiotensin-converting enzyme [ACE] inhibitory) activities of the four aforementioned mixtures were measured. Results: OV and OVF mixtures showed the highest total polyphenol (27.25±0.22 mg TAE/g) and flavonoid contents (27.9 ± 2.14 mg QE/g), respectively. DPPH radical scavenging ability was highest in OV (92.86 ± 0.17%). The highest ABTS radical scavenging activity was registered in the OVF mixture (42.88±1.19%). α-glucosidase and ACE inhibitory activity measurements were highest in the OVF mixture (79.75±0.15% and 88.61±0.08%, respectively). Conclusion: Highest physiological activity levels (i.e., anti-oxidation and enzymatic activity) were observed in the olive, grape, and fig (1:1:1) mixture, hence, its regular consumption could improve metabolic syndrome.

Metabolomics Characterization of Phenolic Compounds in Colored Quinoa and Their Relationship with In Vitro Antioxidant and Hypoglycemic Activities.

Chenopodium quinoa Willd. is rich in phenolic compounds and exhibits diverse biological activities. Few studies have focused on the effect of colored quinoa's phenolic profile on potential biological activity. This study used a UPLC-MS/MS-based metabolomic approach to examine the quinoa phenolics and their association with in vitro antioxidant and hypoglycemic properties. In total, 430 polyphenols, mainly phenolic acids, flavonoids, and flavonols, were identified. Additionally, 121, 116, and 148 differential polyphenols were found between the white and black, white and red, and black and red comparison groups, respectively; 67 polyphenols were screened as shared key differential metabolites. Phenylalanine, tyrosine, and the biosynthesis of plant secondary metabolites were the main differently regulated pathways. Black quinoa had better total phenolic contents (643.68 mg/100 g DW) and antioxidant capacity, while white quinoa had better total flavonoid contents (90.95 mg/100 g DW) and in vitro α-amylase (IC50 value of 3.97 mg/mL) and α-glucosidase (IC50 value of 1.08 mg/mL) inhibition activities. Thirty-six polyphenols, including epicatechin and linarin, etc., were highly correlated with in vitro antioxidant activity, while six polyphenols, including tiliroside and chrysoeriol, etc., were highly correlated with in vitro hypoglycemic activity. This study may provide important information for colored quinoa resources to develop their healthy food applications.

Synthesis of Competitive and Noncompetitive Inhibitors of Alpha-Glucosidase and Anticancer Agents.

Imidazoles and phenylthiazoles are an important class of heterocycles that demonstrate a wide range of biological activities against various types of cancers, diabetes mellitus and pathogenic microorganisms. The heterocyclic structure having oxothiazolidine moiety is an important scaffold present in various drugs, with potential for enzyme inhibition. In an effort to discover new heterocyclic compounds, we synthesized 26 new 4,5-diphenyl-1H-imidazole, phenylthiazole, and oxothiazolidine heterocyclic analogues that demonstrated potent α-glucosidase inhibition and anticancer activities. Majority of the compounds noncompetitively inhibited α-glucosidase except for two that exhibited competitive inhibition of the enzyme. Docking results suggested that the noncompetitive inhibitors bind to an apparent allosteric site on the enzyme located in the vicinity of the active site. Additionally, the analogues also exhibited significant activity against various types of cancers including non-small lung cancer. Since tubulin protein plays an important role in the pathogenesis of non-small lung cancer, molecular docking with one of the target compounds provided important clues to its binding mode. The current work on imidazoles and phenylthiazole derivatives bears importance for designing of new antidiabetic and anticancer drugs.

α-Glucosidase Inhibitory Components from Garcinia pedunculata Fruits.

From Garcinia pedunculata Roxb. fruits, two undescribed aromatic compounds including a benzofuran and a depsidone derivative, and a new natural product, together with four known compounds were isolated. Through the analysis of spectroscopic data, high resolution mass spectrum and calculated nuclear magnetic resonance, their structures were determined. The α-glucosidase inhibitory activity of the isolates was evaluated. And compound 3 exhibited a moderate inhibitory effect on α-glucosidase. The molecular docking of compound 3 was performed to elucidate the interaction with α-glucosidase.

