In vivo antifilarial activity of some cyclic and acylic alcohols

Article abstract of DOI:10.1007/s00044-010-9331-4

The filarial nematodes, Wuchereria bancrofti, Brugia malayi, and Brugia timori are the causative agents of lymphatic filariasis. 2-Substituted propanol, cyclohexanol, and cyclooctanol compounds were evaluated for microfilaricidal and macrofilaricidal activity in vivo against Acanthocheilonema viteae and Litomosoides carinii in rodents. In the cyclohexanol series, 2-(piperidin-1-yl) cyclohexanol (2b) showed 88.9% macrofilaricidal activity against A. viteae in vivo, while cyclooctanol series, 2-(4- benzyl piperdin-1-yl) cyclooctanol (2f) showed 100% macrofilaricidal activity against A. viteae. Further, compounds 1-(furan-2-ylamino) ethanol (4a) and 1-(4-benzylpiperidin- 1-yl)-ethyl acetate (5b) showed 81.3% and 83.4% macrofilaricidal activity, respectively, against the same parasite. Interestingly, compounds 2f and 4a showed significant sterilization of female worms in A. viteae. However, these compounds were found inactive against L. carinii. Therefore, the new class of compounds appeared to have promising antifilarial activity.

Full text of DOI:10.1007/s00044-010-9331-4

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2011) 20:430–434
DOI 10.1007/s00044-010-9331-4
ORIGINAL RESEARCH
In vivo antifilarial activity of some cyclic and acylic alcohols
•
Alka Agarwal Satish K. Awasthi P. K. Murthy
•
Received: 20 August 2009 / Accepted: 16 February 2010 / Published online: 16 March 2010
Ó Springer Science+Business Media, LLC 2011
Abstract The filarial nematodes, Wuchereria bancrofti,
Brugia malayi, and Brugia timori are the causative agents
of lymphatic filariasis. 2-Substituted propanol, cyclohexa-
nol, and cyclooctanol compounds were evaluated for mi-
crofilaricidal and macrofilaricidal activity in vivo against
Acanthocheilonema viteae and Litomosoides carinii in
rodents. In the cyclohexanol series, 2-(piperidin-1-yl) cy-
clohexanol (2b) showed 88.9% macrofilaricidal activity
against A. viteae in vivo, while cyclooctanol series, 2-(4-
benzyl piperdin-1-yl) cyclooctanol (2f) showed 100%
macrofilaricidal activity against A. viteae. Further, com-
pounds 1-(furan-2-ylamino) ethanol (4a) and 1-(4-ben-
zylpiperidin-1-yl)-ethyl acetate (5b) showed 81.3% and
83.4% macrofilaricidal activity, respectively, against the
same parasite. Interestingly, compounds 2f and 4a showed
significant sterilization of female worms in A. viteae.
However, these compounds were found inactive against
L. carinii. Therefore, the new class of compounds appeared
to have promising antifilarial activity.
Introduction
Lymphatic filariasis is a vector-borne disease, which has
threatened approximately 1 billion people world wide,
especially living in the tropical and subtropical regions of the
world. Till now, there is no vaccine available to cure filariasis
and vector control is not a viable approach. Therefore, a
concerted global effort is needed to interrupt the transmis-
sion of Lympahtic filariasis. Lymphatic filariasis (elephan-
tiasis), caused by Wuchereria bancrofti, Brugia malayi, and
Brugia timori, is one of the most dreaded diseases in world
(Ottesen, 2000). W. bancrofti causes more than 90% of these
infections and *10% of the infected population is affected
by Brugia spp. Human are the only known host for W. ban-
crofti (Annomyous, 2008). In South and South East Asia,
mosquito acts as carrier for transmission of filarial nematode
parasite in humans. Adult worms are most often found in the
lymphatic system and cause symptoms of the disease such as
acute lymphangitis, lymphadenitis, and filarial fever. Repe-
ated episodes of acute manifestations lead to disfiguring and
ultimately to elephantiasis. Recently, the World Health
Organization (WHO) reported that more than 120 million
people are infected world wide by filariasis and at least
40 million people are reported disabled both physically
and psychosocially. At present, diethylcarbamazine (DEC)
(Ottesen et al., 1990) (Fig. 1a) and ivermectin (Bennett et al.,
1988) are frequently used for effective reduction of micro-
filarial counts for up to a year but they cause many side
effects. On the other hand, the effect of DEC on adult filarial
parasites is limited. A large number of benzimidazole
2-carbamates show macrofilaricidal activity by the perito-
neal route but suffers from various drawbacks (Sharma,
1990; Campbell, 1985).
Keywords Cyclic and acyclic alcohols Á Epoxide Á
Antifilarial activity Á In vivo
A. Agarwal (&)
Department of Medicinal Chemistry, Institute of Medical
Sciences, Banaras Hindu University, Varanasi 221005, India
e-mail: shivangiag@rediffmail.com; alka_ag_2000@yahoo.com
S. K. Awasthi
Chemical Biology Laboratory, Department of Chemistry,
University of Delhi, Delhi 110007, India
e-mail: awasthisatish@yahoo.com;
skawasthi@chemistry.du.ac.in
Ivermectin does not kill the parasites but sterilizes
female reproductive potentials of the filarial parasites.
P. K. Murthy
Parasitology Division, CDRI, Lucknow, India
123

