Design, synthesis and anti-TMV activities of novel chromone derivatives containing dithioacetal moiety

Article abstract of DOI:10.1016/j.bmcl.2019.126945

Thirty-five novel chromone derivatives containing dithioacetal moiety were designed, synthesized, and their anti-TMV activities were evaluated through half-leaf method. The results showed compound c23 illustrates highly curative, protective and inactivating activities against TMV at 500 mg/L, with the values of 68.8%, 58.8%, 86.0% respectively, which were superior to that of Ribavirin (42.3%, 49.8%, 68.4%, respectively) and similar to that of Ningnanmycin (59.4%, 52.4%, 88.4%, respectively). The EC₅₀ value of inactivating activities of compound c23 is 9.3 mg/L, which was better than that of Ribavirin (135.2 mg/L), and equivalent to that of Ningnanmycin (8.8 mg/L). Furthermore, compound c23 can destroy the integrity of TMV-CP, resulting in reduced infectivity of TMV. Meanwhile, compound c23 can combine with TMV protein coat and hydrolyze TMV protein coat to impact the process of self-assembling of TMV, with the association constant (K_d) 4.5 mg/L. This finding suggests that chromone derivatives containing dithioacetal moiety can be used as new antiviral agent.

Full text of DOI:10.1016/j.bmcl.2019.126945

Journal Pre-proofs
Design, Synthesis and Anti-TMV Activities of Novel Chromone Derivatives
Containing Dithioacetal Moiety
Miao Li, Ningning Zan, Maoxi Huang, Donghao Jiang, Deyu Hu, Baoan Song
PII:
S0960-894X(19)30931-X
https://doi.org/10.1016/j.bmcl.2019.126945
BMCL 126945
DOI:
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
16 November 2019
21 December 2019
28 December 2019
Please cite this article as: Li, M., Zan, N., Huang, M., Jiang, D., Hu, D., Song, B., Design, Synthesis and Anti-TMV
Activities of Novel Chromone Derivatives Containing Dithioacetal Moiety, Bioorganic & Medicinal Chemistry
Letters (2019), doi: https://doi.org/10.1016/j.bmcl.2019.126945
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Design, Synthesis and Anti-TMV Activities of Novel Chromone
Derivatives Containing Dithioacetal Moiety
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Miao Li, Ningning Zan, Maoxi Huang, Donghao Jiang, Deyu Hu, Baoan Song*
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State Key Laboratory Breeding Base of Green Pesticide and Agricultural
Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering,
Ministry of Education, Guizhou University, Huaxi District, Guiyang 550025, China.
*Address of the corresponding author
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Fax: 0086-851-88292170; E-mail: basong@gzu.edu.cn.

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ABSTRACT: Thirty-five novel chromone derivatives containing dithioacetal moiety
were designed, synthesized, and their anti-TMV activities were evaluated through
half-leaf method. The results showed compound c23 illustrates highly curative,
protective and inactivating activities against TMV at 500 mg/L, with the values of
68.8%, 58.8%, 86.0% respectively, which were superior to that of Ribavirin (42.3%,
49.8%, 68.4%, respectively) and similar to that of Ningnanmycin (59.4%, 52.4%,
88.4%, respectively). The EC50 value of inactivating activities of compound c23 is 9.3
mg/L, which was better than that of Ribavirin (135.2 mg/L), and equivalent to that of
Ningnanmycin (8.8 mg/L). Furthermore, compound c23 can destroy the integrity of
TMV-CP, resulting in reduced infectivity of TMV. Meanwhile, compound c23 can
combine with TMV protein coat and hydrolyze TMV protein coat to impact the
process of self-assembling of TMV, with the association constant (Kd) 4.5 mg/L. This
finding suggests that chromone derivatives containing dithioacetal moiety can be used
as new antiviral agent.
KEYSWORDS: chromone derivatives, dithioacetal moiety, anti-TMV activities,
mechanism

