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A number of medicines have been developed to treat malaria with chloroquine and its derivatives' as the mainstay therapy. In recent years, P. falciparum has become increasingly resistant to conventional anti-malarial drugs, and the search for new anti¬malarial compounds by combining natural sources and synthetic approaches is still underway(Gessler, M.C. Nkunya, M.H.H.; Mwasumbi, L.B.; Heinrick, M.; Tanner, M. ACTA Tropica et al.,1994)( Tran, Q.L. Tezuka, Y. ; Ueda, J.Y. ; Nguyen, N.T. ; Maruyama Y.1 ; Begum, K.; Kim, H.S.; Wataya, Y.; Tran, Q.K.; Kabota, et al.,2003) As a part of search(Iwasa, K.;Nishiyama, Y.; Ichimaru, M.; Moriyasu, M.; Kim. H.S. Wataya, Y.; Yamori, T.; Takashi, T , et al.,1999)( Fujimoto, K.; Marisaki, D.; Yoshida, M.; Namba, T.; Kim, H.S., Wataya, Y.; Kourai, H.; Kakuta, H.; Sasaki, K. Bioorg, et al.,2006)( Kumura, N.; Izumi, M.; Nakajima, S.; Shimizu, S. ; Kim, H.S.; Wataya, Y.; Baba, et al.,2005), for novel anti-malarial agents from plants or via chemical synthesis, prepared derivatives of chalcones. Many natural and synthetic possess anti-malarial activity(Kanokmedhkul, S.; Kanokmedhakul, K; Nambuddee, K.; Kongsaeree P. J. Nat et al.,2004)( Beldjoudi, N.; Mambu, L.; Lobaieed, M. Greelier, P. Ramanitrohasimbola, D.; Rasoanaivo, P.; Martin, M.T.; Frappier et al.,2003)( Auffret, G.; Labaied, M.; Frappier, F.; Rasoanaivo, P.; Grellier, P.; Lewin, G. Bioorg et al.,2007) . chalcones have a diverse array of substituents on the two aromatic rings. Depending on the substitution pattern on the two aromatic rings, chalcones have a wide range of biological activities, including anti-malarial activity16-19. The potential anti-malarial activity of chalcones has generated great interest(Chen M.; Theander T.G.; Christchsch B.S.; Hviid L.; Zhai L; Kharazmi A et al.,1994). It is believed that anti-malarial chalcones act against falcipain-2 a malarial cysteine protease(Li R.; Kenyon G.L.; Cohen F.E.; Chen X. Gong B.; Dominguez, J.N. Davidson E.; Kurzban G.; Miller R.E. Nuzum E.O. Rosenthal P.J.; Mckerrow J.H et al.,1995) In the present study, new chalcones were synthesized and evaluated for in-vitro anti-malarial activity against P. falciparum.

All malaria parasites are obligate intracellular protozoa of the genus Plasmodium with a complex life cycle consisting of sexual reproduction (sporogonic phase) in invertebrates, e.g. mosquito and asexual reproduction (schizogonic phase) in vertebrates e.g. mammals, birds and reptiles⁽Chen M.; Theander T.G.; Christchsch B.S.; Hviid L.; Zhai L; Kharazmi A et al.,1994⁾⁽ Chen M.; Brogger C.S.; Zhai L.; Rasmussen M.H. Theander T.G.; Fronkjaer S.; Steffansen S.; Davidsen J. Kharazmi A. J. Iffect et al.,1997⁾

Malaria is transmitted to human by the intravenous inoculation of sporozoites by the bile of an infected female Anopheline mosquito (in Africa mainly A. gambiae), but in rare cases transmission occurs throughexposure to infected blood products or congenitally(Liu M.; Wilairat P.; Croft. S.L.; Lay-Choo A, Go Mei-Lin Bioorg Med et al.,2003)

The asexual parasites digest the host haemoglobin in their acidic food vacuoles requirements⁽Charris J.E. Dominguez J.N.; Gamboa N.; Rodrigues J.R. ; Angel J.E. Eur. J. Med et al., 2005⁾ , but this process is also necessary to provide room for parasite growth within the erythrocyte²⁴. The haemoglobion degradation results in thegeneration of free radicals and heam, which is polymerized with the aid of liquid to form an insoluble pigment, haemozoin.

The Intraerythrocytic Develomenttal Cycle (IDC) of P. falciparum lasts ~ 48h. Blood schizonts, release up to 32 merozoites. The merozoite release causes the typical febrile attacks on days 1 and 3 in falciparum malaria, hence named “tertian malaria”. More erythrocytes are invaded by the released merozoites and the next IDC commences.

