A new cycloartane triterpenoid from the leaves and stems of Fritillaria hupehensis

A new triterpenoid has been isolated from the leaves and stems of Fritillaria hupehensis Hsiao et K.C.Hsia.Its structure wasestablished as(23Z)-9,19-cycloart-23-ene-3α,25-diol 1 through chemical and spectroscopic studies including 2D NMR.Anotherknown triterpenoid 9,19-cycloart-25-ene-3β,24ξ-diol 2 was also isolated.     

Amyloid peptide Aβ40 inhibits aggregation of Aβ42: evidence from molecular dynamics simulations

Effects of amyloid beta (Aβ) peptide Aβ(40) on secondary structures of Aβ(42) are studied by all-atom simulations using the GROMOS96 43a1 force field with explicit water. It is shown that in the presence of Aβ(40) the beta-content of monomer Aβ(42) is reduced. Since the fibril-prone conformation N? of full-length Aβ peptides has the shape of beta strand-loop-beta strand this result suggests that Aβ(40) decreases the probability of observing N? of Aβ(42) in monomer state. Based on this and the hypothesis that the higher is the population of N? the higher fibril formation rates, one can expect that, in agreement with the recent experiment, Aβ(40) inhibit fibril formation of Aβ(42). It is shown that the presence of Aβ(40) makes the salt bridge D23-K28 and fragment 18-33 of Aβ(42) more flexible providing additional support for this experimental fact. Our estimation of the binding free energy by the molecular mechanics-Poisson-Boltzmann surface area method reveals the inhibition mechanism that Aβ(40) binds to Aβ(42) modifying its morphology.     

Synthesis of Methyl 2-O-, 3-O-, 4-O-, 6-O-, 2,3-Di-O- and 4,6-Di-O-β-D-Galactopyranosyl-β-D-glucopyranoside

Abstract

Synthesis of methyl O-β-D-galactopyranosyl-(1→2)-β-D-glucopyranoside 1, methyl O-β-D-galactopyranosyl-(1→3)-β-D-glucopyranoside 2, methyl O-β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside 3, methyl O-β-D-galactopyranosyl-(1→6)-β-D-glucopyranoside 4, methyl O-β-D-galactopyranosyl-(1→4)-[O-β-D-galactopyranosyl-(1→6)]-β-D-glucopyranoside 5, and methyl O-β-D-galactopyranosyl-(1→2)-[O-β-D-galactopyranosyl-(1→3)]-β-D-glucopyranoside 6, using 2,3,4,6 tetra-O-acetyl-α-D-galactopyranosyl trichloroacetimidate or 2,3,4,6 tetra-O-acetyl-α-D-galactopyranosyl bromide as a glycosyl donor and selectively protected derivatives of methyl O-β-D-glucopyranoside as glycosyl acceptors are described.     

Stochastic kinetic study of protein aggregation and molecular crowding effects of Aβ40 and Aβ42

Two isoforms of β-amyloid peptides, Aβ40 and Aβ42, differ from each other only in the last two amino acids, IA, at the end of Aβ42. They, however, differ significantly in their ability in inducing Alzheimer's disease (AD). The rate curves of fibril growth of Aβ40 and Aβ42 and the effects of molecular crowding have been measured in in vitro experiments. These experimental curves, on the other hand, have been fitted in terms of rate constants for elementary reaction steps using rate equation approaches. Several sets of such rate parameters have been reported in the literature. Employing a recently developed stochastic kinetic method, implemented in a browser-based simulator, popsim, we study to reveal the differences in the kinetic behaviors implied by these sets of rate parameters. In particular, the stochastic method is used to distinguish the kinetic behaviors between Aβ40 and Aβ42 isoforms. As a result, we make general comments on the usefulness of these sets of rate parameters.     

Development of a method for the quantitative determination of neerotsizin (luteolin 7-O-β-D-glucopyranoside) in the leaves of Ferula varia

A method is proposed for determining nefrotsizin (luteolin 7-O--D-glucopyranoside) in the radical leaves ofFerula varia. which is based on the extraction of nefrotsizin from the raw material, its identification by TLC, elution from the plate, and spectrophotometric determination.Institute of Chemistry of Plant Substances, Uzbekistan Republic of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 217–220, March–April, 1993.     

