A STABLE REDDISH PURPLE ANTHOCYANIN IN THE LEAF OF GYNURA-AURANTIACA CV PURPLE PASSION

The anthocyanin (GAA) in the epidermis and hair of the leaf of Gynura aurantiaca cv. 'Purple Passion' was isolated and identified as cyanidin tetra-glucoside acylated by three molecules of caffeic acid and one molecule of malonic acid. GAA was also isolated from the lower epidermis of the leaf of G. bicolor DC. GAA showed a very stable reddish purple color from weakly acid to neutral pH region, but the color of the deacylated compound disappeared rapidly in the same region. This indicated that the attached organic acids must play an essential role in the stabilization of the color. Comparison of the profiles of the visible absorption spectra of the intact epidermal peels and cells of G. aurantiaca and G. bicolor with those of GAA dissolved in various pH solutions suggested that the pH of the epidermal vacuole containing GAA was nearly 4.3. GAA was indistinguishable from the anthocyanin (rubrocinerarin) which we had previously isolated from the purplish red flowers of Senecio cruentus DC. by means of UV-Vis, NMR and Mass spectra.