Evaluation of chalcone derivatives for their role as antiparasitic and neuroprotectant in experimentally induced cerebral malaria mouse model.

Cerebral malaria is a severe complication of Plasmodium falciparum infection with a complex pathophysiology. The current course of treatment is ineffective in lowering mortality or post-treatment side effects such as neurological and cognitive abnormalities. Chalcones are enormously distributed in spices, fruits, vegetables, tea, and soy-based foodstuffs that are well known for their antimalarial activity, and in recent years they have been widely explored for brain diseases like Alzheimer's disease. Therefore, considering the previous background of chalcones serving as both antimalarial and neuroprotective, the present study aimed to study the effect of these chalcone derivatives on an experimental model of cerebral malaria (CM). CM-induced mice were tested behaviorally (elevated plus maze, rota rod test, and hanging wire test), biochemically (nitric oxide estimation, cytokines (IL-1, IL-6, IL-10, IL-12p70, TNF, IFN-y), histopathologically and immunohistochemically, and finally ultrastructural changes were examined using a transmission electron microscope. All three chalcones treated groups showed a significant (p < 0.001) decrease in percentage parasitemia at the 10th day post-infection. Mild anxiolytic activity of chalcones as compared to standard treatment with quinine has been observed during behavior tests. No pigment deposition was observed in the QNN-T group and other chalcone derivative treated groups. Rosette formation was seen in the derivative 1 treated group. The present derivatives may be pioneered by various research and science groups to design such a scaffold that will be a future antimalarial with therapeutic potential or, because of its immunomodulatory properties, it could be used as an adjunct therapy. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03676-y.

Antimalarial and immunomodulatory potential of chalcone derivatives in experimental model of malaria.

BACKGROUND: Malaria is a complex issue due to the availability of few therapies and chemical families against Plasmodium and mosquitoes. There is increasing resistance to various drugs and insecticides in Plasmodium and in the vector. Additionally, human behaviors are responsible for promoting resistance as well as increasing the risk of exposure to infections. Chalcones and their derivatives have been widely explored for their antimalarial effects. In this context, new derivatives of chalcones have been evaluated for their antimalarial efficacy. METHODS: BALB/c mice were infected with P. berghei NK-65. The efficacy of the three most potent chalcone derivations (1, 2, and 3) identified after an in vitro compound screening test was tested. The selected doses of 10 mg/kg, 20 mg/kg, and 10 mg/kg were studied by evaluating parasitemia, changes in temperature, body weights, organ weights, histopathological features, nitric oxide, cytokines, and ICAM-1 expression. Also, localization of parasites inside the two vital tissues involved during malaria infections was done through a transmission electron microscope. RESULTS: All three chalcone derivative treated groups showed significant (p < 0.001) reductions in parasitemia levels on the fifth and eighth days of post-infection compared to the infected control. These derivatives were found to modulate the immune response in a P. berghei infected malaria mouse model with a significant reduction in IL-12 levels. CONCLUSIONS: The present study indicates the potential inhibitory and immunomodulatory actions of chalcones against the rodent malarial parasite P. berghei.

Pharmacokinetic evaluation of Chalcone derivatives with antimalarial activity in New Zealand White Rabbits.

OBJECTIVE: Malaria is a major global health concern with the urgent need for new treatment alternatives due to the alarming increase of drug-resistant Plasmodium strains. Chalcones and its derivatives are important pharmacophores showing antimalarial activity. Determination of the pharmacokinetic variables at the preliminary step of drug development for any drug candidates is an essential component of in vivo antimalarial efficacy tests. Substandard pharmacokinetic variables are often responsible for insufficient therapeutic effect. Therefore, three chalcone derivatives, 1, 2, and 3, having antimalarial potency were studied further for potential therapeutic efficacy. RESULTS: In vivo pharmacokinetic studies of these three derivatives were performed on New Zealand White rabbits. The three derivatives were administered intra-peritoneally or orally at effective dose concentration and blood samples at different time points were collected. The determination of drug concentration was done through reverse phase-high performance liquid chromatography. The peak plasma concentration of derivative 1, 2, and 3 were 1.96 ± 0.46 µg/mL (intraperitoneal route), 69.89 ± 5.49 µg/mL (oral route), and 3.74 ± 1.64 µg/mL (oral route). The results indicate a very low bioavailability of these derivatives. The present study gives a benchmark to advance the investigation of more derivatives in order to revamp the pharmacokinetic variables while maintaining both potency and metabolic constancy.

