Enantioseparation of some chiral flavanones using microbial cyclic beta-(1-->3),(1-->6)-glucans as novel chiral additives in capillary electrophoresis

Cyclic beta-(1-->3),(1-->6)-glucans, microbial cyclooligosaccharides produced by Bradyrhizobium japonicum USDA 110, were used as novel chiral additives for the enantiomeric separation of some flavanones such as eriodictyol, homoeriodictyol, hesperetin, naringenin, and isosakuranetin in capillary electrophoresis (CE). Among the flavanones, eriodictyol was separated with the highest resolution (R(s) 5.66) and selectivity factor (alpha 1.18) when 20mM cyclic beta-(1-->3),(1-->6)-glucans were added to the background electrolyte (BGE) at pH 8.3.     

Lysis of yeast cell walls. Lytic beta-(1 leads to 6)-glucanase from Bacillus circulans WL-12.

When grown in a mineral medium with yeast cell walls or yeast glucan as the sole carbon source, Bacillus circulans WL-12 produces wall-lytic enzymes in addition to non-lytic beta-(1 leads to 3) and beta-(1 leads to 6)-glucananases. The lytic enzymes were isolated from the culture liquid by adsorption on insoluble yeast glucan in batch operation. After digestion of the glucan, the mixture of enzymes was chromatographed on hydroxylapatite on which the lytic activity could be resolved into one lytic beta-(1 leads to 6)glucanase and two lytic beta-(1 leads to 3)-glucanase was further purified by chromatography over diethylamino-ehtyl-agarose and carboxymethyl cellulose. Its specific activity on pustulan was 6.2 units per mg of protein. The enzyme moved as a single protein with a molecular weight of 54000 during sodium dodecylsulphate electrophoresis in slab gels. Hydrolysis of pustulan went thorugh a series of oligosaccharides, leading to a mixture of gentiotriose, gentiobiose and glucose. The enzyme also produced small amounts of gentiobiose from laminarin and pachyman and on this basis its lytic activity on yeast cell walls,was attribut beta-(1 leads to 3)-linked oligosaccharides were not detected. The lytic beta-(1 leads to 6)-glucanase has an optimum pH of 6.0. Pustulan hydrolysis followed Michaelis-Menten kinetics. A Km of 0.29 mg pustulan per ml and a V of 9.1 micro-equivalents of glucose released/min per mg of enzyme were calculated. The enzyme has no metal ion requirement. The lytic beta-(1 leads to 6)-glucanase differs in essence from the non-lytic beta-(1 leads to 6)-glucanase of the same organism by its positive action on yeast cell walls and yeast glucan and its much lower specific activity on soluble pustulan.     

A protein-glucan intermediate during paramylon synthesis.

A sodium deoxycholate extract containing glucosyltransferase activity was obtained from a particulate preparation from Euglena gracilis. It transferred glucose from UDP-[14C]glucose into material that was precipitated by trichloroacetic acid. This material released beta-(1 leads to 3)-glucan oligosaccharides into solution on incubation with weak acid, weak alkali and beta-(1 leads to 3)-glucosidase. The products of the incubation of the deoxycholate extract with UDP-[14C]glucose were analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Radioactive bands were obtained that had the properties of beta-(1 leads to 3)-glucan covalently linked to protein by a bond labile to weak acid. High-molecular-weight material containing a beta-(1 leads to 3)-glucan was also shown to be present by gel filtration. The bond linking glucan to aglycone is possibly a pyrophosphate linkage. It is proposed that in Euglena gracilis beta-(1 leads to 3)-glucan (paramylon) is synthesized on a protein primer.     

