Synthesis and anti-neuroinflammatory activity of N-heterocyclic analogs based on natural biphenyl-neolignan honokiol

Article abstract of DOI:10.1016/j.bmcl.2018.11.014

Novel isoxazole and pyrazole analogs based on natural biphenyl-neolignan honokiol were synthesized and evaluated for their inhibitory activities against nitric oxide production in lipopolysaccharide-activated BV-2 microglial cells. The isoxazole skeleton

Full text of DOI:10.1016/j.bmcl.2018.11.014

Accepted Manuscript
Synthesis and anti-neuroinflammatory activity of N-heterocyclic analogs based
on natural biphenyl-neolignan honokiol
Yue Yuan, Lalita Subedi, Daesung Lim, Jae-Kyung Jung, Sun Yeou Kim,
Seung-Yong Seo
PII:
S0960-894X(18)30879-5
https://doi.org/10.1016/j.bmcl.2018.11.014
BMCL 26125
DOI:
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
28 August 2018
2 November 2018
8 November 2018
Please cite this article as: Yuan, Y., Subedi, L., Lim, D., Jung, J-K., Kim, S.Y., Seo, S-Y., Synthesis and anti-
neuroinflammatory activity of N-heterocyclic analogs based on natural biphenyl-neolignan honokiol, Bioorganic
& Medicinal Chemistry Letters (2018), doi: https://doi.org/10.1016/j.bmcl.2018.11.014
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Graphical Abstract
To create your abstract, type over the instructions in the template box below.
Fonts or abstract dimensions should not be changed or altered.
Synthesis
and
anti-neuroinflammatory
Leave this area blank for abstract info.
activity of N-heterocyclic analogs based on
natural biphenyl-neolignan honokiol
Yue Yuan, Lalita Subedi, Daesung Lim, Jae-Kyung Jung, Sun Yeou Kim*, Seung-Yong Seo*

Bioorganic & Medicinal Chemistry Letters
Synthesis and anti-neuroinflammatory activity of N-heterocyclic analogs based
on natural biphenyl-neolignan honokiol
Yue Yuana,†, Lalita Subedia,†, Daesung Lima, Jae-Kyung Jungb, Sun Yeou Kima,, Seung-Yong Seoa,
aCollege of Pharmacy, and Gachon Institute of Pharmaceutical Sciences, Gachon University, Incheon 21936, Republic of Korea
bCollege of Pharmacy, Chungbuk National University, Cheongju, Chungbuk 28644, Republic of Korea
ARTICLE INFO
ABSTRACT
Article history:
Received
Revised
Accepted
Available online
Novel isoxazole and pyrazole analogues based on natural biphenyl-neolignan
honokiol were synthesized and evaluated for their inhibitory activities against nitric
oxide production in lipopolysaccharide-activated BV-2 microglial cells. The isoxazole
skeleton was constructed via nitrile oxide cycloaddition from oxime 3 and pyrazole
was generated by condensation of 4-chromone and alkylhydrazine. Among the
analogs, 13b and 14a showed stronger inhibitory activities with IC50 values of 8.9 and
1.2 µM, respectively, than honokiol.
Keywords:
honokiol
biphenyl-neolignan
isoxazole
pyrazole
2018 Elsevier Ltd. All rights reserved.
anti-neuroinflammatory activity
Chronic neuroinflammation induced by activated microglia is
the major cause of neurodegenerative disorders such as
outgrowth in serum-free medium supplemented with B27 and
significantly enhanced neuron survival and growth in serum-free
medium supplemented with N2. We previously reported the
efficient synthesis of biphenyl-neolignans and novel anti-
inflammatory effects of their analogs.6,7 Recently, Kim et al.
demonstrated that the natural neolignan balanophonin delayed
the progression of neuronal cell death by inhibiting NO
production in lipopolysaccharide (LPS)-mediated activated BV2
cells by suppressing iNOS expression.8 Structurally, honokiol
(1) and 4′-O-methylhonokiol (2) consist of a 5,3′-diallyl-
biphenyl skeleton bearing a combination of hydroxy or
methoxy groups on C2 of the A ring and C4′ of the B ring.
