Abstract
Mitraphylline was extracted from Uncaria Kawakamii HAYATA. Mitraphylline was considered to be a steric isomer of uncarine since their compositions were the same and their ultraviolet and infrared spectra showed close similarity. It was assumed that mitraphylline is an isomer with steric configuration of 15-20 positions different from that in uncarine and a β-configuration was presumed for the 4-position by pKa measurement, same as in uncarine-B. From these experimental results, formula (III) was given to mitraphylline.
