The Stability of Bio-active Components in the Bark of Eucommia ulmoides : Eucommiae Cortex

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Eucommiae Cortex (杜仲), an old Chinese drug, is the dried bark of Eucommia ulmoides (Eucommiaceae). It contains lignan glucosides and iridoid glucosides, some of which show hypertensive or anti-stress activity in animals. We found, however, that Japanese commercial Eucommiae Cortex contained smaller amounts of bio-active components, especially iridoid glucosides, than fresh barks. We collected the bark from twenty five year old Eucommia ulmoides trees every month, for thirteen months, and determined the amounts of a lignan, pinoresinol diglucoside, and two iridoid glucosides, geniposidic acid and geniposide in them. The iridoid content of the samples collected during the summer, was markedly lower than that of fresh sample if the bark was dried at room temperature. Further examinations revealed that the bark contains some intracellular enzymes that are responsible for the decomposition of the iridoids, as the loss was effectively prevented by dipping the fresh bark into boiling water for a few minutes before drying or by drying it with a microwave generator. The activity of the relevant enzymes varied seasonally and in accordance with the physiological conditions of the trees: they are more active in the growing season and inactive in dormancy. Since the bark is usually peeled off the trees in the growing season, it was concluded that, to produce a crude drug of good quality, the intracellular enzymes in fresh bark should be inactivated before drying.
1988-06-20

The Stability of Bio-active Components in the Bark of Eucommia ulmoides : Eucommiae Cortex

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