Methylation of anthocyanins by cell-free extracts of flower buds of Petunia hybrida

An O-methyltransferase activity which catalyses the methylation of anthocyanins was extracted from flowerbuds of Petunia hybrida. The methyltransferase uses S-adenosyl-l-methionine as methyl donor. Only anthocyanidin 3(p-coumaroyl)rutinosido-5-glucoside was methylated. No methylating activity towards anthocyanidins, anthocyanidin 3-glucosides, anthocyanidin 3-rutinosides, caffeic acid or p-coumaric acid could be detected.     

Differences in the incorporation pattern of labelled cinnamic acid and l-phenylalanine into the anthocyanins of Petunia hybrida

The incorporation of phenylalanine-[¹⁴C] into anthocyanins of petals of Petunia hybrida is greater than that of cinnamic acid-[¹⁴C]. Moreover, there is a preferential incorporation of phenylalanine-[¹⁴C] into delphinidin 3-monoglucoside, as compared with the incorporation into cyanidin and peonidin 3-monoglucosides.     

Partial purification and characterization of a ribonuclease from Petunia hybrida

A crude extract from leaves of Petunia hybrida contains three ribonucleases (RNases) as revealed by polyacrylamide gel electrophoresis (PAGE). One     

Der substitutionsspezifische einfluss von chalkonen auf die anthocyanbiosynthese bei Petunia hybrida

The effect of two chalcones, 3,4,2′,4′,6′-pentahydroxy- and the 4, 2 ′,4′,6′ -tetrahydroxy- 3-methoxy-chalcone- 4′-glucoside, on the synthesis of different flower anthocyanins in isolated petals of Petunia hybrida has been investigated. The results show that the synthesis of those anthocyanins, which have the same substitution pattern as the chalcone used was increased. This suggests that the chalcones are incorporated into the anthocyanins concerned. When the chalcones were fed together with acetic acid-[1-¹⁴C], this specific substitution effect was detectable only for the 3,4,2′,4′,6′-pentahydroxy-chalcone-4′-glucoside.     

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.     

Beyerene derivatives and other constituents from Petunia patagonica

Two new diterpenes of the beyerene type, ent-19-hydroxy-1 7-acetoxybeyer-15-ene and ent-beyer-15-en-17-oic acid, and two previously characterized kauranoids, ent-16β-hydroxy-17-acetoxykaurane and ent-16β,1 7-dihydroxy-kaurane, as well as two known flavonoids, luteolin-7,3′,4′-trimethyl ether and luteolin-7,3′-dimethyl ether, and a triterpenoid, oleanoic acid, were obtained from a chloroform extract of Petunia patagonica. The new structures were elucidated by spectral data and chemical transformations.     

Medium- and light-induced formation of serpentine and anthocyanins in cell suspension cultures of Catharanthus roseus

By irradiation with fluorescent light, medium-induced cell cultures of Catharanthus roseus accumulated anthocyanins and the indole alkaloid serpentine. The formation of both compounds was inhibited by phosphate and nitrogen-containing mineral salts and stimulated by high sucrose concentrations. The accumulation of serpentine was preceded by an increase and subsequent decrease of its biogenetic precursor ajmalicine, which was the predominant alkaloid of medium-induced cultures in the dark. High concentrations of serpentine or anthocyanins were observed only in a small proportion of all cells present in a medium-induced culture. The aglycones of the anthocyanins were identified as petunidin, malvidin and hirsutidin.     

Biosynthesis of withanolides in Acnistus breviflorus: biogenetic relationships among the main withanolides

To excised leaves and 15-day-old seedlings of Acnistus breviflorus sodium [1-¹⁴C]acetate, [2-¹⁴C]mevalonolactone and [¹⁴C-methyl]methionine were administered in separate experiments. From the absolute incorporation values of withaferin A (1), jaborosalactone A (2) and jaborosalactone D (3) isolated at different times after administration of the tracers, it was deduced that compound 2 is a precursor of both 1 and 3 and that the withanolides are later biodegraded to unknown products. Inoculation of [¹⁴C]jaborosalactone A confirmed its transformation into 1 and 3.     

Floral anthocyanins of some malesian Hibiscus species

In 14 Malesian species of Hibiscus (sensu lato) the most common floral anthocyanin was cyanidin 3-sambubioside. Cyanidin 3-glucoside was found     

Biosynthesis of withanolides in Acnistus breviflorus

Administration of [2?¹⁴C]mevalonolactone to excised leaves of Acnistus breviflorus produced labelled withaferin A and jaborosalactone A. The former was degraded leading to the isolation of glyceric acid from C-25–C-27 of the withanolide. These carbons represented only 2 % of the total radioactivity of withaferin A. The relative radioactivity of these carbons indicated that C-26 is directly derived from C-2 of mevalonolactone suggesting that the 25-pro-R-methyl group of cholesterol or any other sterol intermediate had been oxidized to form the lactone ring of the withanolide. The total radioactivity value found for C-25–C-27 was much lower than the expected 20 % of the total value for the withanolide indicating that the side chain of the sterol precursor had been partially cleaved during the biosynthetic process.     

In vivo synthesis of stigmasterol in Nicotiana tabacum

Six-day-old tobacco seedlings rapidly incorporated and metabolized exogenously supplied [4-¹⁴C]-sitosterol, but none of the radioactivity was recovered from stigmasterol. However, exogenously supplied [2-¹⁴C]-mevalonic acid was incorporated into both sitosterol and stigmasterol. Based on these results it is suggested that the biosynthetic pathway of stigmasterol is not via sitosterol but that both sterols have a common precursor.     