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Plant virus disease can cause seriously damage to global agricultural industry.
Tobacco mosaic virus (TMV) as a paradigm in virology can infect more than 400
species of plants belonging to 36 families1-3, which causes huge economic losses and
food security pressures4. Ningnanmycin and Ribavirin are the most widely used
antiviral agents, while there are disadvantages of them. For example, Ningnanmycin
shows 52.4% curative effect at 500 mg/L in vivo but lose activity in the field.
Ribavirin as a plant viral inhibitor, its antiviral activities are poor (inhibitory activity
is lower than 50.0% at 500 mg/L in vivo). In fact, there is no super chemical pesticide
that can completely inhibit TMV including Ningnanmycin and Ribavirin5. Hence the
controlling of TMV may open the way to effective treatment of phytoviruses.
Natural products are extremely important resources of drug development.
Chromones are benzoannelated γ-pyrone heterocyclic compounds that widely exists in
nature, especially in plants. Chromone has attracted a lot of interest from researcher in
recent years because of its extensive biological activity, such as anti-inflammatory,
antimicrobial, antitumor, antidiabetic and antioxidant6-9. Many chromone derivatives
were reported to possess superior anti-TMV activity. However, they are generally
natural source products that are difficult to be commercialized10-14(Fig. 1). Until now,
simple chromones have been an up-and-coming area of exploration because of their
interesting biological activities or from a synthetic point of view. In addition, many
antivirus mechanism studies of chromone derivatives are about the interaction
between chromone derivatives and human viral protein but seldomly involve in plant

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virus15. Therefore, the mechanism of anti-TMV action of chromone derivatives needs
further investigation.
Our group reported that dithioacetal has anti-plant virus activities for the first time,
finding xiangcaoliusuobingmi had brilliant anti-plant virus activities 16. And we found
that the dithioacetal derivatives C14 and C24 (Fig. 2) with antiviral activities against
TMV were synthesized17,18, however, the inhibitory activities of the compounds were
limited for development of new antiviral agent. Considering that chromone and
dithioacetal group both have potential anti-TMV activity, we intend to combine
chromone with dithioacetal (Fig. 2) by using active compound derivatization method
to obtain a series of target compounds c1-c35 (Fig. 3). We systematically evaluated
their anti-TMV activities and studied its anti-TMV mechanism.
HO
O
O
O
O
O
O
O
O
O
O
O
OH
HO
N
OH
HO
O
OH
OH
O
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Fig. 1. Antitobacco mosaic virus agents from natural sources.
O
O
CHO
HO
O
O
R2
S
O
O
S
Chromone
HO
R2
R1
O
Cl
S
c1-c35
O
O
S
S
O
Br
O
O
O
N
S
HO
O
C24
C14
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Fig. 2. Design of the target compounds

