The inhibition of porcine pancreatic α-amylase and mammalian α-glucosidase by 16 individual flavonoids was determined. The IC50 values for baicalein, (+)-catechin, quercetin, and luteolin were 74.1 ± 5.6, 175.1 ± 9.1, 281.2 ± 19.2, and 339.4 ± 16.3 μM, respectively, against α-glucosidase. The IC50 values for apigenin and baicalein were 146.8 ± 7.1 and 446.4 ± 23.9 μM, respectively, against α-amylase. The combination of baicalein, quercetin, or luteolin with acarbose showed synergistic inhibition, and the combination of (+)-catechin with acarbose showed antagonistic inhibition of α-glucosidase. The combination of baicalein or apigenin with acarbose showed additive inhibition of α-amylase at lower concentrations and antagonistic inhibition at a higher concentration. Kinetic studies of α-glucosidase activity revealed that baicalein alone, acarbose alone, and the combination showed noncompetitive, competitive, and mixed-type inhibition, respectively. Molecular modeling revealed that baicalein had higher affinity to the noncompetitive binding site of maltase, glucoamylase, and isomaltase subunits of α-glucosidase, with glide scores of −7.64, −6.98, and −6.88, respectively. (+)-Catechin had higher affinity to the active sites of maltase and glucoamylase and to the noncompetitive site of isomaltase. After sucrose loading, baicalein dose-dependently reduced the postprandial blood glucose (PBG) level in mice. The combination of 80 mg/kg baicalein and 1 mg/kg acarbose synergistically lowered the level of PBG, and the hypoglycemic effect was comparable to 8 mg/kg acarbose. The results indicated that baicalein could be used as a supplemental drug or dietary supplement in dietary therapy for diabetes mellitus.Keywords: acarbose; baicalein; postprandial blood glucose; synergistic inhibition; α-glucosidase;

•Baicalein from S. baicalensis and O. indicum is used as food supplements in Asia.•Baicalein improves insulin resistance by regulating SOCS3 in vitro and in vivo.•Moderate baicalein consumption reduces the side-effects of acarbose.•Baicalein improves the effect of acarbose on diabetes prevention.Baicalein, a major component in Scutellaria baicalensis and Oroxylum indicum, is used as dietary supplement in Asia. In this study, we characterized the insulin-sensitizing activity of baicalein and found that baicalein improved insulin resistance by reducing the expression of SOCS3, increasing the phosphorylation of IRS1 and Akt1, reducing the phosphorylation of GSK3β and increasing hepatic glycogen level. We further evaluated the preventive effect of baicalein combined with acarbose in mice, aiming to enhance the therapeutic effect and reduce the side-effects of acarbose. The combination reduced the relative risk of progression from prediabetes to diabetes by 83.3% and the dose of acarbose by 80%. The underlying mechanisms include reducing postprandial hyperglycemia, improving insulin resistance, improving lipid metabolism, and reducing oxidative stress. Our results suggest that the consumption of 195–780 mg/d baicalein might improve the efficacy of acarbose on diabetes prevention and reduce the side-effects of acarbose in long-term acarbose users.

AimTo screen a potential PTP1b inhibitor from the microbial origin-based compound library and to investigate the potential anti-diabetic effects of the inhibitor in vivo and determine its primary anti-diabetic mechanism in vitro and in silico.MethodsPTP1b inhibitory activity was measured using recombination protein as the enzyme and p-NPP as the substrate. The binding of the inhibitor to PTP1b was analysed by docking in silico and confirmed by ITC experiments. The intracellular signalling pathway was detected by Western blot analysis in HepG2 cells. The anti-diabetic effects were evaluated using a diabetic mice model in vivo.ResultsAmong 545 microbial origin-based pure compounds tested, trivaric acid, a tridepside, was selected as a PTP1B inhibitor exhibiting strong inhibitory activity with an IC50 of 173 nM. Docking and ITC studies showed that trivaric acid was able to spontaneously bind to PTP1b and may inhibit PTP1b by blocking the catalytic domain of the phosphatase. Trivaric acid also enhanced the ability of insulin to stimulate the IR/IRS/Akt/GLUT2 pathway and increase the glucose consumption in HepG2 cells. In diabetic mice, trivaric acid that had been encapsulated into Eudrgit L100-5.5 showed significant anti-diabetic effects, improving insulin resistance, leptin resistance and lipid profile and weight control at doses of 5 mg/kg and 50 mg/kg.SignificanceTrivaric acid is a potential lead compound in the search for anti-diabetic agents targeting PTP1b.

