Pharmacological basis for the medicinal use of cardamom in asthma

Abstract

Cardamom (Elettaria cardamomum) is widely used in folk medicine for the treatment of asthma. This study describes its airways relaxant potential, with elucidation of possible underlying mechanism. Crude extract of cardamom which tested positive for alkaloids, flavonoids, saponins, sterols and tannins, when tested against carbachol-mediated bronchoconstriction in rats under anesthesia, dose-dependently (10-100 mg/kg) suppressed the carbachol (1 mu mol/kg)-evoked increase in the inspiratory pressure. In isolated rabbit trachea tissues, crude extract of cardamom caused relaxation of both carbachol (1 mu M) and high K+ (80 mM)-induced contractions, like that caused by verapamil, suggesting its Ca++ channel blockade action. These results indicate that cardamom exhibits bronchodilatory effect, mediated through Ca++ antagonist mechanism, which provides sound mechanistic background for its medicinal use in asthma.

Full text

Introduction
Elettaria cardamomum Maton (family: Scitaminaceae)
commonly known as “cardamom” and locally known
as “elaichi” is a perennial herb, indigenous to India,
Pakistan, Burma and Sri Lanka (Nadkarni, 1976). In
addition to its wide use for culinary purpose,
cardamom has been used in traditional medicine for
asthma, constipation, colic, diarrhea, dyspepsia,
hypertension, epilepsy and is considered useful as
antibacterial, antifungal, antiviral, carminative, diuretic
and stomachic (Kapoor, 1990; Duke et al., 2002).
Phytochemical studies revealed that cardamom
contains α-terpineol, myrcene, heptane, subinene,
limonene, cineol, menthone, α-pinene, β-pinene, linalol,
nerolidol, β-sitostenone, phytol, eugenyl acetate,
bisabolene, borneol, citronellol, geraniol, geranyl
acetate, stigmasterol and terpinene (Gopalakrishnan et
al., 1990; Duke, 1992). Despite the fact that cardamom
has been used medicinally, it has not been widely
studied to rationalize its use in hyperactive status of
airways, asthma. In this study, we evaluated that the
bronchodilatory effect of cardamom is mediated
through Ca++ channel blockade, which provide
pharmacological rational for its effectiveness in the
asthma.
Materials and Methods
Plant material and preparation of extract: Dried fruits of
cardamom were purchased from a local market in
Karachi and the sample voucher (EC-SE-07-04-54) was
submitted to the Department of Biological and
Biomedical Sciences herbarium, Aga Khan University,
Karachi. After cleaning of adulterant material, the fruits
were ground with an electric grinder into a coarse
powder. Extraction and fractionation was carried out as
described previously. About 986 g of ground material
A Journal of the Bangladesh Pharmacological Society (BDPS) Bangladesh J Pharmacol 2011; 6: 34-37
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ISSN: 1991-007X (Print); 1991-0088 (Online); DOI: 10.3329/bjp.v6i1.8133
Pharmacological basis for the medicinal use of cardamom in
asthma
Arif-ullah Khan1,2, Qaiser Jabeen Khan1,3 and Anwarul-Hassan Gilani1
1Natural Product Research Division, Department of Biological and Biomedical Sciences, Aga Khan University
Medical College, Karachi 74800, Pakistan; 2Institute of Pharmaceutical Sciences, Kohat University of Science and
Technology, Kohat 26000, Pakistan; 3Faculty of Pharmacy and Alternative Medicine, The Islamia University of
Bahawalpur 63100, Pakistan.
Abstract
Cardamom (Elettaria cardamomum) is widely used in folk medicine for the
treatment of asthma. This study describes its airways relaxant potential, with
elucidation of possible underlying mechanism. Crude extract of cardamom
which tested positive for alkaloids, flavonoids, saponins, sterols and tannins,
when tested against carbachol-mediated bronchoconstriction in rats under
anesthesia, it dose-dependently (10-100 mg/kg) suppressed the carbachol (1
µmol/kg)-evoked increase in the inspiratory pressure. In isolated rabbit
trachea tissues, crude extract of cardamom caused relaxation of both carbachol
(1 µM) and high K+(80 mM)-induced contractions, like that caused by
verapamil, suggesting its Ca++ channel blockade action. These results indicate
that cardamom exhibits bronchodilatory effect, mediated through Ca++
antagonist mechanism, which provides sound mechanistic background for its
medicinal use in asthma.
Article Info
Received: 30 July 2011
Accepted: 1 August 2011
Available Online: 3 August 2011
Keywords:
Asthma
Bronchodilation
Ca++ channel blocker
Cardamom
Number of Figures: 2
Number of Refs: 14
Correspondence: AHG
e-mail: anwar.gilani@aku.edu
This work is licensed under a Creative Commons Attribution 3.0 License. You are free to copy, distribute and perform the work. You must attribute
the work in the manner specified by the author or licensor.

