Isoflavones from Pterodon apparicioi

The trunk wood of Pterodon apparicioi contains five known compounds: 7-hydroxy-6,4′-dimethoxy-, 7-hydroxy-6-methoxy-3′,4′-methylenedioxy-, 6,7,2′,3′,4′-pentamethoxy-, 6,7,2′,4′,5′-pentamethoxy- and 6,7,2′-trimethoxy-4′,5′-methylenedioxyisoflavone. In addition, there are four new substances, namely 7,3′-dihydroxy-6,4′-dimethoxy-, 7-hydroxy-6,2′,4′,5′-tetramethoxy-, 7,2′-dimethoxy-4′,5′-methylenedioxy- and 7,8,2′-trimethoxy-4′,5′-methylenedioxyisoflavone.     

Labdane derivatives and flavones from Gutierrezia dracunculoides

An investigation of the aerial parts of Gutierrezia dracunculoides afforded, in addition to known compounds, three new labdane derivatives, all related to lambertianic acid, 17-hydroxy- and 17-acetoxylambertianic acid and 7α- hydroxylambertianic acid, two esterified and three highly oxygenated flavones, 5,7,4′-trihydroxy-3,3′-dimethoxy- flavone-4′-O- [2-methylbutyrate] and isovalerate, 3′,5′-dihydroxy-3,5,6,7,8,4′-hexamethoxyflavone, 5,3′,5′-trihydroxy- 3,6,7,8,4′-pentamethoxyflavone and 5,7,3′,5′-tetrahydroxy-3,6,8,4′-tetramethoxyflavone. The structures were elucidated by spectroscopic methods and a few chemical transformations.     

Two new C-methylated flavonoids from Myrica gale

From the leaves of Myrica gale 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone has been isolated. The fruits yielded 2′-hydroxy-4′,6′-dimethoxy-3′-methyldihydrochalcone. The constitutions were deduced from spectroscopic data and confirmed by synthesis.     

New water soluble flavone and xanthone glycosides from Hypericum canariense L.

The water soluble portion of the aerial parts of Hypericum canariense L. yielded after acetylation the 5,7,3′4′-tetra- and 7,3′4′-triacetates of a new flavonoid 5,7,3′,4′-tetrahydroxy-3-O-β-d-(methyl 2,3,4-triacetoxypyranuronyl)-quercetin, the 3′-acetate of a new flavonoid 3′-hydroxy-5,7,4′-trimethoxy-3-O-β-d-(methyl 2,3,4-triacetoxypyranuronyl)-quercetin, the 3′-acetate and the 3′5′-diacetate of the new flavonoid 5,3′dihydroxy-7,4′-dimethoxy-3-β-d-(methyl 2,3,4-triacetoxypyranuronyl)-quercetin, the xanthone derivative mangiferin 2′,3′,4′,6′-tetraacetate and the latter's new 1,3,6,7′-tetramethoxy, 1,3,6-trimethoxy-4-acetoxy and 1,7-diacetoxy-3,6-dimethoxy analogs.     

Synthesis of dihydrochalcones of Myrica gale

4,4,6-Trimethyl-2-(3-phenylpropionyl)cyclohexane-1,3,5-trione, 2′-hydroxy-4′,6′-dimethoxy-3′-methyldihydrochalcone, 2′,6′-dihydroxy-4′-methoxy-3′,5′-dimethyldihydrochalcone and 2,2,5-trimethyl-4(3-phenylpropionyl)cyclopent-4-ene-1,3-dione, constituents of Myrica gale, have been synthesized.     

Isoflavones from Xanthocercis zambesiaca

In addition to the previously described 7-hydroxy-8,4′-dimethoxy- and 7,3′-dihydroxy-8,4′-dimethoxy-isoflavone the heartwood of Xanthocercis zambesiaca has been shown to contain 7-hydroxy-8,3′,4′-trimethoxy-,3′,4′-dimethoxy-6,7-methylenedioxy- and 8,3′,4′-trimethoxy-6,7-methylenedioxy-isoflavone. A technique of determining isoflavone hydroxylation patterns by deuterium labelling is described.     

4-Arylcoumarins from Coutarea hexandra

Four new 4-arylcoumarins have been isolated from Coutarea hexandra and their structures established as 5,7,4′-trimethoxy-4-phenylcoumarin, 4′-hydroxy-5,7-dimethoxy-4-phenylcoumarin, 3′-hydroxy-5,7-4′-trimethoxy-4-phenylcoumarin and 3′,4′-dihydroxy-5,7-dimethoxy-4-phenylcoumarin.     

