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.     

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.     

Neue prenylflavanone aus Helichrysum hypocephalum

From the aerial parts of H. hypocephalum several new prenylated flavones were isolated, their structures being elucidated by spectroscopic methods and by some chemical transformations. In addition, a new lactone derived from oleic acid is present.     

A validated spectrophotometric method for quantification of prenylated flavanones in pacific propolis from Taiwan

Introduction – Because of its chemical diversity, the only way to standardise propolis is to specify multiple standards for different propolis types according to the corresponding chemical profile. So far, this has been done only for European propolis. Objective – To develop a rapid low‐cost spectrophotometric procedure for quantification of bioactive prenylated flavanones in Taiwanese propolis. Methodology – The proposed method quantifies the total flavanones on the basis of their absorption as coloured phenylhydrazones formed by interaction with 2,4‐dinitrophenylhydrazine. The procedure was validated through model mixture of compounds representing the composition of Taiwanese propolis according to previous studies. The major flavanones of the propolis samples (propolins C, D, F and G) were quantified by HPLC. Antiradical activity against DPPH was also measured. The DNP (dinitrophenylhydrazine) spectrophotometric method is applied for the first time for quantification of prenylated flavanones. Results – Spectophotometric procedure applicable to new type propolis (Macaranga type) was developed with recovery between 105 and 110% at the concentration range of 0.573–1.791 mg/mL. Six propolis samples were analysed by spectrophotometry using the procedure developed and validated, and by HPLC as the results demonstrated satisfactory agreement. Neither the spectrophotometric data nor the values measured by HPLC showed significant correlation with the antiradical activity against DPPH. Conclusion – The proposed spectrophotometric procedure is useful for routine analyses of Macaranga‐type propolis, because of its simplicity, repeatability and acceptable accuracy. Its application to a number of commercial samples could be used as a basis for standardisation and quality control of Pacific propolis. Copyright © 2009 John Wiley & Sons, Ltd.     

Flavonoids and polyacetylenes in Dahlia tenuicaulis

5,7,4′-Trimethoxyflavanone, 5-hydroxy-7,4′-dimethoxyflavanone, 2′-hydroxy-4,4′,6′-trimeth-oxychalcone, and a new naturally occurring compound, 5,7,4′-trimethoxyflavan-4-ol have been isolated from the leaves of Dahlia tenuicaulis Sorensen. Two chalcones, 4,2′,4′-trihydroxychalcone and 3,2′,4′-trihydroxy-4-methoxychalcone, and 5-hydroxy-7,4′-dimethoxyflavanone have been isolated from the flower heads. Minute amounts of the polyacetylene 1,3-diacetoxy-tetradeca-4,6-diene-8,10,12-triyne have been found in both leaves and flower heads, whereas 1-acetoxy-tetradeca-4,6-diene-8,10,12-triyne was present only in the flower heads.     

New prenylated isoflavones from Millettia pachycarpa

Isolation of four new isoflavones from a new collection of Millettia pachycarpa is reported. Proof of the structure of lupinifolol, previously isolated from M. pachycarpa, by synthesis of dehydrolupinifolol is described.     

New prenylflavanoids from marshallia grandiflora

The investigation of Marshallia grandiflora afforded four new flavanoids, their structures being elucidated by spectroscopic methods. This type of compound is rare in Compositae and similar compounds have only been isolated from species of the tribe Heliantheae and Inuleae. The chemotaxonomic situation is discussed briefly.     

Rhynchospermin. A prenylated flavanol from Rhynchosia cyanosperma

A new flavanol has isolated from the leaves of Rhynchosia cyanosperma and identified as 8-C-prenylquercetin 7,4′-dimethyl ether (rhynchospermin).     

Amorinin,A prenylated chromenoflavanone from Amorpha fruticosa

A diprenylated chromenoflavanone has been characterized from the root bark of Amorpha fruticosa.     

Neue phloroglucin-derivate aus Helichrysum natalitium und Helichrysum bellum

Helichrysum natalitium afforded four new phloroglucinol derivatives, while from H. bellum two further compounds of this type have been isolated; H. platypterum yielded two known derivatives. The new structures were elucidated by spectroscopic methods and some chemical transformations. The chemotaxonomical situation is briefly discussed.     

New prenylated isoflavones and a prenylated dihydroflavonol from Millettia pachycarpa

Extraction of Millettia pachycarpa Benth. gave 5,7,4′-trihydroxy-6,8-diprenylisoflavone (1a), 5,7,4′-trihydroxy-6,3′-diprenylisoflavone (2a), 5,7,3′,4′-tetrahydroxy-6,8-diprenylisoflavone (3a) and (2R, 3R)-5,4′-dihydroxy-8-prenyl-6″,6″-dimethylpyrano[2″,3″: 7,6]-dihydroflavonol (4a) whose structures were established by chemical transformations and spectroscopic means. Pectolinarigenin and salvigenin were isolated from Buddleia macrostachya Benth.     

Prenylated p-coumarates from Werneria stuebelii

The aerial parts of Werneria stuebelii afforded in addition to β-cedrene and bicyclogermacrene eight derivatives of methyl p-coumarate, all being formed by prenylation. The structures were elucidated by their molecular formulae and their ¹H NMR spectra. The chemotaxonomy of the Andean genus Werneria is discussed briefly.     

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.     

A diterpene related to erythroxydiol from Helichrysum refluxum

From Helichrysum refluxum, in addition to known compounds, a diterpene acid related to erythroxydiol Z was isolated. The structure was elucidated by NMR techniques.     

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.     

Flavanones and xanthones from Maclura pomifera

(+-)Euchrestaflavanones B and C and 8-prenyltoxyloxanthone C have been isolated from the root bark of Maclura pomifera. A study of the cyclization of alvaxanthone under varying conditions is reported.