Ultrastructural alterations in Plasmodium falciparum induced by chalcone derivatives.

OBJECTIVE: Chalcones (1, 3-diaryl-2-propen-1-ones) and their derivatives are widely explored from the past decade for its antimalarial activity. To elucidate their mechanism of action on the malaria parasite, the ultrastructural changes with the action of these derivatives in different organelles of the parasite were studied in vitro. Infected RBCs [CQ sensitive (MRC-2) and CQ resistant (RKL-9) Plasmodium strain] were treated with three chalcone derivatives 1, 2 and 3 and standard drugs, i.e., CQ and artemisinin at twice their respective IC50 values for 24 h and then harvested, washed, fixed, embedded and stained to visualize ultra-structure changes before and after intervention of treatment under in vitro condition through transmission electron microscope. RESULTS: The ultrastructural changes demonstrate the significant disturbance of all parasite membranes, including those of the nucleus, mitochondria and food vacuole, in association with a marked reduction of ribosomes in the trophozoites and cessation of developing schizonts which suggest multiple mechanisms of action by which chalcone derivatives act on the malaria parasite. The present study opens up perspectives for further exploration of these derivatives in vivo malaria model to discover more about its effect and mechanism of action.

In vitro anti-malarial efficacy of chalcones: cytotoxicity profile, mechanism of action and their effect on erythrocytes.

BACKGROUND: Malaria extensively leads to mortality and morbidity in endemic regions, and the emergence of drug resistant parasites is alarming. Plant derived synthetic pharmaceutical compounds are found to be a foremost research to obtain diverse range of potent leads. Amongst them, the chalcone scaffold is a functional template for drug discovery. The present study involves synthesis of ten chalcones with various substitution pattern in rings A and B and assessment of their anti-malarial efficacy against chloroquine sensitive and chloroquine resistant strains as well as of their cytotoxicity and effect on haemozoin production. METHODS: The chalcones were synthesized by Claisen-Schmidt condensation between equimolar quantities of substituted acetophenones and aryl benzaldehydes (or indole-3-carboxaldehyde) and were screened for anti-malarial activity by WHO Mark III schizont maturation inhibition assay. The cytotoxicity profile of a HeLa cell line was evaluated through MTT viability assay and the selectivity index (SI) was calculated. Haemozoin inhibition assay was performed to illustrate mode of action on a Plasmodium falciparum strain. RESULTS: The IC50 values of all compounds were in the range 0.10-0.40 µg/mL for MRC-2 (a chloroquine sensitive strain) and 0.14-0.55 µg/mL for RKL-9 (a chloroquine resistant strain) of P. falciparum. All the chalcones showed low cellular toxicity with minimal haemolysis. The statistically significant reduction (p < 0.05) in the haemozoin production suggests a similar mechanism than that of chloroquine. CONCLUSIONS: Out of ten chalcones, number 7 was found to be a lead compound with the highest potency (IC50 = 0.11 µg/mL), as compared to licochalcone (IC50 = 1.43 µg/mL) and with high selectivity index of 85.05.

Anti-conjunctivitis effect of fresh juice of xGraptoveria (Crassulaceae): A phytochemical and ethnobotanical study.