Production and ecological significance of yeast cell wall-degrading enzymes from oerskovia

Motile actinomycetes capable of degrading walls of viable yeast cells were isolated from soil and identified as Oerskovia xanthineolytica. A lytic assay based on susceptibility of enzyme-treated cells to osmotic shock was developed, and 10 of 15 strains of O. xanthineolytica, Oerskovia turbata, and nonmotile Oerskovia- like organisms from other collections were found to possess yeast lytic activities. All lytic strains produced laminaranase and alpha-mannanase, but the amounts, determined by reducing group assays, were not proportional to the observed lytic activities. The Oerskovia isolates demonstrated chemotactic, predatory activity against various yeast strains and killed yeasts in mixed cultures. Of 15 carbon sources tested for production of lytic enzyme, purified yeast cell walls elicited the highest activity. Glucose repressed enzyme production and caused cells to remain in the microfilamentous and motile rod stages of the Oerskovia cell cycle. Crude lytic activity was optimal at pH 5.6 to 7.0 and inactivated by heating for 6 min at 50 degrees C. Partial purification by isoelectric focusing showed that all lytic activity was associated with four beta-(1-->3)-glucanases. The absence of protein disulfide reductase, N-acetyl-beta-d-hexosaminidase, and phosphomannanase in crude preparations indicated that the principal enzyme responsible for yeast wall lysis was a beta-(1-->3)-glucanase that produced relatively little reducing sugar from yeast glucan.     

Cellulose synthesis by extracts of Acanthamoeba castellanii during encystment. Stimulation of the incorporation of radioactivity from UDP-(14C)glucose into alkali-soluble and insoluble beta-glucans by glucose 6-phosphate and related compounds.

1. The activity of a particulate enzyme prepared from encysting cells of Acanthamoeba castellanii (Neff), previously shown to catalyze the incorporation of glucose from UDP-[14C]glucose into both alkali-soluble and alkali-insoluble beta-(1 leads to 4) glucans, was stimulated several fold by glucose-6-phosphate and several related compounds. 2. Incorporation was observed when [14C]glucose-6-P was incubated with the particles in the presence of UDP-glucose. The results of product analysis by partial acid hydrolysis indicated that glucose-6-P stimulates the formation of both alkali-soluble and alkali-insoluble beta-(1 leads to 4) glucans from UDP-[14C]glucose and was itself incorporated into an alkali-insoluble beta-(1 leads to 4)glucan. 3. When particles incubated with UDP-[14C]glucose and glucose-6-P were reisolated and then reincubated with unlabeled UDP-glucose and glucose-6-P, a loss of counts from the alkali-soluble fraction was detected along with a corresponding rise in the radioactivity of the alkali-insoluble fraction. This suggests that the alkali-soluble beta-glucan was converted to an alkali-insoluble product and possibly may be an intermediate stage in cellulose synthesis.     

Beta-glucanases in the yeast Cryptococcus albidus var. aerius. Production and separation of beta-glucanases in asynchronous cultures.

beta-Glucanases were detected in cell-free extracts of the yeast Cryptococcus albidus var. aerius when grown on glucose as the sole carbon source. The production of beta-glucanases was followed in log-phase cells and stationary-phase cells; the maximal production of beta-(1 leads to 3) and beta-(1 leads to 6) glucanases takes place respectively in log-phase and stationary-phase cells. The results show that there are marked differences in the elution profiles on Sephadex G-50 of fractions containing beta-glucanase from cells grown for 12, 24, 48, 72, and 96 h. The possibility either of replacement changes in fractions containing beta-glucanase activity or of a different synthesis of each beta-glucanase during the growth of the yeast is discussed. The results suggest that all fractions containing beta-glucanases hydrolyze both beta-(1 leads to 3) and beta-(1 leads to 6) linkages. Evidence in support of the conclusion that a low molecular form of beta-glucanase has a molecular weight of 2100 +/- 100 is also shown.     