Although numerous studies have examined biphenyl-
neolignan derivatives, few studies have evaluated heterocyclic
substituents in the A or B ring of a biphenyl-neolignan.9
Neolignans were reported to have poor absorption, high
systemic clearance, and low oral bioavailability, although they
were potentially effective for treating CNS disorders.10 For
therapeutic use, chemical modifications can be used to
increase neuroprotective activity and optimize the
Parkinson’s disease and Alzheimer’s disease, as well as ischemic
brain diseases.1,2 Microglia are the primary immune cells that
play a crucial role in the innate immune response in the normal
brain and central nervous system (CNS).3 Although activated
microglia scavenge dead cells from the CNS and secrete different
neurotrophic factors for neuronal survival, severe activation
causes various autoimmune responses leading to neuronal cell
death and brain injury. Activated microglia promote neuronal
injury by releasing proinflammatory and cytotoxic factors,
including tumor necrosis factor-α, nitric oxide (NO), inducible
nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2).
Thus, inhibition of NO production in activated microglia may be
effective for treating neurodegenerative disorders.
The natural products biphenyl-neolignans honokiol (1) and
4′-O-methylhonokiol (2) were isolated from Magnolia
officinalis and have been reported to exert a wide range of
biological and pharmacological effects, including anti-
inflammatory, anti-allergic, anti-cancer, anti-osteoclastogenic,
anti-bacterial, anti-thrombotic, anti-depressant, and anti-
neurodegenerative activities4 (Figure 1). Among these
biological activities, the neuroprotective and neurotropic
effects of honokiol and its related analogs are regarded as a
major characteristic.5 For instance, honokiol was shown to have
neurotrophic activity in cultures of rat cortical neurons at
physicochemical properties of CNS drugs. Our focuses on the
synthesis and medicinal chemistry of biphenyl-neolignan;
here, we describe the synthesis and biological evaluation of
two heterocyclic analogs with isoxazole and pyrazole
scaffolds as novel neuroprotective agents. In this study, we
investigated the inhibitory activities of isoxazole and pyrazole
derivatives on NO production and iNOS and COX-2 expression
concentrations of 0.1 ~ 10 µM. Honokiol promoted neurite
———
 Corresponding author. Tel.: +82-32-820-4949; fax: +82-32-820-4829. E-mail: syseo@gachon.ac.kr (S.-Y.S.) and sunnykim@gachon.ac.kr
(S.Y.K.). † These authors have contributed equally to the preparation of this manuscript

in LPS-activated BV-2 cells.
Figure 1. Structure of natural biphenyl-neolignans honokiol and 4-O'-
methylhonokiol.
The goal of this work was to improve the neuroprotective
activity and physicochemical properties, such as metabolic
stability and membrane permeability of the blood-brain barrier,
of honokiol.11 Therefore, we introduced an intramolecular
hydrogen bond between the phenol group on the A ring and a
neighboring moiety to reduce metabolic changes. Honokiol
analogs with an N-heterocycle as a surrogate for the B ring of
biphenyl-neolignans have been reported previously. To
identify, anti-neuroinflammatory agents based on biphenyl-
neolignan, both isoxazole and pyrazole were used as N-
heterocyclic scaffolds to replace the B ring. (Figure 2) To
decrease lipophilicity (clogP and t-PSA values), an
alkoxymethyl group and a piperazinylmethyl group were
incorporated at the C5 position of isoxazole. Using pyrazole
analogs, N-allyl, benzyl, and phenyl were introduced to
replace the allyl group in the B ring. The effect of these
changes on the methoxy group in the A ring was examined to
determine their structure-activity relationship.
