Chemical characterization of the main bioactive polyphenols from the roots of Morus australis (mulberry).

Morus species, commonly known as mulberry, is widely distributed in China. The mulberry tree is a high-value plant in agriculture. Morus australis is one of the major Morus species growing in Northern China. However, the biological properties of the main constituents of M. australis roots were not well studied. In the present study, through extensive chromatographic and spectral analysis, 12 phenolic compounds were isolated and identified from the M. australis roots. Compounds 1, 2, 8, 9 and 12 were isolated from M. australis roots for the first time. Antitumor activities of these polyphenols were studied on the A549 cell line. Compounds 1, 5 and 6 exhibited cytotoxicity on A549 cells and induced apoptosis in A549 cells via the intrinsic mitochondrial pathway. They also mediated inhibition of autophagic flux contributed cell death via the PI3k/Akt/mTOR pathway. In order to explore more potential bioactivities of these isolates, α-glucosidase, acetylcholinesterase and tyrosinase inhibitory activities were studied, and the results demonstrated that the inhibitory activity of these polyphenols on enzymes was not defined by their basic structural skeletons, but by the substituted position.

LC-MS guided isolation of diterpenoids from Sapium insigne with α-glucosidase inhibitory activities.

Ten new (1-10) and ten known (11-20) diterpenoids involving ent-atisane, ent-seco-atisane, ent-kaurane and ent-seco-kaurane types were isolated from Sapium insigne under the guidance of LCMS-IT-TOF analyses. Their structures were characterized by extensive spectroscopic analyses (HRESIMS, UV, IR, 1D and 2D NMR). A putative biosynthetic pathway was proposed for ent-seco-atisane diterpenoids. Their inhibitory activities on α-glucosidase in vitro were tested for the first time. Compound 4 showed moderate inhibitory effect on α-glucosidase with an IC50 value of 0.34 mM via a noncompetitive inhibition mechanism (Ki = 0.27 mM). The preliminary structure-activity relationships of the ent-atisane diterpenoids inhibiting α-glucosidase were discussed.

Isolation and identification of α-glucosidase and protein glycation inhibitors from Stereospermum colais.

Stereospermum colais (family Bignoniaceae) is a well-known pharmacologically potent medicinal plant reported in traditional systems of medicine. Phytochemical investigation of the roots of S. colais resulted in the isolation of seven compounds, and the metabolites were screened for its α-glucosidase enzyme inhibition and anti-glycation property. The compounds identified were ß-sitosterol (1), 2-(4'-hydroxyphenyl) ethyl undecanoate (2), 2-(4'-hydroxyphenyl)ethyl pentadecanoate (3), 5α-ergosta-7,22-dien-3ß-ol (4), ursolic acid (5), lapachol (6), and pinoresinol (7). Ursolic acid, lapachol, and pinoresinol possessed IC50 values of 119.01, 130.29, and 125.62 nM, respectively, compared to standard ascorbic acid with an IC50 value of 201.01 nM. The other compounds failed to show the activity. Results of the current study showcased the possible exploration of this medicinal plant for the treatment of type 2 diabetes in line with the development of phytopharmaceutical industry.

New phenolics from the flowers of Punica granatum and their in vitro α-glucosidase inhibitory activities.

Two new phenolics, a 3-substituted coumarin, 7,8-dihydroxy-3-carboxymethylcoumarin-5-carboxylic acid, and a hydrolyzable tannin, namely punicatannin C, together with 10 known phenolics, were isolated from the flowers of pomegranate (Punica granatum). Their structures were determined on the basis of extensive spectroscopic analyses including HRESIMS, 1D and 2D NMR data. All the isolates were evaluated for in vitro α-glucosidase inhibitory activities.

Bioassay-guided isolation and quantification of the alpha-glucosidase inhibitory compound, glycyrrhisoflavone, from Glycyrrhiza uralensis.

