Flavonoids from Limnophila indica

Two flavonoids, (2S)-5,7,3',4'-tetramethoxyflavanone (1) and 5,7,2',5'-tetramethoxyflavone (2) together with three known flavonoids, 7-O-methylwogonin (3), skullcapflavone I (4) and 5-hydroxy-7,2'-dimethoxyflavone (5) were isolated from the whole plant of Limnophila indica. The structures of compounds 1-5 were elucidated on the basis of spectral and chemical studies.     

Flavonoids from the pods of Millettia erythrocalyx

From the pods of Millettia erythrocalyx, 2'-hydroxy-3,4-dimethoxy-[2',3':4',3']-furanochalcone, 2',3-dihydroxy-4-methoxy-4'-gamma,gamma-dimethylallyloxychalcone, (-)-(2S)-6,3',4'-trimethoxy-[2',3':7,8]-furanoflavanone, 3',4'-methylenedioxy-[2',3':7,8]-furanoflavonol and 6,3'-dimethoxy-[2',3':7,8]-furanoflavone were isolated, along with six other known flavonoids. Their structures were elucidated through analysis of their spectroscopic data.     

Flavonoids and terpenoids from Helichrysum forskahlii

Three new flavonoids, namely helichrysone A (1), helichrysone B (2) and helichrysone C (3) were isolated from the aerial parts of Helichrysum forskahlii, together with 10 known flavonoids, three triterpenes, and one sesquiterpene. The structures of the new flavonoids 1-3 were established by 1D and 2D NMR spectral data. In addition, the antimicrobial activities of the isolated compounds were determined.     

Flavonoids from Cleistocalyx operculatus

Two flavonoids 3'-formyl-4',6'-dihydroxy-2'-methoxy-5'-methylchalcone and (2S)-8-formyl-5-hydroxy-7-methoxy-6-methylflavanone together with five known compounds, were isolated from the dried buds of Cleistocalyx operculatus. Their structures were determined on the basis of spectroscopic analyses (UV, IR, EIMS, (1)H, (13)C NMR and HMBC).     

Flavonoids from the aquatic plant Eriocaulon buergerianum

Four flavonoids including (2S)-3',4'-methylenedioxy-5,7-dimethoxyflavan and hispidulin 7-(6-E-p-coumaroyl-beta-D-glucopyranoside), and one tocopherol were isolated from the capitulum of Eriocaulon buergerianum KOERN. Their structures were established by spectral and chemical evidence.     

Flavonoids from shoots and roots of Trifolium repens (white clover) grown in presence or absence of the arbuscular mycorrhizal fungus Glomus intraradices

White clover (Trifolium repens) plants were grown in the presence or absence of the arbuscular mycorrhizal fungus Glomus intraradices. Flavones, 4',5,6,7,8-pentahydroxy-3-methoxyflavone and 5,6,7,8-tetrahydroxy-3-methoxyflavone, as well as two flavones 3,7-dihydroxy-4'-methoxyflavone and 5,6,7,8-tetrahydroxy-4'-methoxyflavone never previously reported in plants, were isolated. The known 3,5,6,7,8-pentahydroxy-4'-methoxyflavone, 2',3',4',5',6'-pentahydroxy-chalcone, 6-hydroxykaempferol, 4',5,6,7,8-pentahydroxyflavone and 3,4'-dimethoxykaempferol were also obtained. Analysis of extracts obtained from roots and shoots revealed that the compositions of the flavonoid mixtures varied with growing conditions. Quercetin, acacetin and rhamnetin accumulated in roots of inoculated plants, whereas they were not detected in non-inoculated plants.     

Flavonoids from shoots, roots and roots exudates of Brassica alba

Analysis of extracts obtained from shoots, roots and exudates of Brassica alba revealed the presence of 3,5,6,7,8-pentahydroxy-4'-methoxy flavone in shoots, as well as 2',3',4',5',6'-pentahydroxy chalcone and 3,5,6,7,8-pentahydroxy flavone in roots and exudates. Apigenin was also found in the shoots and roots, but not in the root exudates.     

Flavonoids from Andrographis lineata

Three flavonoids, 5,7,2',3',4'-pentamethoxyflavone (1), 2'-hydroxy-2,4',6'-tri methoxychalcone (2) and dihydroskullcapflavone I (3), together with 17,19,20-trihydroxy-5beta, 8alpha H, 9beta H,10alpha-labd-13-en-16,15-olactone (4), a known diterpenoid and six known flavonoids, 5-hydroxy-7,8-dimethoxyflavanone (5), 5-hydroxy-7,8,2',3',4'-pentamethoxyflavone (6), 5,2'-dihydroxy-7-methoxyflavanone (7), 5,2'-dihydroxy-7,8-dimethoxyflavone (8), 5,2'-dihydroxy-7-methoxyflavone (9) and 5,2'-dihydroxy-7-methoxyflavone 2'-O-beta-D-glucopyranoside (10) were isolated from the whole plant of Andrographis lineata. The structures of these compounds were elucidated on the basis of spectral and chemical studies.     

