Biliary excretion and enterohepatic recycling of proscillaridin a after oral administration to man

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Abstract
A single oral dose of proscillaridin A (1.0–1.5 mg) was given to six patients with T-tube drainage of the common bile duct, and simultaneous samples of bile and plasma were collected at various times during the following 24 hours. Glycoside activity was assayed by the86Rb-uptake inhibition technique. Peak activities in plasma (mean 0.80 ng/ml) were attained after 0.5–2 h, and in bile (mean 6.9 ng/ml) after 1–4 h. Subsequently, proscillaridin activity in bile was less than 5 ng/ml for the remainder of the sampling period, and 10–100 times higher than that in plasma. Bile samples treated with β-glucuronidase and sulphatase showed 100–200 fold increase in glycoside activity. Deconjugation was also produced by treatment with enteric contents. The results suggest that conjugation of unchanged proscillaridin is a major metabolic route. After excretion in the bile, the conjugates may be split in the intestine and reabsorbed as active glycoside.