Involvement of beta-1,4-galactosyltransferase V in malignant transformation-associated changes in glycosylation

In spite of marked changes in the glycosylation upon malignant transformation of cells, no biological significance of beta-1, 4-galactosyltransferase (beta-1,4-GalT) activities has been elucidated. When beta-1,4-GalT activities toward 1 mM GlcNAcbeta-S-pNP were determined using homogenates of NIH3T3 and its transformant, MTAg, MTAg contained 1.3 times higher activities. Northern blot analysis, however, revealed that the beta-1,4-GalT V gene expression increases by three times with a decrease in that of beta-1,4-GalT II by one-fifth and without significant changes in those of other beta-1,4-GalTs in MTAg. Analysis of beta-1,4-GalT V acceptor-specificity showed that the GlcNAcbeta1-->6Man group of the GlcNAcbeta1-->6(GlcNAbeta1-->2)Manalpha1- branch is galactosylated. These results indicate that changes in beta-1,4-GalT II and V activities are important for the altered glycosylation.     

Lysis of yeast cell walls. Lytic beta-(1 leads to 3)-glucanases from Bacillus circulans WL-12.

Bacillus circulans WL-12 when grown in a mineral medium with yeast cell walls or yeast glucan as the soli carbon source, produced five beta-glucanases. Two beta-(1 leads to 3)-glucanases (I and II), which are lytic to yeast cell walls, were isolated from the culture liquid by batch adsorption on yeast glucan, and separated by chromatography on hydroxylapatite. Lytic beta-(1 leads to 3)-glucanase I was further purified by carboxymethylcellulose chromatography. The specific activity of lytic beta-(1 leads to 3)-glucanase I on laminarin was 4.1 U per mg of protein. The enzyme moved as a single protein with a molecular weight of 40000 during sodium dodecylsulfate electrophoresis in slab gels. It was specific for the beta-(1 leads to 3)-glucosidic bond but the enzyme did not hydrolyze laminaribiose. Hydrolysis of laminarin went through a series of oligosaccharides, and laminaribiose and glucose accumulated till the end of the reaction. A small amount of gentibiose was also produced from laminarin. Products from yeast cell walls and yeast glucan included laminaripentaose, laminaritriose, laminaribiose, glucose and gentiobiose, but no laminaritetraose was detected. This glucanase has an optimum pH of 5.5.     

Presence of erythroglycan on human K-562 chronic myelogenous leukemia-derived cells

Total glycopeptides from human K-562 cells, labeled metabolically with [3H]glucosamine or [3H]mannose, were prepared by extracting the cells with organic solvents to remove lipids and by digesting the residue with pronase. 3H-labeled glycopeptides were fractionated on Sephadex G-50 revealing a high molecular weight fraction (Mr = 7,000 to 11,000), comprising approximately 10% of the [3H]glucosamine and 25% of the [3H]mannose label. Digestion of this glycopeptide fraction with endo-beta-galactosidase from Escherichia freundii, specific for a repeating structure of Gal(beta 1 leads to 4)GlcNAc(beta 1 leads to 3), results in the following four products as resolved by Bio-Gel P-2 gel filtration: 1) a disaccharide with the structure beta-2-deoxy-2-acetamidoglucosyl leads to beta-galactose; 2) a trisaccharide with the structure beta-galactosyl leads to beta-2-deoxy-2-acetamidoglucosyl leads to beta-galactose; 3) a tetrasaccharide with the sequence alpha-N-acetylneuraminyl leads to beta-galactosyl leads to beta-2-deoxy-2-acetamidoglucosyl leads to beta-galactose; and 4) a larger, complex fragment which contains mannose and beta-2-deoxy-2-acetamidoglucose and which is probably the protein linkage region. In addition, visualization of radiolabeled glycoproteins by fluorography on polyacrylamide gels revealed a 105,000-dalton "Band 3"-like glycoprotein and other bands that were sensitive to endo-beta-galactosidase. These results indicate that the K-562 cell line bears a glycopeptide, erythroglycan, which has been found on erythrocytes, and that this polymer is expressed mainly in the fetal form as a linear chain.     

