Development of a novel series of vinylic halogenated fatty acids and their potential biomedical applications.
Download
Advisor
Carballeira, Nestor M.Type
DissertationDegree Level
Ph.D.Date
2021-01-29Metadata
Show full item recordAbstract
Marine sponges and anemones have provided most of the naturally occurring halogenated vinylic fatty acids (FA) known to date. Red algae such as A. taxiformis and Bonnemaisonia nootkana biosynthesize interesting brominated and chlorinated FA. Some of these compounds exhibit antifungal activity but their antiprotozoal and antibacterial activity remain unexplored.
In this work we report the synthesis and characterization of a novel series of halogenated vinylic FA with different chain lengths: 2-allyl-3-bromo-2E-nonadecenoic acid (1a), 2-allyl-3-chloro-2E-nonadecenoic acid (2a), 2-allyl-3-bromo-2E-dodecenoic acid (1b), 2-allyl-3-chloro-2E-dodecenoic acid (2b), 2-allyl-3-bromo-2E-hexadecenoic acid (1c), and 2-allyl-3-chloro-2E-hexadecenoic acid (2c) in synthetically useful yields (38-83%), which allow us to study their potential as antileishmanial and antibacterial agents.
The inhibitory effect of the FA’s with the longest chain (19 carbons) 1a and 2a, and the ones with the shortest chain (12 carbons) 1b and 2b on LTopIB and hTopIB was explored. The brominated FA 1a displayed a higher inhibitory potential to both enzymes than the chlorinated analog (LTopIB EC50 = 7.4 ± 0.2 μM, hTopIB EC50 = 12.7 ± 0.0 μM). The reduction of the carbon chain length from 19 to 12 carbons (1b and 2b) proved detrimental. The mechanism of the inhibition of LTopIB by the halogenated vinylic FA 1a and 2a follows a Gimatecan-independent mechanism. The long-chain FA 1a and 2a also displayed higher toxicity towards amastigotes than towards promastigotes demonstrating that these FA can distinguish between the different stages of the leishmanial parasite and display differential toxicities towards each stage. Molecular modeling studies of 1a and 2a determined, that in fact, the brominated FA 1a forms a halogen bond (binding energy = -4.85 kcal/mol) with a DNA phosphate group and an ionic interaction between the carboxylate and Lys 262, which supports the higher potency of 1a (IC50 = 7.4 μM) over its chlorinated analog 2a (IC50 = 25.7 μM).
The shorter chain FA’s antibacterial potential was also studied (1b, 2b, 1c, and 2c) against 5 clinical isolates of methicillin-resistant Staphylococcus aureus (CIMRSA) strains. Using microdilution susceptibility testing, we determined that the most significant inhibition was obtained with brominated FA 1c for all five CIMRSA strains studied. Moreover, 1c showed inhibitory effects comparable to, and- on some occasions (as with CIMRSA XII and XIII), even better than Ciprofloxacin (Cipro). The brominated hexadecenoic acid 1c also displayed a 19% cytotoxicity against Vero Cells at 100 μg/mL and in kinetic growth assays demonstrated to be toxic to CIMRSA XIII at a significantly lower concentration than Cipro (31.2 μg/mL of 1c vs 250 μg/mL of Cipro), which reveals the potency of 1c as an antibacterial agent towards CIMRSA strains. Our results indicate that the mechanism of action of 1c on the inhibition of these CIMRSA involves disrupting of the cell wall. We also determined that the brominated hexadecenoic FA inhibited the norB expression in S. aureus, suggesting that the bacteria is not resistant to 1c, which makes it a great antibacterial candidate.
In this work we report the synthesis and characterization of a novel series of halogenated vinylic FA with different chain lengths: 2-allyl-3-bromo-2E-nonadecenoic acid (1a), 2-allyl-3-chloro-2E-nonadecenoic acid (2a), 2-allyl-3-bromo-2E-dodecenoic acid (1b), 2-allyl-3-chloro-2E-dodecenoic acid (2b), 2-allyl-3-bromo-2E-hexadecenoic acid (1c), and 2-allyl-3-chloro-2E-hexadecenoic acid (2c) in synthetically useful yields (38-83%), which allow us to study their potential as antileishmanial and antibacterial agents.
The inhibitory effect of the FA’s with the longest chain (19 carbons) 1a and 2a, and the ones with the shortest chain (12 carbons) 1b and 2b on LTopIB and hTopIB was explored. The brominated FA 1a displayed a higher inhibitory potential to both enzymes than the chlorinated analog (LTopIB EC50 = 7.4 ± 0.2 μM, hTopIB EC50 = 12.7 ± 0.0 μM). The reduction of the carbon chain length from 19 to 12 carbons (1b and 2b) proved detrimental. The mechanism of the inhibition of LTopIB by the halogenated vinylic FA 1a and 2a follows a Gimatecan-independent mechanism. The long-chain FA 1a and 2a also displayed higher toxicity towards amastigotes than towards promastigotes demonstrating that these FA can distinguish between the different stages of the leishmanial parasite and display differential toxicities towards each stage. Molecular modeling studies of 1a and 2a determined, that in fact, the brominated FA 1a forms a halogen bond (binding energy = -4.85 kcal/mol) with a DNA phosphate group and an ionic interaction between the carboxylate and Lys 262, which supports the higher potency of 1a (IC50 = 7.4 μM) over its chlorinated analog 2a (IC50 = 25.7 μM).
The shorter chain FA’s antibacterial potential was also studied (1b, 2b, 1c, and 2c) against 5 clinical isolates of methicillin-resistant Staphylococcus aureus (CIMRSA) strains. Using microdilution susceptibility testing, we determined that the most significant inhibition was obtained with brominated FA 1c for all five CIMRSA strains studied. Moreover, 1c showed inhibitory effects comparable to, and- on some occasions (as with CIMRSA XII and XIII), even better than Ciprofloxacin (Cipro). The brominated hexadecenoic acid 1c also displayed a 19% cytotoxicity against Vero Cells at 100 μg/mL and in kinetic growth assays demonstrated to be toxic to CIMRSA XIII at a significantly lower concentration than Cipro (31.2 μg/mL of 1c vs 250 μg/mL of Cipro), which reveals the potency of 1c as an antibacterial agent towards CIMRSA strains. Our results indicate that the mechanism of action of 1c on the inhibition of these CIMRSA involves disrupting of the cell wall. We also determined that the brominated hexadecenoic FA inhibited the norB expression in S. aureus, suggesting that the bacteria is not resistant to 1c, which makes it a great antibacterial candidate.
Rights
© 2021 Denisse Alequin TorresCollections
Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivs 3.0 United States