Widely targeted metabolomics-based analysis of the impact of L. plantarum and L. paracasei fermentation on rosa roxburghii Tratt juice

Rosa roxburghii Tratt fruits (RRT) exhibit extremely high nutritional and medicinal properties due to its unique phytochemical composition. Probiotic fermentation is a common method of processing fruits. Variations in the non-volatile metabolites and bioactivities of RRT juice caused by different lactobacilli are not well understood. Therefore, we aimed to profile the non-volatile components and investigate the impact of L. plantarum fermentation (LP) and L. paracasei fermentation (LC) on RRT juice (the control, CG). There were both similarities and differences in the effects of LP and LC on RRT juice. Both of the two strains significantly increased the content of total phenolic, total flavonoid, and some bioactive compounds such as 2-hydroxyisocaproic acid, hydroxytyrosol and indole-3-lactic acid in RRT juice. Interestingly, compared with L. paracasei, L. plantarum showed better ability to increase the content of total phenolic and these valuable compounds, as well as certain bioactivities. The antioxidant capacity and α-glucosidase inhibitory activity of RRT juice were notably enhanced after the fermentations, whereas its cholesterol esterase inhibitory activity was reduced significantly. Moreover, a total of 1466 metabolites were identified in the unfermented and fermented RRT juices. There were 278, 251 and 134 differential metabolites in LP vs CG, LC vs CG, LC vs LP, respectively, most of which were upregulated. The key differential metabolites were classified into amino acids and their derivatives, organic acids, nucleotides and their analogues, phenolic acids and alkaloids, which can serve as potential markers for authentication and discrimination between the unfermented and lactobacilli fermented RRT juice samples. The KEGG enrichment analysis uncovered that metabolic pathways, purine metabolism, nucleotide metabolism and ABC transporters contributed mainly to the formation of unique composition of fermented RRT juice. These results provide good coverage of the metabolome of RRT juice in both unfermented and fermented forms and also provide a reference for future research on the processing of RRT or other fruits.

A comparison of phenolic compounds, antioxidant activity, and α-glucosidase inhibitory activities of apple chips dried and fried by vacuum combined infrared radiation

In this study, the effects of different drying (180–325 W and 100–400 mmHg) and frying (250–350 W and 400 mmHg) parameters on phenolic compounds, bioaccessibilities, antioxidant activities, and α-glucosidase inhibitory activities of apple chips dried and fried by vacuum-combined infrared radiation were investigated. Catechin (12.15–34.48 mg/kgDM), epicatechin (34.33–137.07 mg/kgDM), procyanidin B1 (14.07–30.05 mg/kgDM), procyanidin B2 (48.10–95.76 mg/kgDM), procyanidin C1 (14.95–42.97 mg/kgDM), chlorogenic acid (262.70–397.97 mg/kgDM), and rutin (0–5.94 mg/kgDM) were identified in apple chips. The phenolic content of apple chips increased with increasing infrared power during the drying and frying process. The phenolic contents of fried apple chips were generally higher than dried apple chips. However, the bioaccessibility rates of total flavan-3-ols in dried apple chips were higher than those of fried apple chips. It was determined that the initial total phenolic, flavonoid, and flavan-3-ol contents and antioxidant activity levels of the samples decreased after in-vitro gastrointestinal digestion. It was determined that all drying and frying samples showed higher α-glucosidase inhibitory activities (15.52–28.77 mg/mL) compared to acarbose (30.87 mg/mL). The apple chips dried and fried by infrared radiation had higher phenolic content, antioxidant activity, bioaccessibility, and α-glucosidase inhibitory activity than their counterparts (convectional drying and deep-fat frying, respectively). Vacuum-combined infrared drying and frying is a promising method to preserve the phenolic content, antioxidant, and antidiabetic activities of apple chips, especially at high temperature applications. Further research is needed on new designs for the production of fruit chips using infrared radiation and their effects on bioactive components.Graphical abstract

Phytochemical Profiling and Biological Activities of Pericarps and Seeds Reveal the Controversy on "Enucleation" or "Nucleus-Retaining" of Cornus officinalis Fruits.