Biosynthesis of (1→3),(1→4)-β-glucan in developing endosperms of barley (Hordeum vulgare)

A (1→3),(1→4)-β-glucan synthase catalysing the synthesis of (1→3),(1→4)-β-glucan (mixed-linkage glucan) was investigated using microsomal membranes prepared from developing barley (Hordeum vulgare L. cv. Shikokuhadaka 97) endosperms harvested 21 days after flowering. The microsomal fraction produced (1→3),(1→4)-β-glucan by incorporation of [¹⁴C]Glc from UDP-[¹⁴C]Glc. The production of (1→3),(1→4)-β-glucan was ascertained by specific enzymatic digestion with endo-(1→3),(1→4)-β-glucanase (lichenase; EC 3.2.1.73) from Bacillus amyloliquefaciens, which released a radiolabelled trisaccharide (3-O-β-cellobiosyl-glucose) and a tetrasaccharide (3-O-β-cellotriosyl-glucose), the diagnostic oligosaccharides for the identification of (1→3),(1→4)-β-glucan. Digestion of the products with exo-(1→3)-β-glucanase (EC 3.2.1.58) from Basidiomycete QM806 released radiolabelled Glc, indicating that not only (1→3),(1→4)-β-glucans but also (1→3)-β-glucans (callose) had been formed due to the presence of (1→3)-β-glucan (callose) synthase (EC 2.4.1.34) in the microsomal fraction. The activity of (1→3),(1→4)-β-glucan synthase was maximal at pH 9.0 and at 25°C and in the presence of at least 2 mM Mg²⁺. The apparent K_m and V_max values for UDP-Glc were 0.33 mM and 480 pmol min⁻¹ mg protein⁻¹, respectively. Investigating the dependence of enzyme activity on developmental stage (7–35 days after flowering) of the endosperms, we found an increase of activity during the initial development reaching a maximum at 19 days, followed by a gradual decrease as the endosperms matured. The amount of (1→3),(1→4)-β-glucan in the cell walls of the endosperms, however, increased gradually towards maturation, even after 19 days. Analysing the relationship between enzyme activity and (1→3),(1→4)-β-glucan deposition in cell walls of endosperms prepared from 12 different barley varieties harvested 11–22 days after flowering showed that some varieties had both low activity and low glucan content, and in some both were high. But for several other varieties, the availability of donor substrate and other factors seem to influence the production of (1→3),(1→4)-β-glucan as well.     

A xylosyltransferase that synthesizes beta-(1-->4)-xylans in wheat (Triticum aestivum L.) seedlings

A particulate preparation from 6-day-old seedlings of wheat (Triticum aestivum L.) was found to contain a xylosyltransferase (XylTase) which incorporated xylose (Xyl) from UDP-xylose into exogenous beta-(1-->4)-xylooligosaccharides with 2-aminopyridine-derivatized reducing end groups. High-performance liquid chromatographic analysis showed that the chain elongation of pyridylaminated beta-(1-->4)-xylotriose (Xyl3-PA) occurred by attachment of a series of one, two, or three xylosyl residues, depending on substrate concentrations and reaction times. Methylation analysis and beta-xylosidase digestion of the newly synthesized Xyl4-PA confirmed that the xylosyl residues were incorporated through beta-(1-->4)-linkages. The enzyme was maximally active at pH 6.8 and 20 degrees C, and required Triton X-100, which enhanced activity 5-fold at a concentration of 0.05-2%. Divalent ions, including Mn2+ and Mg2+, did not affect activity. Enzyme activity increased with increasing polymerization of xylosyl residues of the acceptor substrates: for instance, Xyl5-PA was almost 7 times as efficient as Xyl2-PA. The apparent Michaelis constants of the enzyme for Xyl3-PA and UDP-xylose were 13.5 and 7.9 mM, respectively. The enzyme also catalyzed incorporation of radioactive sugars (Xyl together with a small portion of L-arabinose) from UDP-[14C]xylose into higher beta-(1-->4)-xylooligosaccharides (degree of polymerization > 7) with or without (4-O-methyl-)glucuronosyl side chains at activities comparable to those observed for pyridylaminated xylooligosaccharides, and into several heteroxylans but with much lower efficiency. Enzymatic hydrolysis of the product with a beta-xylanase degraded it into mainly xylobiose, providing further evidence that the xylosyl residues are incorporated through beta-(1-->4)-linkages.     