Globrauneine A–F: six new triterpenoid esters from the leaves of Globimetula braunii

Abstract

Phytochemical study was conducted on the leaves of Globimetula braunii which is a hemi parasitic plant belonging to the family Loranthaceae. Extraction was carried out using cold extraction method with increasing polarity of solvents i.e n-hexane, CH₂Cl₂ and MeOH. The components were separated by chromatographic technique and the structures of the compounds were elucidated by extensive spectroscopic analyses including MS, FTIR, 1D and 2D NMR, HRMS and chemical methods. Six new pentacyclic triterpenoid esters named as globrauneine A (1), globrauneine B (2), globrauneine C (3), globrauneine D (4), globrauneine E (5), and globrauneine F (6), together with six known compounds (7 – 12) were successfully isolated from the leaves of G. braunii growing on Piliostigma thonningii. These results depict a substantial support to the chemotaxonomy of the genus Globimetula.     

RP-HPLC-DAD method for the identification of two potential antioxidant agents namely verminoside and 1-O-(E)-caffeoyl-β-gentiobiose from Spathodea campanulata leaves

A simple and reliable high-performance liquid chromatographic method was successfully developed for the study of fingerprint chromatograms of extract and fractions from the leaves of Spathodea campanulata (SC) using verminoside (1) and 1-O-(E)-caffeoyl-β-gentiobiose (2) as marker compounds. Antioxidant activity of SC was determined by using free radical of 2,2-diphenyl-1-picryl-hydrazyl-hydrate as an experimental model. The docking study of selected target, tyrosinase and ligands (ascorbic acid, compounds 1 and 2) was performed through Autodock Vina v0.8. Fingerprints of methanol, chloroform, ethylacetate, n-butanol and water extracts could resolve 13, 11, 22, 16 and 5 peaks, respectively. Extract, fractions and compounds 1 and 2 previously isolated from SC displayed remarkable antioxidant activity with radical-scavenging activity ranging from 2.5 to 6.7 μg/mL. In silico study identified compounds 1 and 2 as potential inhibitors of tyrosinase correlating with the observed antioxidant activity in vitro.     

A new compound with cytotoxic activities from the leaves of Panax ginseng C.A. Meyer

A new compound, 3,6,20（S）-trihydroxy- 12,23-epoxydammar-24-ene,6,20-di-O-β-D-glucopyranoside （1）, was isolated from the leaves of Panax ginseng C.A. Meyer, whose structural elucidation was carried out by means of spectral analysis （including IR, HR- FAB-MS and NMR）. This compound showed the moderate cytotoxic activities against U937 and HeLa cells by using the MTT method.     

(–)-β-Homoarginine anhydride,a new antioxidant and tyrosinase inhibitor,and further active components from Trichosanthes truncata

Abstract

One new amino acid derivative, (–)-β-homoarginine anhydride 1, as well as nine known compounds were isolated from Trichosanthes truncata. The structures of the isolates were elucidated by spectroscopic methods. Among them, compounds 5 and 11 could notably dose-dependently inhibit ROS productions in HaCaT keratinocyte cells without cytotoxicity in the concentration range of 0.2–20?μM. In cell-free mushroom tyrosinase assay, compounds 1–5, 10 and 11 had more potential anti-tyrosinase activities with IC₅₀ values of 106.9–255.6?μM than arbutin that were similar to predicted values of binding affinity calculated by molecule docking. The most active 2 had hydrogen bonds (Ser77, Glu309, Phe454) and electrostatic charges (Glu309, Glu248) interactions with mushroom tyrosinase, respectively. Our data manifested that T. truncata and its components are potentially to be developed as anti-aging and whitening agents for skin disorders.     

