- Quinochalcones and flavonoids from fresh florets in different cultivars of Carthamus tinctorius L.
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The flavonoid constituents in fresh florets of the three distinctive cultivars of Carthamus tinctorius L. were purified and identified to investigate flavonoid biosynthesis in the petals. From the orange flower of cv. Kenba (K.), four new compounds, anhydrosafflor yellow B (1), two kaempferols, 9 and 13, and a quercetin, 17, were isolated, as well as the twelve known compounds, and their structures were determined by spectral data, chemical reactions, and molecular mechanics calculations. From the yellow flower of cv. Ogon-hanagasa (O.), two flavonols and two quinochalcones, and from the white flower of cv. Shiro-bana (S.), three flavonols were isolated. These compounds were the same as those contained in cv. K. To compare the flavonoid constituents among the three cultivars, crude extracts were analyzed by a LC/PDA/MS system. In cv. K., six quinochalcones and eleven flavonols were identified. In cv. O., three quinochalcones and nine flavonols were identified, but the red pigment, carthamin (4), and its precursor, precarthamin (3), were not detected. In cv. S., four flavonols without a 6-hydroxyl group were identified. On the basis of a comparative study on the constituents among these three cultivars, a possible biosynthetic pathway to form quinochalcones via the intermediate, pentahydroxychalcone (19), is proposed.
- Kazuma, Kohei,Takahashi, Takashi,Sato, Katsura,Takeuchi, Hisatomo,Matsumoto, Takeshi,Okuno, Toshikatsu
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- Biomimetic synthesis of carthamin, a red pigment in safflower petals, via oxidative decarboxylation
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Carthamin, a natural red pigment derived from safflower, was discovered centuries ago and has been utilized in several industries such as dye, food coloring, and natural medicine industries. Although it has been used since Egyptian times, its structural features were only determined in the mid-1900s when pioneering studies were conducted to elucidate the carthamin structure and assign its stereochemistry. Reproducing the complex biosynthesis of carthamin has been a common research goal since then. However, this has been rendered complex because of the unstable precursors and low yields from the multiple steps involved in the synthesis. Herein, we report the total synthesis of carthamin via a four-step procedure using (S)-C-β-D-glucosylquinochalcone as the starting compound. The synthesis involves mild conditions, short reaction time, and readily available compounds. After de-O-methylation, condensation, oxidative decarboxylation, and saponification, carthamin was obtained in an overall yield of 9.5% through the proposed method.
- Abe, Yuka,Sohtome, Takuo,Sato, Shingo
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