Three prenylated flavanoids from Helichrysum athrixiifolium

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

Flavonoids of Chromolaena odorata

A dichloromethane extract of Chromolaena odorata has yielded 2′-hydroxy-3,4,4′,5′,6′-pentamethoxychalcone, 2′,4-dihydroxy-4′,5′,6′-     

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.     

Two dithiacyclohexadiene polyacetylenes from Chaenactis douglasii and Eriophyllum lanatum

We have isolated two dithiapolyacetylenes from the roots of Chaenactis douglasii and from the plant roots as well as root cultures of Eriophyllum lanatum, namely 1-(2-methylethyn)-4-(hex-1,3-diyn-4-ene)-2,3-dithiacyclohexa-4,6-diene, and 1-(4-methylbut-1,3-diyn)-4-(but-1-yn-3-ene)-2,3-dithiacyclohexa-4,6-diene. We propose the trivial names thiarubrine A and thiarubrine B for these compounds.     

Polyunsaturated compounds of Centaurea scabiosa

Roots, green parts, and flower heads of Centaurea scabiosa were examined separately. Twenty-five polyacetylenes, 4 polyenic aldehydes, 1,8,11,14-heptadecatetraene, and the flavone apigenin were isolated and characterized. Three C₁₇ hydrocarbons with from one to three isolated double bonds and a series of minor compounds were also isolated.     

Neue chalkon-derivate aus südafrikanischen Helichrysum-arten

The investigation of two South African Helichrysum species afforded in addition to known compounds two new chalcone derivatives, four related dihydrochalcones,5,7,8-trimethoxyflavone and 5-methoxy-7,8-methylenedioxyflavone. The structures are elucidated by spectroscopic methods and some chemical transformations. The chemotaxonomic situation in the large genus Helichrysum is discussed, in the light of these results.     

Sesquiterpene-coumarin ethers and polyacetylenes from Bfrocchia cinerea

The roots of Brocchia cinerea afforded, in addition to known spiroketalenolether polyynes and sesquiterpene-coumarin ethers, two new isofraxidin-derived sesquiterpene ethers as well as the new 8-farnesyl-scopoletin. The structures of the new compounds were elucidated on the basis of spectroscopic evidence. The chemotaxonomic significance of sesquiterpene-coumarin ether and spiroketalenolether accumulation within the tribe Anthemideae is discussed.     

Flavanol glucosides from rhubarb and Rhaphiolepis umbellata

Investigations of rhubarb and the bark of Rhaphiolepis umbellata led to the isolation of new flavan-3-ol glucosides. Their structures were elucidated on the basis of ¹H and ¹³C NMR analysis hydrolytic studies as (+)-catechin 5-O-β-d-glucopyranoside and (?)-catechin 7-O-β-d-glucopyranoside.     

植物原花青素生物合成及调控研究进展

原花青素是通过类黄酮途径生成的一类多酚类化合物.原花青素具有重要的生物学功能,不仅是植物应对生物和非生物胁迫的一种重要防御手段,还能影响植物外观、风味和品质,因此原花青素合成途径一直是作物性状改良的研究热点.该文主要在模式植物拟南芥研究的基础上,综述了原花青素生物合成研究的最新进展,讨论了原花青素遗传工程应用前景和主要...     

Flavonoids of geigeria

Chromatographic separation of the ethanol extract of Geigeria burkei resulted in the isolation and characterization of two known flavonoids, 5,7,3′,4′-tetrahydroxy-6-methoxyflavone and 5,7,4'-trihydroxy-6 methoxyflavone. ¹³CNMR data, as well as the respiratory inhibition and uncoupling of oxidative phosphorylation, is reported for the first time.     

Chemotaxonomy of the genus pleiotaxis*

Pleiotaxis rugosa afforded several acetylenic compounds, the sesquiterpenes janerin and the corresponding methacrylate as well as three chalcones, one not being reported previously. The compounds isolated indicate that this genus may be better placed in the Cynareae than in the Mutisieae.     

7-O-Galloyl-(+)-catechin and 3-O-galloylprocyanidin B-3 from Sanguisorba officinalis

7-O-Galloyl-(+)-catechin and 3-O-galloylprocyanidin B-3, along with gambiriins A-1 and B-3 and four polygalloylglucoses, have been isolated fro     

Mosquito larvicidal activity of polyacetylenes from species in the Asteraceae

Twenty-four polyacetylenes isolated from species in the Asteraceae were screened for their near-UV-mediated larvicidal properties to the mosquito, Aedes aegypti. Dosage resonse lines for three of the most active compounds were prepared. One of these, σ-terthienyl from Tagetes was more toxic than DDT when near-UV radiation was provided. A scaled up trial with this compound in a simulated field situation demonstrated its potential as a larvicide. The effects of the radiation dose on larval survival were studied and the action spectra for the phototoxic effects of three compounds on larvae were obtained with narrowband interference filters. Because of the close agreement between the action and absorption spectra, it appears most probable that the polyacetylene is the primary absorbing compound. The potential of polyacetylenes as larvicides and their role in plant herbivore relations are discussed.     

Mass Spectra of Volatile Sulfur Compounds in Foods

The absolute configurations of twelve α-aryl and α,β-diarylalkylamines were studied as N-acyl derivatives by circular dichroism (CD) measurements and by gas chromatography (GC).

The signs of Cotton effects for the S-configuration around 260 nm were positive and those around 210 nm were negative, although some exceptions were found due to the substituents on the benzene nuclei. In contrast, the GC behavior was considered less sensitive to the substituents on the benzene nuclei, and the elution orders were an R-before S-configuration consistently on a chiral OA-300 column. The absolute configurations of some amines were estimated in this study. GC as well as CD measurements could be a promising method for the assignment of the absolute configuration.     

Flavonoids and tannins of Acacia species

The heartwoods of Acacia giraffae and A. galpinii were selected from South African Acacias as representative of those with abnormally high and minimal tannin contents respectively. A. galpinii contains amongst other analogues, the first natural (+)-2,3-trans-3,4-trans-teracacidin (7,8,4′-trihydroxy-flavan-3,4-diol and novel 3-O-methyl-, 7,8-di-O-methyl- and 7,8,4′-tri-O-methylflavonol analogues. (−)-2,3-cis-3,4-cis-Melacacidin (7,8,3′,4′-tetrahydroxyflavan-3,4-diol) is also present, but tannins are absent. By contrast, from the large excess of leueofisetinidin tannins which characterizes the wood of A. giraffae, only (+)-catechin, (+)-2,3-trans-3,4-trans-leucofisetinidin (7,3′,4′,trihydroxyflavan-3,4-diol and all-trans-(+)-leueofisetinidin-(+)-catechin could be isolated.