Prediabetes is defined as blood glucose levels above normal but below diabetes thresholds, and up to 70% of individuals with prediabetes will eventually develop diabetes if left untreated. Acarbose, the first FDA approved anti-prediabetes agent, has some disadvantages, such as reducing the risk of diabetes by only 36%, side effects and limited effects on complications. The aim of this study is to develop a new agent to treat prediabetes and to investigate the anti-prediabetes effects and mechanisms of acarbose and an Oroxylum indicum seed extract (OISE) in prediabetic mice. The combined drugs can reduce the dose of acarbose by 80% and reduce the risk of diabetes by 75%, which is one fold higher than acarbose monotherapy. The combined drugs showed synergistic anti-prediabetes effects and could be effective in preventing the complications of prediabetes. The combined drugs could improve glucose tolerance, improve lipid metabolism and reduce oxidative stress and tissue damage. For the mechanisms, the combined drugs can reduce synergistically postprandial hyperglycaemia by inhibiting α-glucosidase. Furthermore, baicalein in OISE was demonstrated to be a major component in reducing oxidative stress and chrysin was the primary compound that activated PPARγ.

•The inhibition of α-amylase and α-glucosidase by nine triterpenes is determined.•The SAR of enzyme inhibition between pentacyclic triterpenes is investigated.•Corosolic acid and oleanolic acid synergistically inhibit α-amylase with acarbose.•The mechanism of the synergistic inhibition is explained by the inhibition types.In this paper, the inhibition of α-amylase and α-glucosidase by nine pentacyclic triterpenes was determined. For α-amylase inhibitory activity, the IC50 values of ursolic acid, corosolic acid, and oleanolic acid were 22.6 ± 2.4 μM, 31.2 ± 3.4 μM, and 94.1 ± 6.7 μM, respectively. For α-glucosidase inhibition, the IC50 values of ursolic acid, corosolic acid, betulinic acid, and oleanolic acid were 12.1 ± 1.0 μM, 17.2 ± 0.9 μM, 14.9 ± 1.9 μM, and 35.6 ± 2.6 μM, respectively. The combination of corosolic acid and oleanolic acid with acarbose showed synergistic inhibition against α-amylase. The combination of the tested triterpenes with acarbose mainly exhibited additive inhibition against α-glucosidase. Kinetic studies revealed that corosolic acid and oleanolic acid showed non-competitive inhibition and acarbose showed mixed-type inhibition against α-amylase. The results provide valuable implications for the triterpenes (ursolic acid, corosolic acid, and oleanolic acid) alone or in combination with acarbose as a therapeutic agent for the treatment of diabetes mellitus.Download high-res image (119KB)Download full-size image

Protein tyrosine phosphatase 1B (PTP1B) inhibitors as potential therapies for diabetes and obesity have attracted much attention in recent years. Six varic acid analogues were isolated from two strains of fungi and evaluated for PTP1B inhibition activities. The structure-activity relationships were also characterized and predicted by molecular modeling. Further kinetic studies indicated the reversible and competitive inhibition manner of varic acid analogues. Trivaric acid showed insulin-sensitizing effect not only in vitro but also in vivo, representing a promising lead compound for further optimization.Download high-res image (196KB)Download full-size image

With the aim of finding more potential inhibitors against NADH-fumarate reductase (specific target for treating helminthiasis and cancer) from natural resources, Talaromyces wortmannii was treated with the epigenome regulatory agent suberoylanilide hydroxamic acid, which resulted in the isolation of four new wortmannilactones derivatives (wortmannilactones I–L, 1–4). The structures of these new compounds were elucidated based on IR, HRESIMS and NMR spectroscopic data analyses. These four new compounds showed potent inhibitory activity against NADH-fumarate reductase with the IC50 values ranging from 0.84 to 1.35 μM.

