A new NMR approach for structure determination of thermally unstable biflavanones and application to phytochemicals from Garcinia buchananii

Previous activity‐guided phytochemical studies on Garcinia buchananii stem bark, which is traditionally used in Africa to treat various gastrointestinal and metabolic illnesses, revealed xanthones, polyisoprenylated benzophenones, flavanone‐C‐glycosides, biflavonoids, and/or biflavanones as bioactive key molecules. Unequivocal structure elucidation of biflavonoids and biflavanones by means of NMR spectroscopy is often complicated by the hindered rotation of the monomers around the C‐C axis (atropisomerism), resulting in a high spectral complexity. In order to facilitate an unrestricted rotation, NMR spectra are usually recorded at elevated temperatures, commonly over 80 °C, which effects in a single set of resonance signals. However, under these conditions, one of the target compounds of this investigation, (2R,3S,2″R,3″R)‐manniflavanone ( 1 ), undergoes degradation. Therefore, we demonstrated in the present study that the 1,1‐ADEQUATE could be successfully used as a powerful alternative approach to confirm the C‐C connectivities in 1 , avoiding detrimental conditions. However, a moderate increase in temperature up to 50 °C was sufficient to deliver sharp signals in the proton NMR experiment of (2R,3S,2″R,3″R)‐isomanniflavanone ( 2 ) and (2″R,3″R)‐preussianone ( 3 ). In addition, two new compounds could be isolated, namely (2R,3S,2″R,3″R)‐GB‐2 7″‐O‐β‐d ‐glucopyranoside ( 4 ) and (2R,3S,2″R,3″R)‐manniflavanone‐7″‐O‐β‐d ‐glucopyranoside ( 5 ), and whose structures were elucidated by spectroscopic analysis including 1D and 2D NMR and mass spectrometry methods. The absolute configurations were determined by a combination of NMR and electronic circular dichroism (ECD) spectroscopy. The aforementioned compounds exhibited high anti‐oxidative capacity in the H₂O₂ scavenging, hydrophilic Trolox equivalent antioxidant capacity (H‐TEAC) and hydrophilic oxygen radical absorbance capacity (H‐ORAC) assays. Copyright © 2015 John Wiley & Sons, Ltd.     

Dapholidins A – C,New Isomeric Biisoflavonoids From Daphne oleoides

Three new isomeric biisoflavonoids, dapholidins A–C ( 1 – 3 , resp.), have been isolated from the AcOEt‐soluble fraction of the MeOH‐soluble extract of the roots of Daphne oleoides, along with the known compounds daphwazirin ( 4 ), daphnetin 8‐O‐β‐D ‐glucopyranoside ( 5 ), daphnin ( 6 ), daphneticin 4″‐O‐β‐D ‐glucopyranoside ( 7 ), and 6,7‐dihydroxy‐3‐methoxy‐8‐[2‐oxo‐2H‐1‐benzopyran‐7‐(O‐β‐D ‐glucopyranosyl)‐8‐yl]‐2H‐1‐benzopyran‐2‐one ( 8 ). The structures of the new compounds were determined by spectroscopic analyses, including 1D‐ and 2D‐NMR.     

Five New Biflavonoids from Daphne aurantiaca

Five new biflavonoids, 1 – 5 , were isolated from the stem bark of Daphne aurantiaca. The structures were elucidated as 2,2″‐bisteppogenin ( 1 ), 2,2″‐bisteppogenin 7‐O‐β‐glucopyranoside ( 2 ), 2′′′‐dehydroxy‐2,2″‐bisteppogenin ( 3 ), 2′′′‐dehydroxy‐2,2″‐bisteppogenin 7‐O‐β‐glucopyranoside ( 4 ), and 7‐methoxyneochamaejasmin B ( 5 ) on the basis of spectral analyses.     

