The cathartic effect of isobarbaloin, a stereoisomer of barbaloin (com
pound principally responsible for the cathartic activity of Aloe), was
examined in male rats by oral administration. Individual differences
in sensitivity in the laxative activity of isobarbaloin and barbaloin
was not found. The cathartic activity (ED,,) of isobarbaloin in barbal
oin positive rats was 19.2 mg/kg, nearly equal to that of barbaloin (1
9.5 mg/kg). Also, isobarbaloin administered orally was demonstrated to
decompose to aloe-emodin-9-anthrone (active metabolite of barbaloin)
as well as to barbaloin. Therefore, it is considered that the mechanis
m underlying the cathartic effect of isobarbaloin is the same as that
of barbaloin.