;Among the Ipomoea plants, both Ipomoea nil and Ipomoea tricolor display bright blue flowers, and Ipomoea purpurea exhibits dark purple flowers. While all of these flowers contain cyanidin-based anthocyanin pigments, the mutants of I. nil, I. purpurea, and I. tricolor carrying the magenta, pink, and fuchsia alleles, respectively, produce reddish flowers containing pelargonidin derivatives, and all of them are deficient in the gene for flavonoid 3¢-hydroxylase (F3¢H). The magenta allele in I. nil is a nonsense mutation caused by a single C to T base transition generating the stop codon TGA, and the cultivar Violet carries the same mutation. Several tested pink mutants in I. purpurea carry inserts of the 0.55-kb DNA transposable element Tip201 belonging to the Ac/Ds superfamily at the identical site. No excision of Tip201 from the F3¢H gene could be detected, and both splicing and polyadenylation patterns of the F3¢H transcripts were affected by the Tip201 integration. The fuchsia allele in I. tricolor is a single T insertion generating the stop codon TAG, and the accumulation of the F3¢H transcripts was drastically reduced by the nonsense-mediated RNA decay. Spontaneous mutations in Ipomoea, including a possible founder mutation in the pink allele, are also discussed.

No abstract

Five new ternatins 1-5 have been isolated from Clitoria ternatea flowers, and the structures have been determined by chemical and spectroscopic methods as delphinidin 3-malonylG having 3'-GCG-5'-GCG, 3'-GCG-5'-GC, 3'-GCGCG-5'-GC, 3'-GCGC-5'-GCG, and 3'-GCGC-5'-GC side chains, respectively, in which G is D-glucose and C is p-coumaric acid. Pigment 1 had symmetric 3',5'-side chains. Compounds 3 and 4 are structural isomers. These ternatins were shown to form an intramolecular stacking between the aglycon ring and the 3',5'-side chains in solution.

Two series of structurally related anthocyanins, extracted from the blue flowers of Evolvulus pilosus cv. Blue Daze and from the blue-purple flowers of Eichhornia crassipes, exhibit remarkable colour stabilities in aqueous solution at mildly acidic pH values. All the pigments possess the same chromophore (delphinidin), but a different pattern of glycosylation and acylation. Moreover, one of the pigments has an apigenin 7-glucoside molecule (a flavone) attached to the glycosidic chain by two ester bonds with malonic acid, instead of an aromatic acid and is the only known anthocyanin with such a structure. All the molecules studied, except one which has only a 3-gentiobioside (a disaccharide) as substituent, denote an effect of reduction in the hydration constant when compared with the parent delphinidin 3-glucoside or 3,5-diglucoside molecules, which supports the existence of intramolecular hydrophobic interactions between the chromophoric skeleton and the acyl or flavonoid groups. The role played by the sugar units on the hydrophobicity/hydrophilicity of the pigments is also discussed.

Eight new anthocyanins 1-8 (ternatins C1, C2, C3, C4, C5, and D3 and preternatins A3 and C4) were isolated from Clitoria ternatea flowers. By the application of chemical, UV-vis, and FABMS methods, the structures of 1-6 were postulated as delphinidin 3-malonylglucoside having 3'-GCGC-5'-G, 3'-GCGCG-5'-G, 3'-GC-5'-G, 3'-GCG-5'-G, 3'-G-5'-G, and 3'-GC-5'-GC, and compounds 7 and 8 as delphinidin 3-glucoside having 3'-GCG-5'-GCG and 3'-GCG-5'-G as side chains, respectively, in which Dp is delphinidin, G is D-glucose, and C is p-coumaric acid. The structures of the compounds 1, 3-5, and 7 were established completely by additional NMR methods.