C-galactosylflavones from Polygonatum multiflorum

8-C-Galactosylapigenin and 6-C-galactosyl-8-C-arabinosylapigenin were isolated from the leaves of Polygonatum multiflorum (L.) All. Structural assignments for the latter compound were made on the basis of mass, CD and ¹³C-NMR spectra.     

New C-glycosylflavones from Mollugo distica

Four C-glycosylflavones isolated from Mollugo distica were identified as 8-C-β-d-glucopyranosyl-genkwanin, 8-C-α-l-arabinopyranosylgenkwanin and their 2″-rhamnosides.     

Flavonoids of Plagiochila asplenioides

Besides an apigenin- and a luteolin-di-C-glycoside, 5 previously unknown di-C-glycosides of tricetin were identified in the gametophytic and sporophytic tissues of Plagiochila asplenioides. Two of them were new 6,8-di-C-hexopyranosyltricetins, and two were new 6-C- hexopyranosyl-8-C-pentopyranosyltricetins. 6-C-Hexopyranosyl-8-C-pentopyranosyltricetin-5′-methyl ether was also found.     

Structure of a 6,8-di-C-pentosylapigenin from Mollugo pentaphylla

One of the di-C-pentosylflavones isolated from Mollugo pentaphylla was identified as 6-C-β-d-xylopyranosyl-8-C-α-l-arabinop     

C-glycosylflavones from Oryza sativa

Eight flavone C-glycosides isolated from rice plant were found to act as probing stimulants for planthoppers. They have been identified as the known compounds schaftoside, neoschaftoside, carlinoside, isoorientin 2″-glucoside and the new constituents neocarlinoside (6-C-β-D-glucopyranosyl-8-C-β-L-arabinopyranosylluteolin), isoscoparin 2″-glucoside (chrysoeriol 6-C-β-D-(2-O-β-D-glucopyranosyl)glucopyranoside) and its 6?-p-coumaric and ferulic acid esters.     

Flavone C-glycosides of two Metzgeria species

Six known tricin and apigenin di-C-glycosides, including 2″-O-ferulylisoschaftoside, have been identified in gametophytic material of Metzgeria conjugata. M. leptoneura contains a new di-C-glycoside, tricin 6-C-xyloside-8-C-hexoside. The chemotaxonomic relevance of the flavonoid patterns is briefly discussed.     

In vitro synthesis of mycolic acids by the fluffy layer fraction of Bacterionema matruchotii

Biosynthetic activity for mycolic acid occurred in the fluffy layer fraction but not in the 5000g supernatant of Bacterionema matruchotii. With [1-¹⁴C]palmitic acid as precursor for the in vitro system, the predominant product was identified as C_32:0 mycolic acid by radio-gas-liquid chromatographie (radio-GLC) and gas chromatographic/mass spectroscopic analyses; if [1-¹⁴C]stearic acid was used, two major radioactive peaks appeared on GLC: one corresponding to the peak of (C_34:0 + C_34:1) mycolic acids and the other to (C_36:0 + C_36:1) mycolic acids. By pyrolysis/radio-GLC analysis, C_32:0 mycolic acid synthesized by [1-¹⁴C]palmitic acid was pyrolyzed at 300 °C to form palmitaldehyde (the mero moiety) and methyl palmitate (the branch moiety). The pH optimum for the incorporation of [1-¹⁴C]palmitate into bacterionema mycolic acids was 6.4 and the reaction required a divalent cation. The in vitro system utilized myristic, palmitic, stearic and oleic acids (probably via their activated forms) well as precursors, among which myristic and palmitic acids were more effective than the rest. Avidin showed no effect on the biosynthesis of mycolic acid from ¹⁴C-palmitate whereas cerulenin, a specific inhibitor of β-ketoacyl synthetase in de novo fatty acid synthesis, inhibited the reaction at a relatively higher concentration. Thin-layer chromatographic analysis of lipids extracted from the reacting mixture without alkaline hydrolysis showed that both exogenous [1-¹⁴] fatty acid and synthesized mycolic acids were bound to an unknown compound by an alkali-labile linkage and this association seemed to occur prior to the condensation of two molecules of fatty acid.     