Flavonol Glycosides with α‐Glucosidase Inhibitory Activities and New Flavone C‐Diosides from the Leaves of Machilus konishii

Seventeen flavonoids, five of which are flavone C‐diosides, 1 – 5 , were isolated from the BuOH‐ and AcOEt‐soluble fractions of the leaf extract of Machilus konishii. Among 1 – 5 , apigenin 6‐C‐β‐D ‐xylopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 2 ), apigenin 8‐C‐α‐L ‐arabinopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 4 ), and apigenin 8‐C‐β‐D ‐xylopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 5 ) are new. Both 4 and 5 are present as rotamer pairs. The structures of the new compounds were elucidated on the basis of NMR‐spectroscopic analyses and MS data. In addition, the ¹H‐ and ¹³C‐NMR data of apigenin 6‐C‐α‐L ‐arabinopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 3 ) were assigned for the first time. The isolated compounds were assayed against α‐glucosidase (type IV from Bacillus stearothermophilus). Kaempferol 3‐O‐(2‐β‐D ‐apiofuranosyl)‐α‐L ‐rhamnopyranoside ( 12 ) was found to possess the best inhibitory activity with an IC₅₀ value of 29.3 μM .     

Two new acylated flavonoid glycosides from Morina nepalensis var. alba Hand.‐Mazz.

From the whole plant of Morina nepalensis var. alba Hand.‐Mazz., two new acylated flavonoid glycosides ( 1 and 2 ), together with four known flavonoid glycosides ( 3–6 ), were isolated. Their structures were determined to be quercetin 3‐O‐[2″′‐O‐(E)‐caffeoyl]‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐galactopyranoside (monepalin A, 1 ), quercetin 3‐O‐[2″′‐O‐(E)‐caffeoyl]‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐glucopyranoside (monepalin B, 2 ), quercetin 3‐O‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐galactopyranoside (rumarin, 3 ), quercetin 3‐O‐β‐D ‐galactopyranoside ( 4 ), quercetin 3‐O‐β‐D ‐glucopyranoside ( 5 ) and apigenin 4^′‐O‐β‐D ‐glucopyranoside ( 6 ). Their structures were determined on the basis of chemical and spectroscopic evidence. Complete assignments of the ¹H and ¹³C NMR spectra of all compounds were achieved from the 2D NMR spectra, including H–H COSY, HMQC, HMBC and 2D HMQC‐TOCSY spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Biflavonoids,Lignans, and Related Compounds from the Roots of Diplomorpha canescens

Two new biflavonoids, 14″‐O‐methyldihydrodaphnodorin B ( 1 ) and 14″‐O‐methyldaphnodorin J ( 2 ), along with 16 known compounds, i.e., dihydrodaphnodorin B ( 3 ), daphnodorin J ( 4 ), 3″‐epidihydrodaphnodorin B ( 5 ), daphnodorin B ( 6 ), neochamaejasmin B ( 7 ), sikokianin B ( 8 ), (?)‐syringaresinol ( 9 ), (?)‐syringaresinol 4‐O‐β‐D ‐glucopyranoside ( 10 ), (+)‐nortrachelogenin ( 11 ), (?)‐lariciresinol ( 12 ), (?)‐pinoresinol ( 13 ), syringin ( 14 ), syringinoside ( 15 ), daphnoretin ( 16 ), phorbol 13‐acetate ( 17 ), and methyl paraben ( 18 ) were isolated from the roots of Diplomorpha canescens (Meisn.) C.A. Meyer . The structures were determined on the basis of spectroscopic data.     