Two new sesquineolignans from the seeds of Crataegus pinnatifida and their β-amyloid aggregation inhibitory activitiy

Two new sesquineolignans, hawthornsesquinins K and L (1 and 2), were isolated from the seeds of Crataegus pinnatifida. Their structures were determined by spectroscopic analyses, including 1D, 2D NMR and HRESIMS data. All isolated compounds were tested for their β-amyloid aggregation inhibitory activity and neuroprotective effects against H₂O₂-induced damage in SH-SY5Y cells. The results indicated that compound 1 showed prominent inhibition of Aβ_1–42 aggregation and significant neuroprotective effect on H₂O₂-induced cellular damage in SH-SY5Y cells.     

A new alkaloid and arbutin from the whole plant of Huperzia serrata

A new Lycopodium alkaloid together with a phenolic glyco-side-arbutin, were isolated from the whole plant of Huperzia serrata. The new compound was assigned the trivial name of huperzine I. The structures of these two compounds were determined on the basis of spectral evidence.     

A new dihydrobenzofuran lignan and potential α-glucosidase inhibitory activity of isolated compounds from Mitrephora teysmannii

A new dihydrobenzofuran lignan, (2R,3S)-2-(3′,4′-dimethoxyphenyl)-5-(3-hydroxypropyl)-7-methoxy-2,3-dihydrobenzofuran-3-methyl acetate, named as mitredrusin (1), was isolated from the leaves of Mitrephora teysmannii (Annonaceae) together with 12 known compounds including a related dihydrobenzofuran lignan: (?)-3′,4-di-O-methylcedrusin (2), four polyacetylenic acids: 13(E)-octadecene-9,11-diynoic acid (3), 13(E),17-octadecadiene-9,11-diynoic acid (4), octadeca-9,11,13-triynoic acid (5) and octadeca-17-en-9,11,13-triynoic acid (6), five lignans: (?)-eudesmin (7), (?)-epieudesmin (8), (?)-phillygenin (9), magnone A (10) and forsythialan B (11) and two megastigmans: (3S,5R,6S,7E,9R)-7-megastigmene-3,6,9-triol (12) and annoionol A (13). The chemical structures of these compounds were established on the basis of their 1-D and 2-D NMR spectroscopic data. All compounds were evaluated for their α-glucosidase inhibitory activity. Among these isolates, polyacetylenic acids 3 and 4 showed more than 20-fold much higher activity compared with that of the antidiabetic drug acarbose.     

The initial stage of structural transformation of Aβ42 peptides from the human and mole rat in the presence of Fe2+ and Fe3+: Related to Alzheimer's disease

The early stage of secondary structural conversion of amyloid beta (Aβ) to misfolded aggregations is a key feature of Alzheimer's disease (AD). Under normal physiological conditions, Aβ peptides can protect neurons from the toxicity of highly concentrated metals. However, they become toxic under certain conditions. Under conditions of excess iron, amyloid precursor proteins (APP) become overexpressed. This subsequently increases Aβ production. Experimental studies suggest that Aβ fibrillation (main-pathway) and amorphous (off-pathway) aggregate formations are two competitive pathways driven by factors such as metal binding, pH and temperature. In this study, we performed molecular dynamic (MD) simulations to examine the initial stage of conformational transformations of human Aβ (hAβ) and rat Aβ (rAβ) peptides in the presence of Fe²⁺ and Fe³⁺ ions. Our results demonstrated that Fe²⁺ and Fe³⁺ play key roles in Aβs folding and aggregation. Fe³⁺ had a greater effect than Fe²⁺on Aβs’ folding during intermolecular interactions and subsequently, had a greater effect in decreasing structural diversity. Fe²⁺ was observed to be more likely than Fe³⁺ to interact with nitrogen atoms from the residues of imidazole rings of His. rAβ peptides are more energetically favorable than hAβ for intermolecular interactions and amorphous aggregations. We concluded that most hAβ structures were energetically unfavorable. However, hAβs with intermolecular β-sheet formations in the C-terminal were energetically favorable. It is notable that Fe²⁺ can change the surface charge of hAβ. Furthermore, Fe³⁺ can promote C-terminal folding by binding to Glu22 and Ala42, and by forming stable β-sheet formations on the C-terminal. Fe³⁺ can also pause the main-pathway by inducing random aggregations.     

