Artemisinins and synthetic peroxides as highly efficient antimalarials

Malaria is devastating disease and global public health problem, with nearly half world population exposed to risk. Illness is caused by five Plasmodium species, P falciparum, P ovale, P viva; P malaria and P knowlesi, from which P falciparum is the most serious one causing cerebral malaria and is the major reason for malaria mortality. Vaccine against malaria is not expected in the near future and chemotherapy remains as most feasible alternative for treatment of the disease. The development of widespread drug-resistance to chloroquine (CQ), the most successful antimalarial drug up to date, has resulted in severe health issues for countries in malaria endemic regions. Organic peroxides, like artemisinins, 1,2,4-trioxanes, 1,2,4-trioxolanes, 1,2,4,5-tetraoxanes and their chimeras, are the best choice for malaria treatment nowadays. These therapeutics are fast acting, non-toxic, low costing and without reported data of parasite resistance. Stability of peroxide bonds enables synthetic comfort and resulting in diversity of synthesized structures. The most important classes of peroxide antimalarials with promising representatives are reviewed and possible mechanisms of action were presented in details

Malarija stara bolest - novi izazovi

Malaria is one of the most deadly diseases in world affecting more than 500 million people with over 2 million deaths per year. Four species of Plasmodium cause human disease: Plasmodium vivax (P. vivax), Plasmodium malarie (P. malarie), Plasmodium ovale (P. ovale) and Plasmodium falciparum (P. falciparum). For the treatment of malaria there is a great number of drugs available, but limiting factors are: high prices, toxicity and increased resistance of parasite. For these reasons there is great need for development of new drugs, increasing control of existing and finding new admission in treatment of malaria

Malarija stara bolest - novi izazovi

Malaria is one of the most deadly diseases in world affecting more than 500 million people with over 2 million deaths per year. Four species of Plasmodium cause human disease: Plasmodium vivax (P. vivax), Plasmodium malarie (P. malarie), Plasmodium ovale (P. ovale) and Plasmodium falciparum (P. falciparum). For the treatment of malaria there is a great number of drugs available, but limiting factors are: high prices, toxicity and increased resistance of parasite. For these reasons there is great need for development of new drugs, increasing control of existing and finding new admission in treatment of malaria

Peroksidni antimalarici

The problem of endemic malaria continues unabated globally. Malaria affects 40 % of the global population, causing an estimated annual mortality of 1.5-2.7 million people. The World Health Organization (WHO) estimates that 90 % of these deaths occur in sub-Saharan Africa among infants under the age of five. While a vaccine against malaria continues to be elusive, chemotherapy remains the most viable alternative towards treatment of the disease. During last years, the situation has become urgent in many ways, but mainly because of the development of chloroquine-resistant (CQR) strains of Plasmodium falciparum (Pf). The discovery that artemisinin (ART, 1), an active principle of Artemisia annua L., expresses a significant antimalarial activity, especially against CQR strains, opened new approaches for combating malaria. Since the early 1980s, hundreds of semi-synthetic and synthetic peroxides have been developed and tested for their antimalarial activity, the results of which were extensively reviewed. In addition, in therapeutic practice, there is no reported case of drug resistance to these antimalarial peroxides. This review summarizes recent achievements in the area of peroxide drug development for malaria chemotherapy.Širenje malarije je stalno prisutan problem na globalnom nivou. Od malarije godišnje oboli 40 % svetske populacije i oko 1,5-2,7 miliona ljudi umre. Prema podacima Svetske zdravstvene organizacije, 90 % smrtnih slučajeva je u zemljama podsaharske Afrike, među kojima dominiraju deca starosti do 5 godina. Usled nemogućnosti razvoja vakcine, hemoterapija ostaje kao jedini pouzdan oblik lečenja od ove bolesti. Poslednjih godina problem borbe protiv malarije postaje urgentan iz brojnih razloga, među kojima je najznačajniji razvoj hlorokin-rezistentnih sojeva parazita. Otkriće da artemizinin (ART, 1) i njegovi derivati pokazuju izuzetnu efikasnost prema hlorokin-rezistentnim sojevima otvorilo je velike mogućnosti u borbi protiv malarije. Od tada, posebno tokom 80-tih godina, sintetisan je veliki broj jedinjenja i rezultati njihove aktivnosti opisani su u mnogim naučnim publikacijama. Osim toga, u kliničkoj praksi nisu zabeleženi primeri pojave rezistencije parazita prema ovoj klasi antimalarika. U ovom revijalnom radu opisani su najnoviji rezultati u razvoju peroksidnih antimalarika