Med Chem Res (2011) 20:430–434
431
O
(TLC), benzene was evaporated off in vacuo and the res-
idue was purified by column chromatography using chlo-
roform and methanol as eluent. All compounds were
obtained as oil and reported as such.
a
N
N
C
N
MIF
b
100
90
80
70
60
50
40
30
20
10
0
Synthesis of acetate analogs: general method
MAF
Various cyclohexane-1-ol were stirred in dry pyridine
(20 ml) at room temperature for about 15 min. In the
reaction mixture, acetic anhydride (5 ml) was added, and
the reaction mixture was stirred at room temperature for
about 6 h. Pyridine was evaporated in vacuo. Water was
added and the reaction mixture was extracted with ethyl
acetate. The combined organic solvent was dried and
concentrated under vacuum. The compound was obtained
as oil, which was purified by column chromatography
using the chloroform and methanol as eluent. Identities of
all the synthesized compounds were confirmed by IR,
NMR, and MS data.
2b
2f
4a
5b
Compounds
Fig. 1 a Chemical structure of antifilarial drug diethylcarbamazine
(DEC). b Antifilarial activity of various compounds against A. viteae
Earlier study showed that phenoxycyclohexane derivatives
show potent antifilarial activity on purified phosphoenol
pyruvate (PEP)-carboxylase. In phenoxycyclohexane ser-
ies, compound 2-p-tolyoxy-cyclohexanol and ester analog
2-p-tolyloxy cyclohexylester were shown potent antifilarial
activity with Ki values of 122 and 93 lm (Loiscan, 1993;
Loiscan et al., 1993). Moreover, phenoxycyclohexane
derivatives inhibited the enzyme in noncompetitive manner
and killed the parasite. In addition, in recent years, more
and more newer molecules were evaluated against filarial
parasites (Mathew and Kalayansundaram, 2007; Mathew
et al., 2007, 2008; Singh et al., 2008; Kalayansundaram
et al., 2009). These evaluated compounds showed low
antifilarial activity and high toxicity and could not be
developed as antifilarial drug.
2-(Piperidin-1-yl)-cyclohexanol (2b)
Yield 1.60 g (91.4%), oil, IR (KBr): 3419, 2939, 2864,
1730, 1625, 1448 cm-1, MS m/z 184 (M ? 1); 1H
NMR(CDCl3): d 3.13 (s,1H, OH), d 2.8 (s,1H), d 2.65
(m,1H), d 2.39(m,1H), d 2.1(d,1H), d 2.0–1.9 (m,4H), d
1.8–1.75 (m,4H), d 1.6–1.59 (m,4H), d 1.4–1.15 (m,4H),
Elemental analysis: C11H21NO Calc. C,72.08; H,11.55, N,
7.64; found: C, 71.61; H, 11.73, N,7.69.
2-(4-Benzylpiperidin-1-yl)-cyclo-octanol (2f)
Yield 1.50 g (85.2%), oil, IR (KBr): 3500,
2895,2785,1750,1450 cm-1, MS m/z 302 (M ? 1), 1H
NMR(CDCl3) : d 7.30–7.1 (m,5H), d 3.2–2.7 (m,6H),
2.6–2.3(m,6H), d 2.2–1.90 (m,6H), d 1.8–1.0 (m,8H),
Elemental analysis: Calcd. For C20H31NO: C, 79.68; H,
10.36; N, 4.65; found: C, 80.66; H, 10.39; N, 4.60.
Recently, we have reported antifilarial activity in simple
1, 3-diaryl-1-one (Awasthi et al., 2009). Further, in con-
tinuation of our endeavors to develop an ideal adulticide,
substituted 2-amino cyclic and acyclic alcohols and their
acetate analogs were synthesized and analyzed for their in
vivo filaricidal activity.
1-(Furan-2-ylamino)-ethanol (4a)
Yield 1.75 g (67.3%), oil, IR (KBr): 3300, 2755,
1
2785,1752, 1650 cm-1, MS (m/z) 128(M ? 1), H NMR
Experimental
(CDCl3): d 7.3 (s,1H), d 6.2–6.0 (m, 2H), 4.7 (s, 1H),
3.9–3.79 (bs,2H,OH,NH), d 1.3–1.0 (m, 3H, CH3), Ele-
mental analysis: Calcd. for C6H9 NO2: C,56.6, H,7.08, N,
11.02, found: C, 55.9; H, 7.29, N, 10.9.
Synthesis of cyclic and acyclic alcohols: general
method
Respective epoxide (10.2 mmol) was stirred in dry benzene
(20 ml) for about 15 min followed by addition of primary
or secondary amine (10.1 mmol). The reaction mixture was
stirred at room temperature for about 6 h. On completion of
the reaction, as checked by the thin layer chromatography
(4-Benzylpiperidin-1-yl)-ethyl acetate (5b)
Yield 0.80 g (67.8%), oil, IR (KBr): 3500, 2855, 2685,
1750, 1650 cm-1, MS m/z 261 (M?), 1H NMR (CDCl3): d
7.4–7.2 (m,5H), d 4.65–4.5 (d,1H), d 3.0–2.85 (m,2H), d
123

