Formation of tetrahydroanthracenes in tissue cultures of Cassia bicapsularis L.
A callus culture of Cassia bicapsularis L. (Fabaceae) was established on Murashige-Skoog medium supplemented with 1.0mg/L 2,4-D and 0.1mg/L kinetin  and grown in the dark. It produced two new yellow fluorescent compounds which are tetrahydroanthracenes. These compounds were absent from in vitro plants. Similarly, our previous studies of the active constituents showed that intact plants cultivated in Egypt produced flavonoids and anthraquinones only. The structures of the new compounds from the callus culture were established on the basis of spectral and chemical evidence in comparison with literature data .
The yellow fluorescent compounds showed typical features of 2H,4–3,8,9-trihydroxy-tetrahydroanthracene, which can lose water and isomerize to the corresponding anthrones. These latter quite unstable compounds are oxidized to anthraquinones in the presence of O2 .
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