The fruits of Cornus officinalis are used not only as a popular health food to tonify the liver and kidney, but also as staple materials to treat dementia and other age-related diseases. The pharmacological function of C. officinalis fruits with or without seeds is controversial for treating some symptoms in a few herbal prescriptions. However, the related metabolite and pharmacological information between its pericarps and seeds are largely deficient. Here, comparative metabolomics analysis between C. officinalis pericarps and seeds were conducted using an ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry, and therapeutic effects were also evaluated using several in vitro bioactivity arrays (antioxidant activity, α-glucosidase and cholinesterase inhibitory activities, and cell inhibitory properties). A total of 499 secondary metabolites were identified. Thereinto, 77 metabolites were determined as key differential metabolites between C. officinalis pericarps and seeds, and the flavonoid biosynthesis pathway was identified as the most significantly different pathway. Further, 47 metabolites were determined as potential bioactive constituents. In summary, C. officinalis seeds, which demonstrated higher contents in total phenolics, stronger in vitro antioxidant activities, better α-glucosidase and butyrylcholinesterase inhibitory activities, and stronger anticancer activities, exhibited considerable potential for food and health fields. This work provided insight into the metabolites and bioactivities of C. officinalis pericarps and seeds, contributing to their precise development and utilization.

Inhibitory Activities of Thai Culinary Vegetables against Key Enzymes Relevant to Diabetes Mellitus and the Kinetics of Enzyme Inhibitions

Diabetes mellitus (DM) is one of the most challenging noncommunicable diseases, as it causes significant costs for medical treatment as well as high morbidity and mortality rates. Dietary plants with antidiabetic properties have been explored as an alternative to synthetic medicines to treat DM because of their safety and nutrition. Hence, the objective of the present study was to determine the inhibitory activities of twenty commonly consumed Thai culinary vegetables against α-glucosidase and α-amylase. All vegetables were extracted using deionized water, ethanol, and hexane at 150 rpm and 30°C for 24 hours. The enzyme inhibitory activities were performed using a colorimetric assay. Diverse results for α-glucosidase and α-amylase inhibitory activities were found for all vegetable extracts. The most potent anti-α-glucosidase activity was obtained from the ethanolic extract of Leucaena leucocephala (Lamk.) de Wit with the half maximal inhibitory concentration (IC50) of 13.39 ± 0.14 μg/mL, followed by the aqueous and ethanolic extracts of Polygonum odoratum Lour with IC50 of 25.60 ± 0.42 and 49.03 ± 0.72 μg/mL, respectively. All the samples exhibited mixed, noncompetitive, and uncompetitive inhibition. It can be concluded that the α-glucosidase and α-amylose inhibitory effects of the investigated extracts may be an indicator of antidiabetic potency, and these extracts might potentially be beneficial as functional components for postprandial hyperglycemia treatment.

Rapid screening of the novel bioactive peptides with notable α-glucosidase inhibitory activity by UF-LC-MS/MS combined with three-AI-tool from black beans

