Mitochondrial toxicity and antioxidant activity of a prenylated flavonoid isolated from Dalea elegans

Design, synthesis and evaluation of carbamate-bridged amino acid prodrugs of cycloicaritin with improved antitumor activity, aqueous solubility and phase II metabolic stability

Cycloicaritin (CICT), a bioactive flavonoid derived from the genus Epimedium, exhibits a variety of beneficial biological activities, including promising anticancer effects. However, its poor oral bioavailability is attributed to its extremely low aqueous solubility and rapid elimination via phase II conjugative metabolism. To overcome these limitations, we designed and synthesized a series of carbamate-bridged prodrugs, protecting the hydroxyl group at the 3-position of cycloicaritin by binding with the N-terminus of a natural amino acid. The optimal prodrug 4b demonstrated a significant increase in aqueous solubility as compared to CICT, as well as improved stability in phase II metabolism, while allowing for a rapid release of CICT in the blood upon gastrointestinal absorption. The prodrug 4b also facilitated oral absorption through organic anion-transporting polypeptide 2B1-mediated transport and exhibited moderate cytotoxicity. Importantly, the prodrug enhanced the oral bioavailability of CICT and displayed dose-dependent antitumor activity with superior safety. In summary, the prodrug 4b is a novel potential antitumor drug candidate, and the carbamate-bridged amino acid prodrug approach is a promising strategy for the oral delivery of CICT.

The phytochemical profiling, pharmacological activities, and safety of malva sylvestris: a review

Malva sylvestris is a plant commonly found in Europe, Asia, and Africa. The leaves and flowers of this plant have been used for centuries in traditional medicine to treat various ailments such as cough, cold, diarrhoea, and constipation. Google Scholar, PubMed, Scopus, and Web of Science were used to search for relevant material on the phytochemical profiling and pharmacologic activities of Malva sylvestris. The techniques used in phytochemical profiling and the pharmacologic activity of each compound were extracted from the included studies, including in vitro, in vivo, and clinical studies. The phytochemical analysis of Malva sylvestris revealed that the leaves and flowers are the most commonly used parts of the plant and contain various bioactive compounds such as flavonoids, mucilages, terpenoids, phenol derivatives, coumarins, sterols, tannins, saponins, and alkaloids. These phytochemicals are responsible for the many pharmacological activities of Malva sylvestris, such as anti-inflammatory, antimicrobial, hepatoprotective, laxative, antiproliferative and antioxidant properties. This review has presented an overview of the antinociceptive and anti-inflammatory activities and the cytotoxic effects of Malva sylvestris on different types of cancer cells. It has also summarised the work on developing copper oxide nanoparticles using Malva sylvestris leaf extract and its potential use in food and medicine. This review aims to highlight the traditional uses, phytochemistry, pharmacological activities, and safety of Malva sylvestris.

Design, Synthesis, and Biological Evaluation of Icaritin Derivatives as Novel Putative DEPTOR Inhibitors for Multiple Myeloma Treatment

Icaritin is an active ingredient in Epimedium, which has a variety of pharmacological activities. However, the low activity of Icaritin and the unclear target greatly limit its application. Therefore, based on the structure of Icaritin, we adopted the strategy of replacing toxic groups and introducing active groups to design and synthesize a series of new analogues. The top compound C3 exhibited better antimultiple myeloma activity with an IC₅₀ of 1.09 μM for RPMI 8226 cells, induced RPMI 8226 apoptosis, and blocked the cell cycle in the S phase. Importantly, transcriptome analysis, cellular thermal shift assay, and microscale thermophoresis assay confirmed that DEPTOR was the target of C3. Moreover, we explored its binding mode with C3. Especially, C3 displayed satisfactory inhibition of tumor growth in RPMI 8226 xenografts without obvious side effects. In summary, C3 was discovered as a novel putative inhibitor of DEPTOR for the treatment of multiple myeloma.

[Inhibitory effect of diethylstilbestrol on clinical strains of Candida albicans susceptible and resistant to azoles]

BACKGROUND

Candida albicans is a microorganism frequently involved in several infections; the patient's oral cavity, caries niches or periodontal disease can sometimes be the reservoir.. The fungal resistance to the available treatments, among other reasons, has led to the search for new antifungal alternatives.

