Diversity-oriented synthesis and activity evaluation of substituted bicyclic lactams as anti-malarial against Plasmodium falciparum.
TL;DR: This study unveils a DOS-mediated exploration of small molecules with novel structural motifs that culminates in identifying a potential lead molecule against malaria.
Abstract: Background: Malaria remains the world’s most important devastating parasitic disease. Of the five species of Plasmodium known to infect and cause human malaria, Plasmodium falciparum is the most virulent and responsible for majority of the deaths caused by this disease. Mainstream drug therapy targets the asexual blood stage of the malaria parasite, as the disease symptoms are mainly associated with this stage. The prevalence of malaria parasite strains resistance to existing anti-malarial drugs has made the control of malaria even more challenging and hence the development of a new class of drugs is inevitable. Methods: Screening against different drug resistant and sensitive strains of P. falciparum was performed for few bicyclic lactam-based motifs, exhibiting a broad spectrum of activity with low toxicity generated via a focussed library obtained from diversity oriented synthesis (DOS). The synthesis and screening was followed by an in vitro assessment of the possible cytotoxic effect of this class of compounds on malaria parasite. Results: The central scaffold a chiral bicyclic lactam (A) and (A’) which were synthesized from (R)-phenylalaninol, levulinic acid and 3-(2-nitrophenyl) levulinic acid respectively. The DOS library was generated from A and from A’, by either direct substitution with o-nitrobenzylbromide at the carbon α- to the amide functionality or by conversion to fused pyrroloquinolines. Upon screening this diverse library for their anti-malarial activity, a dinitro/diamine substituted bicyclic lactam was found to demonstrate exceptional activity of >85% inhibition at 50 μM concentration across different strains of P. falciparum with no toxicity against mammalian cells. Also, loss of mitochondrial membrane potential, mitochondrial functionality and apoptosis was observed in parasite treated with diamine-substituted bicyclic lactams. Conclusions: This study unveils a DOS-mediated exploration of small molecules with novel structural motifs that culminates in identifying a potential lead molecule against malaria. In vitro investigations further reveal their cytocidal effect on malaria parasite growth. It is not the first time that DOS has been used as a strategy to identify therapeutic leads against malaria, but this study establishes the direct implications of DOS in scouting novel motifs with anti-malarial activity.
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TL;DR: Surface-associated TRAP (thrombospondin-related anonymous protein) family proteins are conserved across the phylum of apicomplexan parasites, indicating that motor-binding TRAP family members function not just in parasite motility and cell invasion but also in membrane disruption and cell egress.
56 citations
TL;DR: An (S)‐tryptophanol‐derived isoindolinone was identified as a promising starting scaffold to search for novel antimalarials, combining excellent activity against both stages of the parasite′s life cycle with low cytotoxicity and excellent metabolic and chemical stability in vitro.
Abstract: Malaria continues to be a major cause of morbidity and mortality to this day, and resistance to drugs like chloroquine has led to an urgent need to discover novel chemical entities aimed at new targets. Here, we report the discovery of a novel class of potential antimalarial compounds containing an indolizinoindolone scaffold. These novel enantiopure indolizinoindolones were synthesized, in good-to-excellent yields and excellent diastereoselectivities, by cyclocondensation reaction of (S)- or (R)-tryptophanol and 2-acyl benzoic acids, followed by intramolecular α-amidoalkylation. Interestingly, we were able to synthesize for the first time 7,13b-cis indolizinoindolones in a two-step route. The novel compounds showed promising activity against erythrocytic stages of the human malaria parasite, Plasmodium falciparum, and liver stages of the rodent parasite Plasmodium berghei. In particular, an (S)-tryptophanol-derived isoindolinone was identified as a promising starting scaffold to search for novel antimalarials, combining excellent activity against both stages of the parasite's life cycle with low cytotoxicity and excellent metabolic and chemical stability in vitro.
