C-methylated and C-prenylated isoflavonoids from root extract of Desmodium uncinatum

A pterocarpan, 1,9-dihydroxy-3-methoxy-2-methylpterocarpan (named uncinacarpan) and two isoflavanones, 5,7-dihydroxy-2',3',4'-trimethoxy-6-(3-methylbut-2-enyl)isoflavanone (named uncinanone D) and 5,4'-dihydroxy-7,2'-dimethoxy-6-methylisoflavanone (named uncinanone E), were isolated from the CH(2)Cl(2) root extract of Desmodium uncinatum (Jacq.) DC and characterised by spectroscopic methods. In addition, a rare pterocarpan edudiol and two known abietane diterpenes, 7-oxo-15-hydroxydehydroabietic acid and 7-hydroxycallitrisic acid were identified. The fraction of the root extract that was analysed induced germination of Striga hermonthica seeds, but none of the isolated compounds showed this activity.     

Three isoflavanones with cannabinoid-like moieties from Desmodium canum

Three further derivatives of 5,7,2',4'-tetrahydroxy-6-methyl isoflavanone have been isolated from the root extract of Desmodium canum and assigned the structures 2,3-dihydro-5,7-dihydroxy-6-methyl-3-(1a,2,3,3a,8b,8c-hexahydro-6-hydroxy-1,1,3a-trimethyl-1H-4-oxabenzo[f]cyclobut[c,d]inden-7-yl)-4H-1-benzopyran-4-one (1) 2,3-dihydro-5,7-dihydroxy-6-methyl-3-(6a,7,8,10a-tetrahydro-3-hydroxy-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-2-yl)-4H-1-benzopyran-4-one (2) 2,3-dihydro-5,7-dihydroxy-6-methyl-3-(3-hydroxy-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-2-yl) 4H-1-benzopyran-4-one (3). The three compounds and the previously isolated chromene 4 all derive from the geranylated precursor 5 by a series of cannabinoid-like oxidative rearrangements.     

Two prenylated flavonoids from the stem bark of Erythrina burttii

From the stem bark of Erythrina burttii, a new isoflavone, 5,2',4'-trihydroxy-7-methoxy-6-(3-methylbut-2-enyl)isoflavone (trivial name, 7-O-methylluteone) and a new flavanone, 5,7-dihydroxy-4'-methoxy-3'-(3-methylbutadienyl)-5'-(3-methylbut-2-enyl)flavanone (trivial name, burttinonedehydrate) along with three known isoflavonoids (8-prenylluteone, 3-O-methylcalopocarpin and genistein) were isolated. The structures were determined on the basis of spectroscopic evidence.     

Geranylated flavanones from the secretion on the surface of the immature fruits of Paulownia tomentosa

Chemical investigation of the methanol extract of the viscous secretion on the surface of immature fruits of Paulownia tomentosa furnished nine geranylated flavanones, 6-geranyl-5,7-dihydroxy-3',4'-dimethoxyflavanone (1), 6-geranyl-3',5,7-trihydroxy-4'-methoxyflavanone (2), 6-geranyl-4',5,7-trihydroxy-3',5'-dimethoxyflavanone (3), 6-geranyl-4',5,5',7-tetrahydroxy-3'-methoxyflavanone (4), 6-geranyl-3,3',5,7-tetrahydroxy-4'-methoxyflavanone (5), 4',5,5',7-tetrahydroxy-6-[6-hydroxy-3,7-dimethyl-2(E),7-octadienyl]-3'-methoxyflavanone (6), 3,3',4',5,7-pentahydroxy-6-[6-hydroxy-3,7-dimethyl-2(E),7-octadienyl]flavanone (7), 3,3',4',5,7-pentahydroxy-6-[7-hydroxy-3,7-dimethyl-2(E)-octenyl]flavanone (8), and 3,4',5,5',7-pentahydroxy-3'-methoxy-6-(3-methyl-2-butenyl)flavanone (9), along with six known geranylated flavanones. Among these, compounds 4, 6-9 and the known 6-geranyl-3',4',5,7-tetraahydroxyflavanone (diplacone), 6-geranyl-3,3',4',5,7-pentahydroxyflavanone (diplacol) and 3',4',5,7-pentahydroxy-6-[7-hydroxy-3,7-dimethyl-2(E)-octenyl]flavanone showed potent radical scavenging effects towards DPPH radicals.     

