Evaluation of the antimalarial potential of novel aminoquinolines in vitro and in vivo

Malarija, bolest koja pogađa milione ljudi širom sveta, je parazitska infekcija uzrokovana protozoama roda Plasmodium. Danas je poznato pet vrsta koje izazivaju malariju kod čoveka: P. falciparum, P. vivax, P. malariae, P. ovale i P. knowlesi. Najvirulentnija vrsta je P. falciparum, a malariju koju ona izaziva karakterišu najteži klinički tok bolesti kao i najviša stopa smrtnosti. Vektori odgovorni za prenošenje ove bolesti su ženke komaraca roda Anopheles. Malarija predstavlja najveći zdravstveni problem sa kojim se suočavaju zemlje u razvoju, a najviše stope morbiditeta i mortaliteta beleže se u zemljama Afrike i Jugoistočne Azije. Međutim, usled klimatskih promena i masovnih migracija stanovništva, autohtoni slučajevi malarije sve češće se pojavljuju sporadično (Korzika, Italija, Španija), pa i epidemijski (Grčka), i u zemljama ili regionima u kojima je ova bolest smatrana eradikovanom. Važno je naglasiti da su prevencija i terapija malarije moguće. Međutim, paraziti Plasmodium postaju rezistentni na gotovo sve konvencionalno dostupne antimalarike, anofelični vektori su rezistentni na insekticide, a vakcina i dalje ne postoji. S obzirom na opisanu situaciju, postoji hitna potreba za novim antimalaricima. Sintetski hinolinski derivati najviše obećavaju, među kojima je za hemijske modifikacije najpogodnija struktura 4-aminohinolina. U cilju proširenja znanja u oblasti hemioterapije malarije ispitana je potencijalna antimalarijska aktivnost 37 novosintetisanih aminohinolina sa hemijskim modifikacijama na aminohinolinskom jezgru i bočnom lancu, sintetisanih na Hemijskom fakultetu Univerziteta u Beogradu, u in vitro i in vivo model sistemima. Ispitivanje antimalarijske aktivnost ovih jedinjenja u in vitro sistemu vršeno je kolorimetrijskim esejom laktat dehidrogenaze (LDH esej). Korišćena su dva soja P. falciparum, i to soj 3D7, koji je osetljiv na hlorokvin (CQ) i soj Dd2, koji je rezistentan na CQ. Prvi deo ispitivanja je činila faza skrininga u kojoj je aktivnost svih jedinjenja prema oba soja P. falciparum ispitana u koncentraciji od 500 nM, a odabrana jedinjenja su u sledećoj fazi titrirana do preciznih srednjih vrednosti inhibitornih koncentracija (IC50). CQ je korišćen kao pozitivna kontrola. Antimalarijska aktivnost u in vivo sistemu je ispitana primenom modifikovanog Thompson-ovog testa. Ženke miševa soja C57Bl/6 inficirane su ANKA sojem P. berghei i praćene 30 dana. Ispitivanju aktivnosti jedinjenja prethodila je faza kliničkog praćenja zdravih životinja tretiranih eksperimentalnim jedinjenjima tokom 3 dana u dozi od 160 mg/kg/dan...Malaria, a disease which affects millions of people worldwide, is a parasitic infection caused by protozoans of the Plasmodium genus. Five Plasmodium species are known to cause human malaria, including P. falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi. The most virulent one is P. falciparum, and the malaria which it causes is characterized by the most severe clinical presentation as well as the highest mortality rate. The vectors responsible for the transmission of this disease are female mosquitoes of the Anopheles genus. Malaria is the greatest health problem facing developing countries, with the highest morbidity and mortality rates in Africa and Southeast Asia. Moreover, due to climate change and mass human migration, autochthonous cases of malaria are increasingly appearing sporadically (Corsica, Italy, Spain) or even as local epidemics (Greece), in countries or regions in which the disease was considered eradicated. It is important to emphasize that the prevention and treatment of malaria are possible. However, Plasmodium parasites are developing resistance to nearly all conventional antimalarials, Anopheles vectors are becoming resistant to insecticides, and no vaccine exists to date. Given the current situation, there is an urgent need for new antimalarial compounds. Synthetic quinoline derivatives hold the most promise, with 4-aminoquinolines being the most suitable for chemical modifications. With the aim to expand knowledge in the field of malarial chemotherapy, potential antimalarial activity of 37 novel aminoquinolines with chemical modifications at the aminoquinoline moiety and side chain, synthesized at the University of Belgrade Faculty of Chemistry, were evaluated in both in vitro and in vivo model systems. In vitro evaluation of the antimalarial activity of the synthesized compounds was performed using the colorimetric lactate dehydrogenase (LDH) assay. Two strains of P. falciparum were used, one, 3D7, sensitive to chloroquine (CQ), and one, Dd2, resistant to CQ. Compounds were first screened at a concentration of 500 nM, and selected compounds were then titrated to determine their half maximal inhibitory concentration (IC50). CQ was used as a positive control. In vivo antimalarial activity was investigated using a modified Thompson test. C57Bl/6 female mice were infected with the ANKA strain of P. berghei and monitored for 30 days. Investigation of the animalarial activity of the experimental compounds was preceded by a series of experiments in which healthy mice treated with the compounds during 3 consecutive days at a dose of 160 mg/kg/day were clinically monitored; those that showed signs of gross toxicity were excluded from further investigation..