The EtOAc extract of the roots of Glycyrrhiza uralensis exhibited alpha-glucosidase inhibitory activity. Bioassay-guided fractionation resulted in the isolation of an active prenylflavonoid, glycyrrhisoflavone. Its structure was elucidated by NMR and MS analyses. A simple method to prepare glycyrrhisoflavone from the 95% EtOH extract of the roots of G. uralensis was developed by combination of Diaion HP-20 column chromatography (CC), silica gel CC, and preparative HPLC. An HPLC-PDA method was developed for quantitative determination of glycyrrhisoflavone in the roots of G. uralensis. The sample was extracted with MeOH and analyzed using a reversed-phase column with isocratic elution with CH3CN-H2O (0.06% trifluoroacetic acid) (42:58) at a flow rate of 1.2 mL/min, a column temperature of 40 degrees C, and a detection wavelength of 260 nm. The method allowed the determination of glycyrrhisoflavone in the concentration range of 5-500 microg/mL. The relative standard deviation values of the precision and repeatability were 0.3% and 2.0%, respectively. The limits of detection and quantification were 0.5 microg/mL and 5 microg/mL, respectively. The relative recovery rate was 100.2 +/- 1.8%. Based on the validation results, the HPLC determination method was found to be precise, accurate, and time conservative. This method was applied successfully to nine different root samples of G. uralensis. The amounts of glycyrrhisoflavone in these samples were 15-93 mg/100 g of dried powdered plant material.

[The comparison about inhibition of five Chinese herbal medicines to two different resources alpha-glycosidase].

OBJECTIVE: To compare alpha-glycosidase inhibitor microamount screening models which are established by two different resources alpha-glycosidase to screen the Chinese herbal medicines which have great alpha-glycosidase inhibition. METHODS: Comparing the activities of two different resources alpha-glycosidase with glucose oxidase method, then establishing optimal reaction conditions. Extracting the water soluble compositions of Chinese gallnut, paeoniae radix, Glycyrrhiza, rhubarb, fructus by boiling ,then using the alpha-glycosidase inhibition model to check and compare their alpha-glycosidase inhibitions. RESULTS: Five Chinese herbal medicines all had alpha-glycosidase inhibition, and the greatest was Chinese gallnut. CONCLUSION: The activities of two resources alpha-glycosidase are certainly different, but they do not have significant influence on findings of screening alpha-glycosidase inhibitors in vitro. Water soluble compositions of five Chinese herbal medicines have alpha-glycosidase inhibition.

[Detection for alpha-glucosidase-inhibiting polyhydroxyalkaloid ingredients of Commelina communis L. by ESIMS].

For detecting polyhydroxyalkaloids-type alpha-glucosidase-inhibiting ingredients of Commelina communis L grown in China, total alkaloids were obtained from the plant by extraction with water, removal of precipitation after the addition of alcohol, enrichment and purification by ion exchange resin and sephadex LH 20 chromatography. Polyhydroxyalkaloids in the total alkaloids were detected by ion trap electron-spray ionization mass spectra (ESIMS). Several reported and unreported polyhydroxyalkaloids in the plant were detected from the material collected from Jixi county, Anhui province. The crude drug growing in China contains alpha-glucosidase-inhibiting polyhydroxyalkaloids and can be used to therapy in diabetes.

[Preliminary study on the alpha-glucosidase inhibitor from Glycyrrhiza uralensis Fisch].

OBJECTIVE: To extract and isolate alpha-glucosidase inhibitor from Glycyrrhiza uralensis Fisch. METHODS: The aqueous extract of Glycyrrhiza uralensis Fisch. was extracted by petroleum, ethyl acetate and n-butanol. In addition, the inhibitory activity against alpha-glucosidase of every fraction was determined and the inhibitory kinetics of ethyl acetate fraction was investigated. RESULTS: The inhibitory activities of four fractions were 68.93%, 83.2%, 32.17% and 10.79% respectively. Compared with the aqueous extract (69.77%), the inhibitory activity of ethyl acetate fraction was higher. Ethyl acetate fraction was shown to be a fast-binding, dose-dependent and competitive model with a Ki value of 34 microg/ml. CONCLUSION: It is hoped to obtain good alpha-glucosidase inhibitors by separating ethyl acetate fraction of aqueous extract of Glycyrrhiza uralensis Fisch further.

Yeast and mammalian alpha-glucosidase inhibitory constituents from Himalayan rhubarb Rheum emodi Wall.ex Meisson.