Prenylated flavonoids of the leaves of Macaranga conifera with inhibitory activity against cyclooxygenase-2

Two prenylated flavonoid derivatives, 5-hydroxy-4'-methoxy-2",2"-dimethylpyrano-(7,8:6",5")flavanone (1) and 5,4'-dihydroxy-[2"-(1-hydroxy-1-methylethyl)dihydrofurano]-(7,8:5",4")flavanone (2), were isolated from an ethyl acetate-soluble extract of the leaves of Macaranga conifera using an in vitro activity-guided fractionation procedure based on the inhibition of cyclooxygenase-2. Also obtained were eight known compounds, 5,7-dihydroxy-4'-methoxy-8-(3-methylbut-2-enyl)flavanone (3), lonchocarpol A (4), sophoraflavanone B (5), 5,7-dihydroxy-4'-methoxy-8-(2-hydroxy-3-methylbut-3-enyl)flavanone (6), tomentosanol D (7), lupinifolinol (8), isolicoflavonol (9), and 20-epibryonolic acid (10). The structures of compounds 1 and 2 were determined using spectroscopic methods. All isolates were tested for their inhibitory effects against both cyclooxygenases-1 and -2, and selected compounds were evaluated in a mouse mammary organ culture assay.     

Isoflavonoids from roots of Erythrina zeyheri

Five isoflavonoids, (+/-)-7,2',4'-trihydroxy-8,3'-di(gamma,gamma-dimethylallyl)isoflavanone, (3R)-7,4'-dihydroxy-2'-methoxy-6,8-di(gamma,gamma-dimethylallyl)isoflavanone, (3R)-7,2',4'-trihydroxy-6,8-di(gamma,gamma-dimethylallyl)isoflavan, 2',4'-dihydroxy-8-gamma,gamma-dimethylallyl-2",2"-dimethylpyrano-[5,6:6,7]isoflavan and (6aS, 11aS)-3,6a-dihydroxy-9-methoxy-4,10-di(gamma,gamma-dimethylallyl)pterocarpan, along with five known compounds, were isolated from the roots of Erythrina zeyheri. Their structures were established on the basis of spectroscopic evidence, and their antibacterial activities against methicillin-resistant Staphylococcus aureus (MRSA) were estimated by determining minimum inhibitory concentrations.     

Homoisoflavanones from Disporopsis aspera

From cytotoxic extracts of the roots of Disporopsis aspera Engl. (Liliaceae) a homoisoflavanone, disporopsin (3-(2',4'-dihydroxy-benzyl)-5,7-dihydroxy-chroman-4-one) (1) and three rare methyl-homoisoflavanones, 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6-methyl-chroman-4-one (2), 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6,8-dimethyl-chroman-4-one (3) and 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6-methyl-8-methoxy-chroman-4- one (4) along with five other known compounds, N-trans-feruloyl tyramine (5), adenine (6), 5-(hydroxymethyl)-2-furfural (7), beta-sitosterol (8) and beta-sitosteryl glucopyranoside (9) were isolated. The structures of compounds 1-2 were elucidated by spectral data (1, 2-D NMR and EIMS). The four homoisoflavanones (1-4) were found to be cytotoxic against a series of human cancer cell lines (HCT15, T24S, MCF7, Bowes, A549 and K562) with IC(50) ranging from 15 to 200 microM. Possible biosynthesis routes for homoisoflavonoids (1-4) are discussed.     