Chemistry of toxic range plants. Highly oxygenated flavonol methyl ethers from Gutierrezia microcephala

The perennial American desert shrub, Gutierrezia microcephala, contains 20 flavonol methyl ethers displaying nine different oxygenation patterns. These include 11 new flavonols: 5,7-dihydroxy-3,6,8,3′,4′,5′-hexamethoxyflavone, 5,7,4′-trihydroxy-3,6,8,3′,5′-pentamethoxyflavone, 5,7,3′-trihydroxy-3,6,8,4′,5′-pentamethoxyflavone, 5,7,2′,4′-tetrahydroxy-3,6,8,5′-tetramethoxyflavone, 5,7,3′,4′-tetrahydroxy-3,6,8-trimethoxyflavone, 5,7,8,3′,4′-pentahydroxy-3,6-dimethoxyflavone, 3,5,7,3′,4′-pentahydroxy-6,8-dimethoxyflavone, 5,7,4′-trihydroxy-3,6,8-trimethoxyflavone, 5,7,8,4′-tetrahydroxy-3,3′-dimethoxyflavone, 5,7,8,3′,4′-pentahydroxy-3-methoxyflavone and 5,7,8,4′-tetrahydroxy-3-methoxyflavone. In addition, the following known flavonols were isolated: 5,7-dihydroxy-3,8,3′,4′,5′-pentamethoxyflavone, 5,7,4′-trihydroxy-3,8-dimethoxyflavone, 5,7,4′-trihydroxy-3,8,3′-trimethoxyflavone, 5,7,3′,4′-tetrahydroxy-3,8-dimethoxyflavone, 5,7,4′-trihydroxy-3,6,3′-trimethoxyflavone, 5,7,3′,4′-tetrahydroxy-3-methoxyflavone, 5,4′-dihydroxy-3,6,7,8,3′-pentamethoxyflavone, 5,7,4′-trihydroxy-3,6,8,3′-tetramethoxyflavone and 3,5,7,4′-tetrahydroxy-6,8,3′-trimethoxyflavone.     

Diarylpropanes from the wood of Iryanthera grandis

Trunk wood of Iryanthera grandis contains 1(2′-hydroxy-4′,6′-dimethoxyphenyl)-3-(3″,4″-methylenedioxyphenyl)-propane and 1(2′-hydroxy-4′,6′-dimethoxyphenyl)-3-(3″-methoxy-4″-hydroxyphenyl)-propane, as well as three additional known diarylpropanes, a new flavan (±)-5,7-dimethoxy-4′-hydroxyflavan and the known (±)-7,4′-dihydroxy-3′-methoxyflavan.     

Flavonoids from Artemisia ludoviciana var. ludoviciana

Nineteen flavonoids were isolated from Artemisia ludoviciana var. ludoviciana, including a new 2′- hydroxy- 6-methoxyflavone, 5,7,2′,4′-tetrahydroxy-6,5′-dimethoxyflavone. The known compounds include quercetagetin 3,6,3′,4′-tetramethyl ether, eupatilin, 5,7-dihydroxy-3,6,8,4′-tetramethoxyflavone, luteolin 3′,4′-dimethyl ether, jaceosidin, 5,7,4′-trihydroxy-3,6-dimethoxyflavone, tricin, hispidulin, chrysoeriol, kaempferol 3-methyl ether, apigenin, axillarin, eupafolin, selagin and luteolin together with three flavones which were previously isolated for the first time from Artemisia frigida: 5,7,4′-trihydroxy-6, 3′,5′-trimethoxyflavone, 5,7,3′-trihydroxy-6,4′,5′-trimethoxyflavone and 5,7,3′,4′-tetrahydroxy-6,5′- dimethoxyflavone.     

Homoisoflavonoids from the medicinal plant Portulaca oleracea

Four homoisoflavonoids named portulacanones A−D, identified as 2′-hydroxy- 5,7-dimethoxy-3-benzyl-chroman-4-one, 2′-hydroxy-5,6,7-trimethoxy-3-benzyl-chroman-4-one, 5,2′-dihydroxy-6,7-dimethoxy-3-benzyl-chroman-4-one, and 5,2′-dihydroxy-7-methoxy-3-benzylidene-chroman-4-one, were isolated from aerial parts of the plant Portulaca oleracea along with nine other known metabolites. Their structures were established on the basis of extensive spectroscopic analyses. Portulacanones A−D is the first group of homoisoflavonoids so far reported from the family Portulacaceae. They represent a rare subclass of homoisoflavonoids in nature with a structural feature of a single hydroxyl group substituted at C-2′ rather than at C-4′ in ring B of the skeleton. Three homoisoflavonoids and the known compound 2,2′-dihydroxy-4′,6′-dimethoxychalcone selectively showed in vitro cytotoxic activities towards four human cancer cell lines. Especially 2,2′-dihydroxy-4′,6′-dimethoxychalcone showed cytotoxic activity against cell line SGC-7901 with an IC₅₀ value of 1.6 μg/ml, which was more potent than the reference compound mitomycin C (IC₅₀ 13.0 μg/ml).     