A new short route for the production of Δ2-cyclopentenone from cyclopentadiene

Summary A new 3-stage method for the production of ²-cyclopentenone from cyclopentadlene with an over-all yield of 15% has been described.     

Medicinal plants of Thailand. I structures of rheedeiosides A-D and cis-entadamide A β-D-glucopyranoside from the seed kernels of Entada rheedei

Four new oleanane-type triterpene oligoglycosides, named rheedeiosides A, B, C and D, and one new thioamide glycoside, cis-entadamide A β-D-glucopyranoside, were isolated from the seed kernels of a Thai medicinal plant, Entada rheedei SPRENGEL. The rheedeiosides were found to contain N-acetylglucosamine as a sugar component. Their structures were elucidated based on spectral and chemical evidence.     

β-Sonogel-Carbon electrodes: A new alternative for the electrochemical determination of catecholamines

In this work, a new alternative for the electrochemical determination of catecholamines based on β-cyclodextrin-Sonogel-Carbon electrodes is reported. The incorporation of β-CD and graphite in the preparation of the Sonogel-Carbon material leads to a modification of the electrode surface properties which causes a significant increase in the oxidation peak current of biomolecules such as dopamine, l-epinephrine, d,l-norepinephrine and catechol. This phenomenon might be attributed to the formation of an inclusion complex between β-CD and the catecholamines. The amount of β-CD necessary to form the Sonogel electrode was studied and optimization of electrochemical parameters, perm selectivity and mechanical stability of the sensor are discussed. Scanning electron microscopy and electrochemical impedance spectroscopy measurements were employed to characterize the electrical parameters and the structural properties of the new electrode surface, respectively. Cyclic voltammetry (CV) and Adsorptive differential pulse voltammetry (AdDPV) measurements were also used to explore the electrochemical behaviour of the electrode versus the quoted catecholamines. The β-CD-Sonogel-Carbon electrode offers fast and linear responses towards dopamine, norepinephrine, epinephrine and catechol, with good and low detection limits: 0.164, 0.294, 0.699 and 0.059 μmol L⁻¹, respectively.     

Structure and properties of estragonoside — A new flavonoid from the epigeal part ofArtemisia dracunculus

We have studied the chemical and spectral properties of estragonoside — a new flavonoid compound isolated from the epigeal part ofArtemisia dracunculus L. (variety Gribovskii) and having the structure of 4,5,6,7,8-pentahydroxy-3-methoxyflavone 8-O--L-rhamnopyranoside. Pinocembrin 7-O--D-glucopyranoside has also been isolated from the same raw material for the first time.Samara State Medical University, fax (846-2) 33 29 76. Translated from Khimiya Prirodnykh Soedinenii, Vol. 33, No. 1, pp. 61–65, January–February, 1997.     

Preparation and characterization of the inclusion complexes of equol with sulfobutylether-β-cyclodextrin: their antioxidant activity and dissolution evaluation

The formation of inclusion complexes between S-(?)-equol (SEq) and cyclodextrins (CDs) was investigated. The binding constant (K_c) of the SEq/sulfobutylether-β-cyclodextrin (SBE-β-CD) inclusion complex was determined to be 1600 L/mol based on UV data. The phenyl ring of the SEq molecule was found to be inserted from the secondary hydroxyl face of the SBE-β-CD as evidenced from ¹H–¹H rotating frame nuclear Overhauser effect spectroscopy (ROESY) NMR. The thermal properties of the solid SEq/SBE-β-CD inclusion complexes prepared by physical mixing, kneading and freeze-drying methods were studied by differential scanning calorimetry. For the solid complex obtained by the freeze-drying method, the endothermic peak corresponding to the melting point of SEq disappeared. The solid SEq/SBE-β-CD complexes exhibited a high score in antioxidant activity evaluation tests compared to SEq alone. Dissolution test revealed that the solid complex obtained by freeze-drying method had improved dissolution of SEq.