Bot Mag. Tokyo 83: 229-232 (July 25, 1970).

Paper-chromatographic Identification of Flavonoids from a Scarlet-flowering Dahlia and Crystallization of and Butein

Norio SAITO,* Kikuko ISHIZUKA,* and Yoshinobu OSAWA*

Received January 27, 1970

Abstract

Nine major flavonoids were detected in scarlet petals of a dahlia cultivar, Alice ". Among these flavonoids, the two pigments were crystallized from ethanolic extracts, and identified as pelargonin and Butein.

During the survey of genuine in a variety of dahlia cultivarsl,2>, an appreciable amount of yellow pigments was obtained simultaneously from an ethanolic extract of scarlet petals, which was composed mainly of chalcones, especially butein (aglycone of coreopsin) and some others. This preliminary finding has tempted us to carry out a comprehensive study of flavonoids in scarlet petals. While the chalcones were isolated from the yellow flowers of dahlia3,4,5,s,7', the same group of pigments in scarlet dahlia has not been described in the literatureg'. In this work, scarlet petals of Dahlia variabilis DESF, cv. "Alice" were used as material for the examination of major flavonoids, and also for the crystallization of pelargonin and butein.

Material and Methods

Material. A cultivar of scarlet pcmpom dahlia, "Alice ", was used as material, which was cultivated in Matsukata farm in Tokyo. The flower color is described as rosy cerise with white base in England9', while as scarlet in Japan. Extraction and identification. Fresh petals were immersed in 80°o ethanol, and pressed. The resulting yellowish orange extract was filtered by suction, and spotted directly on Toyo-Roshi paper No. 51 together with the authentic samples side by side, and co-chromatographed using the solvents : butanol/acetic acid/water (4: 1 : 5, v/v), acetic acid/hydrochloric acid/water (15 : 3 : 82, v/v), and 30% acetic acid. Individual spots of flavonoids on the chromatograms were cut out, and eluted with appropreate solvents, and used for chromatographic and spectroscopic identifications. Quantitative analysis of major pigments. The pigment solutions quantitatively prepared from the petal extracts were spotted on a sheet of filter paper with a micro-pipette, and chromatographed two-dimentionally using the solvents, butanol/ acetic acid/water (4:1: 5, v/v) and 30% acetic acid, one after another. The flavor noid spots separeted were cut out, eluted with ethanol, and their contents were measured by colorimetric means at definite wave lengths: 382 m~u for butein, 374 m~Cfor 2', 4', 4-trihydroxychalcone, and 500 mp for pelargonin (in 5°o HC1), respectively. * Chemical Laboratory , Meiji-Gakuin University, Tokyo 230 SAITO,N., et al. Vol. 83

Isolation and crystallization of major flavonoids. Fresh petals (2 kg) were immersed in 80% ethanol, heated at 60-70° for one hour, and left overnight. The orange red extract (1.51) was filtered, and concentrated to 1/10 volume . The con- centrate was shaken with an equal volume of ethyl acetate, whereupon the organic layer containing yellow flavonoids was separated from the aqueous layer. The organic layer was evaporated to dryness in vacuo, and the residue was dissolved in hot acetone (60 ml) containing a small amount of water. After standing overnight , pale yellow needle-shaped crystals of butein were obtained (ca. 6 g) (Fig. 1). This was recrystallized twice from aqueous acetone. Yield: ca. 3 g. Anal. Cal. for C15H12O5. H20: H2O 5.84%; C 66.18%; H 4.41%. Found : H2O 5.46, 5.52%; C 66.11, 65.92%; H 4.68, 4.62%. M. p. 210°. UV absorption peaks : 263 and 382 mp in ethanol. The IR data were identical with those of the synthetic specimen of butein (measured by the KBr-method). The -containing, aqueous layer obtained above was added with a small amount of conc. HC1 up to the final concentration of ca. 0.5% acid. The red, acidic solution was concentrated to 1/5 volume and stood for 24 hours in a refri- gerator, whereby pelargonin chloride was gradually separated as crystals (1.65 g). Recrystallization was made four times from hot aqueous ethanol containing 0.5% HCI. Yield ca. 1 g (Fig. 3). Anal. Cal. for C27H31015C1. 3 H20: H2O 9.09%; C 51.41%; H 4.91%. Found : H2O 8.72, 8.73%; C 51.26, 51.13%; H 5.05, 5.02%. M. p. 178-182°. UV-maxima: 273 and 500-505 mp in 5% HCI.