Lipophilic C-methylflavonoids with no B-ring oxygenation in Metrosideros species (Myrtaceae)

Five unusual C-methylflavonoids lacking B-ring oxygenation (2′,4′-dihydroxy-3′,5′-dimethyl-6′-methoxychalcone, 2′,4′-dihydroxy-3′-methyl-6′-methoxychalcone, 2′,6′-dihydroxy-3′-methyl-4′-methoxychalcone, 2′-hydroxy-3′-methyl-4′,6′-dimethoxychalcone and 5,7-dihydroxy-6,8-dimethylflavanone) were found for the first time in Metrosideros excelsa. The flavanone was the major constituent in leaves, whereas 2′,6′-dihydroxy-3′-methyl-4′-methoxychalcone dominated all other aerial plant parts studied. Other Metrosideros species were investigated for these five flavonoids. C₁₉–C₃₆ aldehydes and C₂₂–C₃₂ alcohols were also identified from the dried seed capsules of M. excelsa.     

Flavonols of parthenium section bolophytum

Casticin (V), 5,7,3′,4′-tetrahydroxy-3,6-dimethoxyflavone-7-glycoside (I), 5,7,4′-trihydroxy-6-methoxyflavone-7-glycoside (hispidulin 7-glycoside) (IV), 5,4′-dihydroxy-3,6,7,3′-tetramethoxyflavone (VII) and 5,7-dihydroxy-3,6,3′,4′-tetramethoxyflavone (XII) were found, with the coumarin scopoletin (IX), in various combinations in the three species of Parthenium section Bolophytum. No infraspecific variation was detected in these calciphilic relicts.     

Neolignans from an Aniba species

The trunk wood of an Amazonian Aniba (Lauraceae) species contains, besides dillapiol and the benzodioxane-type neolignan eusiderin, four bicyclo(3.2.1)octanoid neolignans. These comprise representatives of the canellin-type: the known methoxycanellin-A and the novel compounds characterized as (1R, 3S, 4S, 5S, 6S, 7R)-1-allyl-4-hydroxy-3, 5-dimethoxy-7-methyl-6-(3′-methoxy-4′, 5′-methylenedioxyphenyl)-8-oxo-bicyclo(3.2.1)octane; (1R, 3S, 4S, 5S, 6S, 7R)-1-allyl-4-hydroxy-3, 5-dimethoxy-7-methyl-6-(3′, 4′, 5′-trimethoxyphenyl)-8-oxobicyclo(3.2.1)octane and (1R, 4R, 5R, 6S, 7R, 8S)-1-allyl-4, 8-dihydroxy-5-methoxy-7-methyl-6-(3′-methoxy-4′,5′-methylenedioxyphenyl)-3-oxobicyclo(3.2.1)octane.     

Eusiderins and other neolignans from an Aniba species

A previous report disclosed the presence of benzodioxan and bicyclo[3.2.1]octanoid neolignans in the benzene extract of the trunk wood of an Amazonian Aniba (Lauraceae) species. The chloroform extract of the same material contains additionally two new benzodioxan neolignans [rel-(7S,8R)-Δ^8′-7-hydroxy-3,4,5,5′-tetramethoxy-7.0.3′,8.0.4′-neolignan; rel-(7R,8R)-Δ^7′-3,4,5,5′-tetramethoxy-9′-oxo-7.0.3′,8.0.4′-neolignan], two new bicyclo[3.2.1]-octanoid neolignans [(7R,8S,1′S,2′S,3′S,4′R)-Δ^8′-2′,4′-dihydroxy-3,3′-dimethoxy-4,5-methylenedioxy-1′,2′,3′,4′,5′,6′-hexahydro-5′-oxo-7.3′,8.1′-neolignan; (7R,8S,1′R,2′S,3′S)-Δ^8′-2′-hydroxy-3,3′,5′-trimethoxy-4,5-methylenedioxy-1′,2′,3′,4′-tetrahydro-4′-oxo-7.3′,8.1′-neolignan] and a hydrobenzofuranoid neolignan [(7S,8R,1′S,5′S)-Δ^8′-3,3′,5′-tri-methoxy-4,5-methylenedioxy-1′,4′,5′,6′-tetrahydro-4′-oxo-7.0.2′,8.1-neolignan].     