was soaked in 4 liters of the aqueous-methanol (70%)
for three days with occasional shaking. It was filtered
through a muslin cloth and then through a Whatman
qualitative grade 1 filter paper. This procedure was
repeated twice and the combined filtrates were
evaporated on rotary evaporator under reduced
pressure (-760 mmHg) to a thick, semi-solid pasty mass
of dark brown color; i.e. the crude extract of cardamom,
yielding approximately 10.81%, soluble in saline/
distilled water.
Animals: Animals used in this study, such as Sprague-
Dawley rats (230-260 g) and rabbits (1.5-2.0 kg) of either
sex and local breed were housed at the Animal House
of the Aga Khan University, maintained at 23-25 C.
Experiments performed complied with the rulings of
the Institute of Laboratory Animal Resources,
Commission on Life Sciences, National Research
Council (1996) and approved by Ethical Committee of
Aga Khan University.
Chemicals: Carbachol, salbutamol and pentothal sodium
(thiopental sodium) were respectively obtained from
Sigma Chemicals Co., St. Louis, MO, USA, Glaxo
Wellcome and Abbot Laboratories, Karachi, Pakistan.
Chemicals for Krebs solutions include: potassium
chloride (Sigma Chemical Company), calcium chloride,
glucose, magnesium sulphate, potassium dihydrogen
phosphate, sodium bicarbonate and sodium chloride (E.
Merck, Darmstadt, Germany). The chemicals used in
phytochemical analysis include: acetic anhydride,
al um in um chloride, ammonium hy dr ox id e,
dragendorff's reagent, ferric chloride (Sigma Chemical
Co, St Louis, MO, USA), benzene, chloroform,
hydrochloric acid and petroleum ether (BDH
Laboratory supplies, Poole, England). All the chemicals
used were of analytical grade available.
Phytochemical screening: Preliminary screening of the
plant extract for various phytochemical classes was
carried out following the reported methods (Gilani et
al., 2007). Alkaloids were tested by using Dragendorff’s
reagent. Appearance of yellow color with AlCl3reagent
and green or black with aqueous FeCl3 detects
flavonoids and tannins respectively. Plant material
treated with petroleum ether and subsequently
extracted with CHCl3 was noted for green to pink or
pink to purple color after reaction with acetic anhydride
and HCl in succession to detect sterols and terpenes
respectively. Saponins were detected on the basis of
froth upon vigorous shaking. The observation of yellow
florescence under UV light on filter paper impregnated
with the vapours from boiling extract indicates the
presence of coumarins. Benzene extract prepared from
acidified plant material was treated with NH4OH for
anthraquinones based on the appearance of pink, violet
or red color.
Bronchodilatory activity: Rats were anaesthetized with
sodium thiopental (Pentothal, 80-100 mg/kg, i.p.), than
incubated with a tracheal tube and ventilated with a
volume ventilator (Miniature ideal pump, Bioscience,
UK) adjusted at a rate of 70-80 strokes/min to deliver 7-
10 mL/kg of room air. A polyethylene catheter was
inserted into the jugular vein for drugs administration.
Changes in airways resistance (mmHg) were measured
by a pressure transducer (MLT-1199) connected to side
arm of tracheal cannula and recorded by PowerLab
4/25 with running chart software via Quad bridge
amplifier (ADInstruments, Bella Vista, NSW, Australia).
Bronchoconstriction was induced with carbachol (1
µmol/kg), which was reversed within 7-10 min. The
test drug was given to the animals 5-8 min prior to
administration of carbachol. The responses were
expressed as the percent reduction of the carbachol-
evoked bronchospasm (Khan and Gilani, 2009).
Isolated rabbit trachea: Tr ach ea fr om rab bi t,
sacrificed by blow on back of head was dissected out
and kept in Kreb’s solution. The tracheal tube was cut
into rings, 2-3 mm wide, each containing about two
cartilages. Each ring was opened by a longitudinal cut
on ventral side, forming a tracheal chain with smooth
muscle in the center and cartilaginous portions on the
edges Each preparation was then mounted in 20 mL
tissue bath containing Kreb’s solution, maintained at
37ºC and aerated with carbogen (5% CO2in 95% O2).
The composition of Kreb’s solution was (mM): NaCl
118.2, NaHCO325.0, CaCl22.5, KCl 4.7, KH2PO41.3,
MgSO41.2 and glucose 11.7 (pH 7.4). A tension of 1 g
was applied to each of the tracheal strip and was kept
constant throughout the experiment. The tissue was
equilibrated for 1 hr before the addition of any drug.
Then sustained contractions of the agonists, carbachol
(1 µM) and/or K+ (80 mM) were obtained and tracheo-
relaxant effect of the test material was assessed by
adding in a cumulative fashion. Carbachol is a
c h o l i ne rgi c a gon i s t , k n o wn t o c a u s e
bronchoconstriction via stimulation of muscarinic
receptors (Gilani et al., 2010). High K+(> 30 mM) is
known to cause smooth muscle contractions through
opening of voltage-dependent L-type Ca++ channels,
thus allowing influx of extracellular Ca++ causing a
contractile effect and the substance causing inhibition of
high K+-induced contraction is considered as inhibitor
of Ca++ influx (Godfraind et al., 1986). The changes in
isometric tensions of the tracheal strips were measured
via a force-displacement transducer (FT-03) using a
Grass model 7 Polygraph (Grass Instrument Company,
Quincy, MA, USA).
Bangladesh J Pharmacol 2011; 6: 34-37 35

