Anti-malarial property of steroidal alkaloid conessine isolated from the bark of Holarrhena antidysenterica
© Dua et al.; licensee BioMed Central Ltd. 2013
Received: 12 February 2013
Accepted: 30 May 2013
Published: 10 June 2013
In the face of chronic and emerging resistance of parasites to currently available drugs and constant need for new anti-malarials, natural plant products have been the bastion of anti-malarials for thousands of years. Moreover natural plant products and their derivatives have traditionally been a common source of drugs, and represent more than 30% of the current pharmaceutical market. The present study shows evaluation of anti-malarial effects of compound conessine isolated from plant Holarrhena antidysenterica frequently used against malaria in the Garhwal region of north-west Himalaya.
In vitro anti-plasmodial activity of compound was assessed using schizont maturation and parasite lactate dehydrogenase (pLDH) assay. Cytotoxic activities of the examined compound were determined on L-6 cells of rat skeletal muscle myoblast. The four-day test for anti-malarial activity against a chloroquine-sensitive Plasmodium berghei NK65 strain in BALB/c mice was used for monitoring in vivo activity of compound. In liver and kidney function test, the activity of alkaline phosphatase (ALP) was examined by p-NPP method, bilirubin by Jendrassik and Grof method. The urea percentage was determined by modified Berthelot method and creatinine by alkaline picrate method in serum of mice using ENZOPAK/CHEMPAK reagent kits.
Compound conessine showed in vitro anti-plasmodial activity with its IC50 value 1.9 μg/ml and 1.3 μg/ml using schizont maturation and pLDH assay respectively. The compound showed cytotoxity IC50= 14 μg/ml against L6 cells of rat skeletal muscle myoblast. The isolated compound from plant H. antidysenterica significantly reduced parasitaemia (at 10 mg/kg exhibited 88.95% parasite inhibition) in P. berghei-infected mice. Due to slightly toxic nature (cytotoxicity = 14), biochemical analysis (liver and kidney function test) of the serum from mice after administration of conessine were also observed.
The present investigation demonstrates that the compound conessine exhibited substantial anti-malarial property. The isolated compound could be chemically modified to obtain a more potent chemical entity with improved characteristics against malaria.
Malaria is re-emerging as the world's number one killer infection, causing approximately one million deaths annually and 300–400 million infections per annum . The dreaded disease is difficult to eradicate and its control is possible only with coordinated efforts of the general public, healthcare personnel and government agencies. Dhingra and co-workers  challenges the World Health Organization (WHO) observation system; as per WHO more than 10 million malaria cases each year cause 15,000 deaths while based on verbal autopsy investigations between 2001 and 2003, researchers suggest that WHO figures are a huge miscalculate, and the true number is at least 125,000 deaths per year. Moreover exterior Africa, it is the profusely populated Southeast Asia where 30% of the total population is approximated to be at risk of malaria, of which India contributes (80%) most of the cases . The emergence of drug resistance particularly to chloroquine and sulphadoxine-pyrimethamine has led to recommendations that they be replaced with artemisinin-based combination therapy (ACT) for improved efficacy. On the other hand, development of resistance to artemisinins and their associate drugs cruelly limit the utility of ACT in future. Consequently to develop alternative therapy, research on anti-malarials is urgently vital. Plants used in traditional medicines shows potential source of compounds with good anti-malarial activity [4, 5]. Natural plant products and their derivatives have traditionally been a common source of drugs, and represent more than 30% of the current pharmaceutical market [6, 7].
The continuing research directed towards discovery of anti-malarials from plants [8–10], it was noticed that chloroform extract of H. antidysenterica showed the anti-malarial properties against Plasmodium falciparum isolates and P. berghei-infected mice. Therefore, in the present investigation the anti-malarial activity of isolated principle compound conessine from H. antidysenterica is demonstrated against P. falciparum isolates and Plasmodium berghei-infected mice.
Collection of plants and isolation of compound
In vitro anti-plasmodial activity against K1 strain of plasmodium falciparum isolates
In vitro anti-plasmodial sensitivity of compound was assessed at National Institute of Malaria Research, New Delhi, India using Schizont maturation method . Chloroquine sensitive strain FSG of P. falciparum derived from an Indian patient of Shahjahanpur (UP) was used for the study. Culture was maintained in A +ve erythrocytes using RPMI 1640 medium supplemented with AB Rh +ve human serum (10%), sodium bicarbonate (0.2%), HEPES buffer (25 mM) and gentamycin (50 μg ml-1). The culture was treated with selected concentrations of conessine. The prepared blood smears were stained with Giemsa strain after 72 hrs of incubation % maturation of schizonts against positive control was recorded. The compound was also sent to Swiss Tropical Institute, Switzerland for screening of in vitro anti-plasmodial activity using the parasite lactate dehydrogenase (pLDH) assay . In parasite lactate dehydrogenase (pLDH) assay, chloroquine sensitive GHA strain derived from a Ghanaian patient was used and maintained in RPMI 1640 medium supplemented with 25 mM HEPES, 0.37 mM hypoxanthine, 10% A+ve human serum together with 2-4% washed human O +ve erythrocytes and 25 mM NaHCO3. All cultures were conducted at 37 ± 1°C and an atmosphere of 3% oxygen, 4% carbon dioxide and 93% nitrogen. The sterile 384- well microtiter plates were used for performing assays, in which each well containing 2 μl of selected concentration of compound solution with 38 μl of the parasite inoculums (1% parasitaemia, 2% haematocrit). Parasite growth was compared to control wells (100% parasite growth). After 72 h of incubation at 37 ± 1°C, plates were deep-frozen at −20°C. After thawing 5 μl from each well was transferred into another plate together with 25 μl of Malstat™ reagent and NBT (Nitro Blue Tetrazolium, 0.1 mg/ml) and 5 μl of a 1/1 mixture of PES (phenazine ethosulfate, 2 mg/ml). The plates were then kept into darkness for 2 h and the change in colour was measured with a spectrophotometer (at 655 nm). In both methods chloroquine was taken as positive control. The inhibitory concentration value, at which 50% of the parasites kill (IC50) was considered for anti-plasmodial activity.