This work aimed to propose a rapid method to screen the bioactive peptides with anti-α-glucosidase activity instead of traditional multiple laborious purification and identification procedures. 242 peptides binding to α-glycosidase were quickly screened and identified by bio-affinity ultrafiltration combined with LC-MS/MS from the double enzymatic hydrolysate of black beans. Top three peptides with notable anti-α-glucosidase activity, NNNPFKF, RADLPGVK and FLKEAFGV were further rapidly screened and ranked by the three artificial intelligence tools (three-AI-tool) BIOPEP database, PeptideRanker and molecular docking from the 242 peptides. Their IC50 values were in order as 4.20 ± 0.11 mg/mL, 2.83 ± 0.03 mg/mL, 1.32 ± 0.09 mg/mL, which was opposite to AI ranking, for the hydrophobicity index of the peptides was not included in the screening criteria. According to the kinetics, FT-IR, CD and ITC analyses, the binding of the three peptides to α-glucosidase is a spontaneous and irreversible endothermic reaction that results from hydrogen bonds and hydrophobic interactions, which mainly changes the α-helix structure of α-glucosidase. The peptide-activity can be evaluated vividly by AFM in vitro. In vivo, the screened FLKEAFGV and RADLPGVK can lower blood sugar levels as effectively as acarbose, they are expected to be an alternative to synthetic drugs for the treatment of Type 2 diabetes.

Fermentation of millet bran with Bacillus natto: enhancement of bioactivity levels and the bioactivity of bran extract.

Millet bran (MB), a byproduct of millet production, is rich in functional components but it is underutilized. In recent years, researchers have shown that fermentation can improve the biological activity of cereals and their byproducts. This study used Bacillus natto to ferment millet bran to improve its added value and broaden the application of MB. The bioactive component content, physicochemical properties, and functional activity of millet bran extract (MBE) from fermented millet bran were determined. After fermentation, the soluble dietary fiber (SDF) content increased by 92.0%, the β-glucan content by 164.4%, the polypeptide content by 111.4%, the polyphenol content by 32.5%, the flavone content by 16.4%, and the total amino acid content by 95.4%. Scanning electron microscopy revealed that the microscopic morphology of MBE changed from complete and dense blocks to loosely porous shapes after fermentation. After fermentation, the solubility, water-holding capacity, and viscosity significantly increased and the particle size decreased. Moreover, the glucose adsorption capacity (2.1 mmol g-1), glucose dialysis retardation index (75.3%), and α-glucosidase inhibitory (71.4%, mixed reversible inhibition) activity of the fermented MBE (FMBE) were greater than those of the unfermented MBE (0.99 mmol g-1, 32.1%, and 35.1%, respectively). The FMBE presented better cholesterol and sodium cholate (SC) adsorption properties and the adsorption was considered inhomogeneous surface adsorption. Fermentation increased the bioactive component content and improved the physicochemical properties of MBE, thereby improving its hypoglycemic and hypolipidemic properties. This study not only resolves the problem of millet bran waste but also encourages the development of higher value-added application methods for millet bran. © 2024 Society of Chemical Industry.

Evaluation of Anti--amylase and Anti--glucosidase Activity of Canna x Generalis L.H Bailey &amp; E.Z Bailey Rhizome

Canna x generalis L.H Bailey &amp; E.Z Bailey (CG) has been used as folk medicine to treat different diseases. However, scientific information about the pharmacological effects and chemical composition of this plant is still very limited. This study aims to evaluate for the first time the α-amylase and α-glucosidase inhibitory activity of CG rhizome extracts. The rhizome part of CG was extracted with ethanol and then fractionated with n-hexane, ethyl acetate, and water. The total extract and fractions were evaluated for their inhibitory effects on α-amylase and α-glucosidase enzymes in vitro. The results showed that the ethyl acetate fraction had the strongest inhibitory activity against α-amylase and α-glucosidase with IC50 values of 53.19 ± 2.79 and 95.83 ± 6.26 µg/mL, respectively. Therefore, the rhizome part of the CG plant, especially the ethyl acetate fraction, is a potential natural source for searching for active ingredients to prevent and treat diabetes.&#x0D; &#x0D; &#x0D;

Efficient degradation and enhanced α-glucosidase inhibitory activity of apricot polysaccharides through non-thermal plasma assisted non-metallic Fenton reaction

