[Studies on chemical constituents from fruits of Morus alba L]

Chemical investigation of fruits of Mours alba L. lead to the isolation of fifteen compounds by various chromatographies such as silica gel, Sephadex LH-20, RP-C18 column chromatography. Their structures were determined to be: 1-[5-(2-formlfuryl) methyl] dihydrogen 2-hydroxypropane-1, 2, 3-tricarboxylate 2, 3-diethyl ester (1), 1-[2-(furan-2-yl)-2-oxoethyl] pyrrolidin-2-one (2), divaricataester A (3), methyl 1-[2-(furan-2-yl)-2-oxoethyl]-5-oxopyrrolidine-2-carboxylate (4), 1-[2-(furan-2-yl)-2-oxoethyl]-5-oxopyrrolidine-2-carboxylic acid (5), L-pyroglutamic acid (6), L-pyroglutamic acid ethyl ester (7), 3-O-caffeoylquinic acid methyl ester (8), 3-O-caffeoylquinic acid ethyl ester (9), 5-O-caffeoylquinic acid methyl ester (10), 5-O-caffeoylquinic acid ethyl ester (11), 4-O-caffeoylquinic acid methyl ester (12), 4-O-caffeoylquinic acid methyl ester (13), 4-O-caffeoylquinic acid (14), 3-O-caffeoylquinic acid (15), respectively, based on the spectral analysis such as NMR, MS etc. Compounds 1-14 were isolated from this genus for the first time, among which 1 was a new compound.

Identification of a hepatoprotective peptide in wheat gluten hydrolysate against D-galactosamine-induced acute hepatitis in rats

A hepatoprotective peptide, pyroglutamyl leucine (pyroGlu-Leu), was identified in wheat gluten hydrolysate through an in vivo activity-guided fractionation approach based on D-galactosamine-induced acute hepatitis in rats and fractionation of peptides with large-scale preparative ampholine-free isoelectric focusing. The active acidic fraction predominantly consisted of pyroglutamyl peptides and free pyroglutamic acid. Pyroglutamyl peptides were derivatized with phenyl isothiocyanate after removal of a pyroglutamyl residue by pyroglutamate aminopeptidase. The derivatives were purified by reversed-phase HPLC and subjected to sequence analysis. The active fraction contained pyroGlu-Ile, pyroGlu-Leu, pyroGlu-Gln, pyroGlu-Gln-Gln, and free pyroGlu. Ingestion of pyroGlu-Leu at 20 mg/kg body weight significantly decreased serum aspartate and alanine aminotransferases to approximately 30% and 20% of those values of the vehicle group, respectively, which were near the normal levels. Thirty minutes after ingestion of pyroGlu-Leu at 20 mg/kg, the concentration of pyroGlu-Leu in portal blood plasma increased to approximately 2 μM.

[Study on the chemical constituents from the ethyl acetate extracts of Cremastra appendiculata]

OBJECTIVE

To study the chemical constituents from the ethyl acetate extracts of Cremastra appendiculata.

METHODS

The compounds from the ethyl acetate extracts were isolated by the silica gel column and Sephadex LH-20 column chromatography, their structures were elucidated by the spectral analysis and chemical evidence.

RESULTS

Seven componds were separated and identified as fumaric acid (1), dimethylhexyl phthalate (2), L-pyroglutamic acid (3), 2-furoic acid (4), vanillic acid (5), p-coumaric acid (6), protocatechuic acid (7).

CONCLUSIONS

Compounds 1 to 6 are obtained from this plant for the first time.

Two new compounds from the endophytic fungus Colletotrichum sp. L10 of Cephalotaxus hainanensis

Two new compounds, 3-(4-methoxy-3-methyl-2-oxo-2H-pyran-6-yl)butyl pyroglutamate (1) and 2,2'-(1,1'-methylenebis(1H-indole-3,1-diyl))diethanol (2), were isolated from the endophytic fungus of Cephalotaxus hainanensis. Their structures were determined by means of chemical and spectroscopic analysis.

Biological activity and identification of neuropeptides in the neurosecretory complexes of the cabbage pest insect, Mamestra brassicae (Noctuidae; Lepidoptera)

The need for more environmentally sound strategies of plant protection has become a driving force in physiological entomology to combat insect pests more efficiently. Since neuropeptides regulate key biological processes, these "special agents" or their synthetic analogues, mimetics, agonists or antagonists may be useful tools. We examined brain-suboesophageal ganglia and corpora cardiaca-corpora allata complexes of the cabbage moth, Mamestra brassicae, in order to obtain clues about possible peptide candidates which may be appropriate for the biological control of this pest. With the aid of bioassays, reversed phase high performance liquid chromatography, and mass spectrometry, five neuropeptides were unequivocally identified and the presence of a further three were inferred solely by comparing mass spectra with known peptides. Only one neuropeptide with adipokinetic capability was identified in M. brassicae. Data from the established homologous bioassay indicated that the cabbage moths rely on a lipid-based metabolism which is aided by an adipokinetic hormone (viz. Manse-AKH) that had previously been isolated in many different lepidopterans. Other groups of neuropeptides identified in this study are: FLRFamides, corazonin, allatostatin and pheromonotropic peptide.

