Xanthones isolated from Gentianella acuta and their protective effects against H2O2-induced myocardial cell injury

In the present study, two new xanthones, (5′S,8′S)-1,3,5,8-tetrahydroxyxanthone(7→2′)-1,3,5,8-tetrahydroxy-5′,6′,7′,8′-tetrahydroxanthone (1), 5-hydroxy-3,4,6-trimethoxyxanthone-1-O-β-D-glucopyranoside (2), and eight known xanthones (3–10) were isolated from the whole plants of Gentianella acuta. Their structures were identified by the spectroscopic analyses (HR-ESI-MS, and 1D and 2D NMR). Meanwhile, cell-protective effects against H₂O₂-induced H9c2 cardiomyocyte injury and cytotoxic activities of compounds 1–10 were also determined.     

High-performance liquid chromatography micro-fraction bioactive evaluation combined with countercurrent chromatographic separation of antioxidants from Citrus peel and their tyrosinase inhibition activities

In the present study, high-performance liquid chromatography micro-fraction bioactive evaluation and high speed countercurrent chromatography were performed on screening, identification and isolation of antioxidants from Citrus peel. Three compounds were screened as antioxidants and tyrosinase inhibitors using 2,2′-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation scavenging assay and tyrosinase activity test, then they were identified as eriocitrin, narirutin and hesperidin. Moreover, the solvent system ethyl acetate-n-butanol-water (6:4:10, v/v/v) was used for separation of ethyl acetate extract of Citrus peel by high speed countercurrent chromatography. In total, 0.45 mg of eriocitrin with 87.10% purity, 2.04 mg of narirutin with 95.19% purity and 1.35 mg of hesperidin with 95.19% purity were obtained from 20 mg of ethyl acetate extract of Citrus peel in a single run and then each component was subjected to 2,2′-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation scavenging assay and tyrosinase inhibition assay. Eriocitrin showed great antioxidant activity (the half-maximum concentration: 3.65 µM) and tyrosinase inhibition activity (the half-maximum concentration: 115.67 µM), while narirutin and hesperidin exhibited moderate activity. Tyrosinase inhibition activity for eriocitrin in vitro was reported for the first time. Furthermore, molecular docking between eriocitrin and mushroom tyrosinase was also studied.     

Preparative separation of six coumarins from the pummelo (Citrus maxima (Burm.) Merr. Cv. Shatian Yu) peel by high-speed countercurrent chromatography

In this work, six coumarins, including two new ones, 8-(3-hydroxy-2,2-dimethylpropyl)-7-methoxy-2H-chromen-2-one (2) and 5-[(7′,8′-dihydroxy-3′,8′-dimethyl-2-nonadienyl)oxy] psoralen (4), as well as four known ones, 5-[(6′,7′-dihydroxy-3′,7′-dimethyl-2-octenyl) oxy] psoralen (1), marmin (3), epoxybergamottin (5), and aurapten (6) were successfully separated from the crude extract of pummelo (Citrus maxima (Burm.) Merr. Cv. Shatian Yu) peel by high-speed countercurrent chromatography in a single run with petroleum-ether–ethyl acetate–methanol–water (4:6:6:4, v/v). The structures of these six coumarins were elucidated by ESI-MS, extensive 1D and 2D NMR spectroscopy.     

Flavones and Cytotoxic Constituents from the Stem Bark of Muntingia Calabura

Two new flavones, 8‐hydroxy‐7,3′,4′,5′‐tetramethoxyflavone and 8,4′‐dihydroxy‐7,3′,5′‐trimethoxyflavone, together with thirteen known compounds have been isolated from the stem bark of Muntingia calabura. The structures of two new compounds were determined through spectral analyses. Among the isolates, 8‐hydroxy‐7,3′,4′,5′‐tetramethoxyflavone, 8,4′‐dihydroxy‐7,3′,5′‐trimethoxyflavone, and 3‐hydroxy‐1‐(3,5‐dimethoxy‐4‐hydroxyphenyl)propan‐1‐one exhibited effective cytotoxicities (ED₅₀ values = 3.56, 3.71, and 3.27 μg/mL, respectively) against the P‐388 cell line in vitro.     

