Flavonoids from Wyethia glabra

Ten flavonoid compounds, including three new natural products, were isolated from a dichloromethane extract of Wyethia glabra. The known compounds are: orobol 7-methyl ether, orobol 3′-methyl ether, naringenin 7-methyl ether, eriodictyol, 8-C-prenyleriodictyol, 6-C-prenyleriodictyol and 8-C-prenylnaringenin. Eriodictyol 7-methyl ether, 2′,4′,6′-trihydroxy-4-methoxychalcone and 6-C-prenylnaringenin are new natural products. An additional prenylated flavanone was isolated and partially characterized.     

Flavanone and other constituents from Onychium siliculosum

Two new compounds, onitinoside and onysilin along with the known compounds, pinostrobin, onitin, onitisin, campesterol, sitosterol and n-alkanes (C₂₅-C₃₃) were isolated from Onychium siliculosum. Onitinoside and onysilin were identified by spectral and chemical methods as 4-O-glucosyl-6-(2′-hydroxyethyl)-2,2,5,7-tetramethylindan-1-one and 5-hydroxy-6,7-dimethoxyflavanone, respectively.     

Flavonoids from the seeds of Lonchocarpus costaricensis

Seven flavonoids have been isolated from the seeds of Lonchocarpus costaricensis of which four appear to be novel. The new compounds have been identified as the β-hydroxychalcone demethylpraecansone-B and the flavanones 7-(3,3-dimethylallyloxy)-8-(3-hydroxy-3-methyl-trans-but-1-enyl)flavanone, 7-(3,3-dimethylallyloxy)-8-(3,3-dimethylallyl)-5-methoxyflavanone and 8-(3,3-dimethylallyl)-5,7-dimethoxyflavanone.     

Three prenylated flavanoids from Helichrysum athrixiifolium

Helichrysum athrixiifolium afforded in addition to known ones three new prenylated flavanoids, one chalcone and two flavanones.     

Four flavonoids from Ageratum strictum

Four new flavonoids, three flavanones and one chalcone, were isolated from aerial parts of Ageratum strictum. Their structures were establised as 3′6′-dihydroxy-2′, 4′-dimethoxy- 3, 4-methylenedioxy-chalcone, 6-hydroxy-5,7-dimethoxy-3′,4′-methylenedioxyflavanone, 6-hydroxy- 5,7,3′,4′-tetramethoxyflavanone and 6,4′-dihydroxy-5,7,3′-trimethoxyflavanone on the basis of spectral data and chemical degradation.     

A diterpene,a sesquiterpene quinone and flavanones from Wyethia helenioides

The aerial parts of Wyethia helenioides afforded a new geranyl nerol derivative (a 16-hydroxy-18-oic acid), two isomeric prenylated lavanones and a quinone derived from bisabolene. The structures were elucidated by spectroscopic methods and some chemical transformations. The chemotaxonomic situation is discussed briefly.     

Antimicrobial agents from higher plants: Prenylated flavonoids and other phenols from Glycyrrhiza lepidota

Bioassay directed fractionation of extracts of American licorice, Glycyrrhiza lepidota (Leguminosae), resulted in identification of the known bibenzyl, 3,5-dihydroxy-4-(3-methyl-2-butenyl)-bibenzyl, and the known flavanones, glabranin and pinocembrin, as well as the isolation and structure determination of the new flavonol, glepidotin A and the new dihydroflavonol, glepidotin B as antimicrobial agents.     

Highly oxygenated flavonoids from Ageratum corymbosum

The investigation of Ageratum corymbosum resulted in the isolation of four new highly oxygenated flavonoids, and their structures established by spectroscopic and degradative evidence as 5,6,7,5′-tetramethoxy-3′,4′-methylenedioxyflavanone; 5,6,7,8,5′-pentamethoxy-3′,4′-methylenedioxyflavanone; 5,6,7,8,2′,4′,5′-heptamethoxy-flavone and 5,2′,4′-trihydroxy-6,7,8,5′-tetramethoxyflavone. The recently reported gardenin A monomethyl ether and 5′-methoxylucidin dimethyl ether (eupalestin) were also isolated.     

Amoradin,amoradicin and amoradinin,three prenylflavanones from Amorpha fruticosa

Three new prenylflavanones, amoradin, amoradicin and amoradinin, were isolated from the root bark of Amorpha fruticosa. Their structures were deduced from chemical and spectral evidence.     

Trixikingolides and germacrene derivatives from Trixis species

The investigation of two further Trixis species afforded five new sesquiterpenes related to trixikingolide, six new germacrene derivatives and a sesquiterpene derived from rotundene. Some further known compounds were isolated too, which in part may be of chemotaxonomic significance. The structures were elucidated by spectroscopic methods and a few chemical transformations. The relative position of the ester groups in eight of the new sesquiterpenoids however, could not be established with certainty as partial saponifications were not successful.     

Eupatarone,A 2-acetylbenzofuran from Eupatorium sternbergianum

A new benzofuran, eupatarone, together with 2-hydroxy-4, 5-dimethoxybenzaldehyde, 12-hydroxy-2, 3-dihydroeuparine, spathulenol, precocene II, dammaradienol, dammaradienol acetate, 5, 3′-dihydroxy-7, 4′-dimethoxyflavanone and 5, 7-dihydroxy-4′-methoxyflavanone, have been isolated from aerial parts of Eupatorium sternbergianum.     