[Chemical constituents of Changium smyrnioides]

OBJECTIVE

To study chemical constituents of Changium smyrnioides Wolff.

METHODS

The chemical components were isolated and purified by silica gel column and recrystallization. The chemical structures were elucidated on the basis of physico-chemical properties and spectral data.

RESULTS

Ten compounds were isolated and identified as lignoceric acid (1), beta-sitosterol (2), stigmasterol (3), 5-hydroxy-8-methoxypsoralen (4), glycerylmonopalmitate (5), L-pyroglutamic acid (6), succinic acid (7), vanillic acid-4-O-beta-D-glucopyranoside (8 ), vanillic acid (9), daucosterol (10).

CONCLUSION

Compounds 1, 4, 5, 6, 8 and 9 are obtained from the plant for the first time.

A novel adipokinetic peptide in a water boatman (Heteroptera, Corixidae) and its bioanalogue in a saucer bug (Heteroptera, Naucoridae)

The corpora cardiaca (CC) of two water bug species, the water boatman Corixa punctata and the saucer bug Ilyocoris cimicoides, contain a substance that cause hyperlipemia in the migratory locust. The primary sequence of one octapeptide belonging to the adipokinetic hormone (AKH)/red pigment-concentrating hormone (RPCH) family was deduced from the multiple MS(N) electrospray mass data of CC material from each species. Whereas the saucer bug contains the known octapeptide pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp amide, code-named Anaim-AKH, the water boatman has a novel peptide identified as pGlu-Leu/Ile-Asn-Phe-Ser-Pro-Ser-Trp amide, code-named Corpu-AKH. The ambiguity about the amino acid at position 2, i.e. Leu or Ile, in Corpu-AKH was solved by isolating the peptide in a single-step by reversed-phase HPLC and establishing co-elution with the synthetic peptide containing Leu at position 2. Functionally, the peptides regulate lipid mobilization, as evidenced by an adipokinetic effect after injecting synthetic Anaim-AKH and Corpu-AKH into the respective acceptor species. Swimming activity of I. cimicoides also causes hyperlipemia.

Capillary electrophoresis for caffeine and pyroglutamate determination in coffees

In a preliminary study pyroglutamate showed to be over 10 times increased in some lyophilised coffees with respect to brewed or filtered coffees, and probably that increase is related to some stage of the industrial process. Pyroglutamate is known to have a number of remarkable cognitive enhancing effects, which could be also related to the properties of coffee traditionally associated to caffeine. Pyroglutamate improves memory and learning and has anti-anxiety effects in rats. Therefore, a method has been developed and validated for the simultaneous determination of caffeine and pyroglutamate in coffee by capillary electrophoresis. Separation conditions employed MECK conditions with 50 mM borate buffer at pH 9.5 with 130 mM SDS. The applied potential was 10 kV and detection was performed at 200 nm. Afterwards, 10 soluble coffees from the market were measured and caffeine and pyroglutamate levels were compared. Those coffees with higher pyroglutamate with or without caffeine were preliminarily tested for sedative/stimulant properties and cognition enhancing effects in mice. The most relevant finding was a partial reversal of scopolamine-induced amnesia in the passive avoidance paradigm after oral administration of one coffee.

[Studies on chemical constituents in leaf of Isatis indigotica]

OBJECTIVE

To study the chemical constituents of the leaf of Isatis indigotica.

METHOD

Chromatography and spectral analysis were respectively used to isolate and identify the constituents.

RESULT

Three compounds were isolated from the ethanol extracts of theleaf of I. indigotica, and identified as indirubin, tryptanthrin and L-pyroglutamic acid.

CONCLUSION

L-pyroglutamic acid was isolated from the genus for the first time, and tryptanthrin was isolated from the leaf of this plant for the first time.