β-Glucan hydrolases from Aspergillus niger. Isolation of a β-(1→4)-glucan hydrolase and some properties of the β-(1→3)-glucan-hydrolase components

1. The components of an enzyme preparation from Aspergillus niger, which hydrolysed substrates containing beta-(1-->3)- and beta-(1-->4)-glucosidic linkages, were separated by calcium phosphate and Dowex 1 column chromatography. 2. The hydrolytic activity of each fraction from both types of column towards laminaribiose, laminarin, carboxymethylpachyman, pachydextrins, salicin, cellobiose, cellopentaose and swollen cellulose was tested. 3. The activity towards the beta-(1-->3)-glucosidic substrates was found in three well-separated groups of fractions. The differences in action pattern of these groups is discussed. 4. Preparative-scale chromatography that enabled the separation of a beta-(1-->4)-glucan-glucanohydrolase component substantially free of activity towards beta-(1-->3)-glucosidic substrates is described. Residual beta-(1-->3)-glucan-hydrolase activity was removed by adsorption on to insoluble laminarin at pH3.5.     

Structures of the oligosaccharides from the enzymic hydrolysis of hemicellulose by a hemicellulase of Ceratocystis paradoxa.

And endo-hemicellulase (HC-II) of Ceratocystis paradoxa degraded spear-grass hemicellulose B to a series of mixed oligosaccharides. Four neutral oligosaccharides (AraXyl2, AraXyl3, Xyl2, and Xyl3), isolated by preparative paper chromatography, were shown by enzymic and methylation techniques to constitute a series of beta-(1 leats to 4)-D-xylose and O-alpha-L-arabinofuranosyl-(1 leads to 3)-O-beta-D-xylopyranosyl-(1 leads to 4)-O-beta-D-xylopyranosyl-(1 leads to 4)-D-xylose, respectively, the latter being a new compound.     

Structural analysis of multiple bovine P-450(11 beta) genes and their promoter activities

A bovine genomic library was constructed using a cosmid vector, pHC79, and bovine DNA partially digested by EcoRI. Bovine P-450(11 beta) cDNA, pcP-450(11 beta)-2 [Morohashi et al. (1987) J. Biochem. 102,559-568], was used as a probe for screening the genomic library. Ten clones carrying P-450(11 beta) genomic DNA were isolated from 8 x 10(4) colonies and classified into five groups (CB11 beta-1, CB11 beta-3, CB11 beta-7, CB11 beta-20, and CB11 beta-21) according to differences in the restriction endonuclease sites. Nucleotide sequences of amino acid coding regions of the five clones were determined by the dideoxy sequencing method using synthetic nucleotides corresponding to various parts of the cDNA as primers. The nucleotide sequences revealed that three clones, CB11 beta-1, CB11 beta-3, and CB11 beta-21, were pseudogenes. Amino acid sequences coded by the other two clones, CB11 beta-7 and CB11 beta-20, were identical with that coded by a previously described cDNA, pcP-450(11 beta)-3 [Kirita et al. (1988) J. Biochem. 104, 683-686]. The promoter regions of the five clones were introduced in front of chloramphenicol acetyltransferase (CAT) gene of pSV00CAT and used to examine P-450(11 beta) gene regulation in cultured cells. The five recombinant plasmids showed cAMP-responsive CAT activities in Y-1 cells, a cell strain derived from adrenal tumor. The induction rates of the recombinant plasmids carrying the promoters of normal genes, CB11 beta-7 and -20, were larger than those of pseudogenes, CB11 beta-1, -3, and -21. CAT activities expressed by the promoter regions of the normal genes in the presence or absence of cAMP in Y-1 cells were almost equal to that by the promoter region of human P-450(SCC) gene. Though the promoter of the P-450(SCC) gene also showed cAMP-responsive CAT activity in I-10 cells, a cell strain derived from Leyding cell tumor, P-450(11 beta) gene promoter did not express the activity in I-10 cells.     