Analysis of antioxidant compounds in sweet orange peel by HPLC-diode array detection-electrospray ionization mass spectrometry

HPLC-diode array detection-electrospray ionization mass spectrometry was used to determine qualitatively and quantitatively the flavonoid content of several fractions and residues of extracts of Greek navel sweet orange peel (Citrus sinensis) from the region of southern Greece (Leonidi-Tripoli). The main groups of flavonoids found according to HPLC retention times, spectral data and literature references were polymethoxylated flavones, C-glycosylated flavones, O-glycosylated flavones, O-glycosylated flavanones, flavonols and phenolic acids and their derivatives. The ethyl acetate fraction which has been shown in previous work to possess the best radical scavenging activity among the others was found to contain C-glycosylated flavones, polymethoxylated flavones, O-glycosylated flavones, O-glycosylated flavanones, two phenolic acid derivatives and two unknown compounds, all in low concentrations. The group of C-glycosylated flavones was reported for the first time in the peel of Navel sweet orange. The C-glycosylated flavones found according to their spectral characteristics and literature were 6-C-beta-glucosyldiosmin, 6,8-di-C-glucopyranosylapigenin, 6,8-di-C-beta-glucosyldiosmin and two unknown. The results suggest that the ethyl acetate fraction of navel Citrus sinensis peel consists of significant antioxidant compounds and can be used as a food additive of natural origin or a pharmaceutical supplement using as a source of peel the byproducts of the orange juice industry.     

Selectively Deoxygenated Derivatives of β-Maltosyl-(1→4)-Trehalose as Biological Probes. II. the Synthesis of the 4- and 4′″-Monodeoxygenated Analogues

ABSTRACT

Two derivatives of β-maltosyl-(1→4)-trehalose monodeoxygenated at positions 4 or 4′″ have been synthesized in [2+2] block syntheses. After the preparation of precursors with only one free hydroxyl group the deoxy function was introduced by a Barton-McCombie reaction. Thus, glycosylation of 2,3,6-tri-O-benzyl-α-D-glucopyranosyl 2,3,6-tri-O-benzyl-α-D-glucopyranoside (4) with octa-O-acetyl-β-maltose (3) gave tetrasaccharide 5 with only one free hydroxyl group at the 4-position. The 4′-position of an allyl maltoside was available selectively after removal of a 4′,6′-cyclic acetal and selective benzoylation of the 6′-position. Reduction of this derivative 11 afforded allyl O-(2,3-di-O-acetyl-6-O-benzoyl-4-deoxy-α-D-glucopyranosyl)-(1→4)-2,3,6-tri-O-acetyl-β-D-glucopyranoside (14), which was deallylated, activated as an trichloroacetimidate, and coupled to 2,3-di-O-benzyl-4,6-O-benzylidene-α-D-glucopyranosyl 2′,3′,6′-tri-O-benzyl-α-D-glucopyranoside (20). Several compounds were fully characterized by ¹H NMR spectroscopy. Deprotection furnished the monodeoxygenated tetrasaccharides 9 and 23.     