AIM: The parent of xGraptoveria, Graptopetalum paraguayense, is used in Chinese folk medicine for alleviating hepatic disorders, detumescence and detoxication, lowering of blood pressure, inhibition of cancer cells, exerting diuretic effects, relieving pain and infections. No data are available regarding its anti-conjunctivitis effect. The aim of this preliminary study is to test the anti-conjunctivitis properties of xGraptoveria (Crassulaceae) and to identify its bioactive constituents. MATERIALS AND METHODS: Fresh watery juice of leaves of xGraptoveria was extracted with n-butanol and the extract was analyzed using gas chromatography-mass spectrometry (GC/MS). The ethnobotanical appraisal of the anti-conjunctivitis properties of xGraptoveria was based on 11 interviews about the symptoms against which this plant demonstrated positive effect. RESULTS: Fresh juice of xGraptoveria leaves applied directly to the irritated eye 2 times per day cured conjunctivitis in all reported cases. The main groups of organic compounds identified by GC/MS analysis in the fresh extracted leaf juice of xGraptoveria were: Alkylamines, hydroxycarboxylic acids, aliphatic and aromatic carboxylic acids, amino acids, alcohols, aromatic and aliphatic hydrocarbons. CONCLUSION: In this preliminary study, it is suggested that xGraptoveria exerts anti-conjunctivitis activity, through synergistic effect of different chemical compounds, most probably alkylamines and mainly hydroxycarboxylic, aliphatic, and aromatic carboxylic acids.

Synthesis and antioxidant activity of polyhydroxylated trans-restricted 2-arylcinnamic acids.

A series of sixteen polyhydroxylated trans-restricted 2-arylcinnamic acid analogues 3a-p were synthesized through a one-pot reaction between homophthalic anhydrides and various aromatic aldehydes, followed by treatment with BBr3. The structure of the newly synthesized compounds was confirmed by spectroscopic methods and the configuration around the double bond was unequivocally estimated by means of gated decoupling 13C-NMR spectra. It was shown that the trans-cinnamic acid fragment incorporated into the target compounds' structure ensures the cis-configuration of the stilbene backbone and prevents further isomerization along the carbon-carbon double bond. The antioxidant activity of compounds 3a-p was measured against 1,1-diphenyl-2-picrylhydrazyl (DPPH●), hydroxyl (OH●) and superoxide (O2●▬) radicals. The results obtained showed that the tested compounds possess higher activities than natural antioxidants such as protocatechuic acid, caffeic acid and gallic acid. Moreover, it was shown that a combination of two different and independently acting fragments of well-known pharmacological profiles into one covalently bonded hybrid molecule evoke a synergistic effect resulting in higher than expected activity. To rationalize the apparent antioxidant activity and to establish the mechanism of action, a SAR analysis and DFT quantum chemical computations were also performed.

Trends in utilization of the pharmacological potential of chalcones.

Chalcones (1,3-diaryl-2-propen-1-ones) are open chain flavonoids that are widely biosynthesized in plants. They are important for the pigmentation of flowers and, hence, act as attractants to the pollinators. As flavonoids, chalcones also play an important role in defense against pathogens and insects. A longstanding scientific research has shown that chalcones also display other interesting biological properties such as antioxidant, cytotoxic, anticancer, antimicrobial, antiprotozoal, antiulcer, antihistaminic and anti-inflammatory activities. Some lead compounds with various pharmacological properties have been developed based on the chalcone skeleton. Clinical trials have shown that these compounds reached reasonable plasma concentrations and did not cause toxicity. For these reasons, chalcones became an object of continued interest in both academia and industry. Nowadays, several chalcones are used for treatment of viral disorders, cardiovascular diseases, parasitic infections, pain, gastritis, and stomach cancer, as well as like food additives and cosmetic formulation ingredients. However, much of the pharmacological potential of chalcones is still not utilized. The purpose of this review is to describe the recent efforts of scientists in pharmacological screening of natural and synthetic chalcones, studying the mechanisms of chalcone action and relevant structure-activity relationships. Put together, these activities aimed at synthesis of pharmacologically active chalcones and their analogs.

Antibacterial study of the medium chain fatty acids and their 1-monoglycerides: individual effects and synergistic relationships.

