Acetylated allose-containing flavonoid glucosides from Stachys anisochila

In continuation of our chemosystematic study of Stachys (Labiatae) we have isolated the previously reported isoscutellarein 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-β-D-glucopyranoside] (1) and 3′-hydroxy-4′-O-methylisoscutellarein 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-β-D-glucopyranoside] (4) and four new allose-containing flavonoid glycosides from S. anisochila. The new glycosides are hypolaetin 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-β-D-glucopyranside] (6) as well as the three corresponding diacetyl analogues of 1, 4 and 6, isoscutellarein 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-6″-O-acetyl-β-D-glucopyranoside], 3′-hydroxy-4′-O-methylisoscutellarein 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-6″-O-acetyl-β-D-glucopyranoside] and hypolaetin 7-O-[6″'-O-acetyl-β-D-allopyranosyl-(1 → 2)-6″-O-acetyl-β-D-glucopyranoside]. Extensive two-dimensional NMR studies (proton-carbon correlations, COSY experiments) allowed assignment of all ¹H NMR sugar signals and a correction of the ¹³C NMR signal assignments for C-2 and C-3 of the allose.     

18-Norspirostanol derivatives from Trillium tschonoskii

Three 18-norspironstanol oligoglycosides partly acylated in their sugar moieties were isolated from the underground parts of Trillium tschonoskii. Their structures were characterized, as 1-O-[2″,3″,4″-tri-O-acetyl-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl]-epitrillenogenin-24-O-acetate, 1-O-[2″,3″,4″-tri-O-acetyl-α-l-rhamno-pyranosyl-(1 → 2)-α-l-arabinopyranosyl]-epitrillenogenin and 1-O-[2″,4″-di-O-acetyl-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl]-epitrillenogenin-24-O-acetate.     

Acylated flavonol glycosides from Delphinium staphisagria

An ethanolic extract of the aerial parts of Delphinium staphisagria L. from Tenerife yielded four new flavonol glycosides 2″-acetylastragalin, 2″-acetylpaeonoside, quercetin 3-O-(2-acetyl-β-glucopyranoside)-7-O-β-glucopyranoside and 2″-acetylpetiolaroside in addition to astragalin, isoquercitrin, paeonoside, kaempferol 3-O-β-glucopyranoside-7-O-α-rhamnopyranoside, petiolaroside and rutin.     

Endgültige struktur von adonivernith aus Adonis vernalis

The structure of adonivernith, an orientin xyloside earlier isolated from Adonis vernalis, was established as luteolin 8-β-d-glucopyranosyl-2″-O-d-xylopyranoside (orientin 2″-O-β-d-xylopyranoside).     

Fragmentation pattern of permethyl 6-C-glycosylflavones in electron impact mass spectrometry

A mass spectral fragmentation pattern of permethyl 6-C-glycosylflavones is proposed from the MS data of permethyl derivatives mono-O-deuteriomethylated in the 2″-, 3″-, 4″- or 6″-positions. The synthesis of these compounds via O″-glycosyl-6-C-glucosylflavones is described.     

Coumarins from the roots of Prangos uloptera

Three new coumarins, 6-O-[β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyl]-prenyletin, 3″-O-[β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyl]-oxypeucedanin hydrate and 2″-O-[β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyl]-oxypeucedanin hydrate, together with six known coumarins, 3″-O-[β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyl]-heraclenol, 3″-O-(β-d-glucopyranosyl)-heraclenol, tortuoside, 3″-O-(β-d-glucopyranosyl)-oxypeucedanin hydrate, heraclenol and oxypeucedanin hydrate, have been isolated from the roots of Prangos uloptera, and the structures of these coumarins were unequivocally determined by spectroscopic means, notably UV, HRESIMS, and 1D and 2D NMR spectroscopy.     

