Seasonal variations in trans-2-hexenal and linolenic acid in homogenates of Thea sinensis leaves

The seasonal variations in the amounts of C₆-volatile components cis-3-hexenal trans-2-hexenal n-hexanal) and their precursors (linoleic and linolenic acid) in homogenates of Thea sinensis leaves were quantitatively analyzed throughout the year. Formation of trans-2-hexenal began in the middle of April and reached a maximum during July. Towards autumn the aldehyde gradually decreased and, in winter (December to March), was virtually absent. The levels of cis-3-hexenol remained constant during May–December. cis-3-Hexenal showed a similar variation pattern to that of trans-2-hexenal. The major fatty acids in the leaves were palmitic, palmitoleic, oleic, linoleic and linolenic acid, and occurred in non-ionic lipids and phospholipid fractions. The amounts of linoleic and linolenic acid did not show any marked variation except for a big peak in October.     

Formation of 12-oxo-trans-10-dodecenoic acid in chloroplasts from Thea sinensis leaves

Linolenic acid-[1-¹⁴C] was converted to 12-oxo-trans-10-dodecenoic acid, via 12-oxo-cis-9-dodecenoic acid by incubation with chloroplasts of Thea sinensis leaves. Thus, it was confirmed that linolenic acid is split into a C₁₂-oxo-acid, 12-oxo-trans-10-dodecenoic acid, and a C₆-aldehyde, trans-2-hexenal, leaf aldehyde, by an enzyme system in chloroplasts of tea leaves.     

Sterol and lipid components of green Thea sinensis

Petrol. extracts of green tea yielded two straight chain alcohols identified as C₃₀ and C₃₂ alcohols by mass spectrometry, and a mixture of sterols identified as α-spinasterol and stigmast-7-ene-3-β-ol. A new saponin has also been isolated from the methanol extract and shown to be α-spinasterol gentiobioside.     

Subunit composition of alcohol dehydrogenase from Thea sinensis seeds and its substrate specificity for monoterpenes

Alcohol dehydrogenase (alcohol: NAD oxidoreductase, E.C. 1.1.1.1.) was purified from Thea sinensis seeds. Its M.W was 95000 and it was composed of two homogeneous subunits with MWs of 47000. The dissociation into subunits was caused by o-phenanthroline. Substrate specificity for monoterpene alcohols and aldehydes is discussed.     

Caffeine biosynthesis in Camellia sinensis

The metabolism of adenine and guanine, relating to the biosynthesis of caffeine, in excised shoot tips of tea was studied with micromolar amounts of adenine-[8-¹⁴C] or guanine-[8-¹⁴C]. Among the presumed precursors of caffeine biosynthesis, adenine was the most effective, whereas guanine was the least effective. After administration of a ‘pulse’ of adenine-[8-¹⁴C], almost all of the adenine-[¹⁴C] supplied disappeared by 30 hr, and ¹⁴C-labelled caffeine and RNA purine nucleotide (AMP and GMP) synthesis increased throughout the experimental period, whereas the radioactivities of free purine nucleotides, 7-methylxanthine and theobromine increased during the first 10 hr incubation period, followed by a steady decrease. By contrast, more than 45% of the guanine-[8-¹⁴C] supplied remained unchanged even after a 120 hr period. The main products of guanine-[8-¹⁴C] metabolism in tea shoot tips were guanine nucleotides, theobromine, caffeine and the GMP of RNA. The results support the hypothesis that the purine nucleotides are synthesized from adenine and guanine via the pathway of purine salvage. Adenylate is readily converted into other purine nucleotides, whereas the conversion rate of guanylate into other purine nucleotides is very low.The results also support the view that 7-methylxanthine and theobromine are precursors of caffeine. For the origin of the purine ring in caffeine, purine nucleotides in the nucleotide pool rather than in nucleic acids are suggested.     

Lipid biosynthesis by chloroplasts isolated from developing Zea mays

Fatty acid biosynthesis by isolated plastids has been examined in relation to chloroplast development and differentiation in leaves of maize plants grown in light for 7 days. Biosynthesis of fatty acids from acetate by proplastids prepared from the basal regions of the leaf was low and mainly palmitate was synthesized. The greatly increased utilization of acetate for fatty acid biosynthesis as the plastids increased in size was due to an increased synthesis of oleate. The maximum synthesis of total fatty acids and monoenoic fatty acids was obtained in chloroplasts prepared from leaf tissue 6–8 cm from the base of the plant where granal formation was most active. Fully-developed chloroplasts prepared from distal regions of the leaf were less active in fatty acid biosynthesis. Maize chloroplasts failed to synthesize fatty acids when isolated by methods commonly used to prepare active spinach chloroplasts. The method of isolation which included a density gradient gave a high proportion of Class I chloroplasts from maize leaves and incorporated up to about 10% of the acetate used. Biosynthesis of unsaturated fatty acids, especially with chloroplasts prepared from the most mature tissue, was increased by the addition of both mitochondrial and microsomal fractions. Increases in polyunsaturated fatty acids were also obtained but the proportions in the newly-synthesized fatty acids were well below the endogenous levels. Monoenoic synthesis was greatly stimulated by increasing the pH in the range 7·0–8·0 and also the highest proportions of unsaturated fatty acids were obtained at short incubation times.     