The antibacterial activity of the medium chain fatty acids and their 1-monoglycerides was evaluated towards several Gram-positive strains belonging to the genera Staphylococcus, Corynebacterium, Bacillus, Listeria and Streptococcus. The 1-monoglycerides were more active than the fatty acids with monolaurin being the most active compound. Interesting effects were observed when the streptococcal strain Streptococcus pyogenes was used as a test microorganism. First, blocking of the hydroxyl groups of the glycerol moiety of monolaurin led to a compound with remarkable antibacterial activity (MIC, 3.9 microg/ml). Secondly, synergistic relationships were observed between monolaurin and monocaprin as well as between monolaurin and the poorly active lauric acid when their two component mixtures were examined. The mixtures in which one of the components was 2-fold more predominant than the other one were much more active than the pure components taken individually. Moreover, the presence of the components in ratio 1:1 was disadvantageous. Synergistic relationships were also found between monolaurin and monomyristin towards Staphylococcus aureus 209 when monomyristin was in the same quantity as monolaurin or in shortage.

Biomarkers for the prediction of the resistance and susceptibility of grapevine leaves to downy mildew.

We examined metabolic profiles of acetone and butanol extracts obtained from the leaves of 18 seedlings of the Bulgarian wine-making cultivar Storgozia. The acetone extracts contained the components from the leaf surface, while the butanol extracts were enriched with polar components from inside the leaf tissue. The leaves displayed different degrees of resistance and susceptibility to the etiological agent downy mildew, Plasmopara viticola. Based on the statistically significant correlations (P<0.05) between the GC-MS data of the identified metabolites and the estimated leaf resistances, 10 individual components were proposed as possible biomarkers for the downy mildew resistance and susceptibility in grapevine. All were found in the butanol extracts, and can be considered to form two groups: compounds with high correlations (r=+/-0.50 to +/-1.00) - 3-hydroxybutanoic acid, 2,3,4-trihydroxybutanoic acid, 2,3,4-trihydroxybutanoic acid (isomer), hexadecanoic acid, 3-hydroxyhexanoic acid and myo-inositol, and compounds with moderate correlations (r=+/-0.30 to +/-0.49) hydroxybutanedioic acid, alanine, glutamine, arabinoic acid and aldohexoses. Among them, the more polar compounds were related to sensitivity, and only hexadecanoic and the monohydroxycarboxylic acids were related to resistance in grapevine.

Examination of growth inhibitory properties of synthetic chalcones for which antibacterial activity was predicted.

A large series of chalcones were synthesized and studied against Staphylococcus aureus and Escherichia coli. Chalcones were either unsubstituted in ring A or possessed 4'-chloro or 3',4',5'-trimethoxy groups. Their other ring B was variously substituted. It was found that the anti-staphylococcal activity of chalcones was related to the energy difference between the two highest occupied molecular orbitals (HOMO and HOMO-1). Presence of hydroxyl group in ring B was not a determinant factor for the anti-staphylococcal activity, but the lipophilicity of ring A of the hydroxyl chalcones was of importance.

Evaluation of antibacterial activity of synthetic aliphatic and aromatic monoacylglycerols.

The antibacterial activity of synthetic aliphatic and aromatic monoacylglycerols (MAGs) was studied against two human pathogens: Staphylococcus aureus and Escherichia coli. The active compounds inhibited selectively S. aureus. The most active compounds amongst them were those with medium size aliphatic chain and aromatic MAGs with electron withdrawing substituents at the aryl ring. The introduction of one or two-carbon spacer between the aryl ring and the carboxylic function did not influence antibacterial effectiveness.

Hydroxamic acid derivatives of mycophenolic acid inhibit histone deacetylase at the cellular level.

Mycophenolic acid (MPA, 1), an inhibitor of IMP-dehydrogenase (IMPDH) and a latent PPARgamma agonist, is used as an effective immunosuppressant for clinical transplantation and recently entered clinical trials in advanced multiple myeloma patients. On the other hand, suberoylanilide hydroxamic acid (SAHA), a non-specific histone deacetylase (HDAC) inhibitor, has been approved for treating cutaneous T-cell lymphoma. MPA seemed to bear a cap, a linker, and a weak metal-binding site as a latent inhibitor of HDAC. Therefore, the hydroxamic acid derivatives of mycophenolic acid having an effective metal-binding site, mycophenolic hydroxamic acid (MPHA, 2), 7-O-acetyl mycophenolic acid (7-O-Ac MPHA, 3), and 7-O-lauroyl mycophenolic hydroxamic acid (7-O-L MPHA, 4) were designed and synthesized. All these compounds inhibited histone deacetylase with IC50 values of 1, 0.9 and 0.5 microM, and cell proliferation at concentrations of 2, 1.5 and 1 microM, respectively.

