ARTICLE IN PRESS
JID: CCLET
[m5G;June 8, 2021;17:43]
Y. Zhang, Y. Li, H. Li et al.
Chinese Chemical Letters xxx (xxxx) xxx
Table 3
concentration of 50 mg/L, both of the compounds merely exhib-
ited moderate larvicidal activities against such two kinds of pests.
The overall relationships between these compound structures and
the insecticidal activities towards H. armigera and O. nubilalis illus-
trated the similar activity trends of sulfone-containing compound
LC50 values of partial compounds A against P. xylostella.
Compd.
y = ax + b
LC50 (mg/L)
R
A2-2
y = 1.81x + 6.60
y = 1.41x + 6.46
y = 1.25x + 6.51
y = 1.99x + 9.2887
y = 2.55x + 10.96
y = 2.64x + 9.92
y = 1.34x + 7.68
y = 2.25x + 10.64
0.1306
0.0921
0.0614
0.0070
0.0046
0.0137
0.0099
0.0031
0.9938
0.9939
0.9798
0.9644
0.9066
0.8459
0.9889
0.8800
A2-3
A3-3
> sulfoxide-containing compound, CH3 > Cl for R1, and CH3
>
A4-1
C2H5 for R2.
A6-1
To further study the mechanism of the novel sulfide-containing
insecticidal compounds, the effects on the calcium channels of
high bioactive compounds A2-3 and A6-3 were tested by using
central neurons isolated from third-instar larvae of M. separata
with the calcium imaging technique after neuron loading with
A6-2
A6-3
Chlorantraniliprole
fluo-3 AM. Fig. 3 showed the change in [Ca2+
] versus recording
i
time when the central neurons were treated with A2-3, A6-3 and
chlorantraniliprole in the absence of extracellular calcium. There
are two intracellular calcium release channels in neurons named
IP3 receptor (IP3R) and RyR. Free calcium could be released from
calcium stores via RyR or IP3R into the endoplasmic reticulum. 2-
Aminoethoxydiphenyl borate (2-APB) as IP3R antagonist has been
used as blocker to probe aspects of calcium signaling. According
activity of the compounds against P. xylostella was similar to that
against M. separata, that is, smaller substituents in R2 produce bet-
ter bioactivity-CH3 > C2H5 > CH(CH3)2. However, when R1 was
fixed as CH3, the tested compounds with CH2CF3 or CH2CO2CH3 of
R2 almost possessed better bioactivity than those with CH3, C2H5
and CH(CH3)2, which indicates a R2 group with weaker electron-
donating ability may be favorable for the bioactivity improvement
of such kind of structures. Noticeably, all the compounds had fa-
vorable larvicidal activity when R1 = Cl and R2 = CH3, showing a
lethality rate of 40%–80% at 0.01 mg/L. When R2 was fixed as CH3,
the bioactivity sequence corresponding to substituent R1 was Cl >
CH3. Moreover, compounds A2-2, A2-3, A3-3, A4-1, A6-1, A6-2 and
A6-3 were further tested lethal concentration 50% (LC50) values to-
wards P. xylostella and the results are shown in Table 3. These com-
pounds possessed LC50 value of 0.0046–0.1306 mg/L, higher than
that of control chlorantraniliprole (0.0031 mg/L); among which,
thioether-containing compound A6-1 with LC50 value of 0.0046
mg•L−1 exhibited as the best insecticide, and had a great poten-
tial for further investigation.
to the experiment results, it was found that the peaks of [Ca2+
]
i
were all increased by treating the tested compounds with 5 mg/L
A2-3 and A6-3 (Fig. 3A and C). These results demonstrated that
the novel compounds could activate the calcium channels in the
central neurons of the third-instar larvae of M. separata. For fur-
ther study which is the main channel to release the calcium, RyR
or IP3R blocker was used to preincubate the neurons about 5
min. The experiments showed that within the error range, the in-
creasing of calcium had little effect after the blocking agents used
(Fig. 3B and D). Therefore, ryanodine receptor in the central neu-
rons of M. separata is the possible target—that is, these novel com-
pounds may have the same target as that of chlorantraniliprole.
In summary, a series of novel sulfide-containing amide deriva-
tives A were efficiently synthesized via a strategy of modifying
the “amide” structure of anthranilic diamide insecticides, and their
structures were identified by melting points, 1H NMR, 13C NMR,
19 F NMR and elemental analysis or HRMS. The molecular struc-
tures of A2-3 and A4-5 were further confirmed by the X-ray single-
crystal diffraction analysis and firstly reported. The bioassay re-
sults showed that most of the compounds A possess moderate
to high insecticidal activities. Especially, some sulfone-containing
compounds exhibited favorable bioactivities, e.g., compounds A2-
3, A3-3 and A6-3 not only possessed high lethality rate against P.
xylostella (50%–100%) at 0.1 mg/L, but also held good insecticidal
activities towards a variety of agricultural pests such as M. sepa-
rata, C. pipiens pallen, H. armigera and O. nubilalis. It is worth noting
that the larvicidal activity towards P. xylostella for partial thioether-
Partial compounds with favorable activities in preliminary
screening were selected to further test their insecticidal activities
against C. pipiens pallens, H. armigera and O. nubilalis, and the re-
sults are shown in Table 4. We can see that towards C. pipiens pal-
lens, the tested compounds showed high insecticidal activity (95%–
100%) at 25 mg/L; however, when decreasing the test concentra-
tion to 10 mg/L, the compounds showed only moderate insectici-
dal activity (15%–55%). When fixing R1 as CH3, the insecticidal ac-
tivity of sulfone-containing compounds displayed a trend of C2H5
[A3-3, (55
while, when R2 was fixed as CH3, the insecticidal activity trend of
R1 was CH3 [A2-3, (40 0)%] > Cl [A6-3, (15 3)%] for sulfone-
containing compounds. Moreover, it also showed an activity trend
of sulfoxide-containing compound [A2-2, (50 2)%] > sulfone-
containing compound [A2-3, (40 0)%], when both bearing CH3
1)%] > CH3 [A2-3, (40
0)%] for R2 group. Mean-
containing compounds [A4-1: (80
0)%; A6-1: (80
1)%] was
for R1 and R2. All the four tested compounds displayed favorable
larvicidal activities (95%–100%) towards H. armigera and O. nubi-
lalis at 200 mg/L. In particular, sulfone-containing compounds A2-
3 and A6-3 held lethality rate of 97%–100% at 100 mg/L, show-
ing as the best insecticides among the four compounds. At lower
close to that of chlorantraniliprole [(85
1)%] at 0.01 mg/L. The
calcium imaging experiments revealed that the highly insecticidal
A2-3 and A6-3 as the representative compounds are potential RyR
modulators. In addition, the structure–activity relationships were
Table 4
Insecticidal activities of partial compounds A against C. pipiens pallens, H. armigera and O. nubilalis.
Compd.
Larvicidal activity (%) at a concentration of (mg/L)
C. pipiens pallens H. armigera
O. nubilalis
25
10
200
100
50
200
100
50
A2-2
100
97
50
2
0
1
3
97
3
40
3
n.t.∗
35
95
5
10
10
2
n.t.
25
A2-3
3
40
100
95
98
10
2
1
3
100
100
98
98
2
A3-3
100
95
55
5
2
10
n.t.
30
20
0
n.t.
15
A6-3
5
2
15
98
100
97
2
3
97
3
3
2
Chlorantraniliprole
98
100
100
3
100
97
100
98
∗
n.t.: not test.
6