Peroksidni antimalarici

The problem of endemic malaria continues unabated globally. Malaria affects 40 % of the global population, causing an estimated annual mortality of 1.5-2.7 million people. The World Health Organization (WHO) estimates that 90 % of these deaths occur in sub-Saharan Africa among infants under the age of five. While a vaccine against malaria continues to be elusive, chemotherapy remains the most viable alternative towards treatment of the disease. During last years, the situation has become urgent in many ways, but mainly because of the development of chloroquine-resistant (CQR) strains of Plasmodium falciparum (Pf). The discovery that artemisinin (ART, 1), an active principle of Artemisia annua L., expresses a significant antimalarial activity, especially against CQR strains, opened new approaches for combating malaria. Since the early 1980s, hundreds of semi-synthetic and synthetic peroxides have been developed and tested for their antimalarial activity, the results of which were extensively reviewed. In addition, in therapeutic practice, there is no reported case of drug resistance to these antimalarial peroxides. This review summarizes recent achievements in the area of peroxide drug development for malaria chemotherapy.Širenje malarije je stalno prisutan problem na globalnom nivou. Od malarije godišnje oboli 40 % svetske populacije i oko 1,5-2,7 miliona ljudi umre. Prema podacima Svetske zdravstvene organizacije, 90 % smrtnih slučajeva je u zemljama podsaharske Afrike, među kojima dominiraju deca starosti do 5 godina. Usled nemogućnosti razvoja vakcine, hemoterapija ostaje kao jedini pouzdan oblik lečenja od ove bolesti. Poslednjih godina problem borbe protiv malarije postaje urgentan iz brojnih razloga, među kojima je najznačajniji razvoj hlorokin-rezistentnih sojeva parazita. Otkriće da artemizinin (ART, 1) i njegovi derivati pokazuju izuzetnu efikasnost prema hlorokin-rezistentnim sojevima otvorilo je velike mogućnosti u borbi protiv malarije. Od tada, posebno tokom 80-tih godina, sintetisan je veliki broj jedinjenja i rezultati njihove aktivnosti opisani su u mnogim naučnim publikacijama. Osim toga, u kliničkoj praksi nisu zabeleženi primeri pojave rezistencije parazita prema ovoj klasi antimalarika. U ovom revijalnom radu opisani su najnoviji rezultati u razvoju peroksidnih antimalarika