R2
S
O
O
O
S
O
R2
CHO
R1Cl
R2SH
POCl3
R1
R1
R1
DMF;450
C
.
O
OH
K2CO3; ACN; 58oC
O
O
O
NaHSO4 SiO2
O
HO
OH
c1-c30
b1-b6
a1-a6
POCl3
DMF;450C
R2
S
O
O
O
R2
CHO
R2SH
S
HO
HO
O
NaHSO4 SiO2
b7
c31-c35
c1: R1= 4-Chlrobenzyl; R2= CH2CH3;
c2: R1= 4-Chlrobenzyl; R2= CH(CH3)2;
c3: R1= 4-Chlrobenzyl; R2= CH2CH2CH3;
c4: R1= 4-Chlrobenzyl; R2= C(CH3)3;
c5: R1= 4-Chlrobenzyl; R2= CH2CH2CH2CH2CH3;
c6: R1= Benzyl; R2= CH2CH3;
c7: R1= Benzyl; R2= CH(CH3)2;
c8: R1= Benzyl; R2= CH2CH2CH3;
c9: R1= Benzyl; R2= C(CH3)3;
c13: R1= 4-Methylbenzyl; R2= CH2CH2CH3;
c14: R1= 4-Methylbenzyl; R2= C(CH3)3;
c15: R1= 4-Methylbenzyl; R2= CH2CH2CH2CH2CH3;
c16: R1= 2-Chlrobenzyl; R2= CH2CH3;
c17: R1= 2-Chlrobenzyl; R2= CH(CH3)2;
c18: R1= 2-Chlrobenzyl; R2= CH2CH2CH3;
c19: R1= 2-Chlrobenzyl; R2= C(CH3)3;
c20: R1= 2-Chlrobenzyl; R2= CH2CH2CH2CH2CH3;
c21: R1= 4-Fluorobenzyl; R2= CH2CH3;
c22: R1= 4-Fluorobenzyl; R2= CH(CH3)2;
c23: R1= 4-Fluorobenzyl; R2= CH2CH2CH3;
c24: R1= 4-Fluorobenzyl; R2= C(CH3)3;
c25: R1= 4-Fluorobenzyl; R2= CH2CH2CH2CH2CH3;
c26: R1= 4-Bromobenzyl; R2= CH2CH3;
c27: R1= 4-Bromobenzyl; R2= CH(CH3)2;
c28: R1= 4-Bromobenzyl; R2= CH2CH2CH3;
c29: R1= 4-Bromobenzyl; R2= C(CH3)3;
c30: R1= 4-Bromobenzyl; R2= CH2CH2CH2CH2CH3;
c31: R2= CH2CH3;
c32: R2= CH(CH3)2;
c33: R2= CH2CH2CH3;
c34: R2= C(CH3)3;
c35: R2= CH2CH2CH2CH2CH3;
c10: R1= Benzyl; R2= CH2CH2CH2CH2CH3
c11: R1= 4-Methylbenzyl; R2= CH2CH3;
c12: R1= 4-Methylbenzyl; R2= CH(CH3)2;
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Fig. 3. The synthesis route of target compound c1-c35.
The activity of the target compounds towards TMV is listed in Table 1. As we see,
most of target compounds show better inhibitory activity (activities mentioned in
table.1) than Ribavirin (49.8%, 42.3%, 68.4%). Besides, the EC50 values of
inactivating activities of some compounds were superior to that of Ribavirin (135.2
mg/L). Furthermore, the protective effect of c1, c6, c14, c23 and c30 (60.2%, 63.3%,
61.7%, 68.8% and 61.5%, respectively) were better than that of Ningnanmycin
(59.4%). The curative effect of c7, c8, c10, c17, c19, c23, c27, c33, c35 (55.2%,
58.3%, 56.4%, 63.4%, 56.2%, 57.9%, 58.8%, 60.7% and 53.2% respectively) were
better than that of Ningnanmycin (52.4%). The inactivating effect of c6, c23, c24 and
c34 (83.8%, 86.0%, 80.0% and 86.9%, respectively) were equivalent to that of
Ningnanmycin (88.4%). The EC50 of inactivating activities of c23 (9.3 mg/L) was
equivalent to that of Ningnanmycin (8.8 mg/L).