Scheme 1. Synthesis of isoxazole analogs
To synthesize pyrazole analogs, condensation of mono-
substituted hydrazine and 6-bromo-4-chromone was conducted as
shown in Scheme 2.6b,12 Allylhydrazine was prepared using our
previously described method and benzylhydrazine and
phenylhydrazine were commercially available. 6-Bromo-4-
chromone was reacted with three hydrazines at 100 °C to afford
the pyrazoles (11a-11c). O-methylation of 11a-11c using MeI and
K2CO3 generated the aryl bromides (12a-12c), after which Stille
cross-coupling of 12a-12c with allyltributyltin and Pd(PPh3)4
afforded allylated products (13a-13c), respectively, in good yield.
Despite the slightly lower yield than that observed in the
synthesis from 12a-12c, 11a-11c containing a phenolic group
were directly converted to the desired pyrazole analogs (14a-14c).
Catalytic hydrogenation of 14a-14c afforded the saturated
compounds (15a-15c) along with the benzylated compound 15e.
In the same manner, 11a was treated with vinyltributyltin and
Pd(PPh3)4 to afford 14d, which was reduced to 15d under
catalytic hydrogenation.
The inhibitory activities of isoxazole and pyrazole analogs on
iNOS-mediated NO production were evaluated in LPS-activated
BV-2 cells stimulated with 100 ng/mL LPS in the presence or
absence of samples for 24 h. The nitrite level was measured in
the culture media using Griess reagent (1% sulfanilamide and
0.1% N-1-napthylethylenediamine dihydrochloride in 5%
phosphoric acid). For this reaction, 50 μL of the supernatant was
mixed with an equal volume of the Griess reagent and the OD
was measured at 570 nm. NG-Mono-methyl-L-arginine (L-
NMMA), a well-known NO synthase (NOS) inhibitor, was used
as a positive control. Cell viability was measured using the 3-
(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide
(MTT) assay.8
Figure 2. Design of biphenyl-neolignan heterocyclic analogs based on
honokiol and 4′-O-methylhonokiol.
We previously reported the synthesis of honokiol analogs
starting with introduction of isoxazole as a unique surrogate of
the B ring in honokiol7a (Scheme 1). To prepared isoxazole
analogs, oxime (3), generated by treatment of commercially
available 5-bromo-2-methylbenzaldehyde with NH2OH was
converted to three isoxazoles via nitrile oxide cyclcoaddition
using three alkyne reagents; 1-pentyne, propargyl alcohol, and 1-
Boc-4-propargylpiperidine. Stille cross-coupling allylation of
isoxazoles (5a-5c) with allyltributyltin and Pd(PPh3)4 afforded
allylated compounds (6a-6c), followed by demethylation to
provide the desired phenols (7a-7b) in moderate yield. 5b was
treated with NaH and alkyl halide to afford O-alkylated products
(8a-8c), followed by the Stille cross-coupling allylation to afford
allylated products (9a-9c) containing 2-ethoxy-2-oxoethyl, allyl,
and benzyl groups, respectively. The Boc group was removed
from 6c in trifluoroacetic acid-mediated condition and
subsequently three alkyl groups were introduced onto the
nitrogen at the opposite site by N-alkylation using ethyl
bromoacetate, allyl bromide, and benzyl bromide, respectively, to
afford N-alkylated products (10a-10c).

L-NMMA (IC50 = 26.6 µM) and shogaol (IC50 = 5.59 µM).13 Two
derivatives, 14b and 14c which have a benzyl and phenyl group
as N-substituents, showed decreased activity compared to 14a.
Replacement of allyl with vinyl decreased the NO inhibitory
activity with an IC50 = 30.5 µM. The compounds saturated by
reducing the allyl or vinyl group (15a-15e) showed no inhibitory
activity. 13b and 14a showed slight cytotoxicity at 20 μM, but no
cytotoxicity at less than 10 μM (Figure 3(b)).
Table 1. Inhibitory effect of isoxazole compounds on NO
production and viability of LPS-activated BV-2 cells.
a
IC50
Cell viability
(%) b
Compound
R
-
R'
-
cLogP
-
(µM)
L-NMMAc
26.6
17.0
52.3
>200
>200
94.4±4.2
118.4±5.0
115.1±2.7
97.9±2.7
94.1±4.5
-
-
4.49
5.16
3.95
1.59
1
-
-
2
Br
Br
5a
5b
Scheme 2. Synthesis of pyrazole analogs.