Steroidal tetraoxanes: synthesis and biologycal activity

U toku izrade ove doktorske disertacije sintetisani su tetraoksani derivata holne kiseline i ispitana je njihova antimalarijska, citotoksična i antiproliferativna aktivnost. U toku rada dobijeni su sledeći rezultati: 1. Razvijena su dva postupka za sintezu bis-steroidnih tetraoksana: 1) direktna peroksiacetalizacija odgovarajućih 3-keto derivata holne kiseline, 2) derivatizacija prethodno dobijenih bis-steroidnih tetraoksana. Primenom oba postupka sintetisano je 14 bis-steroidnih tetraoksana derivata holne kiseline, 123- 136. Prema prvom postupku sintetisani su bis-steroidni tetraoksani 123 - 128. Proizvodi 123 i 124 dobijeni su reakcijom ketona 119 sa 30% H2O2 / 50% H2SO4, u prinosu od 25% i 28%, a proizvodi 125 - 128 u reakcijama ketona 121 i 122 sa (Me3Si)2O2 / TMSOTf, na 0 oC u prinosu 28 – 50% (Shema 24). Utvrđeno je da u reakcijama ketona 119 sa (Me3Si)2O2 / TMSOTf i 121 i 122 sa 30% H2O2 i 50% H2SO4 dominantno nastaju proizvodi Baeyer – Villiger-ove reakcije. Prema drugom postupku sintetisani su tetraoksani 127– 136124 na dva načina: a) hidrolizom 1,25 M rastvorom NaOH u smeši CH2Cl2 / MeOH na sobnoj temperaturi u toku 3 dana (72 – 79%); b) hidrolizom pomoću NaOH u smeši i-PrOH / H2O (3:1, v/v) na temperaturi ključanja u toku 15 min. (90 – 95%, Shema 24). Kiseline 129 i 130 prevedene su preko mešovitog anhidrida u amide 131 – 136 (54 – 81%) kao i prethodno sintetisane amide 127 i 128 (Shema 25). Izolovana su oba predviđena diastereomera a na osnovu spektralnih podataka i analize monokristala derivata 123 X-zracima, pripisana je struktura sintetisanim derivatima: cis-C(2)C(2a) seriji pripadaju derivati 123, 125, 127, 129, 131, 133 i 135, a trans-C(2)C(2a) seriji pripadaju derivati 124, 126, 128, 130, 132, 134 i 136. 2. Razvijen je postupak za sintezu gem-dihidroperoksida derivata holne kiseline (137, 145 i 146, Shema 29) koji uspešno može da se primeni i za dobijanje gemdihidroperoksida jednostavnih cikličnih ketona (149, 150 i 76, Shema 30). Gem-dihidroperoksidi su sintetisani reakcijom odgovarajućeg ketona i 30% H2O2 u smeši CH2Cl2 / CH3CN (1:3, v/v) u prisustvu katalitičkih količina konc. HCl u visokom prinosu (> 90%). Postupak razvijen u toku ovog rada je jednostavniji, ekonomičniji i bitno poboljšan u odnosu na postupke do sada opisane u literaturi (ref. 45, 47, Shema 13). 3. Sintetisana su 53 mešovita tetraoksana derivata holne kiseline, 138 – 144b. Metil-estri 138 dobijeni su kuplovanjem gem-dihidroperoksida 137 sa jednostavnim, supstituisanim i nesusptituisanim, cikličnim ketonima (~ 30%, Shema 27). Reakcija se vrši u dihlormetanu, u prisustvu katalitičkih količina H2SO4. Reakcijom ciklopentanona, cikloheksanona i ciklooktanona dobijen je i izolovan po jedan proizvod, a svaki od prohiralnih 4-metil-, 4-etil-, 4-t-butil- i 4-fenilcikloheksanona daju oba očekivana diastereoizomera. Reakcijama 2,6-dimetil-, 2-metil-cikloheksanona i. mentona proizvodi su izolovani u obliku odgovarajućih smeša. Reakcija gem-dihidroperoksida 137 sa aromatičnim karbonilnim jedinjenjima - 2-furil-metilketon, 4-nitroacetofenon, 6-metoksitetralon-1-on i pmetoksibenzaldehid - nije dala očekivane proizvode. Selektivnom hidrolizom C(24) metil-estarske grupe tetraoksana 138 sa NaOH u smeši i-PrOH / H2O (3:1, v/v) na temperaturi ključanja dobijene su odgovarajuće karboksilne kiseline 139 (72 – 93%), koje su preko mešovitog anhidrida prevedene u odgovarajuće amide 140 – 144b (~ 80%, Shema 28). Na osnovu spektralnih podataka i analize monokristala kiseline 139g X-zracima određena je konfiguracija C(4”) atoma 4”-metil derivata. Utvrđeno je da derivati 138f, 139f i 140f – 143f pripadaju (4”R) seriji, a da derivati 138g, 139g i 140g – 143g pripadaju (4”S) seriji...Within this thesis a cholic acid-derived 1,2,4,5- tetraoxacyclohexanes (tetraoxanes) were synthesised and characterised, their in vitro antimalarial activity was evaluated and cytotoxicity determined. In addition, the tetraoxanes reported in this thesis were evaluated as potential antiproliferatives against various cancers cell lines. The results can be summarised as follows: 1.Two procedures for preparation of bis steroidal tetraoxanes were developed: 1) direct peroxyacetalisation of the corresponding 3-keto cholic acid derivatives, 2) transformation of the previously prepared tetraoxanes into its derivatives. 14 bis- Steroidal tetraoxanes, 123-136, were prepared utilising both procedures. Tetraoxanes 123-128 were obtained according to the first procedure. Compounds 123 and 124 were prepared by reacting of ketone 119 with 30% H2O2 / 50% H2SO4 in 25% and 28% yield, respectively, while the compounds 125-128 were obtained from the ketones 121 and 122 using TMS2O2 / TMSOTf at 0 oC, in 28-50% yield (Scheme 24). Ketone 119 with TMS2O2 / TMSOTf, as well as ketones 121 and 122 with 30% H2O2 / 50% H2SO4, afforded as main products the Baeyer-Villiger products. Procedure 2) was utilised for preparation of tetraoxanes 127-136. The carboxylic acids 129 and 130 were obtained by selective hydrolysis of C(24) methyl ester moiety of tetraoxanes 123 and 124, respectively, utilising a) hydrolysis with 1.25 M NaOH/CH2Cl2-CH3OH at r.t. for 3 days (72-79%), and b) hydrolysis with NaOH / i-PrOH-H2O (3:1, v/v) at reflux for 15 min (90-95%, Scheme 24). The acids 129 and 130 were further transformed via their mixed anhydrides into corresponding amides 131-136 (54-81%), as well as into previously synthesised amides 127 and 128 (Scheme 25). Both predicted diastereomers were isolated and their structures was assigned from corresponding spectral data and confirmed by X-ray analysis of tetraoxane 123 monocrystal: compounds 123, 125, 127, 129, 131, 133, and 135 belong to cis-C(2)C(2a) series, and to corresponding trans-C(2)C(2a) series belong the compounds 124, 126, 128, 130, 132, 134, and 136. 2. The procedure developed for the synthesis of cholic acid-derived gem-dihydroperoxides (137, 145, 146, Scheme 29) was also applied for synthesis gemdihydroperoxides of simple cyclic systems (149, 150 and 76, Scheme 30). It embodies the treatment of a ketone with 30% H2O2 in CH2Cl2-CH3CN mixture (1:3, v/v) in the presence of cat. HCl (> 90%). The procedure developed within this thesis represents a significant improvement in terms of simplicity and economy as compared with the known ones (ref. 45, 47, Scheme 13). 3. 53 Mixed tetraoxanes derived from cholic acid were prepared (138-144b). Mixed steroidal tetraoxane methyl esters 138 were synthesised by coupling of gemdihydroperoxide 137 to simple substituted and nonsubstituted cycloalkanones (~30%, Scheme 27). The coupling reaction was performed in dichloromethane in the presence of cat. H2SO4. The reaction of cyclopentanone, cyclohexanone and cyclooctanone afforded only one corresponding tetraoxane each, while the reaction of 4-methyl, 4-ethyl, 4-t-butyl, and 4- phenylcyclohexanone afforded both expected diastereomers each. Aromatic ketones failed to produce a tetraoxane in a reaction with the same dihydroperoxide. Selective hydrolysis of tetraoxanes 138 with NaOH / i-PrOH-H2O as above afforded the corresponding acids 139 (72-93%), which were via their mixed anhydrides transformed into corresponding amides 140-144b (~80%, Scheme 28). The configuration at C(4") in 4"-methyl series was determined by X-ray analysis of tetraoxane acid 139g. It is found that tetraoxanes 138f, 139f, and 140f-143f belong to (4"R)-series, while their respective (4"S) diastereoisomers are 138g, 139g, and 140g-143g..