AIMS

To carry out a comparative study of the in vitro effects of diethylstilboestrol (DES) and fluconazole (FLZ) on the growth of clinical strains of C. albicans.

METHODS

Seven strains of C. albicans were used: a) one FLZ-sensitive culture collection strain, ATCC 90028 (ATCC); b) four oral isolates from four oncological patients with periodontal disease (period 8, 9, 10, and 11); and c) two oral isolates from an AIDS patient with oropharyngeal candidiasis: one FLZ- sensitive (2-76), and another FLZ- resistant (12-99). The MIC was evaluated by standard spectrophotometric techniques using the CLSI (M27-A3) guidelines. The inhibitory concentration 50% (IC₅₀) was calculated using functional analysis with the Graph Pad software.

RESULTS

DES inhibited the growth of all C. albicans strains, whether sensitive or resistant to FLZ. Experimental data fitted non-linear functions of inhibitor concentration versus response. Minimum inhibitory concentrations (MIC) for DES and FLZ were as follows: 28.18µg/ml and 4.90µg/ml (ATCC); 17.16µg/ml and 3.14µg/ml (period); 27.64µg/ml and 4.22µg/ml (2-76); 6.16µg/ml and 438.19µg/ml (12-99), respectively.

CONCLUSIONS

DES showed antifungal activity on all clinical C. albicans strains isolated from patients with dental and medical diseases. It showed the highest potency on the FLZ-resistant isolate.

Effects of tamoxifen on periodontal disease and Candida albicans of patients with breast cancer and other pathologies

Candida albicans is involved in periodontal disease, which is influenced by sex hormones.

AIM

To study the effects of the estrogen antagonist tamoxifen (TAM) on periodontal disease of oncological patients; clinical oral strains of C. albicans.

PATIENTS

With periodontitis and breast cancer and other with AIDS were used.

MATERIALS & METHODS

Periodontal disease was evaluated by the academy of periodontology procedures and the growth of clinical C. albicans isolates were evaluated by the Clinical and Laboratory Standards Institute techniques.

RESULTS

Women who consumed TAM for more than 2 years decreased periodontitis severity. In vitro, TAM inhibited the growth of both fluconazole-sensitive and resistant C. albicans.

CONCLUSION

Administered TAM chronically improves periodontal health and has antifungal activity on oral strains isolated from patients with odontologic and medical pathologies.

Neuro-protective role of nanocapsulated curcumin against cerebral ischemia-reperfusion induced oxidative injury

Cerebral ischemia-reperfusion (CIR) accelerates the progression of neurodegeneration by causing mitochondrial dysfunction to overproduce reactive oxygen species (ROS). Curcumin shows protective effects against CIR-induced oxidative damage. Free curcumin (FC) is effective at high doses due to its poor bioavailability. Also the blood-brain barrier (BBB) limits the passage of substances from circulation into the cerebral region. Thus, formulation of curcumin within polyethylene glycol (PEG)-ylated polylactide-co-glycolide (PLGA) nanoparticles (NC) was applied orally to aged rats to explore its role against CIR injury. Mitochondrial damage was evaluated. The levels of pro-inflammatory cytokines and components of apoptotic pathway were studied. Unlike FC, NC pre-treatment exerted better neuro-protection by ameliorating ROS-mediated oxidative damage and prevented CIR-induced neuronal apoptosis. Therefore, curcumin incorporated PEGylated PLGA nanoparticles may be used as a suitable delivery vehicle to the brain as they can increase curcumin bioavalability and the released curcumin may confer protection to the neurons against CIR-induced oxidative damage.