MDR-reversal activity of chalcones.

The ability of 11 chalcones with 3,4,5-trimethoxy substitution on ring A to inhibit the transport activity of P-glycoprotein was studied. Flow cytometry was applied in multidrug-resistant human mdr1 gene-transfected mouse lymphoma cells (L 5178 Y). The reversal of multidrug resistance (MDR) was investigated by measuring the accumulation of rhodamine-123 in cancer cells. Verapamil was applied as a positive control. The majority of the tested compounds were proved to be effective inhibitors of the outward transport of rhodamine-123. In the MTT test, chalcones 2, 3, 5 and 7 exhibited the strongest antiproliferative effects, with 50% inhibitory dose (ID50) =0.19, 0.19, 0.29 and 0.14 microg/mL, respectively. The least effective compounds were 1, 4, 8 and 11, with ID50 values in the range of 1.5-3.5 microg/mL. The antiproliferative effect was shown to be affected by the type of substitution at the p-position on ring B. Chalcone 7, with a p-chloro group on ring B, was the most effective in MDR reversal, causing a marked increase in drug accumulation from 0.4 to 40 microg/mL. In combination with epirubicin, compound 7 displayed synergistic properties while compound 3 exhibited an additive effect. The data presented here indicated that some calcone derivatives can be regarded as effective compounds for reversal of MDR.

Preliminary study on biomarkers for the fungal resistance in Vitis vinifera leaves.

We examined the leaf chemical composition of six seedlings obtained by self-pollination of the Bulgarian wine-making variety Storgozia as well as the cultivar Bouquet, which is the susceptible parent of Storgozia. The chemical composition was investigated in the framework of a program for identification of metabolites associated with disease resistance in grape-vine. Acetone, dichloromethane and butanol extracts, as well as volatiles obtained from fresh material were analyzed by GC/MS. Based on the correlations of the GC/MS data and estimated resistance of the leaves towards the etiological agents of powdery mildew, downy mildew and botrytis as biomarkers for the fungal resistance, we proposed 16 individual metabolites--alpha- and gamma-tocopherol, squalene, alpha-amyrine, stigmasta-3,5-diene-7-one, hexahydrofarnesyl acetone, glycolic acid, 3-hydroxybutanoic acid, 3-hydroxycaproic acid, malic acid, tartaric acid, erythronic acid, arabinoic acid, monoethyl phosphate, undecyl laurate and isopropyl myristate. The obtained correlations were confirmed by cluster analysis.

Synthesis of some phenylpropanoid monoglycerides via the Mitsunobu protocol.

Natural monoglycerides of cinnamic, ferulic and p-coumaric acids were synthesized in good to high overall yields from isopropylidene glycerol via the Mitsunobu reaction and further deprotection of the corresponding acetonides with Amberlyst 15. The method avoids the need of protection of the phenolic hydroxyls. During the Mitsunobu esterifications a strong influence of the acid strength on the efficacy and outcome of the reaction was observed.

Enzymatic chemoselective synthesis of secondary-amide surfactant from N-methylethanol amine.

Efficient selective synthesis of the secondary amide surfactant N-methyl lauroylethanolamide from methyl laurate and N-methylethanol amine by carrier-fixed Chirazyme L-2 (Candida antarctica) using a kinetic strategy has been demonstrated. When different solvents were screened for product yields using Chirazyme L-2, acetonitrile was found to be optimal. The rate of the reaction increased sharply by increasing the molar ratio of the reactants and the reaction temperature. When the reaction was performed at 50 degrees C for 36 h with 50 mmol ester and 100 mmol amine, the product was obtained in a 97.1% yield. With 50 mmol ester and 150 mmol amine, the highest yield (97.3%) was obtained after 16 h of incubation at 50 degrees C. It took only 5 h to get a yield of 95.8% at 60 degrees C using 50 mmol ester and 200 mmol amine. The enzyme activity in the amidation reaction mixture did not decrease notably even after six uses.