•OSMAC strategy could increase the kind of wortmannilactones.•Three new wortmannilactones, wortmannilactones I1-I3, were isolated from medium of Talaromyces wortmannii.•Their structures were assigned by IR, HRESIMS, NMR and ECD.•These new wortmannilactones exhibit selective inhibitory activity against NADH-fumarate reductase.Three new polyketides, wortmannilactones I1-I3, were purified from Talaromyces wortmannii using the One Strain Many Compounds (OSMAC) strategy. The polyketides’ structures were established using IR, 1D and 2D NMR, and HRESIMS analyses and the absolute configurations were identified by comparison of experimental and calculated ECDs. These polyketides exhibit selective inhibitory activity against NADH-fumarate reductase.

•The distributions of IgG in different salting-out extraction systems were investigated.•The optimized SOES in extraction of IgG is ethanol/K2HPO4 system.•The ethanol/K2HPO4 SOES do not cause any obvious change in the structure of IgG.•We provide a new alternative for the separation and purification of immunoglobulin.The distribution of IgG in different salting-out extraction systems (SOESs), including ethanol/K2HPO4, Na2CO3, and trisodium citrate, was investigated. The SOESs that were composed of 20% K2HPO4 (w/w)–14% ethanol (w/w), 19% Na2CO3 (w/w)–13% ethanol (w/w) and 25% trisodium citrate (w/w)–19% ethanol (w/w) showed satisfactory results, with IgG recovery rates as high as 97.4%, 93.1%, and 90.2%, respectively. ELISA, CD and IR analyses confirmed the active retention and structural constant of IgG in the K2HPO4–ethanol system. An optimized system that consisted of 14% ethanol (w/w)–20% K2HPO4 (w/w) (pH 7.0) was selected for extracting active plasma proteins directly from pig plasma. As a result, recovery rates as high as 95.7% for IgG and 93.0% for albumin were achieved. In addition, some contaminating proteins were also removed by this system, which may provide a new alternative method for the separation and purification of immunoglobulin.

Recombinant human serum albumin (rHSA) is considered as an alternative of human serum albumin and used to treat patients with severe burn, shock or blood loss. However, separation and purification of rHSA are difficult and have become the bottle neck in industrial production. In this study, ethanol/K2HPO4 aqueous two-phase system (ATPS) and hydrophobic interaction chromatography (HIC) were integrated to provide a new approach for the extraction and purification of rHSA from high density fermentation broth. Using a 0.01–73 L ATPS scale, the extraction of rHSA from the fermentation broth attained an average recovery of 100.4%. At the same time, 99.8% of cells and 87.2% of polysaccharides as well as some other protein impurities were also removed. The activity of proteinase A in the broth was also remarkably decreased. The purified rHSA appeared as a single band on reduced SDS–PAGE gel, and it had a purity of 99.1% as determined by HPLC. It was essentially identical to the plasma-derived HSA in terms of molecular weight and circular dichroism spectrum. The total recovery of rHSA was 75.2%, which was 1.1–2.0 times higher than that obtained from conventional processes. Residual polysaccharide was reduced to 1.61 μg/mg rHSA and the degree of coloring was lower than that of plasma-derived HSA. The procedure employed in this study has the advantages of simple operation, shorter time, low energy consumption and high yield, and it could produce rHSA with high purity. It is therefore suitable in the production of rHSA and other biological products produced by high-density fermentation.Highlights► A new approach integrated EtOH/K2HPO4 ATPS and HIC were used for rHSA purification. ► ATPS integrated solid–liquid separation, extraction and purification into a single step. ► The new approach could produce rHSA with high purity and yield.

Diosgenin is an important starting material in the steroidal hormone industry. In this paper diosgenin was obtained by biotransformation of steroidal saponins in Dioscorea zingiberensis with the fungus Aspergillus oryzae. In the pre- and post-biotransformed samples, five main steroidal saponins and the aglycone (diosgenin) were identified by evaporative light scattering detector. An LC-UV quantification method for them was established by using C18 column and a mobile phase of aqueous acetonitrile. By means of this method, a good linearity (r > 0.9995) and recovery of the analytes (97.5–101.3%) were obtained for all the compounds. During biotransformation, the sugar chains of saponins were hydrolyzed and the content of the hydrolyzed product (diosgenin) increased 16 times after 84 h fermentation.