Dielectric barrier discharge (DBD) was a commonly used non-thermal plasma (CP) technology. This paper aimed to enhance the biological activity of apricot polysaccharides (AP) by using dielectric barrier discharge (DBD-CP) assisted H2O2-VC Fenton reaction for degradation. The degradation conditions were optimized through response surface methodology. The molecular weight (Mw) of degraded apricot polysaccharides (DAP) was 19.71 kDa, which was 7.25 % of AP. The inhibition rate of DAP (2 mg/mL) was 82.8 ± 3.27 %, which was 106.87 % higher than that of AP. DBD-CP/H2O2-VC degradation changed the monosaccharide composition of AP and improved the linearity of polysaccharide chains. In addition, a novel apricot polysaccharide DAP-2 with a Mw of only 6.60 kDa was isolated from DAP. The repeating units of the main chain of DAP-2 were →4)-α-D-GalpA-(1 →, the branch chain was mainly composed of α-D-GalpA-(1 → 2)-α-L-Rhap-(1→ connected to O-3 position →3,4)-α-D-GalpA-(1→. The complex structure formed by the combination of DAP-2 and α-glucosidase was stable. DAP-2 had a higher α-glucosidase binding ability than the acarbose. These results suggested that DAP-2 had the potential to be developed as a potential hypoglycemic functional food and drug.

Amphiphilic α-Peptoid-deoxynojirimycin Conjugate-based Multivalent Glycosidase Inhibitor for Hypoglycemic Effect and Fluorescence Imaging.

Multivalent glycosidase inhibitors based on 1-deoxynojirimycin derivatives against α-glucosidases have been rapidly developed. Nonetheless, the mechanism based on self-assembled multivalent glucosidase inhibitors in living systems needs to be further studied. It remains to be determined whether the self-assembly possesses sufficient stability to endure transit through the small intestine and subsequently bind to the glycosidases located therein. In this paper, two amphiphilic compounds, 1-deoxynojirimycin and α-peptoid conjugates (LP-4DNJ-3C and LP-4DNJ-6C), were designed. Their self-assembling behaviors, multivalent α-glucosidase inhibition effect, and fluorescence imaging on living organs were studied. LP-4DNJ-6C exhibited better multivalent α-glucosidase inhibition activities in vitro. Moreover, the self-assembly of LP-4DNJ-6C could effectively form a complex with Nile red. The complex showed fluorescence quenching effect upon binding with α-glucosidases and exhibited potent fluorescence imaging in the small intestine. This result suggests that a multivalent hypoglycemic effect achieved through self-assembly in the intestine is a viable approach, enabling the rational design of multivalent hypoglycemic drugs.

Synthesis,Antidiabetic and Antitubercular Evaluation of Quinoline-pyrazolopyrimidine hybrids and Quinoline-4-Arylamines.

Two libraries of quinoline-based hybrids 1-(7-chloroquinolin-4-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine and 7-chloro-N-phenylquinolin-4-amine were synthesized and evaluated for their α-glucosidase inhibitory and antioxidant properties. Compounds with 4-methylpiperidine and para-trifluoromethoxy groups, respectively, showed the most promising α-glucosidase inhibition activity with IC50=46.70 and 40.84 μM, compared to the reference inhibitor, acarbose (IC50=51.73 μM). Structure-activity relationship analysis suggested that the cyclic secondary amine pendants and para-phenyl substituents account for the variable enzyme inhibition. Antioxidant profiling further revealed that compounds with an N-methylpiperazine and N-ethylpiperazine ring, respectively, have good DPPH scavenging abilities with IC50=0.18, 0.58 and 0.93 mM, as compared to ascorbic acid (IC50=0.05 mM), while the best DPPH scavenger is NO2-substituted compound (IC50=0.08 mM). Also, compound with N-(2-hydroxyethyl)piperazine moiety emerged as the best NO radical scavenger with IC50=0.28 mM. Molecular docking studies showed that the present compounds are orthosteric inhibitors with their quinoline, pyrimidine, and 4-amino units as crucial pharmacophores furnishing α-glucosidase binding at the catalytic site. Taken together, these compounds exhibit dual potentials; i. e., potent α-glucosidase inhibitors and excellent free radical scavengers. Hence, they may serve as structural templates in the search for agents to manage Type 2 diabetes mellitus. Finally, in preliminary assays investigating the anti-tubercular potential of these compounds, two pyrazolopyrimidine series compounds and a 7-chloro-N-phenylquinolin-4-amine hybrid showed sub-10 μM whole-cell activities against Mycobacterium tuberculosis.