Streptozotocin-Induced Adaptive Modification of Mitochondrial Supercomplexes in Liver of Wistar Rats and the Protective Effect of Moringa oleifera Lam

The increasing prevalence of diabetes continues to be a major health issue worldwide. Alteration of mitochondrial electron transport chain is a recognized hallmark of the diabetic-associated decline in liver bioenergetics; however, the molecular events involved are only poorly understood. Moringa oleifera is used for the treatment of diabetes. However, its role on mitochondrial functionality is not yet established. This study was aimed to evaluate the effect of M. oleifera extract on supercomplex formation, ATPase activity, ROS production, GSH levels, lipid peroxidation, and protein carbonylation. The levels of lipid peroxidation and protein carbonylation were increased in diabetic group. However, the levels were decreased in Moringa-treated diabetic rats. Analysis of in-gel activity showed an increase in all complex activities in the diabetic group, but spectrophotometric determinations of complex II and IV activities were unaffected in this treatment. However, we found an oxygen consumption abolition through complex I-III-IV pathway in the diabetic group treated with Moringa. While respiration with succinate feeding into complex II-III-IV was increased in the diabetic group. These findings suggest that hyperglycemia modifies oxygen consumption, supercomplexes formation, and increases ROS levels in mitochondria from the liver of STZ-diabetic rats, whereas M. oleifera may have a protective role against some alterations.

Lycopene Prevents Mitochondrial Dysfunction during d-Galactosamine/Lipopolysaccharide-Induced Fulminant Hepatic Failure in Albino Rats

Functional perturbation of mitochondria is associated with fulminant hepatic failure (FHF). d-Galactosamine/lipopolysaccharide (d-GalN/LPS)-induced FHF is a renowned model to evaluate the efficacy of hepatoprotective agents. Lycopene is an antioxidant and phytonutrient from the carotenoid family. The health benefits of lycopene are prominent against cancer and cardiovascular, lung, liver, and skin problems. Recent studies have demonstrated the hepatoprotective, antidyslipidemic, and antioxidant roles of lycopene. The current study was designed to appraise the ability of lycopene to prevent mitochondrial dysfunction during the d-GalN/LPS-induced FHF. The administration of d-GalN/LPS (300 mg and 30 μg/kg body weight, respectively) to the experimental rats induced several disturbances in mitochondrial function. The lipid peroxide and hydrogen peroxide levels were increased (p < 0.05). The activities of mitochondrial antioxidants, tricarboxylic acid (TCA) cycle, and electron transport chain enzymes and the cellular adenosine triphosphate (ATP) content were decreased (p < 0.05). Lycopene (10 mg/kg body weight for 6 days) pretreatment attenuated lipid peroxidation and prohibited the excessive synthesis of hydrogen peroxide. The d-GalN/LPS-induced impairment in ATP production and increased enzyme activities were effectively prevented by the lycopene administration. The lycopene-mediated mitochondrial protection was mainly ascribed to the strong antioxidant potential of this phytonutrient. Molecular modeling results obtained show evidence that lycopene inhibits several lipoxygenases and provides rationale for the observed prevention of lipid peroxidation in the mitochondrial membrane. The carotenoid lycopene combatted oxidative stress, scavenged free radicals, prevented ROS generation, and inhibited the toxic effects of d-GalN/LPS during FHF.

Interactions of a prenylated flavonoid from Dalea elegans with fluconazole against azole- resistant Candida albicans

BACKGROUND

The prenylated flavonoid 2', 4'-dihydroxy-5'-(1'″, 1'″-dimethylallyl)-8-prenylpinocembrin (8PP, formerly 6PP) shows antifungal activity, inhibits rhodamine 6G efflux and reverses fluconazole (FCZ) resistance in azole-resistant Candida albicans overexpressing cdr1, cdr2 and mdr1 transporters.

PURPOSE AND DESIGN

In this paper, we tried to characterize 8PP in vitro interactions on the cell growth and lethality of C. albicans. We also initiated preliminary in vivo toxicological studies on mice.

METHODS

The effects of 8PP and FCZ on cell growth and viability of C. albicans were evaluated by CLSI guidelines. The checkerboard assay was used to search for interactions on cell growth. The time-kill assay was used to study fungicidal effects. Acute toxicity was evaluated at a single dose schedules.