Flavonoids from two Lonchocarpus species of the Yucatan Peninsula

Leaves, stem bark and root of Lonchocarpus xuul and Lonchocarpus yucatanensis were studied separately. A chalcone, 2',4-dimethoxy-6'-hydroxylonchocarpin (), and the flavones 5,4'-dihydroxy-3'-methoxy-(6:7)-2,2-dimethylpyranoflavone (2) and 5,4'-dimethoxy-(6:7)-2,2-dimethylpyrano-flavone (3), together with the known carpachromene (4), were isolated from the leaves of both species. Similarly, the previously reported flavans xuulanin (5) and 3beta-methoxyxuulanin (6), together with the novel 3beta,4beta,5-trimethoxy-4'-hydroxy-(6:7)-2,2-dimethylpyranoflavan (7), 3-hydroxy-4,5-dimethoxy-(6:7)-2,2-dimethyl-pyranoflavan (8), and 3,4-dihydroxy-5-methoxy-(6:7)-2,2-dimethylpyranoflavan (10), were isolated from the stem bark and root of both species. Finally, the known 2',4'-dihydroxy-3'-(3-methylbut-2-enyl) chalcone (13) was obtained from the root of L. xuul only. The structures of the various metabolites were established by interpretation of their spectroscopic data.     

Acylated flavonoids and phenol glycosides from Veronica thymoides subsp. pseudocinerea

A new acylated flavone glucoside, 3'-hydroxyscutellarein 7-O-(6'-O-protocatechuoyl)-beta-glucopyranoside (1), and a new phenol glucoside, 3,5-dihydroxyphenethyl alcohol 3-O-beta-glucopyranoside (6) were isolated from Veronica thymoides subsp. pseudocinerea together with seven known flavone, phenol and lignan glycosides; 3'-hydroxyscutellarein 7-O-(6'-O-trans-feruloyl)-beta-glucopyranoside (2), 3'-hydroxy, 6-O-methylscutellarein 7-O-beta-glucopyranoside (3), luteolin 7-O-beta-glucopyranoside (4), isoscutellarein 7-O-(6'-O-acetyl)-beta-allopyranosyl (1' --> 2')-beta-glucopyranoside (5), 3,4-dihydroxyphenethyl alcohol 8-O-beta-glucopyranoside (7), benzyl alcohol 7-O-beta-xylopyranosyl (1" --> 2')-beta-glucopyranoside (8), and (+)-syringaresinol 4'-O-beta-glucopyranoside (9). Compounds 2, 3 and 7-9 were reported for the first time in the genus Veronica. The structures of the isolates were determined by means of spectroscopic (UV, IR, 1D and 2D NMR, HR ESI-MS) methods. Isolated compounds (1-7) exhibited potent radical scavenging activity against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical.     

Isoflavanones from Uraria picta and their antimicrobial activity

Two isoflavanones, 5,7-dihydroxy-2'-methoxy-3',4'-methylenedioxyisoflavanone (2) and 4',5-dihydroxy-2',3'-dimethoxy-7-(5- hydroxyoxychromen-7yl)-isoflavanone (4) along with six known compounds including isoflavanones, triterpenes and steroids were isolated from the roots of Uraria picta. The structures of these compounds were established unambiguously by UV, IR, MS and a series of 1D and 2D NMR analyses. The minimum inhibitory concentrations (MIC) for these compounds were found to be in the range of 12.5-200 microg/ml against bacteria (both Gram positive and Gram negative) and fungi.     

A benzil and isoflavone derivatives from Derris scandens Benth

A benzil derivative: scandione, 2',2"-dihydroxy-4'-methoxy-4",5"-methylenedioxybenzil and two isoflavones: scandenal, 3'-formyl-4',5-dihydroxy-2",2"-dimethylchromeno-[6,7:5",6"]isoflavone and scanderone, 4',5-dihydroxy-3'-prenyl-2",2"-dimethylchromeno-[7,8:6",5"]isoflavone together with fifteen known compounds were isolated from the stem of D. scandens. Their structures were determined by spectroscopic methods. Radical scavenging, antibacterial and hypertensive activities of some of the compounds were investigated.     