Isolation of an anti-angiogenic substance from Agaricus blazei Murill: its antitumor and antimetastatic actions

We previously found that ergosterol isolated from Agaricus blazei inhibited tumor growth through the inhibition of tumor-induced neovascularization. In the present study, we isolated further anti-angiogenic substances (A-1 and A-2) from this fungus using an assay system of angiogenesis induced by Matrigel supplemented with vascular endothelial growth factor, and A-1 was identified as sodium pyroglutamate. Next, we examined the antitumor and antimetastatic actions of A-1 using Lewis lung carcinoma (LLC)-bearing mice. A-1 (30, 100 and 300 mg/kg) inhibited tumor growth and metastasis to the lung. The reduction of the numbers of splenic lymphocytes, CD4+ and CD8+ T cells in LLC-bearing mice was inhibited by the oral administration of A-1 (30, 100 and 300 mg/kg). Further, A-1 increased the number of apoptotic cells of tumors and the numbers of CD8+ T and natural killer cells invading the tumors, and inhibited the increase of von Willebrand factor expression (a measure of angiogenesis) in the tumors. These results suggest that the antitumor and antimetastatic actions of A-1 (sodium pyroglutamate) may be associated with inhibition of the reduction of immune response caused by the tumor growth and tumor-induced neovascularization. This is the first report showing that sodium pyroglutamate isolated from A. blazei as an anti-angiogenic substance has potent antitumor and antimetastatic actions, as well as immune-modulatory activity, in tumor-bearing mice.

Identification of neuropeptides from brains of larval Manduca sexta and Lacanobia oleracea using MALDI-TOF mass spectrometry and post-source decay

The occurrence of neuropeptides in the brain of larvae of the tobacco hawkmoth, Manduca sexta, and tomato moth, Lacanobia oleracea, was investigated using matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF) mass spectrometry (MS) and post-source decay (PSD). Methanolic extracts of 100 brains separated by reversed-phase high performance liquid chromatography yielded numerous ion peaks, some of which were common to both species. In M. sexta six [M+H](+) ions were in agreement with peptides previously structurally characterised from M. sexta (FLRF-amides I, II and III, M. sexta allatostatin, CAP(2b) and myoinhibitory peptide VI), whereas a further five corresponded to other known lepidopteran peptides (cydiastatins 3 and 4, helicostatins 1 and 6 and helicokinin II). Of these the identities of FLRF-amide I, cydiastatins 3 and 4 and CAP(2b) were confirmed by PSD analysis. Fourteen [M+H](+) ions corresponding to known lepidopteran peptides (FLRF-amide I, cydiastatins 2, 3 and 4, helicostatins 1, 5, 6, 7 and 9, CCAP, CAP(2b), M. sexta allatostatin and myoinhibitory peptide VI) were measured in L. oleracea brain extracts. From this insect, cydiastatins 3 and 4, helicostatin 5 and FLRF-amide I were identified by PSD. These peptides had not previously been structurally characterised from L. oleracea.

Isolation and characterization of a novel 5-oxoprolinase (without ATP-hydrolyzing) from Alcaligenes faecalis N-38A

A screening test was undertaken to isolate a microorganism that produced 5-oxoprolinase (without ATP-hydrolyzing). The 5-oxoprolinase (without ATP-hydrolyzing) activity (decyclization activity toward L-pyroglutamate) was found in a cell-free extract of Alcaligenes faecalis N-38A, newly isolated from a soil sample. The enzyme was purified as a homogeneous preparation. The molecular weight of the enzyme was estimated to be 47,000. The decyclization activity was specific for L-pyroglutamate, and independent of ATP and metal ions. The reaction was a reversible one, i.e., cyclization reaction of L-glutamate to yield pyroglutamate was identified.

Analytical and chemical profile of pidotimod

Pidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl)carbonyl]-thiazolidine- 4-carboxylic acid, PGT/1A, CAS 121808-62-6) is a new synthetic immunostimulant, which has proved to possess a high activity. This paper describes its physico-chemical properties, structural identification including polymorphism, detection of impurities, determination of related compounds, separation, quantification and purity assay using high-performance liquid chromatography (HPLC).

Structural characterization of human interferon gamma. Heterogeneity of the carboxyl terminus

Natural human interferon gamma(IFN-gamma) was purified from the conditioned medium of peripheral blood leukocytes using selective silica gel adsorption and antibody-affinity chromatography. SDS-PAGE and Western blot analysis demonstrated three major species with molecular masses of 25 kDa, 20 kDa and 17 kDa. Structural analysis of this natural IFN-gamma preparation demonstrated a pyroglutamate residue at the amino terminus and a heterogeneous carboxyl terminus. The longest and most predominant polypeptide was 138 amino acids in length, which is five residues shorter than the sequence predicted from the cDNA. The presence of multiple-carboxyl-terminal forms indicated possible proteolytic processing during induction or protein purification. Limited proteolytic digestion of full-length recombinant IFN-gamma with endoproteinase Lys-C and trypsin revealed that the carboxyl-terminal 15 residues could be released under conditions in which the core portion of the polypeptide chain remained intact. Thus, the heterogeneity of natural IFN-gamma may be explained by partial proteolytic degradation of the molecule and differences in the degree of glycosylation as previously reported [Rinderknecht, E., O'Conner, B. H. & Rodriguez, H. (1984) J. Biol. Chem. 259, 6790-6797].