The inhibitory effect of the synthesized isoxazole analogs on
NO production is shown in Table 1. The intermediates 5c-5c with
a C5-bromide in the A ring showed no inhibitory activity. The
inhibitory activity of C5-allylated compounds (6a-6c and 7a-7b)
was not improved, although 6c showed weak activity. The
inhibitory activity of isoxazole analogs with an O-alkylated and
N-alkylated on C5 position of the isoxazole ring was evaluated.
Among the alkoxymethyl derivatives, bromide compounds (8a-
8c) showed no inhibitory activity, while allylated compounds (9a
and 9b) showed moderate activity with IC50 = 25.9 and 28.7 μM,
respectively. Compared to 2-ethoxy-2-oxoethyl and the allyl
group, the benzyl group at the C5 position of isoxazole was not
favorable for activity. The piperazine derivatives (10a-10c)
showed no inhibitory activity. Most derivatives did not show any
cytotoxicity. The inhibitory activity of 9a and 9b was not as
strong as that of honokiol, but was similar to that of L-NMMA,
the positive control. These compounds exhibited better drug-like
properties as new agents for treating CNS-related diseases
compared to honokiol. The NO production inhibition by
isoxazole analogs was dependent on the C5-allyl substituent in
the phenyl ring and the O-alkylated analogs have potential
activity compared to the N-alkylated analogs at the C5 position of
isoxazole.
Br
>200
100.2±4.0
4.34
5c
>200
>200
98.2±3.7
4.08
1.72
6a
6b
120.4±5.9
76.9
117.3±8.7
4.48
6c
>200
>200
93.3±1.9
3.84
1.47
7a
7b
126.2±5.8
Br
>200
121.6±1.8
2.68
8a
Br
Br
90.4
94.6±5.2
3.06
3.78
8b
8c
>200
103.8±4.8
25.9
125.8±8.7
2.82
9a
The inhibitory activities of pyrazole analogs against iNOS-
mediated NO production from LPS-stimulated BV-2 cells are
listed in Table 2. We prepared three pyrazole derivatives with N-
allyl, benzyl, and phenyl groups. Based on the functional groups
on honokiol, the allyl and vinyl group were introduced at the C5-
position of the A ring. The C5-bromide intermediates (11a-11d
and 12a-12c) did not inhibit NO production regardless of the
presence or absence of the C2-methyl group in the A ring.
However, the allyl group at the C5 position in the A ring affected
the inhibitory activity. The C2-methoxy derivatives 13b and 13c
significantly inhibited NO production. Particularly, 13b strongly
inhibited NO production with an IC50 = 8.92 µM, which is nearly
2-fold as strong as that of honokiol. Unexpectedly, 14a, which
has two allyl groups at the C5 position of the phenyl ring and N1
position of the pyrazole ring, strongly inhibited NO production
with an IC50 = 1.2 µM, which is 14-fold stronger than that of
honokiol and much stronger than those of the known inhibitors,
28.7
141.0±9.3
144.7±5.9
3.19
3.91
9b
9c
>200
-
>200
93.2±3.0
3.72
10a
-
-
111
100.6±8.5
98.6±7.2
3.72
4.79
10b
10c
>200
a The IC50 value was defined as the concentration (µM) that caused 50%
inhibition of NO production in LPS-activated BV-2 cells; b Cell viability after
treatment with 20 µM of each compound was determined by the MTT assay.
The results are averages of three independent experiments, and the data are
expressed as mean ± SD; C L-NMMA was used as a positive control.

Table 2. Inhibitory effect of pyrazole compounds on NO prod
uction and viability of LPS-activated BV-2 cells.
of COX-2. These results suggest that inhibition of LPS-induced
NO production in BV-2 cells by compound 13b and 14a
occurred mainly through inhibition of iNOS and COX-2
expression.