RESULTS

From the checkerboard design, and using a starting inoculum of 10³CFU/ml, the fractional inhibitory concentration (FIC) of FCZ and 8PP could be determined as 0.11 and 0.50, respectively, with a FIC index value (FICI) of 0.61. This FICI and the isobologram showing a concave shape suggests an additive interaction between them. At a higher starting inoculum (10⁵CFU/ml), C. albicans growth and viability were decreased by FCZ, 8PP and their combination in a concentration-dependent way. For FCZ, minimum fungicidal concentration (MFC) and FC₅₀ (the concentration that kills 50% of the fungal cells) were 4-fold reduced (280-70µM) in combination with 125µM 8PP. A decrease of 3 log units in viable counts with respect to control was reached (3.65 ± 1.05 ‰, p< 0.0001). Thus, both fungistatic compounds when combined achieved an almost complete fungicidal effect at lower concentrations respecting of each of them alone. In preliminary toxicological assessment, lethal dose 50% (LD₅₀) for 8PP by the i.p. route was 357 and 245mg/kg, for female and male adult albino mice, respectively. FCZ LD₅₀ was 785 and 650mg/kg for female and male animals, respectively CONCLUSIONS: In vitro results suggest additive interactions between 8PP and FCZ with respect to C. albicans cell growth. Besides killing per se, 8PP helps FCZ to achieve an almost complete fungicidal effect, which would be crucial to eradicate fungal infections.

Vesicular melatonin efficiently downregulates sodium fluoride-induced rat hepato- and broncho-TNF-α, TGF-β expressions, and associated oxidative injury: a comparative study of liposomal and nanoencapsulated forms

The importance of fluoride as a natural and industrial toxicant is recognized worldwide. We evaluated the regulating role and biological effect of vesicular (liposomal and nanoencapsulated) melatonin (N-acetyl-5-methoxytryptamine) for drug delivery and controlled release on the depletion of inflammatory mediators, as well as oxidative damage in sodium fluoride (NaF)-treated lungs and liver. Hepatic and bronchial damage was induced in Swiss albino rats with a single acute ingestion of NaF (48 mg/kg body weight, oral gavage). NaF exposure caused the generation of reactive oxygen species (ROS); upregulation of TNF-α and TGF-β; decreased activities of antioxidant systems (glutathione, glutathione-S-transferase, superoxide dismutase, catalase), succinate dehydrogenase, membrane microviscosity, and membrane potential; increased activity of lipid peroxidation and nicotinamide adenine dinucleotide hydride oxidase; and increased hepatic and nephrite toxicities (P<0.001) compared to those in normal animals. Charge (-ve/+ve)-specific single liposomal (dicetyl phosphate/stearylamine) and nanoencapsulated melatonin (4.46 mg/kg body weight, intravenous) treatments (2 hours after NaF exposure) significantly (P<0.01/0.001) and maximally (P<0.001) inhibited all alterations developed in NaF-mediated oxidative injuries in rat liver (+ve) and lungs (-ve), demonstrating their strong free radical scavenging, antioxidant and antigenotoxic properties, and vesicular efficiencies of targeting. Overall, these results suggest that nanoencapsulated melatonin might be considered as a more powerful remedial therapy in comparison to liposomes, in terms of its efficacy in regulating NaF-intoxicated oxidative injury.

Protective roles of nanomelatonin in cerebral ischemia-reperfusion of aged brain: Matrixmetalloproteinases as regulators

Cerebral ischemia-reperfusion (CIR) injury occurs as a result of oxygen occlusion in the carotid artery through embolus or thrombus formation or cerebrovascular hemorrhage. The oxygen thrust during reperfusion causes the generation of reactive oxidative species (ROS) which exert a potential threat to neuronal survival. ROS may possibly be arrested by antioxidants. After CIR, extracellular matrix remodeling takes place, which is governed by matrix metalloproteinases (MMPs). Augmentation of lipid per oxidation, perturbation of antioxidant enzyme activities and the loss of pyramidal neuronal cells in rat brain were attributed to CIR injury. Melatonin can readily cross the blood-brain barrier (BBB) to exert protective effects as an antioxidant but it is quickly cleared by the circulating blood. Also melatonin is easily degraded by light and hence is found to be ineffective during daytime. Results of the present study showed that unlike free melatonin (FM), the application of nanocapsulated melatonin (NM) exhibited significantly higher potential even at much lower concentrations to rescue neuronal cells and mitochondria during CIR insult and also restored the activities of antioxidative enzymes and MMPs to their normal levels. Hence, nanoencapsulated melatonin may be considered as a suitable drug delivery system for brain to exert protection against CIR injury.