Cinnamate and shikimate incorporation into 3′,4′- and 3′,4′,5′-hydroxy substituted anthocyanins: Are there alternative pathways?

The incorporation of shikimate-[¹⁴C] and cinnamate-[¹⁴C] into 3′,4′- and 3′,4′,5′-hydroxy substituted anthocyanins was studied in isolated petals of Petunia hybrida. According to the dilution values, the incorporation of shikimate-[¹⁴C] was about 3–6 times better than that of cinnamate-[¹⁴C]. However a comparison of the incorporation of the 2 precursors on a relative basis showed no significant differences in the relative proportions of the specific activities of the 3′,4′-dihydroxysubstituted cyanidin-3-monoglucoside and the 3′,4′,5′-trihydroxysubstituted delphinidin-3-monoglucoside. This result and the [¹⁴C]-incorporation behaviour of the 3′-methoxy-4′-hydroxysubstituted peonidin-3-monoglucoside do not support the hypothesis that there are alternative pathways of flavonoid biosynthesis.     

Characterization of PhPRP1, a histidine domain arabinogalactan protein from Petunia hybrida pistils

An arabinogalactan protein, PhPRP1, was purified from Petunia hybrida pistils and shown to be orthologous to TTS-1 and TTS-2 from Nicotiana tabacum and NaTTS from Nicotiana alata. Sequence comparisons among these proteins, and CaPRP1 from Capsicum annuum, reveal a conserved histidine-rich domain and two hypervariable domains. Immunoblots show that TTS-1 and PhPRP1 are also expressed in vegetative tissues of tobacco and petunia respectively. In contrast to the molecular mass heterogeneity displayed by the pistil proteins, the different isoforms found in seedlings, roots, and leaves each has a discrete size (37, 80, 160, and 200 kDa) on SDS-PAGE gels. On the basis of their chemistry, distinctive domain architecture, and the unique pattern of expression, we have named this group of proteins HD-AGPs (histidine domain-arabinogalactan proteins).     

Metabolism of [2-3H]- and [6-3H]-nicotinic acid in intact Nicotiana tabacum plants

Earlier observations of Dawson on the relative incorporation of [2-³H]- and [6-³H]-nicotinic acid into nicotine have been confirmed in intact Nicotiana tabacum plants. All the tritium in the nicotine derived from [2-³H]-nicotinic acid was located at C-2 of the pyridine ring. However the radioactive nicotine derived from [6-³H]-nicotinic acid was not labelled specifically at C-6 with tritium. By carrying out feeding experiments with [6-¹⁴-C, 2-³H]- and [6-¹⁴C, ³H]-nicotinic acids, it was established that there was very little loss of tritium from C-2 and C-6 of nicotinic acid during 5 days of metabolism in the tobacco plant.     

Biosynthesis of steroidal withanolides in Withania somnifera

Administration of 24-methylene-cholesterol-[28-³H] to Withania somnifera, yielded [³H] radioactivity in the isolated withaferin A and withanolide D, whereas administered 24-(R,S)-methyl-cholesterol-[28-³H] was not incorporated into these compounds. 24-Methylene-cholesterol is, therefore, proposed as a sterol precursor of the withanolides. A novel procedure is described for the isolation of withanolides from W. somnifera. This method in conjunction with an improved procedure for administration of labelled sterols and mevalonolactone produces a greatly increased yield of labelled withanolides.     

Amo 1618 effects on incorporation of 14C-MVA and 14C-acetate into sterols in Nicotiana and Digitalis seedlings and cell-free preparations from Nicotiana

Incorporation of radioactivity from acetate-[¹⁴C] and MVA-[¹⁴C] into sterols and sterol precursors in tobacco was inhibited by Amo 1618; differing patterns of accumulation were obtained with the two precursors, suggesting more than one point of inhibition. This was borne out with cell-free preparations with which it was demonstrated that both HMG-CoA reductase and squalene-2,3-epoxide cyclase were inhibited, the latter more strongly than the former. GLC analysis of gross sterol and hydrocarbon fractions confirmed previous indications that incorporation of radioactivity into individual sterols was inhibited by Amo 1618. Finally, incorporation of MVA-[¹⁴C] into sterols and sterol precursors of Digitalis was significantly altered by the retardant, thus expanding the generality of the relationship between sterol (particularly 4-desmethylsterol) biosynthesis inhibition and retardant effect.     

Biosynthesis of trans-2-hexenal in chloroplasts from Thea sinensis

The biosynthetic pathway of trans-2-hexenal, leaf aldehyde, in isolated chloroplasts of Thea sinensis leaves. was examined using a tracer experiment. A high and specific incorporation of radioactivity into cis-3-hexenal and trans-2-hexenal, was observed when linolenic acid-[U-¹⁴C] was incubated with the isolated chloroplasts. Thus, trans-2-hexenal was biosynthesized via cis-3-hexenal from linolenic acid in the chloroplasts.     

Biosynthesis of tropane ester alkaloids in Datura

Datura meteloides plants were fed via the roots with [1″,2′-¹⁴C]tigloyl hygroline and as a control, [2′-¹⁴C]hygrine. After a week the alkaloids were isolated and degraded. Despite hydrolysis of the putative precursor it was possible, by label ratio, to show that esterification occurs after, and not before, the tropane ring has been synthesized. Hygroline is proposed as a possible intermediate.