Biology Reference
In-Depth Information
Table 15.14.
Acute toxicity of ethyl acetate, MeOH and
n
-hexane extracts against larvae of last stage
S.
frugiperda.
a
Concentration
(ppm)
% Survival
b
S. frugiperda
% Survival
b
T. molitor
LD
50
c
S. frugiperda
LD
50
T. molitor
Compounds
Control
0.0
100.0
100
Ethyl acetate
2.0
79.5 ± 3.80b
91.5 ± 5.1a
7.99
13.74
10.0
41.2 ± 2.00b
65.2 ± 3.9b
25.0
15.9 ± 0.85b
15.9 ± 0.77c
50.0
0
0
n
-Hexane
2.0
67.0 ± 3.70b
77.4 ± 2.9b
4.56
5.43
10.0
30.0 ± 2.25b
27.3 ± 2.21c
25.0
7.0 ± 0.55a
10.1 ± 0.67d
50.0
0
0
MeOH
2.0
90.9 ± 4.69b
90.0 ± 4.9a
24.0
24.2
10.0
78.9 ± 3.95b
78.0 ± 3.8b
25.0
50.2 ± 3.51c
50.0 ± 3.3c
50.0
0
0
Me-Ced
2.0
95.1 ± 4.75
36.65
10.0
78.1 ± 3.90
25.0
59.3 ± 2.96
50.0
45.0 ± 2.25
Gedunin
10.0
54.7 ± 2.73b
10.78
25.0
14.1 ± 0.71c
a
After 24 h, survival of adults was recorded (percentage relative to controls).
b
Mean of three replicates. Means followed by
the same letter within a column after ± standard error values are not significantly different in a Student-Newman-Keuls
(SNK) test at
p
<0.05 (treatments are compared by concentration to control).
c
The LD
50
is the lethal dose producing 50%
survival.
ecdysone receptors (Dinan, 2001). From
Table 15.8 it is possible to infer that
n
-hexane
and ethyl acetate extracts accelerate the
time of pupation for larvae of
T. molitor
.
The
n
-hexane extract contains a high per-
centage of long-chain
n-
alkanes (Table 15.8)
and exhibited acute toxicity to larvae of this
insect with regard to the number of larvae
that reached the pupal stage.
n
-alkane compounds in the
n
-hexane extract
results in an increasing IGR activity. This
finding suggests that these components
could play an important role in both the
insecticidal and IGR activity of
C. micro-
phylla
extracts. The
n
-hexane and ethyl
acetate extracts from
C. microphylla
have
very good potency that was comparable to
gedunin, Me-Yuc, Me-Myrt and Me-Ced pre-
viously reported (Céspedes
et al.
, 2000, 2004,
2005, 2006).
Preceding experimental observations sug-
gest that acute toxicity and growth inhibition
of our extracts may be due to inhibition of
a proteinase, ETH and other polyphenol
oxidases (PPO) that could be bound to these
types of compounds or move throughout cel-
lular membranes and could produce white
substance accumulation (deposits) in vacu-
oles in similar form to that reported by
Delgado
et al.
(2011) and Halse
et al.
(1993).
This target has been demonstrated for other
compounds of natural origin (Karban and
Baxter, 2001; Kessler and Baldwin, 2002;
Céspedes
et al.
, 2005).
15.5.18 Remarks for
C. microphylla
On the basis of these results, we suggest that
the insect growth inhibition caused by
n-
hexane and ethyl acetate extracts from
C. microphylla
could be due to synergistic
effects. These plant extracts may be consid-
ered to be efficient IGRs, as well as having
activity similar to phytoecdysteroids, as
was evidenced by their significant inhibition
of moulting processes. These extracts had
potent insecticidal and growth inhibitory activ-
ities. Probably the presence of long-chain
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