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Table 1. Antiviral activities of target compounds c1-c35 against TMV in vivo.
EC50 for TMV
inactivating
activitya（mg/L）
protective
activitya（%） activitya（%）
curative
inactivating
activitya（%）
Compd.
c1
60.2±6.6
23.1±3.4
45.8±3.3
42.7±5.5
38.6±1.4
63.3±4.9
43.4±1.4
49.2±4.3
37.9±1.1
58.3±0.5
47.5±0.2
40.3±6.3
33.8±3.9
61.7±2.9
39.4±5.3
43.4±5.3
42.4±0.9
38.9±2.2
39.9±3.5
39.4±5.3
58.1±4.9
39.4±5.3
68.8±3.7
46.1±3.4
47.1±6.5
47.3±5.4
57.1±5.2
55.0±4.1
47.1±4.8
61.5±1.5
43.6±4.1
45.7±4.3
30.6±6.9
20.3±3.5
43.3±4.1
42.3±2.3
59.4±5.8
51.5±3.7
50.6±2.8
43.5±4.7
44.0±6.6
43.5±4.3
49.3±4.8
55.2±3.1
58.3±5.6
37.4±6.7
56.4±2.4
52.0±2.0
63.4±2.6
38.0±4.7
34.3±6.1
47.6±5.9
50.1±5.1
56.2±3.7
31.5±6.0
57.9±2.6
45.5±4.0
42.0±4.7
46.2±0.9
58.8±2.1
27.5±4.4
54.7±3.9
50.8±2.0
52.8±4.8
35.9±2.6
52.8±1.1
38.1±4.8
39.8±5.2
47.8±5.0
60.7±3.0
41.7±5.5
53.2±4.7
49.8±3.2
52.4±3.9
64.6±6.1
53.4±4.2
76.2±3.9
57.1±4.8
70.1±4.9
83.8±3.5
68.3±6.1
55.7±3.7
55.5±4.3
62.0±2.6
58.4±2.8
61.9±0.9
60.9±3.5
63.9±3.1
58.6±5.5
61.9±4.1
78.1±4.3
50.4±1.1
64.9±4.3
62.0±4.2
53.2±3.8
59.0±2.4
86.0±0.8
80.0±1.4
78.4±3.3
57.4±5.7
52.2±1.5
67.1±5.4
69.6±5.4
58.4±4.0
64.6±4.0
73.0±3.3
75.1±3.9
86.9±2.0
70.0±1.0
68.4±1.4
88.4±2.5
161.4±2.1
317.8±1.5
79.5±2.9
243.8±2.1
115.0±2.5
26.1±4.1
137.3±3.5
198.6±2.8
290.7±1.8
180.2±2.1
226.3±1.5
183.1±2.3
200.4±1.4
168.2±2.5
223.3±2.3
188.8±2.0
66.2±2.9
373.1±2.5
166.6±2.4
183.2±2.7
315.7±2.2
218.4±2.2
9.3±3.9
c2
c3
c4
c5
c6
c7
c8
c9
c10
c11
c12
c13
c14
c15
c16
c17
c18
c19
c20
c21
c22
c23
c24
54.3±5.5
65.6±2.7
238.3±3.0
338.4±1.4
145.7±2.8
128.4±2.3
225.8±3.2
170.6±2.5
102.7±1.8
88.4±2.6
11.0±3.0
120.4±3.2
135.2±1.3
8.8±2.9
c25
c26
c27
c28
c29
c30
c31
c32
c33
c34
c35
Ribavirinb
Ningnanmycinb
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Footnotes: a average of three replicates; bNingnanmycin and Ribavirin was used as the control.

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The TEM image was gained by using FEI Talors F200C made by America. We can
see the granular morphology of TMV (Fig. 4A) is straight, well-proportioned,
rod-shaped and some of them are array regularly. The treated TMV particles interact
with compound c23 for 30 min (Fig. 4D). The morphology of TMV granular became
smaller, shorter and arrayed in messy. TMV particles interact with negative control
Ningnanmycin for 30 min (Fig. 4B). The change of morphology of TMV granular was
just as same as the change mentioned above. TMV particles were broken after
interacting with Ribavirin (Fig. 4C), but the fracture of TMV particles is not serious to
c23 and Ningnanmycin. The change of morphology of TMV was possibly due to the
ability of small molecule which can crush the interaction between coat protein
subunits. Resulting in breaking viral particle, loosing structure and disordered
arrangement.
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Fig. 4. The effect on the morphology of TMV particles of compounds CK (A), Ningnanmycin +