(a)
a
Cell
IC50
Compound
11a
R
R'
Br
Br
viability
cLogP
3.36
(µM)
(%) b
111.73
112.8±5.2
109.3±8.0
>200
4.53
11b
Br
Br
>200
>200
107.4±5.1
92.2±2.4
4.54
3.51
11c
12a
(b)
Br
Br
>200
124.0±3.9
4.68
12b
>200
>200
121.8±1.7
109.0±2.9
4.70
3.62
12c
13a
68.6±14.5
4.78
13b
8.92
35.96
112.2±9.4
59.9±5.4
4.80
3.33
13c
14a
(c)
1.2
73
125.0±9.3
99.5±8.0
4.49
4.51
14b
14c
92.45
30.47
91.33
104.7±2.5
129.4±4.1
2.98
4.10
14d
15a
109.4
125.4±2.9
4.98
15b
(d)
116.06
>200
126.0±6.5
108.8±0.5
5.00
3.57
15c
15d
H
-
60.22
26.58
94.7±2.6
94.4±4.2
3.11
-
15e
L-NMMAc
-
a The IC50 value was defined as the concentration (µM) that caused 50%
inhibition of NO production in LPS-activated BV-2 cells; b Cell viability after
treatment with 20 µM of each compound was determined by the MTT assay.
The results are averages of three independent experiments, and the data are
expressed as mean ± SD; C L-NMMA was used as a positive control.
Figure 3. Role of 13b and 14a to inhibit nitrite production, expression of
inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) against
LPS-activated BV-2 cells. (a) Inhibitory effect of 13b and 14a on NO
production in LPS-activated BV-2 cells. (b) Effect of 13b and 14a on cell
viability. (c) Inhibitory effect of 13b and 14a on iNOS expression. (d)
Inhibitory effect of 13b and 14a on COX-2 expression. All data are presented
as the mean ± standard error of the mean of three independent experiments.
***P < 0.001 indicate significant differences compared with treatment with
LPS alone, while ###P < 0.001 indicate significant differences compared with
an untreated control group. Here Ctl is control, LPS is lipopolysaccharide. L-
NMMA was used as positive control.
Compounds 13b and 14a inhibited NO production in a dose-
dependent manner (Figure 3(a)). To further investigate the
mechanism of action of 13b and 14a, we evaluated the effect of
13b and 14a on iNOS protein and COX-2 enzyme expression in
LPS-activated BV-2 cells. As shown in Figure 3(c) and Figure 4,
compounds 13b and 14a strongly inhibited iNOS expression in a
dose-dependent manner. Particularly, 14a shows more potent
inhibition of iNOS. As shown in Figure 3(d) and Figure 4,
compounds 13b and 14a also showed strong dose-dependent
inhibition of COX-2. Similarly, 14a shows more potent inhibition

6. (a) Kwak, J.-H.; Cho, Y. A.; Jang, J.-Y. ; Seo, S.-Y. ; Lee,
H.; Hong, J. T.; Han, S.-B.; Lee, K.; Kwak, Y. -S.; Jung, J.-
K. Tetrahedron 2011, 67, 9401-9404. (b) Sun, W; Kim, T.
S.; Choi, N. S.; Seo, S.-Y. Bull. Korean Chem. Soc. 2018,
39, 126-129.
7. (a) Lee, B.; Kwak, J.-H.; Huang, S.-W.; Jang, J.-Y. ; Lim,
S.; Kwak, Y. -S.; Lee, K.; Kim, H. S.; Han, S.-B.; Hong, J.-
T.; Lee, H.; Song, S.; Seo, S.-Y. ; Jung, J.-K. Bioorg. Med.
Chem. 2012, 20, 2860-2868. (b) Kim, S.; Ka, S.-O; Lee,
Y. ; Park, B.-H.; Fei, X.; Jung, J.-K.; Seo, S.-Y. ; Bae, E. J.
PLoS One 2015, 10, e0117120.
Figure 4. Effect of compounds 13b and 14a on iNOS and COX-2 protein
8. Lim, S. Y.; Subedi, L.; Shin, D.; Kim, C. S.; Lee, K. R.;
Kim, S. Y. Biomol. Ther. 2017, 25, 519-527.
expression in LPS-stimulated BV-2 cells.
