Constituents from the testas of Castanea mollissima Blume with α-glucosidase inhibitory activity

In the screening of biologically active constituents from medicinal plants, the 75% EtOH extract of the testas of Castanea mollissima Blume showed potent α-glucosidase inhibitory activity. By means of various chromatographic methods, the extract gave a new dammarane-type triterpene 1 along with 17 known compounds. The structure of 1 was determined to be 3β-acetoxy-20-oxo-21-nordammaran-23-oic acid by HRMS and NMR studies including 2D NMR experiments. The new compound and some known compounds showed potent α-glucosidase inhibitory activity with acarbose as a positive control.     

Triterpene saponins with α-glucosidase inhibition and cytotoxic activity from the leaves of Schefflera sessiliflora

From the leaves of Schefflera sessiliflora De P. V., two new triterpene saponins including one oleanane-type saponin, named scheffleraside C (1) and one lupane-type saponin scheffleraside D (2), together with six known triterpene saponins (3–8), were isolated by various chromatography methods. Among them, 3 was found for the first time from natural sources, while 6–8 were isolated for the first time from the genus Schefflera. Their structures were elucidated by IR, UV, HR-ESI-MS, NMR 1D and 2D experiments, and comparison of their NMR data with previously reported data. Their α-glucosidase inhibition and cytotoxic activity against MCF-7 human breast cancer cell lines were evaluated. The isolates (1, 3–5, 8) showed stronger α-glucosidase inhibitory activity (IC₅₀ = 5.99–76.58 μM) than the standard drug acarbose (IC₅₀ = 214.50 μM). At the concentration of 100 μg/ml, the isolates (1, 2) showed appreciable cytotoxic activity (67.92, 63.83%, respectively).     

A new ester of fatty acid from a methanol extract of the whole plant of Amaranthus spinosus and its α-glucosidase inhibitory activity

Abstract

Context: Amaranthus spinosus Linn. (Amaranthaceae), commonly known as “spiny pigweed”, is used both in the Indian traditional system and in folk medicine to treat diabetes.

Objective: The present study evaluates the scientific basis of antidiabetic activity of chloroform fraction of methanol extract of A. spinosus and of an isolated constituent of A. spinosus.

Materials and methods: HPLC analysis was performed to determine the purity and the amount of the constituent present in the plant extract. The yeast α-glucosidase inhibition technique was used to determine the antidiabetic activity of A. spinosus. Acarbose was used as a standard. An appropriate therapeutic approach for preventing diabetes mellitus and obesity is to retard the absorption of glucose by inhibition of α-glucosidase.

Results: One novel fatty acid with strong α-glucosidase inhibitory activity – (14E, 18E, 22E, 26E) – methyl nonacosa-14, 18, 22, 26 tetraenoate [1] (IC₅₀ value 6.52?µM/mL) and β-sitosterol [2] were purified. Compound 1 was found to be more potent than the methanol extract. HPLC quantative analysis revealed that 0.15% of compound 1 and 0.06% of compound 2 were present in the plant extract.

Conclusion: This novel fatty acid can potentially be developed as a novel natural nutraceutical for the management of diabetes.     

The α-glucosidase inhibitory activity of avicularin and 4-O-methyl gallic acid isolated from Syzygium myrtifolium leaves

Diabetes Mellitus is the main cause of death on a global scale. In 2019, there were 463 million people with diabetes, and WHO predicts that by 2030, there will be 578 million. As an antidiabetic agent, α-glucosidase inhibitors are one of the methods employed to reduce the prevalence of diabetes. Diabetes is traditionally treated with Syzygium as a primary material, medicine, fruit, ornamental plant, and source of carpentry. This investigation aimed to examine the inhibitory effect of seven species of Syzygium against α-glucosidase enzyme using an in vitro assay and isolate active substances and ascertain their concentrations in each sample. As a solvent, ethanol was used in maceration to extract the substance. Afterward, the extract underwent a series of fractionation techniques, including liquid–liquid extraction, vacuum liquid chromatography, column chromatography, and preparative Thin Layer Chromatography (TLC) for purification and isolation. The compound's structures were elucidated using TLC, UV–Visible spectrophotometry, and nuclear magnetic resonance (NMR) spectroscopy. Based on concentrations of 100 and 200 µg/mL, Syzygium myrtifolium exhibited the most significant inhibitory effect, followed by other species of Syzygium. The proportion of ethyl acetate had the strongest activity (IC₅₀ 0.40 ± 0.02 µg/mL) contrasted to positive control acarbose (IC₅₀ 55.39 ± 0.67 g/mL) and quercitrin (IC₅₀ 6.47 ± 0.40 µg/mL). Avicularin and 4-O-methyl gallic acid were discovered in the ethyl acetate fraction of Syzygium myrtifolium with IC₅₀ values of 17.05 ± 0.75 µg/mL and 25.19 ± 0.21 µg/mL, respectively. As α-glucosidase inhibitory, the results of this study indicate Syzygium myrtifolium can be used as a dietary supplement to manage hyperglycemia.     