The methanolic extract of rhizome of Himalayan rhubarb Rheum emodi displayed mild yeast as well as mammalian intestinal alpha-glucosidase inhibitory activity. However, further fractionation of active extract led to the isolation of several potent molecules in excellent yields, displaying varying degrees of inhibition on two test models of alpha-glucosidase. Rhapontigenin, desoxyrhapontigenin, chrysophanol-8-O-beta-d-glucopyranoside, torachrysone-8-O-beta-d-glucopyranoside displayed potent yeast alpha-glucosidase inhibition. However chrysophanol-8-O-beta-d-glucopyranoside, desoxyrhaponticin and torachrysone-8-O-beta-d-glucopyranoside displayed potent to moderate mammalian alpha-glucosidase inhibitory activity. Other compounds displayed mild activity on both the tests. Except desoxyrhapontigenin and rhapontigenin that increased Vmax, other compounds including crude extract decreased the Vmax significantly (p<0.02) in yeast alpha-glucosidase test. Further kinetic analysis on mammalian alpha-glucosidase inhibition showed that chrysophanol-8-O-beta-d-glucopyranoside, desoxyrhaponticin and torachrysone-8-O-beta-d-glucopyranoside may be classified as mixed-noncompetitive inhibitors. However, desoxyrhapontigenin and rhapontigenin may be classified as modulators of enzyme activity. Presence and position of glycoside moiety in compounds appear important for better inhibition of mammalian alpha-glucosidase. This is the first report assigning particularly, mammalian intestinal alpha-glucosidase inhibitory activity to these compounds. Chrysophanol-8-O-beta-d-glucopyranoside, desoxyrhaponticin, desoxyrhapontigenin and rhapontigenin have been isolated in substantial yields from R. emodi for the first time. Therefore, these compounds may have value in the treatment and prevention of hyperglycemia associated diabetes mellitus.

Experimental treatment of complications in alloxan diabetic rats with alpha-glucosidase inhibitor from the Chinese medicinal herb ramulus mori.

AIM: To assess the effects of the alpha-glucosidase inhibitor Sangzhi (Ramulus mori, SZ) on the relief of diabetic symptoms of hyperglycemia and the prevention of its late complications in alloxan diabetic rats with high-calorie chow. METHODS: The aqueous extract of Sangzhi was given orally to alloxan diabetic rats for 15 days. The hyperglycemic symptoms were observed. The blood glucose, lipid levels and the nephrotic representations were measured. RESULTS: When alloxan diabetic rats on high-calorie chow were treated with SZ, the hyperglycemic symptoms were improved, the blood lipid levels were improved, the ratio of kidney over body weight and the blood N-acetyl-beta-D-glucosaminidase (NAG) activity were lowered. The degree of renal pathological changes was significantly reduced. CONCLUSION: SZ may be useful for treating diabetes and its complications.

Characterization of alpha-maltotetraohydrolase produced by Pseudomonas sp. MS300 isolated from the deepest site of the mariana trench.

We have isolated a Pseudomonas-like amylase producer, the strain MS300, which displayed a large halo on starch medium, from the deepest site of the Mariana Trench. The strain MS300 produced two major and two minor alpha-maltotetraohydrolases (G4-amylase). The two major G4-amylases share the same molecular weight of 55,000 but had different pI values, 5.0 and 4.7, respectively. The optimum temperature for activity of both major G4-amylases is 40 degrees C, and the optimum pH is 6.8 for one and 8.9 for the other. MS300 produced more amylase under high hydrostatic pressure than under atmospheric pressure. Strain MS300 may be active in the deep sea at a depth of 10,897 m.

Purification to homogeneity and properties of plant glucosidase I.

Glucosidase I was purified about 3600-fold to apparent homogeneity from the microsomal fraction of mung bean seedlings. The purified enzyme removed the terminal alpha1,2-linked glucose from Glc3Man9GlcNAc2-peptide or the endoglucosaminidase H (Endo H)-released oligosaccharide. Glucosidase I activity was inhibited by kojibiose [Glc(alpha1-2)Glc], but not by other glucose disaccharides. Removal of up to four mannose residues from the N-linked oligosaccharide had little effect on its utilization as a substrate for glucosidase I. The enzyme had a subunit molecular weight of 97 kDa on SDS gels and this was shifted to 94 kDa after treatment with Endo H or Endo F, suggesting that glucosidase I is an N-glycoprotein having one oligomannose-type oligosaccharide. Amino acid sequences of this enzyme showed considerable identity to the enzyme cloned from a human hippocampus cDNA library. The enzyme was inhibited by castanospermine, deoxynojirimycin, MDL, and trehazolin, but not by australine or kifunensine. On the other hand, the other processing glucosidase, glucosidase II, is sensitive to inhibition by australine, but not by trehazolin. Thus, these two inhibitors are useful to distinguish glucosidase I from glucosidase II. The mung bean glucosidase I is quite sensitive to the histidine modifying reagent diethyl pyrocarbonate, whereas the pig liver glucosidase I is not. On the other hand, pig liver and pig brain glucosidase I preparations are sensitive to the sulfhydryl reagent NEM (N-ethylmaleimide), whereas the plant enzyme is not. These sensitivities to amino acid modifiers suggest significant differences between the plant and animal glucosidase I, in terms of catalytic site or protein conformation.

