Showing papers on "Flavanone published in 1978"

Changes in the levels of enzymes of phenylpropanoid and flavonoid synthesis during phaseollin production in cell suspension cultures of Phaseolus vulgaris

Abstract: The extractable activities of phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, p -coumaric acid-coenzyme A ligase, flavanone synthase and chalcone—flavanone isomerase showed significant increases in bean cell cultures in response to treatment with autoclaved ribonuclease, a potent inducer of phaseollin biosynthesis in this system. Increases in the activities of all the enzymes occurred within 6 h after ribonuclease treatment, but the subsequent development of activities was not coordinated. The flavanone synthase catalysed the formation of naringenin (4′,5,7-trihydroxyflavanone) from malonyl coenzyme A and p -coumaroyl coenzyme A. Synthesis of liquiritigenin (4′,7-dihydroxyflavanone) was not detected when soluble cytoplasmic or particulate preparations were incubated with the above substrates in the presence of NADPH or NADH generating systems. The results are discussed in terms of current views on isoflavonoid biosynthesis and the known changes in phenylpropanoid metabolism occurring in the cultures.

Genetic control of chalcone-flavanone isomerase activity in Callistephus chinensis.

Abstract: A mutant blocked in anthocyanin synthesis leads to an accumulation of 4,2′,4′,6′-tetrahydroxy-chalcone-2′-glucoside (isosalipurposide) in blossoms of Callistephus chinesis (L.) Nees, whereas in geno-types with the wild-type allele, higher oxidized flavonoids and anthocyanins are synthesized. Measurements of chalcone-flavanone isomerase activity of 18 lines of Callistephus chinensis showed a clear correlation between accumulation of chalcone in the recessive genotypes (ch ch) and deficiency of this enzyme activity. Both the chemogenetic and the enzymologic evidence lead to the following conclusions: 1. The first product of the synthesis of the flavonoid skeleton should be tetrahydroxychalcone.-2. The chalcone-flavanone isomerase catalyzes the formation of flavanone from chalcone in a stereospecific way and there-with furnishes the substrate for the further reactions in the flavonoid biosynthesis.

Pigment synthesis in maize aleurone from precursors fed to anthocyanin mutants.

Abstract: Aleurone tissue of c2 Pr, C2 pr, or c2 pr genotypes can utilize either of two flavanones (naringenin, homoeriodictyol) or a flavanonol (dihydroquercetin) to synthesize anthocyanin. The anthocyanins formed have substitution patterns corresponding to those of the precursors, but c2 Pr tissue can hydroxylate the 4′-OH precursor at the 3′ position. The results presented suggest that C2 acts before the flavanone step and that the hydroxylation gene (Pr) can act after C2.

Characterization, development and localization of "flavanone synthase" in tulip anthers.

Abstract: 1. “Flavanone synthase” was isolated from anthers of Tulipa cv. “Apeldoorn” and partially purified by (NH4) 2SO4 fractionation, gel chromatography and isoelectric focussing. The enzyme preparation was free of chalcone-flavanone isomerase activity. 2. p-Coumaroyl-CoA, caffeoyl-CoA and feruloyl-CoA were found to be efficient substrates of the synthase. The products formed were naringenin (5,7,4′-trihydroxyflavanone), eriodictyol (5,7,3′,4′-tetrahydroxyflavanone) and homoeriodictyol (5,7,4′-trihydroxy-3′-methoxyflavanone), respectively. Addition of thiol reagents at concentrations exceeding 10-3 м caused inhibition of the enzyme. “ Release products” , however, were not detectable. Although exclusively chalcones accumulate in the tulip anther, only flavanones but no chalcones were detectable in our in vitro system. 3. The apparent Km values for p-coumaroyl-CoA, caffeoyl-CoA and feruloyl-CoA were 1 .7× 10-6 м, 1.6× 10-6 м and 2 .5 ×10-6 м, respectively. Similar data were observed for malonyl- CoA. 4. No cofactors are required for the synthase reaction. The enzyme is strongly inhibited by the reaction products flavanone and coenzyme A . Maximum enzyme activity was found at pH 8.0 and 30 °. The molecular weight was approx. 55,000. 5. Synthase activity develops in early postmeiotic stages of microsporogenesis. Highest specific activities of the enzyme coincide with a maximum in chalcone accumulation within the anthers. 6. The contents of anthers was separated into two fractions, pollen and tapetum. Highest specific activities were observed with tapetum fractions, while pollen fractions exhibited only very low activities. The high enzyme activity in the tapetum fraction points to the important role of the tapetum in the biosynthesis of flavonoids in the loculus of anthers.

A convenient synthesis of lonchocarpin and isolonchocarpin

Abstract: 1, 1-Dimethyl propargylation of 7-hydroxyflavanone (5) with 2-chloro-2-methyl-3-butyne in the presence of K2CO3, Me2CO, KI and DMF yielded a mixture of four compounds. Its 1, 1-dimethyl propargyl ether (6) and the corresponding chalcone (7) resulted in major amounts; their corresponding cyclised products (2 and 1) also formed albeit in smaller amounts. These cyclised products, lonchocarpin (1) and isolonchocarpin (2) were the sole products when the above mixture was heatedN, N-dimethylaniline. Lonchocarpin (1) is best synthesized by 1,1-dimethyl propargylation of 2′ 4′-dihydroxychalcone (8) followed by heating inN, N-dimethylaniline, because it was noted that in the above two reactions, the flavanone ring tends to open out whereas the chalcone does not cyclise.