Journal of Chromalography, 403 (1987) 285-287 Elsevier Science Publishers B.V.. Amsterdam - Printed in The Netherlands

CHROM. 19 653

Note

Spray reagent for the detection of coumarins and flavonoids on thin-

layer plates

PARTHASARATHI GHOSH, PRABAL SIL and SWAPNADIP THAKUR*

Naturaf Products Laboratory, Department of Chemistry, University of Burdwan, Burdwan 713104 (India)

(Received April 22nd, 1987)

Thin-layer chromatography (TLC) has already proved its worth in the dew- tion of various types of chemical compounds having different structures. Its wide application to natural product chemistry is of prime importance. In TLC, spray reagents have been successfully utilized for detection of oxygen heterocycles, viz., coumarins and flavonoids. The most effective reagent for the detection of coumarins is methanolic potassium hydroxider; diazotized sulphanilic acid2 is also well estab- lished for this purpose. The Lewis acids, e.g., aluminium chloride3 and antimony(III) chloride*, basic lead acetate4, p-toluenesulphonic acid5 and iodine-potassium iodide6 are well documented for the detection of flavonoids. Benedict’s reagent7 has been used for the simultaneous detection of coumarins and flavonoids in TLC, Chalconcss can be detected by spraying sulphuric acid-ferric chloride followed by irradiation of the spots with short-wavelength UV light.

In continuation of our work on spray regents - g l 1 for the detection of different classes of compounds in TLC, we present the spray reagent chlorosulphonic acid for the detection of both coumarins and flavonoids.

EXPERIMENTAL

Materials The samples, coumarins and flavonoids, were isolated from different plant

sources. The plates (0.2 mm) were prepared using silica gel G (BDH, India) and an UNOPLAN apparatus (Shandon, U.K.). The samples were spotted with a 25-~1 pipette (Shandon).

Reagent Chlorosulphonic acid was from Fluka (Switzerland). The spray reagent was

prepared by diluting the ice-coId acid in chloroform (4:1), very cautiously since it reacts violently.

TLC All the samples were dissolved in methanol and were applied to silica gel G

plates by a measuring pipette. After development in benzene-ethyl acetate (3.1), the plates were air dried and sprayed uniformly with the prepared reagent.

0021-9673/87/$03.50 0 1987 Elsevier Science Publishers B.V.

286 NOTES

RESULTS AND DISCUSSION

AS shown in Table I, the chalcones, aurantiacin and pedicinin, and flavanones gave responses at very low concentration in comparison with coumarin and even flavones. Higher concentrations of coumarins were required for colouration, and coumarin itself did not produce any colour even at higher concentration. The linear coumarin, umbelliferone, gave a response at much higher concentration in compar- ison with the other samples tested. The different colours obtained could not be used to distinguish the linear, furano or pyrano coumarins. In the case of flavonoids yellow colourations were observed with the reagent. Based on these results, the for: mation of a molecular complex rather than a charge-transfer complex is indicated.

TABLE I

COLOUR REACTIONS OF COUMARINS AND FLAVONOIDS WITH CHLOROSULF’HONIC ACID AFTER CHROMATOGRAPHY ON SILICA GEL G PLATES

Class

Coumarin (linear)

(furano)

(pyrano)

Flavone

Isoflavone Flavanone

Chalcone

-

Compound Co/our Limit of detection (pz)

Coumarin Umbelliferone Auraptenol Auraptenol acetate Meranzin hydrate acetate Murrangatin acetate Suberosin Suberenol Crenulatin Bergaptan Xanthotoxin Xanthotoxol Herdclenol Imperatorin Isopimpinellin Seselin Luvangatin Velutin Didymocarpin Didymocarpin A 3,5,6,7,3’,4’,5’-Heptamethoxy- Yellow

flavone Pilloin Yellow

7-Hydroxyflavanone Yellow

5,7,8-Trihydroxy-6-methoxy- Yellow

flavanone Aurantiacin Yellow

Flemichapparin Yellow

Flemichapparin A Yellow

Pedicinin Yellow

- -

Violet 100 Brown 20 Pink 4 Yellow 4 Violet 0.8 Pink 20 Pink 2 Yellow 4 Yellow 1 Yellow 4 Brown 1 Pink 10 Violet 4 Pink 0.8 Yellow 4 Yellow 8 Yellow 0.4 Yellow 1 Yellow 1

0.4

0.4 0.004 0.002

0.04 0.4 0.4 0.002

287

NOTES

ACKNOWLEDGEMENT

We thank Professor N. Adityachowdhury, Bidhan Chandra Krishi Viswavi- dyalaya, India for authentic samples of some coumarins and Aavonoids.

REFERENCES

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8 H. M. Chawla, S. S. Chibber and R. Saigal, 1. Chromatogr,l 138 (1977) 243,

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