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Med Chem Res (2011) 20:430–434
2.6–2.4 (m,4H), d 2.1–1.95 (merged,5H), d 1.8–1.6
(s,3H,COCH3), d 1.25–1.0 (m,3H,CH3), Elemental analy-
sis: Calcd for C16H23ÁNO2: C, 73.53; H, 8.87; N, 5.36;
found: Calcd for C16H23NO2: C, 73.59; H, 8.91; N, 5.33,
found : C, 72.9; H, 8.2; N, 4.95.
intra-uterine contents. Female parasites with empty uteri or
uteri containing dead or degenerated developmental stages,
including mf, were considered as sterilized worms. The
percent sterilization of female worms was calculated from
the number of worms sterilized out of the total live female
worms recovered. The antifilarial activities of various
compounds (2a–f, 3a–e, 4a–c, and 5a–c) are summarized
in Table 1.
Models
Litomosoides carinii in cotton rats (Sigmodon hispidus) and
Acanthocheilonema viteae in Mastomys coucha were used
for the present study. The models are recommended
by WHO for the experimental chemotherapy of filariasis
(Abiose et al., 1995; WHO, 1982).
Results
The micro- and macrofilariacidal action of cyclic and
acylic and acetylated alcohols were evaluated. All syn-
thesized compounds in cyclohexanol, cyclooctanol, and
propane-2-ol series having various substituents at position
2 (2a–f, 3a–e, 4a–c, and 5a–c) were evaluated for their
antifilarial activity in vivo against A. viteae at 50 mg/kg
and L. carinii at 30 mg/kg 9 5 days by the i.p. route. In
the cyclohexanol series, compound, 2-(piperidin-1-yl)cy-
clohexanol (2b) was found most active. It showed 88.9%
adulticidal activity against A. viteae at 50 mg/kg 9 5 days.
Introduction of 4-methylpiperazine at position 2 (2e)
was found toxic against A. viteae at the does level (50 mg/
kg 9 5 days). The other compounds of the alcohol series
2(acd) were inactive and did not elicit antifilarial activity.
In the cyclooctanol series, only two substituents were
introduced at position 2 like 4-benzylpiperidine and mor-
pholine (2f and 2g). The compound 2-(4-benzylpiperidin-
1-yl)-cyclo-octanol (2f) was most potent and showed 100%
macrofilaricidal activity at 200 mg/kg 9 5 days and
81.3% sterilization of female worms at lower dose
(100 mg/kg 9 5 days). Acetylation of hydroxyl group in
compounds (3a–e) resulted loss of antifilarial activity.
However, compounds 2-(morpholino)-cyclooctanol (2g)
and their acetate analog 3g were not evaluated against
micro- and macrofilaricidal activity.
Administration of the compounds
Compounds that were insoluble in water were pulverized to
fine powder and from which the suspensions were made in
distilled water containing 0.1% T-80. Compounds were
administered at varying doses (100–200 mg/kg 9 5 days,
i.p.) as described earlier (Kumar et al., 1984; Lammeler
and Wolf, 1977). Standard drug DEC was used for com-
parison. Two to three animals were used per group for each
dose level and at least two replicates were used for con-
firmation of the activity.
Assessment of antifilarial activity
The micro and macrofilaricidal activities of the synthesized
compounds (2a–e, 3a–e, 4a–c, and 5a–c) were evaluated
against the above mentioned models as per methods of
Lammler and Wolf (Lammeler and Wolf, 1977; Chatterjee
et al., 1992). Microfilarial counts in 10 ll blood from tail
vein were made just before start of treatment and thereafter
at weekly intervals till sixth week. Alteration in mf
(microfilarial) count in relation to pretreatment (before
treatment) level was calculated to ascertain the effect on
microfilaraemia and fall in microfilarial count observed
on the first week was considered microfilaricidal efficacy
of the compound. On the sixth week, the treated and
control animals were killed and adult worms recovered
from pleural cavity (L. carinii) or subcutaneous tissues
(A. viteae) of the animals were examined under microscope
for motility and mortality (Chatterjee et al., 1992). The
percent mortality was calculated by comparing the number
of live worms recovered from the experimental animals
with that recovered from matched untreated infected
controls. All the surviving female worms recovered
from each animal were teased individually on a glass
slide and observed under microscope for condition of the
In third series, 1, 2-epoxy propane three substituents
like furan-2ylamino; N-benzyl piperidine and 2-methyl
piperidine were introduced. The results showed that
compound 1-(furan-2-ylamino) ethanol (4a) showed
81.3% adulticidal activity at 200 mg/kg 9 5 days. More-
over, we also observed that 82% of female worms were
sterilized at the dose level of 100 mg/kg. However,
compounds 4b and 4c did not elicit antifilarial activity.
Further, compound 1-(4-benzyl piperidin-1-yl)-ethyl ace-
tate (5b) showed 83.4% adulticidal activity at 200 mg/
kg 9 5 days and no sterilization of female worms was
observed. Interestingly, introduction of furan-2-yl amino
and 4-benzyl piperidine at position two in 1, 2-epoxy
propane series (5a and 5c) did not improve the antifilarial
activity and remained inactive.
123