27 citations
TL;DR: It is shown that ionic imbalance caused by scaffold 7 induces autophagy that leads to onset of apoptosis in the parasite evident by the loss of mitochondrial membrane potential (ΔΨm) and DNA degradation.
Abstract: Natural products offer an abundant source of diverse novel scaffolds that inspires development of next generation anti-malarials. With this vision, a library of scaffolds inspired by natural biologically active alkaloids was synthesized from chiral bicyclic lactams with steps/scaffold ratio of 1.7:1. On evaluation of library of scaffolds for their growth inhibitory effect against malaria parasite we found one scaffold with IC50 in low micro molar range. It inhibited parasite growth via disruption of Na+ homeostasis. P-type ATPase, PfATP4 is responsible for maintaining parasite Na+ homeostasis and is a good target for anti-malarials. Molecular docking with our scaffold showed that it fits well in the binding pocket of PfATP4. Moreover, inhibition of Na+-dependent ATPase activity by our potent scaffold suggests that it targets parasite by inhibiting PfATP4, leading to ionic imbalance. However how ionic imbalance attributes to parasite's death is unclear. We show that ionic imbalance caused by scaffold 7 induces autophagy that leads to onset of apoptosis in the parasite evident by the loss of mitochondrial membrane potential (ΔΨm) and DNA degradation. Our study provides a novel strategy for drug discovery and an insight into the molecular mechanism of ionic imbalance mediated death in malaria parasite.
18 citations
TL;DR: Interestingly, the benzoxazine derivatives of eugenol with GO nanoparticle exhibited enhanced therapeutic potential in cancer cells and significant role of these derivatives on parasite suggesting its multi-pharmacological capability.
Abstract: Natural products from medicinal plants have always attracted a lot of attention due to their diverse and interesting therapeutic properties. We have employed the principles of green chemistry involving isomerization, coupling and condensation reaction to synthesize a class of compounds derived from eugenol, a naturally occurring bioactive phytophenol. The compounds were characterized structurally by 1H-, 13C-NMR, FT-IR spectroscopy and mass spectrometry analysis. The purity of compounds was detected by HPLC. The synthesized compounds exhibited anti-cancer activity. A 10–12-fold enhancement in efficiency of drug molecules (~ 1 µM) was observed when delivered with graphene oxide (GO) as a nanovehicle. Our data suggest cell death via apoptosis in a dose-dependent manner due to increase in calcium levels in specific cancer cell lines. Interestingly, the benzoxazine derivatives of eugenol with GO nanoparticle exhibited enhanced therapeutic potential in cancer cells. In addition to anti-cancer effect, we also observed significant role of these derivatives on parasite suggesting its multi-pharmacological capability.
14 citations
TL;DR: Levulinic acid (LEV) has been identified as a key building block chemical produced entirely from biomass and its derivatives can be used to synthesize a variety of value-added chemicals, such as 2-but...
Abstract: Levulinic acid (LEV) has been identified as a key building block chemical produced entirely from biomass. Its derivatives can be used to synthesize a variety of value-added chemicals, such as 2-but...
5 citations
References
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TL;DR: The majority of nonantibacterial activities discovered for β-lactam derivatives during the last 15 years are based on their ability to form a stable covalent complex with nucleophile in the active site of enzymes regulating fundamental physiological processes in mammalian organism such as serine and cysteine proteases, LDL phospholipase A2, A-independent transacylase and some still indeciphered enzymes as discussed by the authors.
Abstract: The majority of nonantibacterial activities discovered for β-lactam derivatives during the last 15 years are based on their ability to form a stable covalent complex with nucleophile in the active site of enzymes regulating fundamental physiological processes in mammalian organism such as serine and cysteine proteases, LDL phospholipase A2, A-independent transacylase and some still indeciphered enzymes. Regulation of their catalytic activity both in vitro and in vivo by compounds designed on the cephalosporin, penicillin and 2-azetidinone base was successfully exploited in the treatment of inflammatory, respiratory, cardiovascular disorders, cancer and other pathologic processes. Availability of X-ray crystallographic data for target enzymes and computational molecular modelling in combination with wide possibilities of structural modifications for commercial natural and synthetic β-lactams and the chiral blocks allow to consider this class of organic compounds as a perspective source of mechanism based nonantibacterial drugs.