Flavone 8‐C‐Glycosides from Haberlea rhodopensis Friv. (Gesneriaceae)

Phytochemical profiling of a MeOH extract from Haberlea rhodopensis by a combination of liquid/liquid extraction, and preparative and semi‐preparative HPLC afforded three new flavone C‐glycosides, hispidulin‐8‐C‐(2″‐O‐syringoyl)‐β‐glucopyranoside ( 3 ), hispidulin 8‐C‐(6‐O‐acetyl‐β‐glucopyranoside) ( 4 ), and hispidulin 8‐C‐(6‐O‐acetyl‐2‐O‐syringoyl‐β‐glucopyranoside) ( 5 ), along with two known phenolic glycosides, myconoside ( 1 ) and paucifloside ( 2 ). The structures were established by extensive spectroscopic analyses including 1D‐ and 2D‐NMR (COSY, HSQC, and HMBC), and HR‐ESI‐TOF‐MS, and by comparison with published data.     

Revised structures of avenacosides A and B and a new sulfated saponin from Avena sativa L.

The revised structures of avenacosides A and B and a new sulfated steroidal saponin isolated from grains of Avena sativa L. were elucidated. Their structures and complete NMR assignments are based on 1D and 2D NMR studies and identified as nuatigenin 3‐O‐{α‐l ‐rhamnopyranosyl‐(1→2)‐[β‐D‐glucopyranosyl‐(1→4)]‐β‐d ‐glucopyranoside}‐26‐O‐β‐d ‐glucopyranoside (1), nuatigenin 3‐O‐{α‐l ‐rhamnopyranosyl‐(1→2)‐[β‐d ‐glucopyranosyl‐(1→3)‐β‐d ‐glucopyranosyl‐(1→4)]‐β‐d ‐glucopyranoside}‐26‐O‐β‐d ‐glucopyranoside (2), and nuatigenin 3‐O‐{α‐l ‐rhamnopyranosyl‐(1→2)‐[β‐d ‐6‐O‐sulfoglucopyranosyl‐(1→4)]‐β‐d ‐glucopyranoside}‐26‐O‐β‐d ‐glucopyranoside (3). Copyright © 2012 John Wiley & Sons, Ltd.     

Stereochemical assignment of five new lignan glycosides from Viscum album by NMR study combined with CD spectroscopy

The chemical study of the leaves and twigs of Viscum album led to the isolation of five new lignan glycosides, namely, ligalbumosides A–E (2‐6) and one known lignan glycoside, alangilignoside C (1). The structures of five new lignan glycosides were determined to be (7R,8S,8'S)‐4,9,4'‐trihydroxy‐3,5,3',5'‐tetramethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (2), (7S,8S,7'S,8'R)‐4,9,4'‐trihydroxy‐3,5,3',5',7'‐pentamethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (3), (7R,8R,7'S,8'S)‐4,9,4'‐trihydroxy‐3,5,3',5',7'‐pentamethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (4), (7S,8R,7'S,8'R)‐4,9,4'‐trihydroxy‐3,5,3',5',7'‐pentamethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (5), and (7R,8S,7'R,8'S)‐4,9,4',7'‐tetrahydroxy‐3,5,3',5'‐tetramethoxy‐7,9'‐epoxylignan 9‐O‐β‐D‐glucopyranoside (6) using 1D‐, 2D‐NMR, and CD spectra, chemical methods, as well as comparing the results with those reported in the literature. Copyright © 2012 John Wiley & Sons, Ltd.     

Four new ursane‐type saponins from Morina nepalensis var. alba

Four new ursane‐type saponins, monepalosides C–F, together with a known saponin, mazusaponin II, were isolated from Morina nepalensis var. alba Hand.‐Mazz. Their structures were determined to be 3‐O‐α‐L ‐arabinopyranosyl‐(1 → 3)‐&[alpha;‐L ‐rhamnopyranosyl‐(1 → 2)]‐α‐L ‐arabinopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranoside (monepaloside C, 1 ), 3‐O‐α‐L ‐arabinopyranosyl‐(1 → 3)‐&[alpha;‐L ‐rhamnopyranosyl‐(1 → 2)]‐β‐D ‐xylopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranoside (monepaloside D, 2 ), 3‐O‐α‐L ‐arabinopyranosyl‐(1 → 3)‐&[beta;‐D ‐glucopyranosy‐(1 → 2)]‐α‐L ‐arabinopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranoside (monepaloside E, 3 ) and 3‐O‐β‐D ‐xylopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranoside (monepaloside F, 4 ) on the basis of chemical and spectroscopic evidence. 2D NMR techniques, including ¹H–¹H COSY, HMQC, 2D HMQC‐TOCSY, HMBC and ROESY, and selective excitation experiments, including SELTOCSY and SELNOESY, were utilized in the structure elucidation and complete assignments of ¹H and ¹³C NMR spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Clintoniosides A – C,New Polyhydroxylated Spirostanol Glycosides from the Rhizomes of Clintonia udensis