Chemical modification of the nonreducing,terminal group of maltotriose

O-α-d-Galactopyranosyl-(1→4)-O-α-d-glucopyranosyl-(1→4)-d-glucopyranose (12) was prepared by inversion of configuration at C-4″ of 2,3,2′,3′,6′,2″,3″-hepta-O-acetyl-1,6-anhydro-4″,6″-di-O-methylsulfonyl-β-maltotriose (7), followed by O-deacylation, acetylation, acetolysis, and de-O-acetylation. The intermediate 7 was obtained by treatment of 1,6-anhydro-β-maltotriose (2) with benzal chloride in pyridine, followed by acetylation, removal of the benzylidene group, and methane-sulfonylation. Selective tritylation of 2 and subsequent acetylation afforded 2,3,2′,3′,6′,2″,3″,4″-octa-O-acetyl-1,6-anhydro-6″-O-trityl-β-maltotriose (6), which was O-detritylated and p-toluenesulfonylated to give 2,3,2′,3′,6′,2″,3″,4″-octa-O-acetyl-1,6-anhydro-6″-O-p-tolylsulfonyl-β-maltotriose (13). Nucleophilic displacement of 13 with thioacetate, iodide, bromide, chloride, and azide ions gave 6″-S-acetyl- (14), 6″-iodo- (15), 6″-bromo- (16), 6″-chloro- (19), and 6″-azido- (20) 1,6-anhydro-β-maltotriose octaacetates, respectively. 6″Deoxy- (18) and 6″-acetamido-6″-deoxy (21) derivatives of 1,6-anhydro-β-maltotriose decaacetates were also prepared from 15 and 16, and 20, respectively. Acetolysis of 14, 15, 16, 18, 19, and 21 afforded 1,2,3,6,2′,3′,6′,2″,3″,4″-deca-O-acetyl-6″-S-acetyl (22), -6″-iodo (23), -6″-bromo (24), -6″-deoxy (25), -6″-chloro (26), and -6″-acetamido-6′-deoxy (27) derivatives of α-maltotriose, respectively. O-Deacetylation of 24, 25, and 26 furnished 6″-bromo-(28), 6″-deoxy- (29), and 6″-chloro- (30) maltotrioses, respectively, which on acetylation gave the corresponding β-decaacetates.     

Acylflavonoid C-glycosides from Eleusine coracana

Chromatographic fractionation of the methanolic extract of the shoots of Eleusine coracana led to the identification of three novel acylflavonoid glycosides, 6″-O-3-hydroxy-3-methylglutaroylorientin (1), 6″-O-malonylvitexin (2), and 4″-O-3-hydroxy-3-methylglutaroylvitexin (3) as well as five known flavonoid glycosides, orientin (4), isoorientin (5), vitexin (6), isovitexin (7), and 6″-O-3-hydroxy-3-methylglutaroylvitexin (8). The structures of these compounds were established on the basis of NMR and mass spectral data.     

Characterization and quantification of flavonoid glycosides in the Prunus genus by UPLC-DAD-QTOF/MS

Widely distributed in plants, flavonoids reduce the incidence of cancer and cardiovascular disease. In this study, flavonoid content and composition in members of the Prunus genus were evaluated using liquid chromatography with diode array and electrospray ionization mass spectrometric detection (UPLC-DAD-ESI/QTOF-MS). Flavonoids in plants of the Prunus genus include the basic structures of kaempferol, quercetin, and catechin, and exist as mono-, di-, or tri-glycoside compounds mono-acylated with acetic acid. A total of 23 individual flavonoids were isolated and confirmed, three of which appear to be newly identified compounds: quercetin 3-O-(2″-O-acetyl)neohesperidoside, quercetin 3-O-(4″-O-acetyl)rutinoside, and kaempferol 3-O-(4″-O-acetyl)rutinoside. Japanese apricot and Chinese plum contained the highest amounts of flavonoids in the Prunus genus. During the ripening stage of Japanese apricot, the total flavonol content was reduced, while the catechin content was increased.     

