Bulletin Autumn‧Winter 1996

Trichosanthin—The Ancient Remedy Reveals Additional Modem Uses A n E f f ec t i ve A b o r t i o n D r u g For centuries tien hua fen, the tuber of a humb l e c l i mb i ng plan t Trichosanthes kirilowii which grows wild in eastern China, has been used by the Chinese to induc e abortion. According to the Compendium of Materia Medica compiled b y Li Shi Z h e n i n the Ming dynasty, tien hua fen can reset menstruation and expel retained placentas. Chinese scientists conducting chemical and pharmacological analyses on the plant in the 1970s i d e n t i f i e d a p r o t e in to be responsible for inducing the abortion, and named it trichosanthin. In the late 70s, researchers from CUHK began to conduct research on trichosanthin and discovered that it can suppress the growth of certain tumour cells. As a medicinal protein, trichosanthin is not without its shortcomings. Its curative effects are short-lived as it remains in the body only for a limited period of time. Besides, it defeats its o wn purpose by inducing the production of antibodies. It can also cause skin allergies, fever, muscle pains, and even the sudden lowering of blood pressure. Resea r ch o n T r i c h o s a n t h i n Dr. P.C. Shaw of the Department of Biochemistry has since 1987 been working on the protein engineering of trichosanthin so as to i mp r o ve its pha rmaco l og i ca l performance and elucidate the role of constituent am i n o acids. His w o r k is supported by a direct grant and three earmarked grants from the Research Grants Council (see table). A related plant protein, a-momorcharin, wit h functions similar to trichosanthin, is the research subject of another team from the same department, headed by Prof. W.K.K. Ho. T r i c h o s a n t h i n Production in the L a b o r a t o r y - - A n I m p o r t a n t Breakthrough Trichosanthin for research purpose s used to be extracte d from the tuber of Trichosanthes kirilowii. As the Hong Kong climate is not conducive to the growth of this plant, researchers often had to purchase it f r om mainland China. This technical problem is now solved by isolating the relevant DNA sequence fro m the tuber of the plant and inserting it into the bacteria Escherichia coli to enabl e the r a p id production of the protein. The trichosanthin so derived has the same biological functions as that extracted f r om the plant. This successful a t t emp t at ' s y n t h e s i z i n g' trichosanthin made it possible for the protein to be p r o d u c ed i n large quantitie s in laboratories in a purified form. A n Interdisciplinary E f f o r t to S t r e n g t h e n C u r a t i v e P r o p e r t i e s a n d M i n i m i z e S i d e E f f e c t s I n 1989 Dr. H .W. Y e u ng of the B i o c h em i s t r y De p a r t me n t and his c o l l a b o r a t o rs i n th e US f o u n d t hat trichosanthin can inhibit the reproduction of the AIDS virus in infected cells without affecting norma l cells. Clinical trials also The climbing plant Trichosanthes Kirilowii Chinese University Bulletin Autumn . Winter 1996 22