Phytochemical analyses were carried out on the rhizomes of Clintonia udensis (Liliaceae) with particular attention paid to the steroidal glycoside constituents, resulting in the isolation of three new polyhydroxylated spirostanol glycosides, named clintonioside A ( 1 ), B ( 2 ), and C ( 3 ). On the basis of their spectroscopic data, including 2D‐NMR spectroscopy, in combination with acetylation and hydrolytic cleavage, the structures of 1 – 3 were determined to be (1β,3β,23S,24S,25R)‐1,23,24‐trihydroxyspirost‐5‐en‐3‐yl O‐β‐D ‐glucopyranosyl‐(1→4)‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐glucopyranoside ( 1 ), (1β,3β,23S,24S)‐3,21,23,24‐tetrahydroxyspirosta‐5,25(27)‐dien‐1‐yl O‐α‐L ‐rhamnopyranosyl‐(1→2)‐O‐[β‐D ‐xylopyranosyl‐(1→3)]‐β‐D ‐glucopyranoside ( 2 ), and (1β,3β,23S,24S)‐21‐(acetyloxy)‐24‐[(6‐deoxy‐β‐D ‐gulopyranosyl)oxy]‐3,23‐dihydroxyspirosta‐5,25(27)‐dien‐1‐yl O‐α‐L ‐rhamnopyranosyl‐(1→2)‐O‐[β‐D ‐xylopyranosyl‐(1→3)]‐β‐D ‐glucopyranoside ( 3 ).     

Four New Lariciresinol‐Based Lignan Glycosides from the Roots of Rhus javanica var. roxburghiana

The four new lariciresinol‐based lignan glycosides, (?)‐lariciresinol 4′‐(6″‐O‐feruloyl‐β‐D ‐glucopyranoside) ( 1 ), (?)‐lariciresinol 4′‐(4″,6″‐di‐O‐feruloyl‐β‐D ‐glucopyranoside) ( 2 ), 5,5′‐dimethoxylariciresinol 4′‐(4″,6″‐di‐O‐feruloyl)‐β‐D ‐glucopyranoside) ( 3 ), and 4‐O‐[α‐(1,2‐dihydroxyethyl)syringyl]‐5,5′‐dimethoxylariciresinol 4′‐(4″,6″‐di‐O‐feruloyl‐β‐D ‐glucopyranoside) ( 4 ), together with two known ones, lariciresinol 4′‐β‐D ‐glucopyranoside) ( 5 ) and tortoside B ( 6 ), were isolated from the BuOH extract of Rhus javanica var. roxburghiana roots, and their structures were established by means of various spectroscopic techniques.     