Two isovitexin 2″-O-glycosides from primary leaves of Secale cereale

Two isovitexin 2″-O-glycosides have been isolated from primary leaves of rye and identified as isovitexin 2″-O-arabinoside and isovitexin 2     

Flavonoid diversification in different leaf compartments of Primula auricula (Primulaceae)

Populations of Primula auricula L. subsp. auricula from Austrian Alps were studied for flavonoid composition of both farinose exudates and tissue of leaves. The leaf exudate yielded Primula-type flavones, such as unsubstituted flavone and its derivatives, while tissue flavonoids largely consisted of flavonol 3-O-glycosides, based upon kaempferol (3, 4) and isorhamnetin (5–7). Kaempferol 3-O-(2″-O-β-xylopyranosyl-[6″-O-β-xylopyranosyl]-β-glucopyranoside) (3) and isorhamnetin 3-O-(2″-O-β-xylopyranosyl-[6″-O-β-xylopyranosyl]-β-glucopyranoside) (6) are newly reported as natural compounds. Remarkably, two Primula type flavones were also detected in tissues, namely 3′-hydroxyflavone 3′-O-β-glucoside (1) and 3′,4′-dihydroxyflavone 4′-O-β-glucoside (2), of which (1) is reported here for the first time as natural product. All structures were unambiguously identified by NMR and MS data. Earlier reports on the occurrence of 7,2′-dihydroxyflavone 7-O-glucoside (macrophylloside) in this species could not be confirmed. This structure was now shown to correspond to 3′,4′-dihydroxyflavone 4′-O-glucoside (2) by comparison of NMR data. Observed exudate variations might be specific for geographically separated populations. The structural diversification between tissue and exudate flavonoids is assumed to be indicative for different ecological roles in planta.     

Dilignol glycosides from needles of Picea abies

(2R,3R)-2 3-Dihydro-2-(4′-hydroxy-3′-methoxyphenyl)-3-(hydroxymethyl)-7-methoxy-5-benzofuranpropanol 4′-O-β-d-glucopyranoside [dihydrodehydrodiconiferyl alcohol glucoside], (2R,3R)-2 3-dihydro-7-hydroxy-2-(4′-hydroxy-3′-methoxyphenyl)-3-(hydroxymethyl)-5-benzofuranpropanol 4′-O-β-d-glucopyranoside and 4′-O-α-l-rhamnopyranoside, 1-(4′-hydroxy-3′-methoxyphenyl)-2- [2″-hydroxy-4″-(3-hydroxypropyl)phenoxy]-1, 3-propanediol 1-O-β-d-glucopyranoside and 4′-O-β-d-xylopyranoside, 2,3-bis[(4′-hydroxy-3′-methoxyphenyl)-methyl]-1,4-butanediol 1-O-β-d-glucopyranoside [(?)-seco-isolariciresinol glucoside] and (1R,2S,3S)-1,2,3,4-tetrahydro-7-hydroxy-1-(4′-hydroxy-3′-methoxyphenyl)-6-methoxy-2 3-naphthalenedimethanol α²-O-β-d-xylopyranoside [(?)-isolariciresinol xyloside] have been isolated from needles of Picea abies and identified.     

Flavonoid glucuronides from Picria fel-terrae

Three flavonoid glucuronides are reported from a n-BuOH extract of Picria fel-terrae (Scrophulariaceae). The structures were established by UV, one- and two-dimensional NMR and mass spectrometry as apigenin 7-O-β-glucuronide, luteolin 7-O-β-glucuronide and apigenin 7-O-β-(2″-O-α-rhamnosyl)glucuronide, the latter one being a new compound.     

Phenolic compounds from Vepris heterophylla

From the leaves of Vepris heterophlylla, trans-sinapic acid methyl ester, 2″-O-glucosylisovitexin, 2″-O-glucosylvitexin, isovitexin     

C-glycosylflavones from Oryza sativa

Eight flavone C-glycosides isolated from rice plant were found to act as probing stimulants for planthoppers. They have been identified as the known compounds schaftoside, neoschaftoside, carlinoside, isoorientin 2″-glucoside and the new constituents neocarlinoside (6-C-β-D-glucopyranosyl-8-C-β-L-arabinopyranosylluteolin), isoscoparin 2″-glucoside (chrysoeriol 6-C-β-D-(2-O-β-D-glucopyranosyl)glucopyranoside) and its 6?-p-coumaric and ferulic acid esters.     