Selectively Deoxygenated Derivatives of β-Maltosyl-(1→4)-Trehalose as Biological Probes

ABSTRACT

The four derivatives of β-maltosyl-(1→4)-trehalose have been synthesized, which are monodeoxygenated at the site of one of the primary hydroxyl groups. The tetrasaccharides were constructed in [2+2] block syntheses. Thus, 6′″-deoxy-β-maltosyl-(1→4)-trehalose was prepared by selective iodination of allyl 2,3,6,2′,3′-penta-O-acetyl-β-maltoside (3) followed by catalytic hydrogenolysis and coupling with 2,3-di-O-benzyl-4,6-O-benzylidene-α-D-glucopyranosyl 2′,3′,6′-tri-O-benzyl-α-D-glucopyranoside (9), and 6″-deoxy-β-maltosyl-(1→4)-trehalose by selective iodination of allyl 4′,6′-O-isopropylidene-β-maltoside (14), coupling with 9, and one-step hydrogenolysis at the tetrasaccharide level. For the synthesis of 6′-deoxy-β-maltosyl-(1→4)-trehalose, the diol 2,3-di-O-benzyl-4,6-O-benzylidene-α-D-glucopyranosyl 2′,3′-di-O-benzyl-α-D-glucopyranoside (22) was selectively iodinated and glycosylated with acetobromomaltose followed by catalytic hydrogenolysis. The 6-deoxy-β-maltosyl-(1→4)-trehalose was obtained upon selective iodination of a tetrasaccharide diol.     

Regio‐ and stereospecific assembly of dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidines] from simple precursors using a one‐pot procedure: synthesis,spectroscopic and structural characterization,and a proposed mechanism of formation

The synthesis and characterization of three new dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine] compounds are reported, together with the crystal structures of two of them. (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐Chlorophenyl)‐1‐hexyl‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₂₈H₃₀ClN₃O₂S₂, (I), (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐chlorophenyl)‐1‐benzyl‐5‐methyl‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₃₀H₂₆ClN₃O₂S₂, (II), and (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐chlorophenyl)‐5‐fluoro‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₂₂H₁₇ClFN₃O₂S₂, (III), were each isolated as a single regioisomer using a one‐pot reaction involving l ‐proline, a substituted isatin and (Z)‐5‐(4‐chlorobenzylidene)‐2‐sulfanylidenethiazolidin‐4‐one [5‐(4‐chlorobenzylidene)rhodanine]. The compositions of (I)–(III) were established by elemental analysis, complemented by high‐resolution mass spectrometry in the case of (I); their constitutions, including the definition of the regiochemistry, were established using NMR spectroscopy, and the relative configurations at the four stereogenic centres were established using single‐crystal X‐ray structure analysis. A possible reaction mechanism for the formation of (I)–(III) is proposed, based on the detailed stereochemistry. The molecules of (I) are linked into simple chains by a single N—H…N hydrogen bond, those of (II) are linked into a chain of rings by a combination of N—H…O and C—H…S=C hydrogen bonds, and those of (III) are linked into sheets by a combination of N—H…N and N—H…S=C hydrogen bonds.     

Efficient analysis of phytochemical constituents in the peel of Chinese wild citrus Mangshanju (Citrus reticulata Blanco) by ultra high performance liquid chromatography–quadrupole time‐of‐flight‐mass spectrometry

An efficient ultra high‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry method was developed for separation and profiling of phytochemical constituents of Chinese wild mandarin Mangshanju (Citrus reticulata Blanco). All constituents were well separated within 16 min. Based on retention times, accurate mass, MS^E fragments, and/or reference standards as well as databases, a total of 81 compounds were unambiguously identified or tentatively assigned including flavonoid glycosides, acylated flavonoid glycosides, flavones, polymethoxylated flavonoids, and limonoids as well as four other compounds. Among them, 22 polymethoxylated flavones and ten polymethoxylated flavanones/chalcones were identified in Mangshanju, more types than other citrus reported before. A basic procedure for identifying flavonoid‐O‐glycosides and the aglycones including polymethoxylated flavonoids was proposed. In addition, this method was successfully used to analyze another four mandarin germplasms, Cenxi suan ju, Xipi gousi gan, Nanfeng miju, and Or, showing that Mangshanju contained two characteristic compounds distinct from the other four citrus species. This study systematically profiled phytochemical constituents of Mangshanju, which was helpful for further utilization of Mangshanju owing to its abundant bioactive compounds.     