New triterpenes from Salacia hainanensis Chun et How with α-glucosidase inhibitory activity

Fractionation of the methanol extract from the roots of Salacia hainanensis Chun et How showing the potent inhibitory activity on α-glucosidase afforded two new lupane derivatives, 3α,28-dihydroxy-lup-20(29)-en-2-one (1) and 3α-hydroxy-lup-20(29)-en-2-one (2), a new friedelane derivative, D:A-friedo-oleanane-7α,30-dihydroxy-3-one (3), and a novel natural product, 2,3-seco-lup-20(29)-en-2,3-dioic acid (4), along with four known compounds (5-8). Their structures were established on the basis of spectral analysis, especially on the data afforded by 2D NMR and high-resolution mass spectra experiments. All of them showed a much stronger inhibiting activity on α-glucosidase than the positive control (acarbose, IC?? = 5.83 μM). Constituents with α-glucosidase inhibitory activity from this plant are reported for the first time.     

New triterpenes from Salacia hainanensis Chun et How with α-glucosidase inhibitory activity

Fractionation of the methanol extract from the roots of Salacia hainanensis Chun et How showing the potent inhibitory activity on α-glucosidase afforded two new lupane derivatives, 3α,28-dihydroxy-lup-20(29)-en-2-one (1) and 3α-hydroxy-lup-20(29)-en-2-one (2), a new friedelane derivative, D:A-friedo-oleanane-7α,30-dihydroxy-3-one (3), and a novel natural product, 2,3-seco-lup-20(29)-en-2,3-dioic acid (4), along with four known compounds (5–8). Their structures were established on the basis of spectral analysis, especially on the data afforded by 2D NMR and high-resolution mass spectra experiments. All of them showed a much stronger inhibiting activity on α-glucosidase than the positive control (acarbose, IC₅₀ = 5.83 μM). Constituents with α-glucosidase inhibitory activity from this plant are reported for the first time.     

In vitro α-glucosidase inhibitory activity of phenolic constituents from aerial parts of Polygonum hyrcanicum

Background and the purpose of the study

The early stage of diabetes mellitus type 2 is associated with postprandial hyperglycemia. Hyperglycemia is believed to increase the production of free radicals and reactive oxygen species, leading to oxidative tissue damage. In an effort of identifying herbal drugs which may become useful in the prevention or mitigation of diabetes, biochemical activities of Polygonum hyrcanicum and its constituents were studied.

Methods

Hexane, ethylacetate and methanol extracts of P. hyrcanicum were tested for α-glucosidase inhibitory, antioxidant and radical scavenging properties. Active constituents were isolated and identified from the methanolic extract in an activity guided approach.

Results

A methanolic extract from flowering aerial parts of the plant showed notable α-glucosidase inhibitory activity (IC₅₀ = 15 μg/ml). Thirteen phenolic compounds involving a cinnamoylphenethyl amide, two flavans, and ten flavonols and flavonol 3-O-glycosides were subsequently isolated from the extract. All constituents showed inhibitory activities while compounds 3, 8 and 11 (IC₅₀ = 0.3, 1.0, and 0.6 μM, respectively) were the most potent ones. The methanol extract also showed antioxidant activities in DPPH (IC₅₀ = 76 μg/ml) and FRAP assays (1.4 mmol ferrous ion equivalent/g extract). A total phenol content of 130 mg/g of the extract was determined by Folin-Ciocalteu reagent.

Conclusion

This study shows that P. hyrcanicum contains phenolic compounds with in vitro activity that can be useful in the context of preventing or mitigating cellular damages linked to diabetic conditions.     

Xanthones as α-glucosidase inhibitors from the antihyperglycemic extract of Securidaca inappendiculata

Context: Securidaca inappendiculata Hassk. (SI) is used to cure fractures and rheumatoid arthritis in China. Also, it is a potential antidiabetes drug; however, there are no reports on this.