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TMV(B), Ribavirin+ TMV (C), c23+ TMV (D).
Molecular docking studies (Fig. 5) for compound c23 with TMV-CP (PDB
code:1EI7) have shown that the compounds had the ability of embedding between the
two subunits of TMV-CP19 (ASP219, LYS253, GLU222, VAL251, LYS268,
PRO254, VAL75, SER138, TYR139). As we know, there are 2130 coat protein
subunits in TMV structure. These subunits contact each other by the forming
non-covalent. For this kind of special bonding model multiple replication finally
resulted in TMV's symmetrical structure20. Therefore, coat protein subunits played a
critical role in self-assembly of TMV. As we see, the result shown in molecular
docking on the software of Discovery Studio 4.5. ASP219 showed strong hydrogen
bond interaction with compound c23. Following is LYS253, also showed hydrogen
bond with c23. Others coat protein subunits can bind with c23 through a variety of
ways as well. The interaction of these two subunits of TMV-CP was probably weaken
by the interaction between small molecular and TMV-CP leading to the TMV particle
would be unable to self-assembly. The result of Molecular docking studies of
compound c23 with TMV-CP suggests that compound c23 can influence the process
of replication of TMV. This influence may be the reason that compound c23 possess
excellent antiviral activity.
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Fig. 5. Molecule docking results of compounds c23 (A-C).
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To study the combine capacity of the target compound to TMV-CP, the binding
constant (Kd) was performed via MST and the results were listed in Table. 2 and Fig.
6. The results evidence that c23 which showed excellent activity towards TMV in
vivo also showed excellent activity towards TMV in vitro. The Kd = 4.5 ± 1.3 μM.
The Kd of compound c23 is similar to Ningnanmycin (Kd= 4.9± 2.2 μM). Ribavirin
showed moderate bonding ability with TMV-CP. The Kd = 134.9±54.5 μM. The
activity in vitro results as determined by MST are consistent with the activity in vivo.
Table 2 Interaction results of the commercial antiviral agents and c23 with TMV CP
EC50 for TMV inactivating activity a
Compd.
Kd a (μM)
（mg/L）
c23
4.5±1.3
9.3±3.9
Ribavirinb
134.9±54.5
4.9±2.2
135.2±1.3
8.8±2.9
Ningnanmycinb
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Footnotes: aaverage of three replicates; bNingnanmycin and Ribavirin was used as the control.
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Fig. 6 Microscale thermophoresis (MST) test results of compound c23 (A), Ribavirin (B),

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Ningnanmycin (C).
In this study, a series of chromone derivatives containing dithioacetal moiety were
designed and synthesized. The bioassay indicated that the great majority of target
compounds show good anti-TMV activities at 500 mg/L in vivo. Among them,
compound c23 shows excellent inactivating activities to TMV, with EC50 value of 9.3
mg/L. therefore, c23 was selected as a new lead for further mechanism studies.
Compound c23 can bind with coat protein subunits (ASP219 and LYS253) in a strong
hydrogen bonding mode by molecular docking software simulating. This bonding
destroys the integrity of TMV and leads it lose its infectivity. The binding constant Kd
was obtained in MST, with the value of 4.5μM. Besides, the granular morphology of
TMV was suffered substantial fracture after reacting with compound c23 under TEM
observation. The results suggest that Chromone derivatives containing dithioacetal
were important substructure for the novel pesticide development. This finding could
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be important foundation and basis for the research of antiviral agents.
Acknowledgement
This work has received the financial support of the National Natural Science
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Foundation of China (No. 21732002).
Supporting Information
1
The synthesis, physical analysis, H NMR spectra, 13C NMR spectra and high
resolution mass spectrum (HRMS) of compounds c1-c35 can be found in the
supplementary data.
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1. Thirty-five novel chromone derivatives containing dithioacetal moiety were
designed and synthesized.
2. Novel chromone derivative c23 with excellent anti-TMV was synthesized.
3. The mechanism to TMV of chromone derivatives were reported for the first time.
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Declaration of interests
☑ The authors declare that they have no known competing financial interests or personal
relationships that could have appeared to influence the work reported in this paper.
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☐The authors declare the following financial interests/personal relationships which
may be considered as potential competing interests:

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