Studies on the Constituents of Formosan Salvia Plebeia R. Br. (I) On the Flavonoid Components of Salvia Plebeia R. Br.

Salvia plebeia R. Br. is an annual herb of Labiatae and is widely distributed in the central area of Taiwan. It has been used as folk-medicine for the treatment of hepatitis and tumors.¹⁾ From the flavonoid enriched fraction (B) of the alcoholic extracts of this plant, four kinds of flavonoid compound were isolated. Two of these were confirmed as 5,4′-dihydroxy-6-methoxy-7-glucosyloxy flavone (I). (homoplantaginin, hispidulin-7-glucoside) and 5, 7, 4′-trihydroxy-6-methoxy flavone (II) (hispidulin) on the basis of their spectral, chemical evidences and comparison with authentic samples. The other two were assigned to be 5, 3′, 4′-trihydroxy-6-methoxy-7-glucosyloxy flavone (III) (nepitrin, eupafolin-7-glucoside) and 5,7,3′,4′-tetrahydroxy-6-methoxy flavone (IV) (eupafolin, nepetin) on the basis of chemical and spectral properties. The flavones, II (hispidulin) and IV (eupafolin), have been shown to have cytotoxic activity against human carcinoma of the nasopharynx carried in cell culture (KB).¹³⁾     

New Monoterpene-Substituted Dihydrochalcones from Piper aduncum

Five New unusual monoterpene-substituted dihydrochalcones, the adunctins A–E (1″S)-1-{2′-hydroxy-4′-methoxy-6′-[4″-methyl-1″-(1?-methylethyl)cyclohex-3″ -en-1″ -yloxy]phenyl}-3-phenylpropan-1-one ( 1 ), (5aR*,8R*,9aR*)-3-phenyl-1-[5′,8′,9′,9′a-tetrahydro-3′-hydroxy-1′-methoxy-8′-(1″-methylethyl)-5′-a-methyldibenzo-[b,d]furan-4′-yl]propan-1-one ( 2 ), (2′R*,4″S*)-1-{6′-hydroxy-4′-methoxy-4″-(1?-methylethyl)spiro[benzo[b]-furan-2′(3′H),1″ -cyclohex-2″ -en]-7′-yl}-3-phenylpropan-1-one ( 3 ), (2′R*,4″R*)-1-{6′-hydroxy-4′-methylethyl-4″-(1?-methylethyl)spiro[benzo[b]furan-2′(3′H),1″-cyclohex-2″-en]-7′-yl}-3-phenypropan-1-one ( 4 ), and (5′aR*,6′S*, 9′R*,9′aS*)-1-[5′a,6′,7′,8′,9′a-hexahydro-3′,6′-methoxy-6′-methyl-9′-(1″-methylethyl)dibenzo[b,d]-furan-4′-yl]-3-phenylpropan-1-one ( 5 ) were isolated from the leaves of Piper aduncum (Piperaceae) by preparative liquid chromatography. In addition, (?)-methyllindaretin ( 6 ), trans-phytol, and α-tocopherol ( = vitamin E) were also isolated and identified. The structures were elucidated by spectroscopic methods, including 1D- and 2D-NMR spectroscopy as well as single-crystal X-ray diffraction analysis. The antibacterial and cytotoxic potentials of the isolates were also investigated.     

Reactions of 2,2′,5′,2′-terfuran

Formylation of 2,2′,5′,2′-terfuran ( 1 ) with N-methylformanilide and phosphorus oxychloride gave 5-formyl-2,2′,5′,2′-terfuran ( 2 ) and 5,5′-diformyl-2,2′5′,2′-terfuran ( 3 ). Reduction of 2 and 3 afforded 5-hydroxymethyl-2,2′,5′,2′-terfuran ( 4 ) and 5,5′ dihydroxymethyl-2,2′,5′,2′-terfuran ( 5 ), respectively. Terfuran 1 reacted with phenylmagnesium bromide to give 5-(phenylhydroxymethyl)-2,2′,5′,2′-terfuran ( 6 ), and was carbonated to 5-carboxy 2,2′,5′,2′-terfuran ( 7 ) and 5,5′-dicarboxy-2,2′,5′,2′-terfuran ( 8 ). Bromination of 1 with N-bromosuccinimide gave 5,5′-dibromo 2,2′,5′,2′-terfuran ( 9 ).     