The cycle (Fig.1.1) continues until the death of the host or death of the parasites due to drug treatment or acquired partial immunity. A few erythrocytic parasites differentiate into sexual forms, named gametocytes. Whaen infected blood containing gametocytes is ingested by a female A. gambiae mosquito, the male gametocyte exflagellates and male gametogenesis and fertilization of the female gamete occurs in the mosquito gut. The zygote develops into an oocyst in the gut wall of the mosquito and infective sporozoites eventually invade the insect salivary glands to be released during the next human blood meal^.

Human Malaria Species

Human have been regarded as the natural hosts of fourspecies of malaria namely P. falciparum, P. malariae, P. vivax, but there are more than 100 Plasmodium species. That infect a variety of hosts such as reptiles, birds, rodents, primates and other mammals. Each species causes a characteristic illness and has unique morphological features in blood smears under the microscope21. P. vivax is the most prevalent world wide and P. falciparum is the most dangerous and virulent species that causes malignant malaria, which is associated with severe complications such as cerebral malaria, renal failure and pulmonary affection2 1.27. P. falciparum infection is potentially lethal due to its ability to invade erythocytes of all ages compared to P. vivax that invades only a subpopulation, i.e., the reticulocytes28. resulting in overwhelming parasitaemias and enhanced growth rate. Moreover, it has the capacity to adhere (cytoadherence) to the peripheral micro-vasculature (capillaries and venules) through sequestration.

All chemical used in experimental work were of analytical grade and purchased from sigma-Aldrich, Merck, CDH, SRL etc. In-vitro Anti-Plasmodial Assay The in-vitro anti-malarial assay was carried out in 96 well microlitere plates. The culture of P. falciparum NF54 strain are routinely maintained in medium RPMI-1640 supplemented with 25mm HEPES, 1% glucose, 0.23% sodium bicarbonate and 20% heat inactivated human serum. The asynchronous parasites of Pf were synchromized after 5% D-sorbital treatment to obtain only the ring stage parasitzed cells. For carrying out the assay, 10 1AL parasites in 100 1.1L RPMEI-1640 medium was uniformly maintained in 10 wells (1 control and 2-10 test wells) of 96 microtitre plate. -100 pt test compound (1mg/mL) was added in 10th cell. Serial dilution of test compound were made from 10th well to 2nd well. The plates were incubated at 37°C in a candle jar. After 36¬40h incubation, the blood smears from each well prepared and stained with giemsa stain. The slides were microscopically observed to record maturation of ring stage parasites intotrophozoites and schizonts in presence of different concentrations. The test concentrations which inhibited the 50% maturation into schizonts were recorded as the fifty percent inhibition concentration (IC50) chloroquine was used as the standard reference drug.

Twenty eight compounds were tested for heir ability to inhibit parasite growth by incubating parasites in different concentrations for 48h, beginning at the ring stage. The development of parasites was comparted with untreated controls. Chloroquine was used as standard drug. The ISO values chloroquine was found to be 0.030 tig/mL. Out of twenty eight compounds, only eight compound viz., compounds 6,9,12,13,14,20,21 and 28 inhibited parasites development at concentration lower 10 jig. However for remaining compounds the IC₅₀ values were found to be greater than 101.ig show there inactivity. The effect of nature of substituted groups on anti­Plasmodial activity has been studied on anti-Plasmodial activity has been studied on para substituted chalcones. IC50 values increase in the order N(Me)₂ < Cl < N (C₂H5)2 < OMe < Br < Me < H from compounds 1 to 7.

IC₅₀ values increase in the order N(C2H5)2 < Cl < OMe < N (Me)₂ < H < Me < Br. While IC₅₀ values of compounds 15 to 21 and 22 to 28 increased in the same order N (C2H5)2 < N (Me)2 < Cl < OMe < Br < H < Me

Table 3.1:In-vitro Anti-Plasmodial activities of 4-(2-chloro-6- substituted-quinolin-3-y1)-3-chloro-1-1443-(4-substituted phenyl)-acrylolyll-phenyl}-azetidine-2-ones.

S. No.	Compound	IC50 µg/ml
1	R1-Ar	150
2	R1-Ar-CL(p)	12
3	R1-Ar-(Br)(p)	60
4	R1-Ar-Me(p)	145
5	R1-Ar-OMe (p)	35
6	R1-Ar-N (Me)2 (p)	9
7	R1-Ar-N(C2H5)2(p)	16

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