Characterization of ndvD,the third gene involved in the synthesis of cyclic beta-(1 --> 3),(1 --> 6)-D-glucans in Bradyrhizobium japonicum

Previously, we identified two genes in Bradyrhizobium japonicum (ndvB, ndvC) that are required for cyclic beta-(1 --> 3),(1 --> 6)-D-glucan synthesis and successful symbiotic interaction with soybean (Glycine max). In this study, we report a new open reading frame (ORF1) located in the intergenic region between ndvB and ndvC, which is essential for beta-glucan synthesis and effective nodulation of G. max. This new gene is designated ndvD (nodule development). The ndvD translation product has a predicted molecular mass of 26.4 kDa with one transmembrane domain. Genetic experiments involving gene deletion, Tn5 insertion, and gene complementation revealed that the mutation of ndvD generated pleiotropic phenotypes, including hypoosmotic sensitivity, reduced motility, and defects in conjugative gene transfer, in addition to symbiotic ineffectiveness. Although deficient in in vivo beta-glucan synthesis, membrane preparations from the ndvD mutant synthesized neutral beta-glucans in vitro. Therefore, ndvD does not appear to be a structural gene for beta-glucan synthesis. Our hypothesis for the mechanism of beta-(1 --> 3),(1 --> 6)-D-glucan synthesis is presented.     

Role of chitinase and beta-1,3-glucanase activities produced by a fluorescent pseudomonad and in vitro inhibition of Phytophthora capsici and Rhizoctonia solani

A study was conducted to investigate the possibility of involvement of chitinase and beta-1,3-glucanase of an antagonistic fluorescent Pseudomonas in growth suppression of phytopathogenic fungi, Phytophthora capsici and Rhizoctonia solani. Fluorescent Pseudomonas isolates GRC(3) and GRC(4) were screened for their antifungal potential against phytopathogenic fungi by using dual culture technique both on solid and liquid media. The percent inhibition was calculated. Various parameters were monitored for optimization of enzyme activities by fluorescent Pseudomonas GRC(3). The involvement of chitinases, beta-1,3-glucanases, and antifungal metabolites of nonenzymatic nature was correlated with the inhibition of P. capsici and R. solani. The results provide evidence for antibiosis as a mechanism for antagonism. The study also confirms that multiple mechanisms are involved in suppressing phytopathogens as evidenced by the involvement of chitinase and beta-1,3-glucanase in inhibition of R. solani but not P. capsici by isolate GRC3.     

四数九里香中的咔唑类生物碱成分及其细胞毒活性研究

为阐明民族药四数九里香Murraya tetramera Huang的药效物质基础,本研究使用色谱分离技术从其醇提取物中分离纯化得7个咔唑类生物碱和1个甾体类化合物,运用波谱方法鉴定为β-谷甾醇(1)、1-甲基-3-丙酰基咔唑(2)、1-甲氧基-3-乙基咔唑(3)、1-甲氧基-3-甲酰基咔唑(4)、1-甲氧基-3-甲基咔唑(5)、1-羧基甲酯-3-甲基咔唑(6)、1-羧基甲酯-3-乙基咔唑(7)、mananimbine(8)。除了化合物1,其他化合物为首次从该植物中分离得到;化合物2～5、7对SMMC-7721的IC50分别为40. 93±0. 66、46. 03±2. 05、114. 21±5. 67、15. 79±0. 99、185. 1±0. 44。结果表明化合物2～5、7对SMMC-7721显现很好的细胞毒活性。     