Biosynthesis of limonoids in Citrus

Analyses of citrus leaves and fruits, and radioisotope tracer work showed that the leaves could synthesize limonoids and that the trees could translocate limonoids from leaves to the fruit. These results suggest that limonoids in citrus fruit tissues are synthesized in leaves and translocated to the fruit. No evidence was found to support the presence of limonoid biosynthetic systems in the fruit tissues.     

cis- and trans-phytoene in Verticillium agaricinum

cis-Phytoene and trans-phytofluene were identified in illuminated cultures of Verticillium agaricinum in addition to the other carotenoids     

Biosynthetic pathway of cucumber alcohol: Trans-2,cis-6-nonadienol via cis-3,cis-6-nonadienal

cis-3,cis-6-Nonadienal and cis-3-nonenal in Cucumis sativus were identified by comparison with synthetic specimens. The identification of these compounds, combined with biochemical evidence, suggests that cucumber alcohol and trans-2-nonenol are biosynthesized via cis-3-unsaturated aldehydes from linolenic and linoleic acid, respectively.     

Biosynthesis of obacunone from nomilin in Citrus limon

Radioactive tracer work showed that [¹⁴C]nomilin was converted to at least four metabolites in Citrus limon. One metabolite was identified as obacunone, showing that obacunone is biosynthesized from nomilin in C. limon.     

Biosynthesis of azetidine-2-carboxylic acid from methionine in Nicotiana tabacum

The administration of dl-methionine-[1¹⁴C] to Nicotia tabacum resulted in the formation of radioactive azetidine-2-carboxylic acid (isolated by dilution) which was specifically labelled on its carboxyl group. This result and other evidence strongly indicates that this imino acid is a normal component of tobacco.     

Biosynthesis of sesquiterpenes in Hymenaea inferred from their quantitative co-occurrence

Leaf pocket resins of 11 species of the tropical arborescent genus Hymenaea are virtually identical qualitatively, but of widely varying quantitative proportions. Within this large range of variability, several strong positive quantitative correlations between resin constituents were found, especially between caryophyllene and β-humulene and between γ-muurolene and δ-cadinene. These data lead to clarification of sesquiterpene biosynthetic routes in Hymenaea. In addition, quantitative relationships found among caryophyllene, α- and β-selinene, γ-muurolene and δ-cadinene are explained only with difficulty by long accepted biosynthetic pathways, and the intermediacy of germacrenes is suggested.     

Lipid biosynthesis by intact mesophyll and bundle sheath chloroplasts from maize

The two dimorphic forms of chloroplast isolated from maize leaves utilized acetate for fatty acid biosynthesis and had similar requirements for cofactors. The oleate:palmitate ratio of the fatty acid products was lower for bundle sheath chloroplasts as was acetate incorporation into total fatty acids. Galactose from UDP-galactose was incorporated into galactolipids by both morphological forms to give monogalactosyl diacylglycerol and digalactosyl diacylglycerol in the ratio of 4:1.     

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.     

Purine base pattern of camellia irrawadiensis

Theobromine and caffeine in the flush shoot leaves of hybrids of tea and other camellia plants were assayed by HPLC. In C. sinensis and C. taliensis of section Thea the caffeine content exceeded 2% and the theobromine content was below 0.2%. However, in C. irrawadiensis of the same section, the theobromine content was more than 0.5% while the caffeine content was below 0.02%. The theobromine content of tea hybrids was also below 0.2%. In sections other than Thea, C. sasanqua, C. japonica and C. vernalis did not contain detectable amounts of theobromine or caffeine.     

Biosynthesis of ecdysterone from cholesterol in Taxus baccata

Biosynthesis of ecdysterone from [4-¹⁴C, 3-³H]cholesterol in Taxus baccata does not involve obligatory oxidation at C-3 during the formation of the A/B-cis ring junction.     

Biosynthesis of bakuchiol,a meroterpene from Psoralea corylifolia

Biosynthesis of bakuchiol was examined using phenylalanine and mevalonic acid as substrates. It has been demonstrated that bakuchiol is derived from one phenylpropane (with the loss of one carbon atom) and two isoprenoid (C₅) units.     

In vivo Biosynthesis of isopentenylacetophenones in Eupatorium rugosum

The biosynthesis of dehydrotremetone in Eupatorium rugosum has been investigated by feeding radioactive precursors to intact plants. The carbon atoms of acetate-[1-¹⁴C] and acetate-[2-¹⁴C] were identified in dehydrotremetone by degradation of the molecule. From the pattern of labeling it was concluded that the acetophenone moiety was derived from acetate via the polyacetate pathway. From the incorporation of mevalonate it appeared that the furan ring and its side chain were formed from an isoprenoid compound. Potential aromatic intermediates were chemically synthesized and also fed to plants but only tremetone was found to be efficiently incorporated into dehydrotremetone. Neither 4-hydroxyacetophenone nor 4-hydroxy-3[isopenten-(2)-yl]-acetophenone were efficiently incorporated into dehydrotremetone.     

Reconstitution of amino acid synthesis by combining spinach chloroplasts with other leaf organelles

By adding leaf peroxisomes to purified intact chloroplasts, glycine synthesis was reconstituted. On adding leaf mitochondria, serine synthesis was also reconstituted. However, aromatic amino acid synthesis which was effected by purified chloroplasts was not enhanced on adding peroxisomes or mitochondria although the rate in whole leaves was considerably higher.