Formation and Distribution of Sennosides in Cassia angustifolia, as Determined by a Sensitive and Specific Radioimmunoassay*

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Abstract
A radioimmunoassay for the quantitation of nanogram-amounts of sennoside B and related compounds in plant extracts is described. The assay makes use of [3H]-8-glucosidorheinanthrone of high specific activity (5.2 Ci/mmol) whose synthesis is reported here. From this material, [3H]-sennoside A and [3H]-sennoside B have also been synthesized. The assay is applied to the analysis of sennoside formation and distribution in Cassia angustifolia VAHL. High levels of sennosides in dried leaves and fruits have been observed whereas the seed alone, as well as stems and roots, contain very little sennoside. In flowers, as much as 4-5% of the dry weight consists of sennoside B and other immunoreactive constituents. Sennosides have been found in cotyledons of three day old seedlings in concentrations comparable to that of the mature leaf. Upon dehydration, leaf levels of sennoside B rise steadily, this rise being inversely correlated with the water loss. The absolute levels of sennoside B formed this way are the same as compared to rapid drying at 60° C.