C-Arabinosylapigenin methyl ethers from Asterostigma riedelianum

The leaves of summer harvested Asterostigma riedelianum were found to contain the following flavonoids all of which are reported for the first time: 6,8-di-C-arabinosylapigenin 7,4′-dimethyl ether, 2″-O-glucosyl-6-C-arabinosylapigenin 7,4′-dimethyl ether and 2″-O-(caffeoyl)glucosyl-6-C-arabinosylapigenin 7,4′-dimethyl ether. Winter harvested A. riedelianum additionally contained the 7-monomethyl ethers of the mono-C-arabinosides.     

Microbial metabolism of cannflavin A and B isolated from Cannabis sativa

Microbial metabolism of cannflavin A (1) and B (2), two biologically active flavonoids isolated from Cannabis sativa L., produced five metabolites (3–7). Incubation of 1 and 2 with Mucor ramannianus (ATCC 9628) and Beauveria bassiana (ATCC 13144), respectively, yielded 6″S,7″-dihydroxycannflavin A (3), 6″S,7″-dihydroxycannflavin A 7-sulfate (4) and 6″S,7″-dihydroxycannflavin A 4′-O-α-l-rhamnopyranoside (5), and cannflavin B 7-O-β-d-4?-O-methylglucopyranoside (6) and cannflavin B 7-sulfate (7), respectively. All compounds were evaluated for antimicrobial and antiprotozoal activity.     

Two acylated flavanone glycosides from Nierembergia hippomanica

Two new acylated flavanone glycosides have been isolated from Nierembergia hippomanica and identified by spectral data as pinocembrin 7-O-β-(3?-O-acetyl)neohesperidoside and pinocembrin 7-O-β-(6″-O-acetyl)neohesperidoside.     

Flavonoid glycosides from needles of Pinus massoniana

Seven flavonoids have been isolated from Pinus massoniana needles and identified as taxifolin and its 3′-O-β-D-glucopyranoside, (+)-catechin, naringenin-7-O-β-D-glucopyranoside and three new flavonoid glycosides, 6-C-methylaromadendrin 7-O-β-D-glucopyranoside, taxifolin 3′-O-β-D-(6″-O-phenylacetyl)-glucopyranoside and eriodictyol 3′-O-β-D-glucopyranoside.     

Dihydrochalcone glucosides and antioxidant activity from the roots of Anneslea fragrans var. lanceolata

Bioassay-guided fractionation of the roots of Anneslea fragrans var. lanceolata led to the isolation of four dihydrochalcone glucosides, davidigenin-2′-O-(6″-O-4″′-hydroxybenzoyl)-β-glucoside (1), davidigenin-2′-O-(2″-O-4″′-hydroxybenzoyl)-β-glucoside (2), davidigenin-2′-O-(3″-O-4″′-hydroxybenzoyl)-β-glucoside (3), and davidigenin-2′-O-(6″-O-syringoyl)-β-glucoside (4), and 13 known compounds. The structures were identified by means of spectroscopic analysis. Davidigenin-2′-O-(6″-O-syringoyl)-β-glucoside (4), 1-O-3,4-dimethoxy-5-hydroxyphenyl-6-O-(3,5-di-O-methylgalloyl)-β-glucopyranoside (5), lyoniresinol (10), and syringic acid (13) showed ABTS [2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)] cation radical scavenging activity, with SC₅₀ values of 52.6 ± 5.5, 26.0 ± 0.7, 6.0 ± 0.2, and 27.5 ± 0.6 μg/mL in 20 min, respectively. Lyoniresinol (10), isofraxidin (12), and syringic acid (13) also showed DPPH [1,1-diphenyl-2-picrylhydrazyl] radical scavenging activity, with SC₅₀ values of 8.4 ± 1.8, 51.6 ± 2.2, and 4.3 ± 0.7 μg/mL in 30 min, respectively.