Flavonoids of the primitive liverwort Takakia and their taxonomic and phylogenetic significance

The flavonoid chemistry of Takakia is described for the first time. T. lepidozioides, thought to be amongst the most primitive of extant liverworts, contains a high level and wide variety of flavone C- and O-glycosides, many of which are unique. New flavonoids include the 8-O-glucuronide and 8-O-xylosylglucoside of takakin (8-hydroxyacacetin), luteolin 6-C-arabinoside-8-C-pentoside, kaempferol 3-O-glucoside-7-O-xyloside and a number of tricetin C-glycosides. The only other known Takakia species, T. ceratophylla, contains the same 4 major constituents but significantly lacks flavonols. The often suggested relationship of Takakia with the order Calobryales is not supported by the available flavonoid data. Biochemical affinities of Takakia with all major liverwort orders are noted and the flavonoid data are interpreted as supporting the concept of Takakia as an isolated branch among the ancestors of modern bryophytes.     

Alkaline decomposition of d-xylose-1-C, d-glucose-1-C, and d-glucose-6-C

The distribution of radioactivity in the three- and four-carbon saccharinic acids, lactic acid and 2,4-dihydroxybutyric acid, obtained from d-xylose-1-¹⁴C, d-glucose-1-¹⁴C, and d-glucose-6-¹⁴C, was measured. The relative importance of the various mechanisms for forming 2,4-dihydroxybutyric acid was determined. Recombination of two-carbon fragments was found to be an important mechanism at the high alkalinity and temperature employed.     

Structural determination of 6-C-diglycosyl-8-C-glycosyl-flavones and 6-C-glycosyl-8-C-diglycosylflavones by mass spectrometry of their permethyl ethers

Permethylated 6-C-diglycosyl-8-C-glycosylflavones and 6-C-glycosyl-8-C-diglycosylflavones gave well defined EIMS including the molecular peak and a fragmentation pattern characteristic of the 6-C-glycosyl residue. X″′-O-glycosides (8-C-disaccharides) are thus easily distinguished from X″-O-glycosides (6-C-disaccharides) and, in the latter, the position of the O-glycosidic bond should be deduced from the MS, after acid hydrolysis. Three new C-glycosylflavones have been characterized in this way from Spergularia rubra and Stellaria holostea.     

C-Glycosylflavones from Zea mays that inhibit insect development

A new C-glycosylflavone isolated from corn silk inhibits the growth and development of the corn earworm, Heliothis zea. This new compound was shown to be a 2″-O-α-l-rhamnosyl-6-C-(6-deoxy-xylo-hexos-4-ulosyl)luteolin. Also found co-occurring in corn silk were minor amounts of the corresponding 6-C-glycosylated analogs of chrysoeriol and apigenin.     

Sesquiterpenoid metabolites from Stereum complicatum

A new sesquiterpene antibiotic, complicatic acid, isolated from cultures of Stereum complicatum (Fr.)Fr. has been shown to be dehydrohirsutic acid C. Hirsutic acid C was also isolated from the same fungus. [2-¹⁴C]-MVA was incorporated into both metabolites and complicatic acid has been shown to be formed from hirsutic acid C both in vivo and in vitro.     

Interconversion of trans, trans and cis, trans farnesol by enzymes from Andrographis

When trans, trans-farnesol [4,8,12-¹⁴C₃,1-³H₂] is isomerized to cis, trans-farnesol by soluble enzymes from Andrographis paniculata tissue cultures, 50% of the tritium label is lost. The same loss is observed when isomerization occurs in the opposite direction. This is in accordance with the proposed mechanism for isomerization via aldehydes.     