Purification to homogeneity and properties of glucosidase II from mung bean seedlings and suspension-cultured soybean cells.

Glucosidase II was purified approximately 1700-fold to homogeneity from Triton X-100 extracts of mung bean microsomes. A single band with a molecular mass of 110 kDa was seen on sodium dodecyl sulfate gels. This band was susceptible to digestion by endoglucosaminidase H or peptide glycosidase F, and the change in mobility of the treated protein indicated the loss of one or two oligosaccharide chains. By gel filtration, the native enzyme was estimated to have a molecular mass of about 220 kDa, suggesting it was composed of two identical subunits. Glucosidase II showed a broad pH optima between 6.8 and 7.5 with reasonable activity even at 8.5, but there was almost no activity below pH 6.0. The purified enzyme could use p-nitrophenyl-alpha-D-glucopyranoside as a substrate but was also active with a number of glucose-containing high-mannose oligosaccharides. Glc2Man9GlcNAc was the best substrate while activity was significantly reduced when several mannose residues were removed, i.e. Glc2Man7-GlcNAc. The rate of activity was lowest with Glc1Man9GlcNAc, demonstrating that the innermost glucose is released the slowest. Evidence that the enzyme is specific for alpha 1,3-glucosidic linkages is shown by the fact that its activity on Glc2Man9GlcNAc was inhibited by nigerose, an alpha 1,3-linked glucose disaccharide, but not by alpha 1,2 (kojibiose)-, alpha 1,4(maltose)-, or alpha 1,6 (isomaltose)-linked glucose disaccharides. Glucosidase II was strongly inhibited by the glucosidase processing inhibitors deoxynojirimycin and 2,6-dideoxy-2,6-imino-7-O-(beta-D- glucopyranosyl)-D-glycero-L-guloheptitol, but less strongly by castanospermine and not at all by australine. Polyclonal antibodies prepared against the mung bean glucosidase II reacted with a 95-kDa protein from suspension-cultured soybean cells that also showed glucosidase II activity. Soybean cells were labeled with either [2-3H]mannose or [6-3H]galactose, and the glucosidase II was isolated by immunoprecipitation. Essentially all of the radioactive mannose was released from the protein by treatment with endoglucosaminidase H. The labeled oligosaccharide(s) released by endoglucosaminidase H was isolated and characterized by gel filtration and by treatment with various enzymes. The major oligosaccharide chain on the soybean glucosidase II appeared to be a Man9(GlcNAc)2 with small amounts of Glc1Man9(GlcNAc)2.

Purification and properties of glucosidase I from mung bean seedlings.

The microsomal enzyme fraction from mung bean seedlings was found to contain glucosidase activity capable of releasing [3H]glucose from the glucose-labeled Glc3Man9GlcNAc. The enzymatic activity could be released in a soluble form by treating the microsomal particles with 1.5% Triton X-100. When the solubilized enzyme fraction was chromatographed on DE-52, it was possible to resolve glucosidase I activity (measured by the release of [3H]glucose from Glc3Man9GlcNAc) from glucosidase II (measured by release of [3H]glucose from Glc2Man9GlcNAc). The glucosidase I was purified about 200-fold by chromatography on hydroxylapatite, Sephadex G-200, dextran-Sepharose, and concanavalin A-Sepharose. The purified enzyme was free of glucosidase II and aryl-glucosidase activities. Only a single glucose residue could be released from the Glc3Man9GlcNAc by this purified enzyme and the other product was the Glc2Man9GlcNAc. Furthermore, this enzyme was inhibited in a dose-dependent manner by kojibiose, an alpha-1,2-linked glucose disaccharide, but not by other alpha-linked glucose disaccharides. These data indicate that this glucosidase is a specific alpha-1,2-glucosidase. The pH optimum for the glucosidase I was about 6.3 to 6.5, and no requirements for divalent cations were observed. The enzyme was inhibited strongly by the glucosidase processing inhibitors, castanospermine and deoxynojirimycin, and less strongly by the plant pyrrolidine alkaloid, 2,5-dihydroxymethyl-3,4-dihydroxypyrrolidine. However, the enzyme was not inhibited by the mannosidase processing inhibitors, swainsonine, deoxymannojirimycin or 1,4-dideoxy-1,4-imino-D-mannitol. The stability of the enzyme under various conditions and other properties of the enzyme were determined.