Artemisinins and synthetic peroxides as highly efficient antimalarials

Malaria is devastating disease and global public health problem, with nearly half world population exposed to risk. Illness is caused by five Plasmodium species, P falciparum, P ovale, P viva; P malaria and P knowlesi, from which P falciparum is the most serious one causing cerebral malaria and is the major reason for malaria mortality. Vaccine against malaria is not expected in the near future and chemotherapy remains as most feasible alternative for treatment of the disease. The development of widespread drug-resistance to chloroquine (CQ), the most successful antimalarial drug up to date, has resulted in severe health issues for countries in malaria endemic regions. Organic peroxides, like artemisinins, 1,2,4-trioxanes, 1,2,4-trioxolanes, 1,2,4,5-tetraoxanes and their chimeras, are the best choice for malaria treatment nowadays. These therapeutics are fast acting, non-toxic, low costing and without reported data of parasite resistance. Stability of peroxide bonds enables synthetic comfort and resulting in diversity of synthesized structures. The most important classes of peroxide antimalarials with promising representatives are reviewed and possible mechanisms of action were presented in details

4-Aminoqionolines as reversible inhibitors of human cholinesterase activity

We synthesised eight derivatives of 4-aminoquinolines differing in the substituents attached to the C(4)-amino group and C(7) carbon of 4-aminoquinoline, and tested their potency to inhibit human AChE and BChE. All of the compounds reversibly inhibited both enzymes with dissociation inhibition (Ki) constants from 0.50 to 50 µM exhibiting selectivity. In other words, for all compounds, AChE exhibited higher affinity than BChE. The most potent inhibitors of AChE were compounds with an octyl chain or adamantane, regardless of the group in position C(7). The shortening of the chain length caused the AChE inhibition decrease by 5-20 times. Docking studies made it clear that the high AChE affinity resulted from simultaneous interactions of the quinoline group with aromatic residues of both the catalytic active site and the peripheral site. In conclusion, the inhibition potency and selectivity classify several novel compounds as leads for further modification and optimization towards the development of new inhibitors of AChE and potential drugs for treatment of neurodegenerative diseases.13th International Meeting on Cholinesterases and and the 7th International Conference on Paraoxonases, 9th to 14th of September 2018 Hradec Králové, Czech Republi