Five diterpenes and other constituents from nine Baccharis species

The investigation of nine Baccharis species afforded, in addition to known compounds, three new clerodane derivatives related to bacchotricuneatin B, two ent-labdane derivatives, two 3-acetoxyflavanones, a benzofuran derivative and a chromene. The overall picture of the chemistry of this large genus is still not very clear.     

Flavanoids from Dalea elegans: Chemical reassignment and determination of kinetics parameters related to their anti-tyrosinase activity

In the first chemical investigation developed on the species Dalea elegans twenty years ago, the occurrence of two prenylated derivatives of pinocembrin was reported: 2′,4′-dihydroxy-5′-(1‴,1‴-dimethylallyl)-6-prenylpinocembrin (6PP) given as a new structure in this family of compounds, and another derivative of already known structure, 6-prenylpinocembrin (6P). In the present paper, their structures were again analyzed by using spectroscopic techniques, especially 2D NMR. Based on the evidence obtained it is proposed the reassignment of both flavanones as: 2′,4′-dihydroxy-5′-(1‴,1‴-dimethylallyl)-8-prenylpinocembrin (8PP) for the first and 8-prenylpinocembrin (8P) for the last. Additionally, triangularin, demethoxymatteucinol, comptonin and 7-hydroxy-5-methoxy-6,8-dimethylflavanone were isolated from aerial parts of D. elegans and informed by the first time for this species. All of these compounds were evaluated in vitro in relation to the antityrosinase effect by using a spectrophotometric method. Compound 8PP (IC₅₀ 2.32 ± 0.01 μM) exhibited the most potency and was two times more active than Kojic acid (IC₅₀ 4.93 ± 0.01 μM) used as a positive control. Triangularin also has shown an important inhibitory activity. Kinetic studies were performed for both compounds. Hence, new tyrosinase inhibitors with potential applications in pharmacy and cosmetic industry are presented.     

Neue sesquiterpene,triterpene, flavanone und andere aromatische verbindungen aus Flourensia heterolepis

The investigation of a further Flourensia species afforded in addition to already known compounds 12 new sesquiterpene acids isolated as their methyl esters, a new eudesmane diol, four lupane derivatives and two flavanones, two cinnamic acid derivatives, also isolated as methyl esters and a ketone. The structures are elucidated mainly by spectroscopic methods and by some chemical transformations. Several of the compounds isolated are more or less similar to those isolated from other Flourensia species; the considerable amounts of eudesmanes, however, are unusual. The overall picture of the genus is still relatively uniform. Close relationships to Helianthella are obvious, while to Helianthus, placed in the same subtribe, no clear relations are visible.     

Flavonoids from Millettia pulchra

Chemical examination of Millettia pulchra yielded (?)-maackiain, (?)-pterocarpin, (?)-sophoranone and the new compounds (6S, 6aS, 11aR)-6α-methoxypterocarpin, (6S, 6aS,11aR)-6α-methoxyhomopterocarpin, (2S)5,7,4′-trihydroxy-8,3′,5′-triprenylflavanone, (2R,3R)7,4′-dihydroxy-8,3′,5′-triprenyldihydroflavanol, 5,7,2′,4′-tetrahydroxy-6,3′-diprenylisoflavone and 5,7,4′-trihydroxy-2′-methoxy-6,3′-diprenylisoflavone.     

Two isomeric flavanones from vitex negundo

Two new flavanoids, characterized as 5,3′-dihydroxy-7,8,4′-trimethoxyflavanone and 5,3′-dihydroxy-6,7,4′-trimethoxyflavanone, have been isolated from the leaves of Vitex negundo.     

Flavanones and dihydroflavonols as biosynthetic intermediates in Matthiola incana

In anthocyanin-producing flowers of Matthiola incana, the presence of naringenin, naringenin 7-glucoside, dihydrokaempferol and dihydrokaempferol 7-glucoside could be demonstrated. The four isolated compounds initiated anthocyanin synthesis after administration to acyanic flowers of genetically defined lines of Matthiola incana and Antirrhinum majus. Therefore, these compounds cannot be regarded as end-products but rather as intermediates in anthocyanin biosynthesis. Furthermore, naringenin 7-glucoside and dihydrokaempferol 7-glucoside most probably act as a pool for their aglycones, which serve as the actual substrates.     

A method to differentiate isomeric C-glucosyl chromones,isoflavones and xanthones

6-C- and 8-C-glucosyl isomeric chromones and isoflavones can be readily distinguished by a study of the NMR signals of their acetates. In a similar manner 2-C- and 4-C-glucosylxanthones can be distinguished.     

Flavonoids in the black rhizomes of Boesenbergia panduta

5-Hydroxy-7-methoxyflavanone, 5,7-dimethoxyflavanone, 5-hydroxy-7-methoxyflavone 5-hydroxy-7,4′-dimethoxyflavone, 5,7-dimethoxyfiavone, 5,7,4′-trimethoxyflavone, 5,7,3′,4′-tetramethoxyflavone, 5-hydroxy-3,7-dimethoxyflavone, 5-hydroxy-3,7,4′-trimethoxyflavone, 3,5,7-trimethoxyflavone and 5-hydroxy-3,7,3′,4′-tetramethoxyflavone have been isolated from the black rhizomes of Boesenbergia pandurata.     

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.