Flavonoids from Merrillia caloxylon

Three chalcones and three flavones isolated from the fruit of Merrillia caloxylon (Rutaceae) have been characterised. Two of the flavones and two of the chalcones are related structurally, i.e. 3′,4′,5,7-tetramethoxyflavone with 2′- hydroxy-3,4,4′,6′-tetramethoxychalcone and 3′,4′,5,5′,7-pentamethoxyflavone with 2′,3-dihydroxy-4,4′,6′- trimethoxychalcone. A minor constituent was tentatively characterized as 5-hydroxy-3′,4′,5′,6,7-pentamethoxyflavone and this is accompanied by 2-hydroxy-3,4,4′,5,6′-pentamethoxychalcone and 5-hydroxy-3′,4′,6,7-tetramethoxyfiavone.     

A 4-arylcoumarin from Coutarea hexandra

The structure of a new 4-arylcoumarin, isolated from Coutarea hexandra, has been established as 5,7-dimethoxy-3′,4′-methylenedioxy-4-phenylcoumarin and confirmed by partial synthesis from 3′,4′-dihydroxy-5,7-dimethoxy-4-phenylcoumarin.     

Biosynthesis of the isoflavan isomucronulatol: Origin of the 2′,3′,4′-oxygenation pattern

Feeding experiments with ¹⁴C-labelled isoflavones in seedlings and pods of bladder senna (Colutea arborescens) have demonstrated that 7-hydroxy-4′-methoxyisoflavone (formononetin), 7,3′-dihydroxy-4′-methoxyisoflavone (calycosin), 7,2′,3′-trihydroxy-4′-methoxyisoflavone (koparin) and 7,2′-dihydroxy-3′,4′-dimethoxyisoflavone are excellent precursors of (3R)-isomucronulatol (7,2′-dihydroxy-3′,4′-dimethoxyisoflavan). 7,2′-Dihydroxy- 4′-methoxyisoflavone (2′-hydroxyformononetin) and 7-hydroxy-3′,4′-dimethoxyisoflavone (cladrin) were, however, poor substrates. Thus, the biosynthetic sequence to isomucronulatol from formononetin involves 3′-hydroxylation, 2′-hydroxylation and then 3′-O-methylation, followed presumably by stereospecific reduction of 7,2′-dihydroxy-3′,4′-dimethoxyisoflavone. Treatment of 2′,3′,4′-trimethoxyisoflavones with aluminium chloride in acetonitrile gives modest yields of 2′,3′-dihydroxy derivatives rather than 2′-monohydroxyisoflavones, and thus provides a convenient access to 2′,3′-dihydroxyisoflavones and related pterocarpans.     

Novel flavonoids from the stem of Popowia cauliflora

Six flavonoids, five of them novel, have been isolated from the whole stem of Popowia cauliflora and identified as: baicalein trimethyl ether, 5-hydroxy-6,7-dimethoxyflavone, 5,7,8-trimethoxyflavanone, 2′-hydroxy-3′,4′,6′-trimethoxychalcone, 2′,3′,4′,6′-tetramethoxychalcone and 2′,4-dihydroxy-3′,4′,6′-trimethoxychalcone, on the basis of spectral data and simple chemical modifications. The value of ¹³C NMR in assigning the positions of methoxy substituents is briefly discussed.     

Neolignans from stem bark of ocotea veraguensis

The stem bark of Ocotea veraguensis has yielded nine neolignans of which five appear to be novel. The new neolignans, which were identified on the basis of spectral characteristics, are^* (7S,8R,1′S,2′S,3′R,4′S)-Δ^8′-2′,4′-dihydroxy-3,3′5′-trimethoxy-4,5-methylenedioxy-1′,2′,3′,4′-tetrahydro-7.3′,8.1′-neolignan, (7S,8R,1′S,3′S,4′S)-Δ^8′-4,4'-dihydroxy-3,3′,5′-trimethoxy-1′,2′,3′,4′-tetrahydro-2′-oxo-7.3′,8.1′-neolignan, (7S,8S,1′R)-Δ^8′-3′,5′-dimethoxy-3,4-methylenedioxy-1′,4′-dihydro-4′-oxo-7.0.2′,8.1′-neolignan, (7S,8S,1′R )-Δ^8′-1′-methoxy-3,4-methylenedioxy-1′,6′-dihydro-6′-oxo-7.0.4′,8.3′-neolignan and (7S,8S)-Δ^8′-2′,6′-dimethoxy-3,4-methylenedioxy-7.0.3′,8.4′,1′.0.7′-neolignan.