9. (a) Bernaskova, M.; Schoeffmann, A.; Schuehly, W.;
Hufner, A.; Baburin, I.; Hering, S. Bioorg. Med. Chem.
2015, 23, 6757-6762. (b) Taferner, B.; Schuehly, W.;
Huefner, A.; Baburin, I.; Wiesner, K.; Ecker, G. F.; Hering,
S. J. Med. Chem. 2011, 54, 5349-5361 (c) Schuehly, W.;
Paredes, J. M.V.; Kleyer, J.; Huefner, A.; Anavi-Goffer, S.;
Raduner, S.; Altmann, K. H.; Gertsch, J. Chem. Biol. 2011,
18, 1053-1064. (d) Schuhly, W.; Hufner, A.; Pferschy-
Wenzig, E.-M.; Prettner, E.; Adams, M.; Bodensieck, A.;
Kunert, O.; Oluwemimo, A.; Haslinger, E.; Bauer, R.
Bioorg. Med. Chem. 2009, 17, 4459-4465. (e) Kong, Z.-L.;
Tzeng, S.-C.; Liu, Y.-C. Bioorg. Med. Chem. Lett. 2005, 15,
163-166. (f) Kumar, A.; Singh, U. K.; Chaudhary, A.
Future Med. Chem. 2013, 5, 809-829.
In summary, we synthesized a series of 17 isoxazole and 18
pyrazole derivatives and evaluated their inhibitory effects on NO
production in LPS-activated BV-2 cells. Among the prepared
compounds, 13b and 14a inhibited NO production in LPS-
activated BV-2 cells by suppressing iNOS and COX-2 expression.
The pyrazole analog 14a was the most potent inhibitor. These
findings provide insight into the structural features influencing
biological activities of this class of compounds and provide a
foundation for further studies of analog design. Recently, retinoid
X receptor was studied as the only binding protein of honokiol
derivatives, although the various biological activities of honokiol
were well known.14 Our synthetic and medicinal chemistry work
would be exploited to design photoaffinity probes for target
identification using a forward chemical genetic approach.15
Further analysis of the mode of action and biological activity in
vivo of these pyrazole analogs as well as their potential as novel
drug candidates is underway.
10. Yu, H. E.; Oh, S. J.; Ryu, J. K.; Kang, J. S.; Hong, J. T.;
Jung, J.-K.; Han, S.-B.; Seo, S.-Y. ; Kim, Y. H.; Park, S.-K.;
Kim, H. M.; Lee, K. Phytother. Res. 2014, 28, 568-578.
11. Chiruta, C.; Schubert, D.; Dargusch, R.; Maher, P. J. Med.
Chem. 2012, 55, 378-389.
12. Xie, F.; Li, S.; Bai, D.; Lou, L.; Hu, Y. J. Comb. Chem.
2007, 9, 12-13.
Acknowledgement
13. Gaire, B. P.; Kwon, O. W.; Park, S. H.; Chun, K.-H.; Kim,
S. Y.; Shin, D.; Choi, J. W. PLoS One 2015, 10, e0120203.
14. (a) Kotani, H.; Tanabe, H.; Mizukami, H.; Makishima, M.;
Inoue, M. J. Nat. Prod. 2010, 73, 1332-1336. (b)
Scheepstra, M.; Nieto, L.; Hirsch, A. K.; Fuchs, S.; Leysen,
S.; Lam, C. V.; in het Panhuis, L.; van Boeckel, C. A.;
Wienk, H.; Boelens, R.; Ottmann, C.; Milroy, L. G.;
Brunsveld, L. Angew. Chem. Int. Ed. 2014, 53, 6443-6448.
(c) Scheepstra, M.; Andrei, S. A.; de Vries, R. M. J. M.;
Meijer, F. A.; Ma, J. N.; Burstein, E. S.; Olsson, R.;
Ottmann, C.; Milroy, L. G.; Brunsveld, L. ACS Chem.
Neurosci. 2017, 8, 2065-2077.