Orally administered beta-glucans enhance anti-tumor effects of monoclonal antibodies

beta-Glucan primes leukocyte CR3 for enhanced cytotoxicity and synergizes with anti-tumor monoclonal antibodies (mAb). We studied readily available (1-->3)-beta- D-glucan using the immune deficient xenograft tumor models, and examined the relationship of its anti-tumor effect and physico-chemical properties. Established subcutaneous (s.c.) human xenografts were treated for 29 days orally with daily beta-glucan by intragastric injection and mAb intravenously (i.v.) twice weekly. Control mice received either mAb alone or beta-glucan alone. Tumor sizes were monitored over time. beta-Glucans were studied by carbohydrate linkage analysis, and high performance size-exclusion chromatography with multiple angle laser scattering detection. Orally administered beta- D-glucan greatly enhanced the anti-tumor effects of mAb against established tumors in mice. We observed this beta-glucan effect irrespective of antigen (GD2, GD3, CD20, epidermal growth factor-receptor, HER-2), human tumor type (neuroblastoma, melanoma, lymphoma, epidermoid carcinoma and breast carcinoma) or tumor sites (s.c. versus systemic). This effect correlated with the molecular size of the (1-->3),(1-->4)-beta- D-glucan. Orally administered (1-->3),(1-->6)-beta- D-glucans also synergized with mAb, although the effect was generally less marked. Given the favorable efficacy and toxicity profile of oral beta- D-glucan treatment, the role of natural products that contain beta-glucan in cancer treatment as an enhancer of the effect of mAb therapy deserves further study.     

杨桃根水提取物化学成分及生物活性的研究

为探究杨桃根中具备降血糖功能的活性成分,采用色谱分离方法从其水提取物中分离得到9个化合物,应用波谱技术对它们的化学结构进行了鉴定,分别命名为prismaconnatoside(1),tarennanosides A(2),(+)-catechin(3),fernandoside(4),7a-[(β-glucopyranosyl) oxy]-lyoniresinol(5),(+)-lyoniresinol 3α-O-β-D-glucopyranoside(6),(-)-lyon-iresinol 3α-O-β-D-glucopyranoside(7),(-)-5’-methoxy-isolariciresinol 3α-O-β-D-glucopyranoside(8)和正辛烷(9)。其中化合物1,2,4,5均为首次从杨桃中分离得到,化合物3为首次从杨桃根中分离得到。对部分单体化合物进行了体外α-葡萄糖苷酶和DPP-IV酶抑制活性测试,化合物1具有较强的α-葡萄糖苷酶抑制活性。     

大黄鱼共生菌Bacillus coagulans LL1103的代谢产物研究

[目的]研究大黄鱼共生菌Bacillus coagulans LL1103的次生代谢产物及其抑菌活性。[方法]利用色谱层析技术对B.coagulans LL1103发酵液乙酸乙酯和正丁醇提取物进行分离纯化;运用波谱技术鉴定化合物的结构;采用微量肉汤稀释法对化合物进行抗菌活性测定。[结果]从大黄鱼内生菌B.coagulans LL1103发酵液中分离并鉴定9个环二肽类化合物,分别为:(1)环(4-羟基-脯氨酸-亮氨酸)、(2)环(异亮氨酸-丙氨酸)、(3)环(脯氨酸-缬氨酸)、(4)环(脯氨酸-苯丙氨酸)、(5)环(脯氨酸-亮氨酸)、(6)环(甘氨酸-丙氨酸)、(7)环(脯氨酸-甘氨酸)、(8)环(脯氨酸-丙氨酸)和(9)环(络氨酸-甘氨酸)。活性评价显示化合物3、7和9对大肠埃希菌(Escherichia coli)具有较强抑制作用,最低抑菌浓度(minimal inhibitory concentration,MIC)分别为8.0、4.0和16.0μg/mL。[结论]从大黄鱼共生菌B.coagulans LL1103的发酵液中分离得到3个对大肠埃希菌(E.coli)具有较好抑制活性的化合物。