Polar Constituents from Sageretia Thea Leaf Characterized by HPLC‐SPE‐NMR Assisted Approaches

Nine glycosides ( 1–9 ) were characterized from the n‐butanol‐soluble fraction of the ethanolic extract of the leaves of Sageretia thea by the general approach. Among these, Compounds 6 and 7 were identified as a mixture. Application of HPLC‐SPE‐NMR in two selected fractions led to the separation of this mixture and the characterization of three additional minors ( 10–12 ). Among these, 7‐O‐methylmyricetin 3‐O‐α‐l ‐arabinofuranoside ( 8 ) is a new natural product and eight compounds, i.e. glucofragulin A ( 1 ), quercetin‐3‐O‐α‐l ‐arabinopyranoside ( 5 ), 3‐O‐β‐d ‐galactopyranoside ( 6 ), 3‐O‐β‐d ‐glucopyranoside ( 7 ), and 3‐O‐α‐l ‐arabinofuranoside ( 11 ), myricetin‐3‐O‐α‐l ‐arabinofuranoside ( 9 ) and 3‐O‐β‐d‐glucopyranoside ( 10 ), and quercetrin ( 12 ), are found for the first time from the title plant.     

Stilbenoids and Phenols in Acanthopanax brachypus

Three new stilbenoids, including α‐(3′‐O‐β‐D ‐glucopyranosyl‐5′‐methoxyphenyl)‐2‐methoxy‐3‐methylbenzofuran ( 1 ), 4‐methyl‐(E)‐resveratrol 3‐(2″‐p‐hydroxybenzoyl)‐O‐β‐D ‐glucopyranoside ( 2 ), and 5‐O‐methyl‐(E)‐resveratrol 3‐(6″‐acetyl)‐O‐β‐D ‐glucopyranoside ( 3 ), together with six known stilbenoids and phenols, acetovanillone 1‐(6′‐vanilloyl)‐O‐β‐D ‐glucopyranoside, eugenyl‐O‐β‐D ‐glucopyranoside, α‐(3′‐hydroxy‐5′‐methoxy‐2′‐methylphenyl)‐2‐hydroxybenzofuran, α‐(3′‐hydroxy‐5′‐methoxyphenyl)‐2‐hydroxybenzofuran, pinosilvin 3‐O‐β‐D ‐glucopyranoside, and (E)‐resveratrol 3‐(6″‐galloyl)‐O‐β‐D ‐glucopyranoside were isolated from the EtOH extract of the stem bark of Acanthopanax brachypus. Their structures were determined by spectral analysis including extensive 2D‐NMR spectral analyses. Compounds 2 and 3 exhibited weak cytotoxicity against human tumor A549 cell line (IC₅₀ values of 4.87 and 5.63 μM , resp.).     

Solution 1H and 13C NMR of new chiral 1,4‐oxazepinium heterocycles and their intermediates from the reaction of 2,4‐pentanedione with α‐L‐amino acids and (R)‐(—)‐2‐phenylglycinol

The reaction of 2,4‐pentanedione ( 1 ) with (R)‐(—)‐2‐phenylglycine methyl ester ( 2 ), (R)‐(—)‐2‐phenylglycinol ( 3 ) and the proteinogenic amino acids (2S,3R)‐(—)‐2‐amino‐3‐hydroxybutyric acid (L ‐threonine) ( 4 ) and (R)‐(—)‐2‐amino‐3‐mercaptopropionic acid (L ‐cysteine) ( 5 ) methyl esters was investigated. The corresponding enamines 6 , 7 and 8 were isolated and characterized spectroscopically whereas 9 , which is unstable, was transformed in situ into 13 . Treatment of 7 , 8 and 9 with boron trifluoride etherate afforded the new [1,4]oxazepines 10 , 11 and [1,4]thiazepine ( 12 ) as their BF₃O^? salts. The structures of the enamines and their corresponding seven‐membered heterocycles were assessed by 1D and 2D NMR spectroscopy. Variable‐temperature experiments revealed different molecular mobility behavior among these heterocycles. Copyright © 2003 John Wiley & Sons, Ltd.     

Phytochemical analysis and antioxidant potential of the leaves of Garcinia travancorica Bedd.

