ABSTRACT
The crude Chinese drug “Uncaria hook” is a hook, or a twig with an attached hook of Uncaria plants seen in today's Chinese and Japanese medicinal markets. However, through herbological studies we found that the botanical origin of Uncaria hook was Uncaria rhynchophylla (Miq.) Miq., and that until the middle of Ming Dynasty in ancient China, the medicinal part used was the twig bark, not the hook itself, and use of the twig with hook was begun in the later Ming Dynasty. This change in practice seems to have been influenced by herbal descriptions written in the Ming Dynasty. Some of these stated that the medical effect of hooks was stronger than that of the bark.To determine the appropriate medicinal part of this crude drug in terms of chemical quality, we analyzed the alkaloid contents of Uncaria rhynchophylla bark, hooks, and twigs collected in Japan. Our result showed that the alkaloid content of the bark was higher than that of the twigs and hooks. Rhynchophylline and hirsutine, the alkaloid contained in Uncaria hook, were reported to improve memory learning and to cure hypertension, respectively. Since the alkaloid content profile of the bark was different from that of the hook, a question arose as to whether the medicinal properties of the part commonly used as “Uncaria hook” meet the requirement of the crude drug. Further pharmacological study is expected.