Med Chem Res (2011) 20:430–434
433
Table 1 Antifilarial activity of various compounds
Cyclic and acyclic
alcohol structure
Compound no.
R
Anti filarial activity against
A. viteae (50 mg/kg 9 5 days)
MIF
MAF
Sterilization
of female worms
2a
2b
2c
2d
2e
2f
n = 1, Aniline
0
0
0
0
0
0
0
0
OH
n = 1, Piperidine
88.9
0
0
R
n = 1, 4-Benzyl piperidine
n = 1, Morpholine
0
0
0
n = 1, 4-Methyl piperazine
n = 2, 4-Benzyl piperidine
Toxic
100a
0
81.3b
n
3a
3b
3c
3d
3e
n = 1, Aniline
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
OCOCH
3
n = 1, Piperidine
R
n = 1, 4-Benzyl piperidine
n = 1, Morpholine
n = 1, 4-Methyl piperazine
n
4a
4b
4c
Furan-2ylamino
0
0
0
81.3
0
82
0
OH
N-Benzyl piperidine
2-methyl piperidine
R
0
0
5a
5b
5c
Furan-2ylamino
0
0
0
0
0
0
0
OCOCH
3
N-Benzyl piperidine
2-Methyl piperidine
83.4
0
R
–
–
90
0
0
O
N
N C N
DEC
DEC Diethylcarbamazine (standard antifilarial drug), MIF Microfilaricidal, MAF Macrofilaricidal
‘0’—inactive
a
200 mg 9 5 days
b
100 mg/kg 9 5 days (p.o.)
Discussion
group of compounds yielded complete loss of antifilarial
activity expect in compound 5b. In fact, the results dem-
onstrate that hydroxyl and bulky groups at position 2 are
critical for antifilarial activity. We presume that acetylation
of hydroxyl group at position 2 in acyclic and cyclic
alcohols perturbed efficient bonding with enzyme but it is
less effective. Interestingly, compounds from all three
series were found inactive against L. carinni. Moreover, we
require evaluating a large number of synthetic compounds
having various synthetic scaffolds and different functional
group that will help us to understand the mode of action on
It is clear from the above results that presence of basic and
hydrophobic piperidine group at position 2 in cyclohexanol
enhanced the antifilarial activity (2b) while polar or less
bulky groups are either toxic or inactive. Further, in
cyclooctanol series, presence of bulky benzyl group at
position 4 in piperidine showed remarkable 100% macro-
filaricidal activity. Thus, hydrophobic and bulky groups
in both cyclohexanol and cyclooctanol series enhanced
antifilarial activity. However, acetylations of hydroxyl
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Compound 2b, 2f, 4a, 5b could be used as standard pre-
cursors for this purpose.
Acknowledgement AA is thankful to the Council of Scientific and
Industrial Research (CSIR) New Delhi, India and Banaras Hindu
University (BHU), Varanasi, India for financial support. SKA is
thankful to Delhi University, Delhi, India for financial support.
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