Pyroglutamyl N-termini of thermal polyamino acids

It has been established indirectly that the N-termini of the thermal polyamino acids are pyroglutamic acid. This was determined by trifluoroacetic acid hydrolysis of the lactam ring followed by Dansyl labelling. The polyamino acids contained Ala, Gly, Glu, Leu, Phe, and Pro. In the experiments described here, the presence of pyroglutamic acid at the N-terminus of a polyamino acid was determined directly by the use of pyrrolidone carboxylyl peptidase. The enzyme catalyzes the removal of pyroglutamyl residues at the N-terminus of polypeptide chains. The polyamino acids used in these studies contained glutamic acid, aspartic acid, alanine, glycine, isoleucine, proline and valine. Alkaline hydrolysis was also used to determine indirectly that the N-termini of these polyamino acids are pyroglutamic acid. Another interesting finding was that many of the amino acids in the polymerization mixture were found to occur penultimate to the N-terminal amino acid. This is interpreted to mean that the diffusible fraction contains many polyamino acids.

Isolation and structure determination of a novel spiro-gamma-lactam, spiro-arogenate

The eucaryotic microorganism, Neurospora crassa, is able under specified conditions (Zamir, L.O., Jung, E., and Jensen, R.A. (1982) J. Biol. Chem. 258, 6492-6496) to synthesize a cyclohexadienyl derivative of prephenic acid having the novel structure of a spiro-gamma-lactam. This L-gamma-(spiro-4-hydroxy-2,5-cyclohexadienyl)-pyroglutamate is herein given the trivial name, spiro-arogenate, to indicate its close relationship to the amino acid, L-arogenate. Spiro-arogenate is quantitatively converted to phenylalanine at mildly acidic pH and can be converted to arogenate by boiling at basic pH. The structure of spiro-arogenate was established through the application of spectroscopic techniques (ultraviolet, 1H-NMR, 13C-NMR, and mass spectrometry). The 1H-NMR and 13C-NMR spectra of spiro-arogenate isolated as the natural product conformed to the spectrum of spiro-arogenate prepared by chemical synthesis by S. Danishefsky and co-workers (Danishefsky, S., Morris, J., and Clizbe, L.A. (1981) J. Am. Chem. Soc. 103, 1602-1604). Circular dichroism established the S configuration of the asymmetric carbon at C-8 of spiro-arogenate.

Reversed-phase high-performance liquid chromatography used to monitor enzymatic cleavage of pyrrolidone carboxylic acid from regulatory peptides

Sequence determination of peptides blocked by amino-terminal pyrrolidone carboxylic acid (PCA) has in the past been hampered by the lack of a reliable and efficient method for removing this residue. We report here a rapid, efficient enzymatic method for removal of PCA. Reversed-phase high-performance liquid chromatography is used to monitor the reaction and to separate unblocked peptide from the reaction product. The method allows direct sequence analysis of newly purified PCA blocked peptides, eliminating the need for complicated enzymatic digestions and chromatography to determine the amino-terminal residue. Only a few micrograms of peptide are required instead of the several milligrams needed in the past.

Pyroglutamic acid. Non-metabolic formation, function in proteins and peptides, and characteristics of the enzymes effecting its removal

The formation of pyrrolidone carboxylic acid (PCA, pGlu) during protein biosynthesis is discussed. Studies are summarized which demonstrate that PCA is formed during the later stages of biosynthesis at the terminal phases of translation or as a post-translational event, just prior to cellular secretion of protein with amino-terminal PCA. Of the studies cited, the most convincing evidence suggests that PCA is derived from glutamine. Enzymes which selectivity remove PCA from the N-terminus, and of benefit in amino-acid sequence analysis, have been isolated and shown to have a ubiquitous distribution in various animal and plant cells. The investigations which lead to the isolation o these enzymes and the procedures for their use in removing amino-terminal PCA from proteins, are described. Finally, the biologic function of PCA and the effects of its chemical modification are discussed using the neuropeptide. Thyrotropin Releasing Factor (TRF) as a specific example.

FR-900148, a new antibiotic. I. Taxonomy, fermentation, isolation and characterization

A strain of Streptomyces, isolated from a soil sample and identified as Streptomyces xanthocidicus, has been found to produce FR-900148, a new antibiotic containing chlorine in its molecule. The antibiotic inhibits both Gram-positive and negative bacteria. However, it is not effective against wild type of Pseudomonas aerguinosa. Its antibacterial action is considered to result from cell wall synthesis inhibition since it causes spheroplast formation from susceptible cells.