The natural products pterosin Z, acetylpterosin Z, originally from the fern
Pteridium aquilinum, and their isopterosin analogues have been synthesized
and their smooth muscle relaxation activity has been measured. All of the
test compounds show activity with pterosin Z being the most active (EC50 =
1.3 +/- 0.1 x 10(-6) M), exhibiting 100 times the activity reported for the
related fern metabolites onitin (EC50 = 1 x 10(-4) M), onotisin (EC50 = 2
x 10(-3) M) and otninoside (EC50 = 7 x 10(-4) M). The smooth muscle relaxan
t activity of pterosin 2 is approximately equipotent with that of the relat
ed fungal pterosin (EC50 of 2.9 +/- 1.6 x 10(-6) M). These results suggest
that smooth muscle relaxant activity is reduced when a phenol group is pres
ent in the pterosin nucleus and when one of the dimethyl groups is derivati
zed.