Antimalarijska, antimikobakterijska i antiproliferativna aktivnost fenil-supstituisanih tetraoksana

Mixed tetraoxanes of the 4"-phenyl-substituted cyclohexyl-spirotetraoxacyclohexyl-spirocholate series have been prepared and evaluated as possible antimalarials, anti-proliferatives and antimycobacterials. The activity of the (4"R or S)-phenyl series against P falciarum D6 and W2 strains was found to be at the level of artemisinin. with two compounds. the acid 4 and the amide 6, exhibiting encouraging anti-TB activity as well. Very promising in vitro results of the said tetraoxanes were obtained against solid tumours and, in some instances. the activity against a selected number of cell lines was higher than that of the antitumor drug paclitaxel.U ovom radu prikazana je sinteza serije mešovitih tetraoksana 4"-fenil-supstituisanih cikloheksil-spirotetraoksacikloheksil-spiroholata, a ispitana je i njihova in vitro aktivnost kao mogućih antimalarika, anti-TBC agenasa i antiproliferativnih jedinjenja. Aktivnost (4"R ili S)-fenil serije na D6 i W2 sojeve P. falciparum vrlo je slična aktivnosti poznatog antimalarika artemizinina. Izraženu anti-TBC aktivnost iskazala su jedinjenja 4 i 6, čija antiproliferativna in vitro aktivnost prema nekim kompaktnim tumorima prevazilazi aktivnost leka paklitaksela

QSAR izučavanje steroidnih 1,2,4,5-tetraoksanskih antimalarika računarskim modelovanjem

A three-dimensional QSAR pharmacophore model for antimalarial activity of steroidal 1,2,4,5-tetraoxanes was developed from a set of 17 substituted antimalarial derivatives out of 27 analogues that exhibited remarkable in vitro activity (below 100 ng/mL) against sensitive and multidrug-resistant Plasmodium falciparum malaria. The pharmacophore, which contains two hydrogen bond acceptors (lipid) and one hydrophobic (aliphatic) feature, was found to map well onto the potent analogues and many other well-known antimalarial trioxane drugs including artemisinin, arteether, artesunic acid, and tetraoxanes. The presence of at least one hydrogen bond acceptor in the trioxane or the tetraoxane moiety appears to be necessary for potent activity of this class of compounds. Docking calculations of some of these compounds with heme are consistent with the above observation as the proximity of the heme iron to the oxygen atom of the trioxane or the tetraoxane moiety favors potent activity of the compounds. Electron transfer from the oxygen of trioxane or the tetraoxane appears to be crucial for mechanism of action of the compounds. This information together with the pharmacophore should enable search for new peroxide containing antimalarial candidates from databases and custom designed synthesis of more efficacious and safer analogues.Izvršeno je trodimenzionalno modelovanje farmakofore za antimalarijsku aktivnost steroidnih 1,2,4,5-tetraoksana na osnovu struktura 17 supstituisanih derivata, izdvojenih iz grupe od 27 analoga koji pokazuju izuzetnu in vitro antimalarijsku aktivnost (ispod 100 ng/mL) prema osetljivim i rezistentnim sojevima Plasmodium falciparum-a. Utvrđeno je da se farmakofora, koju čine dva akceptora vodonične veze (lipidni) i jedno hidrofobno mesto (alifatično), dobro preklapa sa strukturama aktivnih analoga kao i sa strukturama nekih poznatih trioksanskih antimalarika, uključujući artemizinin, arteetar, artesunatnu kiselinu kao i sa strukturama nekih drugih tetraoksana. Za dobru aktivnost ove klase jedinjenja važno je prisustvo bar jednog akceptora vodonične veze na trioksanskom ili tetraoksanskom delu strukture. Izračunavanja interakcija nekih od ovih jedinjenja sa hemom saglasna su sa prethodno iznetim zaključkom da je blizina gvožđa iz hema i trioksanskog ili tetraoksanskog atoma kiseonika važna za dobru aktivnost ovih jedinjenja. Izgleda da je prenos elektrona sa trioksanskog ili tetraoksanskog atoma kiseonika osnova mehanizma dejstva ovih jedinjenja. Izvršena modelovanja farmakofore i interakcija ovih jedinjenja se hemom mogu biti od pomoći u sintezi novih i efikasnijih peroksidnih antimalarika