Fig. 1. butein (x ca. 680) Fig. 2. pelargonin chloride (x ca. 680)

Results and Discussion

The flavonoids in 80% ethanolic extract of scarlet petals of dahlia were separated on the two-dimensional paper chromatogram as shown in Fig. 3, on which about eighteen spots of flavonoids were recognized. Among them, nine major flavonoids were separated and identified in the usual way (Table 1). The anthocyanins are pelargonin (0.48%), pelargonidin-3-glucoside, cyanin, , and probably pelargonidin-3-diglucoside. The chalcones are butein (0.82%), coreopsin, 2', 4', 4-tri- hydroxychalcone (0.310), 2', 4', 4-trihydroxychalcone-4'-glucoside, and aurone (sulph- retin-6-glucoside). Besides, many other unknown spots of minor flavonoid components were observed. Two major flavonoids, butein and pelargonin, were separated and crystallized as needles (Fig. 1 and 2) in the manner described below. It is noteworthy that a large amount of sugar-free pigments, butein and 2', 4', 4- July, 1970 On Major Flavonoids Deteched in a Scarlet-flowering Dahlia 231

Fig. 3. Diagram of typical paper chromatogram of cured petal extract. Designation of the spots : 1, pelargonidin-3-diglucoside (?) ; 2, -3-

- glucoside ; 3, pelargonin ; 4, cyanin ; 5, 2', 4', 4-trihydroxychalcone ; 6, 2', 41,4 trihydroxychalcone-4'-glucoside ; 7, butein ; S, butein-4'-glucoside ; 9, sulphuretin- 6-glucoside.

Table 1. Some chemical properties of the flavonoids isolated from Dahlia variabilis, cultivar "Alice " . 232 SAITO, N., et al. Vol. 83

trihydroxychalcone, was found in an aqueous extract of fresh petals. However, they did not always appear upon quick extraction with aqueous alcohol in the cold.. Therefore, it seems that the aglycones found in the petals are present mostly in the form of glycoside in situ. On the other hand, seasonal change of the. flavonoids in flowers was also examinedd paper-chromatographically during the period from early summer to late autumn. In this case, sugar-free flavonoids were sometimes detected in alcoholic extracts. Possibly, they are only artifacts produced enzymatically during extraction process. In all, the major flavonoids of scarlet-red dahlia "Alice" are pelargonin, butein- 4'-glucoside, and 2', 4', 4-trihydroxychalcone-4'-glucoside. The sugar-free pigments, butein and 2', 4', 4-trihyroxychalcone, may also be found in the petals probably as the products of enzymic fission. The identification of minor flavonoid components is still under way.

Acknowledgement

The authors' thanks are due to Prof. M. Shimokoriyama (University of Tokyo) for his kind supply of authentic specimens of butein-4'-glucoside and sulphretin-6 glucoside, and also to Dr. N. Sugano (Toyama University) for providing the synthetic samples of butein and 2', 4', 4-trihydroxychalcone.

References

1) Saito, N., Hirata,, K., Hotta, R. and Haya- 6) Nordstrom, C. G. and Swain, T., Arch. shi, K., Proc. Japan Acad. 40: 516 (1965). Biochem. Biophys. 60: 329 (1956). 2) Takeda, K., Saito, N. and Hayashi, K., 7) ibid. 73: 220 (1958). Proc. Japan Acad. 44: 352 (1968). 8) Harborne, J. B., Biochemistry of Phenolic 3) Price, J., J. Chem. Soc. 1.01.7,(1939). Compounds" (J. B. Harborne, ed.,), pp 4) Nordstrom, C. G. and Swain, T., ibid. 129, Academic Press, London, (1964). 2764 (1953). 9) Shewell-Cooper, W. E., "The A, B, C of 5) Bate-Smith, E. C. and Swain, T., ibid. Dahlias ", English Univ. Press, London. 2185 (1953). (1961).