Phytochemical analysis of the leaves of Garcinia travancorica, a hitherto uninvestigated endemic species to the Western Ghats of south India, resulted in isolation and characterisation of the polyisoprenylated benzophenones 7-epi-nemorosone (1) and garcinol (2) along with biflavonoids GB-1a (3), GB-1 (4), GB-2 (5), morelloflavone (6) and morelloflavone-7″-O-β-d-glycoside or fukugiside (7). The compounds were identified using various spectroscopic techniques, mainly through NMR and MS. The methanol extract and the biflavonoids 3, 4, 5 and 7 showed potential in vitro antioxidant activities. The IC₅₀ value of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of compound 7 was 8.34 ± 2.12 μg/mL, comparable to that of standard ascorbic acid (3.2 ± 0.50 μg/mL). In the superoxide radical scavenging assay, compound 7 gave IC₅₀ value of 6.95 ± 1.33 μg/mL close to standard ascorbic acid with IC₅₀ value of 5.8 ± 0.25 μg/mL. Validated HPTLC estimation revealed G. travancorica as a rich source of morelloflavone-7″-O-β-d-glycoside (7.12% dry wt. leaves).     

Synthesis and NMR characterization of 6‐Phenyl‐6‐deoxy‐2,3‐di‐O‐methylcellulose

Cellulose ( 1 ) was converted for the first time to 6‐phenyl‐6‐deoxy‐2,3‐di‐O‐methylcellulose ( 6 ) in 33% overall yield. Intermediates in the five‐step conversion of 1 to­ 6 were: 6‐O‐tritylcellulose ( 2 ), 6‐O‐trityl‐2,3‐di‐O‐methylcellulose ( 3 ), 2,3‐di‐O‐methylcellulose ( 4 ); and 6‐bromo‐6‐deoxy‐2,3‐di‐O‐methylcellulose ( 5 ). Elemental and quantitative carbon‐13 analyses were concurrently used to verify and confirm the degrees of substitution in each new polymer. Gel permeation chromotography (GPC) data were generated to monitor the changes in molecular weight (DP_w) as the synthesis progressed, and the compound average decrease in cellulose DP_w was ～ 27%. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the decomposition of all polymers. The degradation temperatures ( °C) and percent char at 500 °C of cellulose derivatives 2 to 6 were 308.6 and 6.3%, 227.6 °C and 9.7%, 273.9 °C and 30.2%, 200.4 °C and 25.6%, and 207.2 °C and 27.0%, respectively. The glass transition temperature (T_g) of­6‐O‐tritylcellulose by dynamic mechanical analysis (DMA) occurred at 126.7 °C and the modulus (E′, Pa) dropped 8.9 fold in the transition from ?150 °C to + 180 °C (6.6 × 10⁹ to 7.4 × 10⁸ Pa). Modulus at 20 °C was 3.26 × 10⁹ Pa. Complete proton and carbon‐13 chemical shift assignments of the repeating unit of the title polymer were made by a combination of the HMQC and COSY NMR methods. Ultimate non‐destructive proof of carbon–carbon bond formation at C6 of the anhydroglucose moiety was established by generating correlations between resonances of CH₂6 (anhydroglucose) and C1′, H2′, and H6′ of the attached aryl ring using the heteronuclear multiple‐bond correlation (HMBC) method. In this study, we achieved three major objectives: (a) new methodologies for the chemical modification of cellulose were developed; (b) new cellulose derivatives were designed, prepared and characterized; (c) unequivocal structural proof for carbon–carbon bond formation with cellulose was derived non‐destructively by use of one‐ and two‐dimensional NMR methods. Copyright © 2002 John Wiley & Sons, Ltd.     