Objective: The study was designed to evaluate the antihyperglycemic activities of fractions and compounds from SI, and attempt to explore the mechanism.

Materials and methods: Antihyperglycemic activities were evaluated by the suppression on serum glucose levels in vivo and α-glucosidase inhibition assays in vitro. Fractions were given to mice by gastric intubation for 8?d. The high, medium, and low doses of fractions were equal to 10, 5, and 2.5?g/kg of the herb [SID (dichloromethane fraction) and SIE (ethyl acetate fraction) were doubled]. The serum glucose was monitored at 1 and 12?h after feeding. The silica gel and LH-20 chromatography were used to isolate active compounds. Structure–activity relationship analysis was based on IC₅₀s and structures.

Results: The IC₅₀s of SID, SIE, SIA (acetone fraction), SIM (methanol fraction), and acarbose were 712, 446, 1123, 1418, and 735?μg/mL. The postprandial and fasting serum glucose levels of SID, SIE, SIA, and SIM (high dose) were 5.5, 5.9, 6.2, 6.3 and 3.7, 3.5, 4.0, 5.0?mmol/L, while those of vehicle control were 7.5 and 5.6?mmol/L. Eleven xanthones isolated all exhibited inhibitory activities, mainly in a non-competitive reversible manner. The IC₅₀s varied from 3.2 to 77.3?μg/mL. Structure–activity relationship analysis exhibited free hydroxyls contributed the most importance to the activity.

Conclusion: The results indicated that xanthones from SI were powerful agents for antidiabetes.     

New steroids from Anemarrhena asphodeloides rhizome and their α-glucosidase inhibitory activity

Two new steroids were isolated from acid hydrolysis residue of the rhizomes of Anemarrhena asphodeloides. Their structures were identified on the basis of several spectroscopic analysis approaches including 1D, 2D-NMR techniques, and MS data, and by the comparison of spectral data of the known compounds. The biological activities of these two isolated compounds were explored on α-glucosidase. Compound 1 displayed 4.7 folds inhibitory activity against α-glucosidase compared with the positive control acarbose.     

Two new phragmalin-type limonoids from Chukrasia tabularis and their α-glucosidase inhibitory activity

Phytochemical investigation on the stems of C. tabularis (Meliaceae) led to the isolation of two new phragmalin-type limonoids, named tabularisins S and T (1–2), along with five known ones (3–7). The structures of the new limonoids were established by spectroscopic methods including UV, IR, HRESIMS, and 1D and 2D NMR. All the compounds were evaluated for α-glucosidase inhibitory activity in vitro. Compounds 2 and 3 exhibited significant inhibitory activity against α-glucosidase with IC₅₀ values of 0.15 and 0.03 mM, respectively (acarbose as positive control, IC₅₀ 0.95 mM).     

Diterpenoids from the roots of Euphorbia fischeriana and their inhibitory effects on α-glucosidase

Abstract

Chemical investigation has been performed on the roots of Euphorbia fischeriana, a traditional Chinese medicine. Three diterpenoids were obtained using various chromatographic techniques, and their structures were determined by spectroscopic data including HRESIMS, 1D NMR, 2D NMR, ECD, and calculated ECD, which gave two new diterpenoids, daphnane type (1) and ent-pimarene type (3). Additionally, the isolated compounds (1–3) displayed moderate inhibitory effects against α-glucosidase in an in vitro bioassay.     

Inhibitory activity of α-amylase and α-glucosidase by plant extracts from the Brazilian cerrado

Diabetes mellitus is the most common disease in the world. One therapeutic approach for treating diabetes is inhibition of α-amylase and α-glucosidase activities to reduce postprandial blood glucose levels. In vitro tests showed that several plant extracts from Brazilian cerrado species can inhibit the activity of α-amylase and α-glucosidase. The extracts of Eugenia dysenterica, Stryphnodendron adstringens, Pouteria caimito, Pouteria ramiflora, and Pouteria torta showed strong α-amylase and α-glucosidase inhibitory activity. Eugenia dysenterica, P. caimito, P. ramiflora, and P. torta aqueous extracts exerted the highest activity against α-amylase (IC??) values of 14.93, 13.6, 7.08, and 5.67 μg/mL, respectively) and α-glucosidase (IC?? values of 0.46, 2.58, 0.35, and 0.22 μg/mL, respectively). Stryphnodendron adstringens ethanol extract also exhibited inhibitory activity against both enzymes (IC??) 1.86 μg/mL against α-amylase and 0.61 μg/mL against α-glucosidase). The results suggest that the activity of these cerrado plants on α-amylase and α-glucosidase represents a potential tool for development of new strategies for treatment of diabetes.     