94 citations
"Diversity-oriented synthesis and ac..." refers background in this paper
...Biologically active lactams range from β-lactams, used in diverse therapeutic areas viz serine-dependent enzyme inhibitors, matrix-metalloprotease inhibitors, and even apoptosis inductors [22,23], the inhibition of HIV-1 protease, antitumor activity, anti-malarial activity, and cholesterol absorption inhibition [24-30], peptides, bicyclic lactams (as potential anticancer and anti-malarials) etc....
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TL;DR: In vitro results suggest that the beta-lactam of ezetimibe merely serves as a ring scaffold to appropriately position the required substituents for inhibitory activity, highlighting several promising strategies for the design of alternative small-molecule cholesterol absorption inhibitors.
Abstract: We have utilized our recently developed in vitro assay to address two key questions in the design of small-molecule cholesterol absorption inhibitors using ezetimibe, the only drug yet approved for the inhibition of cholesterol absorption in the small intestine, as a starting point: (1) the role of glycosylation and (2) the importance of the beta-lactam scaffold of ezetimibe for inhibitory activity. A wide range of nonhydrolyzable phenolic glycosides of ezetimibe were synthesized and demonstrated to be active inhibitors of cholesterol absorption using the brush border membrane vesicle assay. The analogous azetidines provided access to a variety of inhibitors in vitro, suggesting that the beta-lactam of ezetimibe merely serves as a ring scaffold to appropriately position the required substituents. Our findings highlight several promising strategies for the design of alternative small-molecule cholesterol absorption inhibitors that could ultimately be useful in preventing cardiovascular disease by lowering blood cholesterol levels.
74 citations
"Diversity-oriented synthesis and ac..." refers background in this paper
...Biologically active lactams range from β-lactams, used in diverse therapeutic areas viz serine-dependent enzyme inhibitors, matrix-metalloprotease inhibitors, and even apoptosis inductors [22,23], the inhibition of HIV-1 protease, antitumor activity, anti-malarial activity, and cholesterol absorption inhibition [24-30], peptides, bicyclic lactams (as potential anticancer and anti-malarials) etc....
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TL;DR: 6-alkylidene substituted 4-heteryldithio and 4-methylsulfonyl azetidin-2-ones revealed potent cytotoxic properties towards monolayer tumor cells in <10-microM concentrations.
73 citations
"Diversity-oriented synthesis and ac..." refers background in this paper
...Biologically active lactams range from β-lactams, used in diverse therapeutic areas viz serine-dependent enzyme inhibitors, matrix-metalloprotease inhibitors, and even apoptosis inductors [22,23], the inhibition of HIV-1 protease, antitumor activity, anti-malarial activity, and cholesterol absorption inhibition [24-30], peptides, bicyclic lactams (as potential anticancer and anti-malarials) etc....
[...]
TL;DR: This is the first example of beta-lactams inhibiting metallo-proteinases instrumental in cancer invasion and angiogenesis, and these molecules are good candidates for prototype drugs showing selective antibiotic, anti-inflammatory, and anti-invasion properties.
71 citations
"Diversity-oriented synthesis and ac..." refers background in this paper
...They are further differentiated by side chains, unsaturations, heteroatoms, and, in many cases, by the presence of another five- or six-membered rings [20,21]....
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TL;DR: There is potential for developing this class of beta-lactams into novel anticancer agents, and it is shown that lactam 12 induces apoptosis selectively in Jurkat T and simian virus 40-transformed, but not in nontransformed NK and parental normal fibroblast, cells.
71 citations