Two new sesquiterpenoid glycoside compounds from the calyces of Physalis alkekengi L. var. franchetii (Mast.) Makino

Two new sesquiterpenoid glycosides, 8α (H)-eudesmane-1,3,11 (13)-triene-2-one -12-O-β-D-glucopyranoside (1) and dmetelisproside B (2), together with ten known compounds (3–12) were isolated from calyces of Physalis alkekengi L. var. franchetii (Mast.) Makino (PAF). Their structures were unambiguously elucidated through HR-ESI-MS, UV, IR, and NMR spectral data. Compounds 1, 10, and 12 exhibited DPPH scavenging ability with IC50 values of 33.69 ± 6.65, 6.29 ± 0.06, and 25.66 ± 3.06 μM, respectively. Additionally, 10 and 12 demonstrated weak α-glucosidase inhibition activity with IC50 values of 250.9 ± 6.60 and 347.6 ± 2.48 μM, respectively.

Hypoglycemic activity in vivo and in vitro of the Lotus (Nelumbo nucifera Gaertn.) seed skin (testa) phenolic-rich extracts

Lotus (Nelumbo nucifera Gaertn.) seed, a traditional Chinese herbal medicine, exhibits good hypoglycemic activities. However, the bioactive components that are responsible for the biological effects and their underlying mechanisms remain obscure. This study aimed to identify the bioactive components of lotus seed skin phenolic-rich extract (LSSE) and investigate their α-glucosidase inhibitory activity. In vivo study showed that LSSE could significantly decrease the fasting blood glucose levels and the area under the curves with dose-dependent manners in diabetes mellitus mice. And the α-glucosidase activity was decreased by 39.4% after intervention with LSSE. The results also demonstrated that LSSE possessed up to 77.53% rat intestinal maltase inhibitory activity and general sucrase and isomaltase inhibitory activity. A total of 38 phenolic compounds were first quantified in LSSE. Molecular docking analysis further revealed that the bioactive components in LSSE bind with α-glucosidase by hydrogen bonding Van der Waals and hydrophobic interactions. These results indicate the potential use of LSSE for natural hypoglycemic functional foods.

α-Glucosidase Inhibitory Activity of Tea and Kombucha from Rhizophora mucronata Leaves

A decoction of Rhizophora mucronata Lam. mangrove bark is used as an antidiabetic treatment in Asia. Kombucha tea is a fermented beverage, which is also claimed to be antidiabetic. In this work, the potency of R. mucronata leaves as α-glucosidase inhibitor was studied to assess whether it could be a suitable alternative to the use of R. mucronata bark. α-glucosidase inhibitory activities were determined for three extracts prepared from R. mucronata leaves, being the unfermented tea of R. mucronata leaves, the fermented kombucha tea and an 80% methanolic extract of the residual R. mucronata leaves. Flavonoid glycosides were identified in tea powder, kombucha tea and in the crude methanolic extract. Both the unfermented tea and the kombucha tea after 7 days of fermentation inhibited α-glucosidase with IC50 values of 0.12 ± 0.02 mg/mL and 0.09 ± 0.04 mg/mL, respectively. The methanolic extract showed a stronger α-glucosidase inhibitory activity compared to the kombucha tea and tea powder with an IC50 value of 0.0435 ± 0.0007 mg/mL. Acarbose, used as a positive control, inhibited α-glucosidase with an IC50 value of 2.4 ± 0.2 mg/mL. It was found that the three types of preparations of R. mucronata all were potent α-glucosidase inhibitors.