Cytotoxicity on rat skeletal muscle myoblasts (L-6 cells) and selectivity indices (SI)
The cytotoxicity of the compound was determined using reported method [14, 15]. The cell line L-6, rat skeletal muscle myoblasts were seeded in 96-well Costar microtiter plates at 2 × 103/cells/100 ml, 50 ml per well in MEM supplemented with 10% heat inactivated FBS. A three-fold serial dilution ranged from 90 to 0.13 mg/ml of compounds in test medium was added. Plates with a final volume of 100 ml per well were incubated at 37±1°C for 72 h in a humidified incubator containing 5% CO2 and resazurin was added as viability indicator. After an additional 2 h of incubation, the plates were measured with a fluorescence scanner using an excitation wavelength of 536 nm and an emission wavelength of 588 nm. The IC50 values were calculated from the sigmoidal inhibition curves with the SoftmaxPro software.
The selectivity indices (SI) were calculated with the ratio of the IC50 for the L-6 cells to the IC50 for the in vitro anti-plasmodial activity against P. falciparum isolates.
In vivo anti-malarial activity against P. Berghei
Mouse and parasite strain
BALB/c mice (weighing 22–26 g and 4–6 weeks old) of either sex, obtained from the central animal house, Panjab University, Chandigarh were used as experimental models. They were maintained on a standard pellet diet and water ad libitum. Plasmodium berghei (NK- 65) was maintained by intraperitoneal inoculation of 1×106 infected red blood cells (RBCs) to native mice .
The treatment of mice was according to the guidelines of committee for the purpose of control and supervision on experiments on animals (Reg No. 45/1999/CPCSEA), Panjab University, Chandigarh, India.
Compound was dissolved in 70% Tween 80 and 30% ethanol. This solution was further diluted 10-fold with distilled water to result in a stock solution containing 7% Tween and 3% ethanol with which different concentrations of compound, i.e., 10 mg/kg, 20 mg/kg and 50 mg/kg were prepared.
Experimental groups for four-day suppressive test
G4 (Vehicle control)
70% Tween 80 + 30% ethanol
G5 (Infected control)
The mean survival time (MST) of each group was calculated up to 2 weeks (14 days) post inoculation.
Liver and kidney function tests
Adverse effects due to the compound were examined by liver and kidney function tests. The activity of alkaline phosphatase (ALP) was determined by p-NPP method , bilirubin by Jendrassik and Grof method . The urea concentration was determined using modified Berthelot method  and creatinine by alkaline pictrate method  in serum of mice using ENZOPAK/CHEMPAK reagent kits (Reckon Diagnostic Pvt Ltd, Gorwa, Baroda, India). Serum was obtained from four mice of each group by centrifugation of blood at 800 g for 15 min RT. Biochemical assays were performed on day 7 in infected control and on day 10 in treated groups.
Results and discussion
In vitro anti-plasmodial activity of examined compound
Anti-plasmodial activity (IC50μg/ml)
Course of parasitaemia after inoculation of compound in different experimental groups
% survival of animals on day 14
0.8 ± 0.02
3.36 ± 2.1*
2.15 ± 0.4
13.2 ± 2*
2.05 ± 1
14.9 ± 3.12*
6.6 ± 2.4
28.7 ± 4.5NS
7.2 ± 1.8
30.4 ± 3.6
Alkaline phosphatase (ALP) activity, concentration of bilirubin, urea and creatinine in different experimental groups on day 10 post inoculation of compound
ALP (KA units)
1.3 ± 0.5**
160 ± 4.3**
8.55 ± 1.4**
15.3 ± 1.4*
2.6 ± 0.84*
176 ± 2.8**
8.5 ± 2.2**
19.2 ± 3.3**
1.3 ± 0.02**
112 ± 4.22**
10 ± 2.7**
18.33 ± 2.11**
1.31 ± 0.02**
147.5 ± 2.1**
1.8 ± 0.03**
11 ± 2.3
1.05 ± 0.1
38.26 ± 2.6
0.83 ± 0.1
The steroidal alkaloid conessine isolated from the bark of H. antidysentrica exhibited substantial anti-malarial activity with slight cytotoxic nature. The isolated compound could be chemically modified to obtain a more potent chemical entity with improved characteristics or modified compound can become preclinical candidate against malaria.
The authors gratefully acknowledge the financial support of the Uttarakhand State Council for Science and Technology (UCOST), Dehradun, India and UNDP/WHO Special Programme for Research and Training in Tropical Diseases (TDR) for their support. Thanks are also due to Richa Bajpai for editorial assistance.
We also acknowledge the NIMR Publication Committee to approve the contents of paper.
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