3‐O‐Methylquercetin Glucosides from Ophioglossum pedunculosum and Inhibition of Lipopolysaccharide‐Induced Nitric Oxide Production in RAW 264.7 Macrophages

The three new 3‐O‐methylquercetin glucosides 1 – 3 , together with three known congeners and 3‐O‐methylquercetin, were isolated from the fern Ophioglossum pedunculosum (quercetin=2‐(3,4‐dihydroxyphenyl)‐3,5,7‐trihydroxy‐4H‐1‐benzopyran‐4‐one). The new compounds were identified on the basis of spectroscopic analysis as 5′‐isoprenyl‐3‐O‐methylquercetin 4′,7‐di‐β‐D ‐glucopyranoside ( 1 ), 3‐O‐methylquercetin 4′‐β‐D ‐glucopyranoside 7‐[O‐β‐D ‐glucopyranosyl‐(1→2)‐β‐D ‐glucopyranoside] ( 2 ), and 3‐O‐methylquercetin 7‐[O‐β‐D ‐glucopyranosyl‐(1→2)‐β‐D ‐glucopyranoside] ( 3 ). The effect of the isolated compounds on lipopolysaccharide (LPS)‐induced NO production was evaluated. The inhibitory activity of 3‐O‐methylquercetin derivatives decreased markedly with the increasing number of glucosyl groups in the structures.     

Structure elucidation of a sodium salified anthraquinone from the seeds of Cassia obtusifolia by NMR technique assisted with acid–alkali titration

A new sodium salt of anthraquinone named sodium emodin‐1‐O‐β‐gentiobioside, together with nine known compounds, viz. rubrofusarin‐6‐O‐β‐D ‐gentiobioside, chrysophanol‐1‐O‐β‐D ‐glucopyranosyl‐(1–3)‐β‐D ‐glucopyranosyl‐(1–6)‐β‐D ‐glucopyranoside, obtusifolin‐2‐O‐β‐D ‐glucopyranoside, aurantio‐obtusin‐6‐O‐β‐D ‐glucopyranoside, physcion‐8‐O‐β‐D ‐glucopyranoside, 1‐hydroxyl‐2‐acetyl‐3,8‐dimethoxy‐6‐O‐β‐D ‐apiofuranosyl‐(1–2)‐β‐D ‐glucosylnaphthalene, toralactone‐9‐O‐β‐D ‐gentiobioside, aurantio‐obtusin, rubrofusarin‐6‐O‐β‐D ‐apiofuranosyl‐(1–6)‐O‐β‐D ‐glucopyranoside, was isolated from the seeds of Cassia obtusifolia and its structure was elucidated by ¹H and ¹³C NMR technique assisted with acid–alkali titration. The change of chemical shifts of sodium emodin‐1‐O‐β‐gentiobioside before and after acid–alkali titration was also characterized. Copyright © 2011 John Wiley & Sons, Ltd.     

Isoflavonoid Glycosides from the Rhizomes of Iris germanica

Five new di‐ and triglycosides, irigenin 7‐[O‐β‐D ‐glucopyranosyl‐(1→6)‐β‐D ‐glucopyranoside] ( 1 ), 6‐hydroxygenistein 4′‐[O‐β‐D ‐glucopyranosyl‐(1→6)‐β‐D ‐glucopyranoside] ( 2 ), nigricin 4′‐[O‐β‐D ‐glucopyanosyl‐(1→6)‐β‐D ‐glucopyranoside] ( 3 ), nigricin 4′‐[O‐β‐D ‐glucopyanosyl‐(1→2)‐O‐[α‐L ‐rhamnopyranosyl‐(1→6)]‐β‐D ‐glucopyranoside] ( 4 ), and 7‐{4′‐{[2″‐O‐(4′′′′‐acetyl‐2′′′′‐methoxyphenyl)‐β‐D ‐glucopyranosyl]oxy}‐3′‐(β‐D ‐glucopyranosyloxy)phenyl]‐9‐methoxy‐8H‐1,3‐dioxolo[4,5‐g]‐[1 benzopyran‐8‐one‐] ( 5 ), along with a known compound, nigricin 4′‐(β‐D ‐glucopyranoside) ( 6 ), were isolated from the rhizomes of Iris germanica. The structures of these compounds were established by spectroscopic methods, including 2D NMR spectroscopic techniques.