Flavonoids and isoflavonoids from Gynerium sagittatum

Four flavonoids namely (2R,3R)-2,3-trans-7,4'-dimethoxydihydroflavonol, (2R,3S,4S)-2,3-trans-3,4-cis-7,4'-dimethoxy-3,4-flavandiol, 6-hydroxy-7,4'-dimethoxyflavone, 6,7,4'-trimethoxyflavone, along with the known isoflavonoids ferreirin, dihydrocajanin, dalbergioidin, dihydrobiochanin A and biochanin A and other 11 known compounds were isolated from the roots of Gynerium sagittatum. The structural characterization of these compounds was carried out via one- and two-dimensional NMR experiments in combination with ESI-MS. Finally a quantitative analysis of the isoflavones of the methanolic extract was performed by LC-ESI-MS. The high quantity of isoflavonoids found in G. sagittatum makes this plant a good natural source of isoflavonoids.     

Flavonoids from the roots of Millettia erythrocalyx

From the roots of Millettia erythrocalyx, 6-methoxy-[2",3":7,8]-furanoflavanone, 2,5-dimethoxy-4-hydroxy-[2",3":7,8]-furanoflavan, and 3,4-methylenedioxy-2',4'-dimethoxychalcone were isolated, along with ten other known flavonoids. Their structures were elucidated on the basis of analyses of their spectroscopic data.     

Allelochemicals from Stauranthus perforatus, a Rutaceous tree of the Yucatan Peninsula, Mexico

Aqueous leachates and a CHCl3-MeOH (1:1) extract of roots of Stauranthus perforatus showed a significant phytotoxic effect on Amaranthus hypochondriacus and Echinochloa crus-galli. Bioassay-directed fractionation of the active organic extract led to the isolation and characterization of ten secondary metabolites, which included two pyranocoumarins [xanthyletin (1) and 3-(1',1'-dimethylallyl)-xanthyletin (2)], four furanocoumarins [chalepensin (3), ammirin (4), chalepin (5) and 2'-isopropyl-psoralene (6)], two lignans [asarinin (7) and fargesin (8)], one sesquiterpene [4,5-epoxi-beta-caryophyllene (9)], and one alkamide [pellitorine (10)]. From these compounds, 2'-isopropyl-psoralene (6) or anhydromarmesin, is reported for the first time as a natural product, whereas compounds 4-10 are now reported as being present in S. perforatus. Metabolites 1, 3-5 and 10 caused significant inhibition of radicle growth of A. hypochondriacus and E. crus-galli. Furthermore, in a greenhouse experiment the decomposition of the leaves and roots in the soil had a significant inhibitory effect on the growth of weeds. The allelopathic action of the decomposition of roots was evident up to the sixth week of the experiment. The effect of leaves was comparable to that of DPCA (dimethyl tetrachloroterephthalate), a commercial herbicide. Finally different concentrations of Stauranthus root powder were combined with maize kernels and used to feed corn weevil. The treatments resulted in high mortality of this insect.     

Constituents of two Flourensia species

The MeOH extract of aerial parts of Flourensia riparia Grisebach (Asteraceae) afforded a sesquiterpene lactone, 4beta-hydroxy-4,10alpha-dimethyl-7alphaH,8alphaH-eudesman-11-ene-8,12-olide, together with septuplinolide, its isomer at positions C-5 and C-10. In addition, known flavonoids, p-hydroxyacetophenone derivatives, carabrone and isoalantolactone were identified. Three known flavonoids and a benzofuran were isolated from Flourensia campestris Wedd.     

Flavonoids and andrographolides from Andrographis paniculata

Two flavonoids, identified as 5,7,2',3'-tetramethoxyflavanone and 5-hydroxy-7,2',3'-trimethoxyflavone, as well as several other flavonoids, andrographolide diterpenoids, and polyphenols, were obtained from the phytochemical investigation of the whole plant of Andrographis paniculata, a well known medicinal plant. The structures of these compounds were established with the aid of spectroscopic methods, including analysis by 2D NMR spectroscopy.     

Cyclobutanes from Combretum albopunctatum

A dichloromethane extract of the aerial parts of Combretum albopunctatum Suesseng afforded five phenolic compounds-three known flavonoids and two novel cyclobutane chalcone dimers. The chemical structures were determined by standard spectroscopic techniques and the structure and relative stereochemistry of one chalcone dimer, rel-(1 alpha,2 beta)-di-(2,6-dimethoxy-4-hydroxy)-benzoyl-rel-(3 alpha,4 beta)-diphenylcyclobutane, were confirmed by single crystal X-ray diffraction.