Flavone C-glycosides from Coronilla varia

One new and 5 known flavone C-glycosides were isolated from leaves and stems of Coronilla varia. The new compound was shown to be isoorientin 2″-O-rhamnoside. The known compounds were isovitexin, isoorientin, isovitexin 4′-O-glucoside, isoorientin 4′-O-glucoside, and isoorientin 7-O-glucoside.     

Volubilin,a new isoflavone-C-glycoside from Dalbergia volubilis flowers

Dalbergia volubilis flowers after successive extraction with light petroleum, benzene and alcohol yielded β-sitosterol, stigmasterol, biochanin-A and a new isoflavone-C-glycoside named volubilin. The glvcoside on boiling with HI and phenol gave genistein and on ferric chloride oxidation rhamnose. The compound was identified as 8-C-rhamnopyranosyl-genistein-4′,7-dimethyl ether by means of chemical reactions as well as from spectral data.     

Isomollupentin-O-glucosides from Cerastium arvense

Eight C-glycosylflavone O-glycosides including three new compounds: isomollupentin 7-O-glucoside, isomollupentin 4′-O-glucoside and isomollupentin 2″-O-glucoside have been isolated from the leaves and flowers of Cerastium arvense. The 27 C-glycosylflavones identified in this plant are tabulated.     

Structural determination of C-glycosylflavones by mass spectrometry of their permethyl ethers: O-glycosyl-6-C-glycosylflavones

Permethylated O-glycosyl-C-glycosylflavones give well defined MS including an important molecular peak. Permethyl 6-C-glycosylflavones O-glycosylated on a phenolic hydroxyl group are easily distinguished from the isomeric permethyl 6-C-diholosylflavones. In both types, the position of the O-glycosidic bond can be deduced from the MS, eventually after acid hydrolysis. 2″-O-glycosyl-6-C-glycosylflavones can be differentiated from their 8-C isomers.     

C-glycosylanthocyanidins synthesized from C-glycosylflavones

Nine C-glycosyldeoxyanthocyanidins, 6-C-β-glucopyranosyl-7-O-methylapigeninidin, 6-C-β-glucopyranosyl-7-O-methylluteolinidin, 6-C-β-(2″-O-β-glucopyranosylglucopyranosyl)-7-O-methylapigeninidin, 6-C-β-(2″-O-β-glucopyranosylglucopyranosyl)-7,4′-di-O-methylapigeninidin, 8-C-β-glucopyranosylapigeninidin, 8-C-β-(2″-O-α-rhamnopyranosylglucopyranosyl)apigeninidin, 8-C-β-(2″-O-α-(4″′-O-acetylrhamnopyranosyl)glucopyranosyl)apigeninidin, 6,8-di-C-β-glucopyranosylapigeninidin (8), 6,8-di-C-β-glucopyranosyl-4′-O-methylluteolinidin (9), have been synthesized from their respective C-glycosylflavones (yields between 14% and 32%) by the Clemmensen reduction reaction using zinc-amalgam. The various precursors (C-glycosylflavones) of the C-glycosylanthocyanidins were isolated from either flowers of Iris sibirica L., leaves of Hawthorn ‘Crataegi Folium Cum Flore’, or lemons and oranges. This is the first time C-glycosylanthocyanidins have been synthesized. The structures of all flavonoids including the flavone rotamers were elucidated by 2D NMR techniques and high-resolution electrospray MS. The distribution of the various structural forms of 8 and 9 are different at pH 1.1, 4.5, and 7.0, however, the two pigments undergoes similar structural transformations at the various pH values. Pigments 8 and 9 with C-C linkages between the sugar moieties and the aglycone, were found to be far more stable towards acid hydrolysis than pelargonidin 3-O-glucoside, which has the typical anthocyanidin C-O linkage between the sugar and aglycone. This stability may extend the present use of anthocyanins as nutraceuticals, pharmaceuticals or colorants.     

New C-glycosylflavones from Cerastium arvense

Three C-glycosylflavones isolated from Cerastium arvense have been identified as 6-C-xylosyl-apigenin (cerarvensin), its 7-O-glucoside and isovitexin 7,2″-di-O-glucoside.