Viscum album (mistletoe) has been documented as a traditional treatment of
diabetes. In acute 20-min tests, 1-10 mg/ml aqueous extract of mistletoe ev
oked a stepwise 1.1- to 12.2-fold stimulation of insulin secretion from clo
nal pancreatic B-cells. This effect was abolished by 0.5 mM diazoxide and p
rior exposure to extract did not alter subsequent stimulation of insulin se
cretion induced by 10 nnM L-alanine, thereby negating a detrimental effect
on cell viability. The insulin-releasing effect of mistletoe extract was un
altered by 16.7 mM glucose, L-alanine (10 mM), 3-isobutyl-1-methylxanthine
(IBMX) (1 mM), or a depolarising concentration of KCl (25 mM). The ability
of extract to enhance insulin secretion did not depend upon the use of heat
during extract preparation and was not mediated by lectins. These results
demonstrate the presence of insulin-releasing natural product(s) in Viscum
album which may contribute to the reported antidiabetic property of the pla
nt.