Microbial transformation of quercetin and its prenylated derivatives

The microbial transformation studies of 7-O-prenylquercetin (1), 4′-O-prenylquercetin (2) and quercetin (3) were investigated with 20 different microbial strains to discover new metabolites. It was revealed that the fungus Mucor hiemalis was the most appropriate micro-organism which was capable of transforming these flavonoids. Structures of the three new (4–6) and one known (7) metabolites were elucidated as 7-O-prenylquercetin 3-O-β-D-glucopyranoside (4), 4′-O-prenylquercetin 3-O-β-D-glucopyranoside (5), 4′-O-prenylquercetin 3′-O-β-D-glucopyranoside (6) and quercetin 5-O-β-D-glucopyranoside (7) by the spectroscopic methods.     

Simultaneous Determination of Phenolics and Polymethoxylated Flavones in Citrus Fruits by Ultra-High Performance Liquid Chromatography Coupled with Triple-Quadrupole Mass Spectrometry (UHPLC-QqQ-MS)

Phenolic and polymethoxylated flavones are important bioactive components in citrus fruit. Here, a rapid and sensitive method based on ultra-high performance liquid chromatography coupled with triple-quadrupole mass spectrometry (UHPLC-QqQ-MS) was developed for the simultaneous determination of phenolic and polymethoxylated flavones in the peels and pulp of mandarins, tangelos, and oranges. Three phenolic acids and eight flavonoids, including polymethoxylated flavones, were separated and determined using positive and negative ion modes in a single chromatographic run of only 11?min using the multiple reaction monitoring detection mode. The method was validated with high recoveries from 96.1% to 103.5%, good precision with interday relative standard deviations less than or equal to 7.3%, intraday relative standard deviations ≤2.64%, low limits of detection from 1.0 to 18?µg L^–1, and low limits of quantitation in the range from 3.0 to 61?µg L^–1. The application of this UHPLC-QqQ-MS/MS method to the citrus extracts of three cultivars showed that mandarin fruits contained the highest total amounts of the 11 analytes, followed by tangelos and oranges. This study provides a reliable and quantitative method that can be used for the development of functional products and quality evaluation of citrus fruits.     

Synthesis of spiro[1,4-benzothiazine-2,2′-pyrans] starting from methyl β-D-arabino-2-hexulopyranosonate

Dedicated to Professor Klaus Burger on the occasion of his 60th birthday Methyl β-D -arabono-2-hexulopyranosonate 1 has via the novel glycosyl donor 3 been transformed into the thiophenyl glycosides 4 and 5. Catalytic hydrogenation of the nitro compound 4 in alkaline solution led to spontaneous cyclization and deprotection to form the cyclic hydroxamic acid 7. The related lactams 8 and 9 were obtained from amine 5. The spiro[1,4-benzothiazine-2,2′-pyrans] 7–9 are the first representatives of a novel class of heterocycles structurally related to bioactive natural products. As shown by the values for J_3′,4′ and J_4′,5′ the glycosides 4, 5 and 6 adopt a ⁵C₂ conformation of the pyranoid ring whereas the 1,4-benzothiazine system in 7–9 forces a conformational change into the ²C₅ conformation.     