Rapid investigation of α-glucosidase inhibitory activity of Phaleria macrocarpa extracts using FTIR-ATR based fingerprinting

Phaleria macrocarpa, known as “Mahkota Dewa”, is a widely used medicinal plant in Malaysia. This study focused on the characterization of α-glucosidase inhibitory activity of P. macrocarpa extracts using Fourier transform infrared spectroscopy (FTIR)-based metabolomics. P. macrocarpa and its extracts contain thousands of compounds having synergistic effect. Generally, their variability exists, and there are many active components in meager amounts. Thus, the conventional measurement methods of a single component for the quality control are time consuming, laborious, expensive, and unreliable. It is of great interest to develop a rapid prediction method for herbal quality control to investigate the α-glucosidase inhibitory activity of P. macrocarpa by multicomponent analyses. In this study, a rapid and simple analytical method was developed using FTIR spectroscopy-based fingerprinting. A total of 36 extracts of different ethanol concentrations were prepared and tested on inhibitory potential and fingerprinted using FTIR spectroscopy, coupled with chemometrics of orthogonal partial least square (OPLS) at the 4000–400 cm⁻¹ frequency region and resolution of 4 cm⁻¹. The OPLS model generated the highest regression coefficient with R²Y = 0.98 and Q²Y = 0.70, lowest root mean square error estimation = 17.17, and root mean square error of cross validation = 57.29. A five-component (1+4+0) predictive model was build up to correlate FTIR spectra with activity, and the responsible functional groups, such as –CH, –NH, –COOH, and –OH, were identified for the bioactivity. A successful multivariate model was constructed using FTIR-attenuated total reflection as a simple and rapid technique to predict the inhibitory activity.     

The α-amylase and α-glucosidase inhibitory activities of the dichloromethane extracts and constituents of Ferulago bracteata roots

Context: Ferulago (Apiaceae) species have been used since ancient times for the treatment of intestinal worms, hemorrhoids, and as a tonic, digestive, aphrodisiac, or sedative, as well as in salads or as a spice due to their special odors.

Objectives: This study reports the α-amylase and α-glucosidase inhibitory activities of dichloromethane extract and bioactive compounds isolated from Ferulago bracteata Boiss. &; Hausskn. roots.

Materials and methods: The isolated compounds obtained from dichloromethane extract of Ferulago bracteata roots through bioassay-guided fractionation and isolation process were evaluated for their in vitro α-amylase and α-glucosidase inhibitory activities at 5000–400?µg/mL concentrations. Compound structures were elucidated by detailed analyses (NMR and MS).

Results: A new coumarin, peucedanol-2′-benzoate (1), along with nine known ones, osthole (2), imperatorin (3), bergapten (4), prantschimgin (5), grandivitinol (6), suberosin (7), xanthotoxin (8), felamidin (9), umbelliferone (10), and a sterol mixture consisted of stigmasterol (11), β-sitosterol (12) was isolated from the roots of F. bracteata. Felamidin and suberosin showed significant α-glucosidase inhibitory activity (IC₅₀ 0.42 and 0.89?mg/mL, respectively) when compared to the reference standard acarbose (IC₅₀ 4.95?mg/mL). However, none of the tested extracts were found to be active on α-amylase inhibition.

Discussion and conclusions: The present study demonstrated that among the compounds isolated from CH₂Cl₂ fraction of F. bracteata roots, coumarins were determined as the main chemical constituents of this fraction. This is the first report on isolation and characterization of the bioactive compounds from root extracts of F. bracteata and on their α-amylase and α-glucosidase inhibitory activities.     

Inhibitors of α-glucosidase and α-amylase from Cyperus rotundus

Context: A methanol extract of Cyperus rotundus L. (Cyperaceae) rhizomes showed inhibitory activity against α-glucosidase and α-amylase, two enzymes involve in carbohydrate digestion.

Objective: Identification of compounds from C. rotundus rhizomes responsible for the inhibition of α-glucosidase and α-amylase.

Materials and methods: Compounds were identified by a phytochemical investigation using combined chromatographic and spectroscopic methods. α-glucosidase and α-amylase inhibitory activities were evaluated by in vitro enzyme inhibition assays.