This work was supported by grants from the Korea Health
Technology R&D Project through the Korea Health Industry
Development Institute (KHIDI-HI14C1135) and the National
Research Foundation of Korea (NRF-
2016R1D1A1A09917300).
References and notes
1. Campbell, A. Ann. N. Y. Acad. Sci. 2004, 1035, 117-132.
2. Kim, Y. S.; Joh, T. H. Exp. Mol. Med. 2006, 38, 333-347.
3. Kreutzberg, G. W. TINS. 1996, 19, 312-318.
15. (a) Lee, B.; Sun, W.; Lee, H.; Basavarajappa, H.; Sulaiman,
R. S.; Sishtla, K.; Fei, X.; Corson, T. W.; Seo, S.-Y. Bioorg.
Med. Chem. Lett. 2016, 26, 4277-4281. (b) Basavarajappa,
H. D.; Sulaiman, R. S.; Qi, X.; Shetty, T.; Sheik Pran Babu,
S.; Sishtla, K. L.; Lee, B.; Quigley, J.; Alkhairy, S.; Briggs,
C. M.; Gupta, K.; Tang, B.; Shadmand, M.; Grant, M. B.;
Boulton, M. E.; Seo, S.-Y.; Corson, T. W. EMBO Mol.
Med. 2017, 9, 786-801. (c) Sulaiman, R. S.; Park, B.; Sheik
Pran Babu, S. P.; Si, Y.; Kharwadkar, R.; Mitter, S. K.; Lee,
B.; Sun, W.; Qi, X.; Boulton, M. E.; Meroueh, S. O.; Fei,
X.; Seo, S.-Y.; Corson, T. W. ACS Chem. Biol. 2018, 13,
45-52.
4. (a) Lee, Y. -J.; Lee, Y. M.; Lee, C.-K.; Jung, J.-K.; Han, S.
B.; Hong, J. T. Pharmacol. Ther. 2011, 130, 157-176. (b)
Choi, J. H.; Ha, J.; Park, J. H.; Lee, J. Y.; Lee, Y. S.; Park,
H. J. Jpn. J. Cancer Res. 2002, 93, 1327-1333. (c) Kang, J.
S.; Lee, K. H.; Han, M. H.; Lee, H.; Ahn, J. M.; Han, S. B.
Phytother. Res. 2008, 22, 883-888. (d) Kong, C. W.; Tsai,
K.; Chin, J. H.; Chan, W. L.; Hong, C. Y. Shock 2000, 13,
24-28. (e) Weeks, B. S. Med. Sci. Monit. 2009, 15, RA256-
RA262. (f) Xu, Q.; Yi, L. T.; Pan, Y.; Wang, X.; Li, Y. C.;
Li, J. M. Prog. Neuropsychopharmacol. Biol. Psychiatry
2008, 32, 715-725. (g) Shigemura, K.; Arbiser, J. L.; Sun,
S.-Y.; Zayzafoon, M.; Johnstone, P. A.S.; Fujisawa, M.;
Gotoh, A.; Weksler, B.; Zhau, H. E.; Chung, L. W.K.
Cancer 2007, 109, 1279-89.
Supplementary Material
5. (a) Fukuyama, Y.; Nakade, K.; Minoshima, Y.; Yokoyama,
R.; Zhai, H. F.; Mitsumoto, Y. Bioorg. Med. Chem.
Supplementary data associated with this article can be found,
in the online version, at doi:
Lett. 2002, 12, 1163-1166. (b) Woodbury, A.; Yu, S. P.;
Chen, D.; Gu, X.; Lee, J. W.; Zhang, J.; Espinera, A.;
García, P. S.; Wei, L. J. Nat. Prod. 2015, 78, 2531-2536.

Highlights
 Isoxazole and pyrazole analogs in
B ring of honokiol
 Isoxazole and pyrazole were
constructed by nitrile oxide
cycloaddition and condensation of
4-chromone and alkylhydrazine
 Two pyrazole analogs strongly
inhibit NO production in LPS-
activated BV-2 cells by
suppressing iNOS and COX-2
expression