Chemical constituents from leaves and trunk bark of Rinorea oblongifolia (Violaceae)

Abstract

Two new coruleoellagic acid derivatives, 3,4′,5,5′,-tetramethylcoruleoellagic acid (1); 3′,4,4′,5,5′-pentamethylcoruleoellagic acid (2) and a new friedelane-type triterpene derivative rinol (5), were isolated from leaves and trunk bark of Rinorea oblongifolia (Violaceae) along with seven known compounds including 3,3′,4,4′,5′-pentamethylcoruleoellagic acid (3), hexamethylcoruleoellagic acid (4), 28-hydroxyfriedelin (6), friedelin (7), friedelan-3-ol (8), scopoletin (9) and β-sitosterol-3-O-β-D-glucopyranoside (10). Their structures were elucidated by means of spectroscopic methods including IR, 1D and 2D NMR in conjunction with mass spectrometry. Crude extracts of leaves and trunk bark as well as compounds 1–4 were evaluated for their antibacterial activities against 7 pathogenic bacterial strains (Streptococcus pneumoniae ATCC49619, Staphylococcus aureus ATCC 43300, Klepsiella pneumoniae ATCC 700603, Haemophilus influenza ATCC 49247, Escherichia coli ATCC 25922, Pseudomonas aeruginosa HM601, Staphylococcus aureus BAA 977). Compound (3) displayed noteworthy activity against Haemophilus influenza with MIC value of 9.38?µg/mL.     

Regioselective Transformations of 2′,3′-Seconucleosides into Anhydro Structures and Chiral Crown Ethers

Intramolecular cyclisation of properly protected and activated derivatives of 2′,3′-secouridine ( = 1-{2-hydroxy-1-[2-hydroxy-1-(hydroxymethyl)ethoxy]-ethyl}uracil; 1 ) provided access to the 2,2′-, 2,3′-, 2,5′-, 2′,5′-, 3′,5′-, and 2′,3′-anhydro-2′,3′-secouridines 5, 16, 17, 26, 28 , and 31 , respectively (Schemes 1–3). Reaction of 2′,5′-anhydro-3′-O-(methylsulfonyl)- ( 25 ) and 2′,3′-anhydro-5′-O-(methylsulfonyl)-2′,3′-secouridine ( 32 ) with CH₂CI₂ in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene generated the N(3)-methylene-bridged bis-uridine structure 37 and 36 , respectively (Scheme 3). Novel chiral 18-crown-6 ethers 40 and 44 , containing a hydroxymethyl and a uracil-1-yl or adenin-9-yl as the pendant groups in a 1,3-cis relationship, were synthesized from 5′-O-(triphenylmethyl)-2′,3′-secouridine ( 2 ) and 5′-O,N⁶-bis(triphenylmethyl)-2′,3′-secoadenosine ( 41 ) on reaction with 3,6,9-trioxaundecane-1,11-diyl bis(4-toluenesulfonate) and detritylation of the thus obtained (triphenylmethoxy) methylcompound 39 and 43 , respectively (Scheme 4).     

Synthesis and characterization of some nitrogen heterocycles from d-galactose derivatives

The tetrazoles 5-(6′-acetamido-6′-deoxy-1′,2′:3′,4′-di-O-isopropylidene-D-glycero-α-D-galactohexopyranos-6′-yl)tetrazole ( 1 ) and 5-(6′-acetamido-6′-deoxy-1′,2′:3′,4′–di-O-isopropylidene-L-glycero-α-D-galacto-hexopyranos-6′-yl)-tetrazole ( 2 ) were synthesized by the 1,3-dipolar cycloaddition reaction of the epimeric α-acetamidonitriles 5 and 6 , respectively, with sodium azide. Reaction of tetrazole 1 with acetic anhydride in the presence of pyridine afforded the N-acetyl-1,3,4-oxadiazole derivative 3 and the N-acetylacetamido-1,3,4-oxadiazole derivative 7 . The N-acetylacetamido-1,3,4-oxadiazole derivative ( 8 ) was isolated when the tetrazole 2 was allowed to react under the same conditions. The physical and spectroscopic data of the five new compounds 1, 2, 3, 7 and 8 are presented.