A whole plant chlorofor
m-
methanol extract of the orchi
d Epidendrum rigidum inhibite
d ra
dicle growthof
Amaranthus hypochondriacus see
dlings (IC
50 = 300
mages/entities/
mgr.gif">g/
mL). Bioassay-gui
de
d fractionation furnishe
dfour phytotoxins, na
mely, gigantol (
1), batatasin III (
2), 2,3-
di
methoxy-9,10-
dihy
drophenathrene-4,7-
diol (
9), an
d 3,4,9-tri
methoxyphenanthrene-2,5-
diol (
11), along with the known flavonoi
ds apigenin,vitexin, an
d isovetin an
d the triterterpenoi
ds 24,24-
di
methyl-9,19-cyclolanostane-25-en-3
mages/gifchars/beta2.gif" BORDER=0 ALIGN="
mi
ddle">-ol (
14) an
d24-
methyl-9,19-cyclolanostane-25-en-3
mages/gifchars/beta2.gif" BORDER=0 ALIGN="
mi
ddle">-ol (
15). Stilbenoi
ds
1,
2,
9, an
d 11 inhibite
d ra
dicle growthof
A. hypochondriacus with IC
50 values of 0.65, 0.1, 0.12, an
d 5.9
mages/entities/
mgr.gif">M, respectively. Foliar applicationof gigantol (
1) at 1
mages/entities/
mgr.gif">M to 4 week ol
d see
dlings of
A. hypochondriacus re
duce
d shoot elongation by69% an
d fresh weight accu
mulation by 54%. Bibenzyls
1 an
d 2, as well as synthetic analogues 4'-hy
droxy-3,3',5-tri
methoxybibenzyl (
3), 3,3',4',5-tetra
methoxybibenzyl (
4), 3,4'-
dihy
droxy-5-
methoxybibenzyl (
5), 3'
-O-
methylbatatasin III (
6), 3,3',5-trihy
droxybibenzyl (
7), an
d 3,4',5-trihy
droxybibenzyl(
8), were teste
d for phytotoxicity in axenic cultures of the s
mall aquatic plant
Lemna pausicostata. Allbibenzyls
derivatives except
7 an
d 8 inhibite
d growth an
d increase
d cellular leakage with IC
50 valuesof 89.9-180 an
d 89.9-166
mages/entities/
mgr.gif">M, respectively. The natural an
d synthetic bibenzyls showe
d marginalcytotoxicity on ani
mal cells. The results suggest that orchi
d bibenzyls
may be goo
d lea
d co
mpoun
dsfor the
develop
ment of novel herbici
dal agents.Keywor
ds:
Epidendrum rigidum; orchi
daceae; bibenzyls; phenantrenes; stilbenoi
ds; phytotoxicity;cytotoxicity;
Lemna pausicostata;
duckwee
d;
Amaranthus hypochondriacus; gigantol; batatsin III