Isoflavanones from the allelopathic aqueous root exudate of Desmodium uncinatum

Three isoflavanones, 5,7,2',4'-tetrahydroxy-6-(3-methylbut-2-enyl)isoflavanone (1), 4",5"-dihydro-5,2',4'-trihydroxy-5"-isopropenylfurano-(2",3";7,6)-isoflavanone (2) and 4",5"-dihydro-2'-methoxy-5,4'-dihydroxy-5"-isopropenylfurano-(2",3";7,6)-isoflavanone (3) and a previously known isoflavone 5,7,4'-trihydroxyisoflavone [genistein (4)] were isolated and characterised spectroscopically from the root exudate of the legume Desmodium uncinatum (Jacq.) DC. We propose the names uncinanone A, B, and C for compounds 1, 2 and 3, respectively. Isolated fractions containing uncinanone B (2) induced germination of seeds from the parasitic weed Striga hermonthica (Del.) Benth. and fractions containing uncinanone C (3) moderately inhibited radical growth, the first example of a newly identified potential allelopathic mechanism to prevent S. hermonthica parasitism.     

Homoisoflavonoids from Ophiopogon japonicus Ker-Gawler

From the ethyl acetate extract of the tuberous roots of Ophiopogon japonicus (Liliaceae) eight known and five new homoisoflavonoidal compounds were isolated. The new compounds are 5,7-dihydroxy-8-methoxy-6-methyl-3-(2'-hydroxy-4'-methoxybenzyl)chroman-4-one (1), 7-hydroxy-5,8-dimethoxy-6-methyl-3-(2'-hydroxy-4'-methoxybenzyl)chroman-4-one (2), 5,7-dihydroxy-6,8-dimethyl-3-(4'-hydroxy-3'-methoxybenzyl)chroman-4-one (3), 2,5,7-trihydroxy-6,8-dimethyl-3-(3',4'-methylenedioxybenzyl)chroman-4-one (4) and 2,5,7-trihydroxy-6,8-dimethyl-3-(4'-methoxybenzyl)chroman-4-one (5). Their structures have been elucidated by mass and NMR spectroscopy. Compounds 4 and 5 are the first isolated homoisoflavonoids with a hemiacetal function at position 2.     

Homoisoflavonoids and xanthones from the tubers of wild and in vitro regenerated Ledebouria graminifolia and cytotoxic activities of some of the homoisoflavonoids

Eleven homoisoflavonoids and two xanthones were isolated and characterized from the bulbs of Ledebouria graminifolia. Five of the homoisoflavonoids are new compounds and were identified as: 5-hydroxy-7-methoxy-3-(4'-hydroxybenzyl)-4-chromanone, 5-hydroxy-6,7-dimethoxy-3-(4'-hydroxybenzyl)-4-chromanone, 5,7,8-trimethoxy-3-(4'-hydroxybenzyl)-4-chromanone, 5-hydroxy-3',4',7-trimethoxyspiro[2H-1-benzopyran-7'-bicyclo[4.2.0]octa-trien]-4-one, 5,7-dihydroxy-3',4'-dimethoxyspiro[2H-1-benzopyran-7'-bicyclo[4.2.0]octa-trien]-4-one. Structures were elucidated by extensive 1D, and 2D NMR spectroscopy and HRMS. A method for tissue culture was developed and the bulbs of mature plants were found to contain all the compounds isolated from the wild specimens of L. graminifolia.     

Flavonoids from the stem bark of Bolusanthus speciosus

Three flavonoids (bolusanthols A-C), viz an isoflavan and two prenylated isoflavanones, were isolated from the stem bark of Bolusanthus speciosus in addition to four known flavonoids, 5,7,3'-trihydroxy-4'-methoxy-5'-methoxy-gamma,gamma-dimethylallylisoflavanone, 5,7,2'-trihydroxy-4'-methoxy-6,5'-di(gamma,gamma)-dimethylallyl)isoflavanone, 3,5,7,3',4'-pentahydroxy-6-gamma,gamma-dimethylallylflavone and 5,7,2',4'-tetrahydroxy-8,3'-di(gamma,gamma-dimethylallyl)-isoflavanone. The structure of the new compounds were determined to be 4,2',3',4'-tetrahydroxy-6,7-methylenedioxyisoflavan (bolusanthol A), 5,7,3',4'-tetrahydroxy-5'-gamma,gamma-dimethylallylisoflavanone (bolusanthol B), and 5,7,4'-trihydroxy-6,3'-di(gamma,gamma-dimethylallyl)isoflavanone (bolusanthol C) by spectroscopic methods.     