Results: A new (2RS,3SR)-3,4′,5,6,7,8-hexahydroxyflavane (1), together with three known stilbene dimers cassigarol E (2), scirpusin A (3) and B (4) were isolated. Compound 2 inhibited both α-glucosidase and α-amylase activities while the flavane 1 only showed effect on α-amylase, and compounds 3 and 4 were active on α-glucosidase. All four compounds showed significant 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity.

Discussion: The inhibitory activities against α-amylase and α-glucosidase of the C. rotundus rhizomes were reported for the first time. Stilbene dimers are considered as potent inhibitors of α-glucosidase and promising antihyperglycemic agents.

Conclusion: The isolated compounds may contribute to the antidiabetic property of C. rotundus.     

Antagonistic effects of extract from leaves of Ginkgo biloba on glutamate neurotoxicity

目的：观察ＥＧｂ及其所含成分槲皮素和内酯Ｂ对谷氨酸诱导的神经元损伤的拮抗作用．方法：对小鼠下丘脑弓状核作形态学观察和图象分析，采用ＭＴＴ法检测皮层原代培养神经元的活性，用Ｆｕｒａ２测定单个神经元内游离钙离子的浓度（［Ｃａ２＋］ｉ）．结果：ＥＧｂ及其内酯Ｂ能够保护神经元对抗谷氨酸的损伤，阻止谷氨酸诱发的［Ｃａ２＋］ｉ的升高．ＥＧｂ能够逆转谷氨酸诱导的下丘脑弓状核神经元核面积的减少．结论：ＥＧｂ及其内酯Ｂ可以通过降低［Ｃａ２＋］ｉ水平对抗谷氨酸神经毒性，内酯Ｂ很可能是ＥＧｂ中对抗谷氨酸神经毒性的主要成分之一．     

Antioxidant and α-amylase inhibitory activities of extract and isolates from Zygogynum pancheri subsp. arrhantum

One new sesquiterpenoid (5R^*,8R^*,9R^*,10R^*)-cinnamolide (8), and seven known compounds, 5-hydroxy-7-methoxyflavonone (1), 8-hydroxy-3-(4′-hydroxyphenyl)-6,7-(2″,2″-dimethylchromene)-tetralone (2), 8-hydroxy-3-(3′,4′-dihydroxyphenyl)-6,7-(2″,2″-dimethylchromene)-tetralone (3), 1β-E-O-p-methoxycinnamoyl-bemadienolide (4), 1β-O-(E-cinnamoyl)-6α-hydroxy-9-epi-polygodial (5), 1β-O-(E-cinnamoyl)-6α-hydroxypolygodial (6), and 1β-O-E-cinnamoylpolygodial (7) were isolated from the ethyl acetate extract of barks of Zygogynum pancheri subsp. arrhantum (Winteraceae). The structures of these molecules were assigned predominantly based on spectral data. The structure of compound 8 was confirmed by X-ray crystallographic analysis. Compounds 2 and 3 exhibited significant antioxidant activity, whereas compounds 1 and 4–7 showed significant α-amylase inhibitory activity.     

Antioxidant and α-glucosidase inhibitory compounds from Pimpinella candolleana Wight et Arn.

EtOAc and MeOH different extracts of Pimpinella candolleana Wight et Arn. have shown the α-glucosidase inhibitory and antioxidant activities when they were assayed in vitro. Chemical constituents of both extracts were isolated by column chromatography, and identified by MS and NMR spectroscopic data. Nine compounds were isolated, including 3 sterols, 2 flavones, 1 triterpene, 1 glucoside, 1 phenol derivatives, and 1 other compound. Their structures were identified as ursolic acid (1), luteolin (2), urea (3), stigmasta-5,22-dien-3-ol acetate (4), erythrol (5), isovitexin (6), 1-(4-hydroxyphenyl)-1,2-ethanediol (7), daucosterol (8), and β-sitosterol (9). Compound 1 (IC₅₀?=?4.42?μg?ml^?1), 2 (IC₅₀?=?5.96?μg?ml^?1), 4 (IC₅₀?=?67.43?μg?ml^?1) and 6 (IC₅₀?=?68.71?μg?ml^?1) showed α-glucosidase inhibitory activity. Compound 2 (IC₅₀?=?0.99?μg?ml^?1) had antioxidant activity. All compounds except for 1 and 9 were isolated from this genus for the first time.