Statistical analysis: The data expressed are mean 
standard error of mean (SEM, n=number of experiment)
and the median effective concentrations (EC50) with
95% confidence intervals (CI), analyzed by using
GraphPad program (GraphPAD, San Diego, CA, USA).
Results
Crude extract of cardamom was found to contain
alkaloids, flavonoids, saponins, sterols and tannins
while tested negative for the rest of classes (data not
shown).
Crude extract of cardamom at the doses of 10, 30 and
100 mg/kg caused 9.0 2.1, 37.7 5.4 and 83.4 4.4%
(n=4) respective inhibition of carbachol (1 µmol/kg)-
evoked increase in inspiratory pressure of
anaesthetized rats. Salbutamol suppressed the
carbachol (1 µmol/kg)-induced bronchoconstriction at
0.3 mg/kg by 78.7 3.9% (n=4; Figure 1).
In tracheal preparations, pre-contracted with carbachol
(1 µM) and K+ (80 mM), crude extract of cardamom
caused concentration-dependent relaxant effect, being
more potent against K+, with respective EC50 values of
0.85 (0.6-1.3, 95% CI, n=5) and 0.37 mg/mL (0.32-0.43,
n=4; Figure 2A). Verapamil also caused inhibitory
effect, possessing higher potency against K+, with EC50
values of 0.26 (0.18-0.33, n=3) and 0.09 µM (0.06-0.14,
n=3) respectively (Figure 2B).
Discussion
In view of the well known medicinal use in asthma, the
cardamom was tested for its possible bronchodilatory
effect in anaesthetized rats, where it inhibited the
carbachol-evoked bronchospasm, like that caused by
salbutamol, a standard bronchodilator (Barnes, 2006).
Figure 1: Bar chart showing inhibitory effect of the crude extract
of cardamom and salbutamol on the carbachol-mediated
bronchoconstriction in anesthetized rats. Values shown are
mean ± SEM, n=4
10 30 100 0.3
0
25
50
75
100
Salbutamol
Crude extract of cardamom
[mg/kg]
% of Carbachol (1 mol/kg)-induced
Inspiratory Pressure
Figure 2: Concentration-dependent inhibitory effect of (A)
crude extract of cardamom and (B) verapamil against
carbachol and high K+-induced contractions in isolated rabbit
tracheal preparations. Values shown are mean ± SEM, n=3-5
0.03 0.3 3
0
25
50
75
100
Carbachol (1 M)
K+ (80 mM)
A
[Crude extract of cardamom] mg/mL
% of Induced Contraction
0.003 0.03 0.3 3
0
25
50
75
100
Carbachol (1 M)
K+ (80 mM)
B
[Verapamil] M
% of Induced Contraction
36 Bangladesh J Pharmacol 2011; 6: 34-37

The cardamom extract was then studied in isolated
tracheal tissues, to elucidate the possible mode of
bronchodilator action, where crude extract of
cardamom caused relaxation of both carbachol and K+-
induced contractions, like verapamil, a Ca++ antagonist
(Fleckenstein, 1977) used as positive control. High K+
and carbachol are known to cause smooth muscle
contractions through opening of L-type Ca++ channel
and stimulation of muscarinic receptors respectively,
eventually leading to an increase in the intracellular
Ca++ level, resulting in airways constriction (Gilani et
al., 2007). The inhibitory effect of crude extract of
cardamom against the two spasmogens, indicates non-
specific tracheao-relaxant effect, mediated through Ca++
channel blocker-like mechanism (Gilani et al., 2010).
Ca++ antagonists are known to be effective in asthma
(Twiss et al., 2002) and the presence of such activity, as
observed in this study may explain the medicinal use of
cardamom in such disorder of airways hyperactivity.
The results of phytochemical analysis showed that
cardamom contains alkaloids, flavonoids, saponins,
sterols and tannins. The flavonoids are well known for
their bronchodilatory activity (Ghayur et al., 2007) and
the presence of such class of compounds in cardamom
is likely to contribute in its airways relaxing action.
However, the contribution of other constituents cannot
be ignored.
In conclusion, cardamom exhibits bronchodilatory
effect, mediated through Ca++ antagonist mechanism,
which provides pharmacological basis for its
application in the disorder of hyperactive status of
respiratory system, known as asthma.
Acknowledgement
This study was supported by funds made available by
Pakistan Science Foundation.
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