Two isoflavanones from the stem bark of Erythrina sacleuxii

From the stem bark of Erythrina sacleuxii two new isoflavanones, (R)-5,7-dihydroxy-2',4',5'-trimethoxyisoflavanone (trivial name, (R)-2,3-dihydro-7-demethylrobustigenin) and (R)-5-hydroxy-2',4',5'-trimethoxy-2",2"-dimethylpyrano[5",6":6,7]isoflavanone (trivial name, (R)-saclenone) were isolated. In addition the known compounds shinpterocarpin, 2,3-dehydrokievitone, abyssinone V, abyssinone V-4'-methyl ether, erythrinasinate and 4'-O-methylsigmoidin B were isolated. The structures were determined on the basis of spectroscopic evidence.     

Anti-plasmodial flavonoids from the stem bark of Erythrina abyssinica

The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC(50) values of 7.9+/-1.1 and 5.3+/-0.7 microg/ml, respectively. From this extract, a new chalcone, 2',3,4,4'-tetrahydroxy-5-prenylchalcone (trivial name 5-prenylbutein) and a new flavanone, 4',7-dihydroxy-3'-methoxy-5'-prenylflavanone (trivial name, 5-deoxyabyssinin II) along with known flavonoids have been isolated as the anti-plasmodial principles. The structures were determined on the basis of spectroscopic evidence.     

Two benzophenone O-arabinosides and a chromone from Hypericum annulatum

Two benzophenone O-arabinosides, annulatophenonoside (1) and acetylannulatophenonoside (2) were isolated from the methanol extract of the herb of Hypericum annulatum. The structures of the benzophenones were established as 2-O-alpha-L-arabinofuranosyl-3',5',6-trihydroxy-4-methoxybenzophenone (1) and 2-O-alpha-L-3"-acetylarabinofuranosyl-3',5',6-trihydroxy-4-methoxybenzophenone (2) based on spectral and chemical evidence. A chromone, 5,7-dihydroxy-3-methylchromone (3) was isolated from the chloroform extract. Although it has been previously synthesized it is encountered in a plant source for the first time. Co-occurrence of the two new benzophenone O-arabinosides along with the biogenetically related 1,5,7-trihydroxy-3-methoxyxanthone was not found.     

A benzil and isoflavone from Iris tenuifolia

Two compounds, tenuifodione (1) and tenuifone (2), and 12 known compounds, izalpinin (3), alpinone (4), arborinone (5), irilin B (6), irisone A (7), irisone B (8), betavulgarin (9), beta-sitosterol (10), 5,7-dihydroxy-2',6-dimethoxyisoflavone (11), 2',5-dihdroxy-6,7-methylenedioxy flavanone (12), irisoid A (13) and ethyl-beta-d-glucopyranoside (14) were isolated from the whole plant of Iris tenuifolia Pall. All compounds, except 12, were isolated for the first time from this plant. Compounds 2, 3 and 11 have shown a considerable DPPH radical scavenging activity. Structures of these compounds were identified on the basis of spectroscopic techniques, including 2D NMR. Compounds 3, 5 and 7 were also subjected to single-crystal X-ray diffraction analysis and their structures were unambiguously deduced.     

Phenolic glycosides from Phagnalon rupestre

Analysis of the butanol-soluble fraction from the methanolic extract of the aerial parts of Phagnalon rupestre (Asteraceae) has led to the isolation of seven phenolic compounds. Three have been identified on the basis of their NMR spectra as new natural compounds: the lignan 7,7'-bis-(4-hydroxy-3,5-dimethoxyphenyl)-8,8'-dihydroxymethyl-tetrahydrofuran-4-O-beta-glucopyranoside (1), the prenylhydroquinone glycoside 1-O-beta-glucopyranosyl-1,4-dihydroxy-2-(3'-hydroxy-3'-methylbutyl) benzene (2) and the acetophenone glycoside 12-O-beta-glucopyranosyl-9beta,12-dihydroxytremetone (3). The known flavonoids apigenin-7-O-beta-glucoside, luteolin-7-O-beta-glucoside, luteolin-7-O-beta-glucuronide and the acetophenone picein were also isolated.