Vesicular (liposomal and nanoparticulated) delivery of curcumin: a comparative study on carbon tetrachloride-mediated oxidative hepatocellular damage in rat model

The liver plays a vital role in biotransforming and extricating xenobiotics and is thus prone to their toxicities. Short-term administration of carbon tetrachloride (CCl₄) causes hepatic inflammation by enhancing cellular reactive oxygen species (ROS) level, promoting mitochondrial dysfunction, and inducing cellular apoptosis. Curcumin is well accepted for its antioxidative and anti-inflammatory properties and can be considered as an effective therapeutic agent against hepatotoxicity. However, its therapeutic efficacy is compromised due to its insolubility in water. Vesicular delivery of curcumin can address this limitation and thereby enhance its effectiveness. In this study, it was observed that both liposomal and nanoparticulated formulations of curcumin could increase its efficacy significantly against hepatotoxicity by preventing cellular oxidative stress. However, the best protection could be obtained through the polymeric nanoparticle-mediated delivery of curcumin. Mitochondria have a pivotal role in ROS homeostasis and cell survivability. Along with the maintenance of cellular ROS levels, nanoparticulated curcumin also significantly (P<0.0001) increased cellular antioxidant enzymes, averted excessive mitochondrial destruction, and prevented total liver damage in CCl₄-treated rats. The therapy not only prevented cells from oxidative damage but also arrested the intrinsic apoptotic pathway. In addition, it also decreased the fatty changes in hepatocytes, centrizonal necrosis, and portal inflammation evident from the histopathological analysis. To conclude, curcumin-loaded polymeric nanoparticles are more effective in comparison to liposomal curcumin in preventing CCl₄-induced oxidative stress–mediated hepatocellular damage and thereby can be considered as an effective therapeutic strategy.

Establishment of drug delivery system nanocapsulated with an antioxidant (+)-catechin hydrate and sodium meta borate chelator against sodium fluoride induced oxidative stress in rats

Oxidative stress a major cause of fluoride induced toxicity and mitochondrial impairment in common in experimental rats during chronic exposure of fluoride. Attempts have been made in the present experiment to diminish oxidative damage, combined therapy with (+)-catechin hydrate (an antioxidant) and sodium meta borate (chelator) were used. Fluoride intoxication in rats was performed by using 13mg/kg NaF and both antioxidant CH and chelator SMB were used at a concentration of 8.98μM/kg body weight. Mixture of CH and SMB in free or in PLGA nanocapsule encapsulated form were prepared. The efficacies of those formulations were tested in combating free radical mediated oxidative insult produced by sodium fluoride (NaF). The amalgamated therapy used in this experiment was shown to reduce fluoride levels in liver, brain and kidney from 9.5, 5.5, 6.3μg/g to 4.6, 2, 2.6μg/g, respectively. Our result indicated that the combined chelator and antioxidant therapy in nanocapsulated drug delivery system could provide a projection in combating fluoride induced mitochondrial impairment in rat model.

Suppression of CLIC4/mtCLIC enhances hydrogen peroxide-induced apoptosis in C6 glioma cells

CLIC4/mtCLIC (referred to here as CLIC4) is one of the seven-member family of chloride intracellular channels (CLIC). CLIC4 localizes to the mitochondria, nucleus, cytoplasm and other organellular compartments and participates in the apoptotic response to stress. However, the role of CLIC4 in oxidative stress and apoptosis is not well understood. In this study, we showed the important role of CLIC4 in apoptosis of C6 glioma cells induced by hydrogen peroxide (H2O2). Our results showed that CLIC4 protein expression was upregulated following H2O2-induced C6 cell apoptosis. The upregulation of CLIC4 protein expression was paralleled with an increased Bax/Bcl-2 ratio, cytochrome c and cleaved caspase-3 protein expression upon H2O2-induced C6 cell apoptosis. Suppression of CLIC4 expression by RNA interference enhanced cell apoptosis, but the ratio of Bax/Bcl-2 was not involved in this process. Dissipation of mitochondrial membrane potential and nuclear translocation of CLIC4 were involved in the activation of apoptosis induced by H2O2. Our data indicate that CLIC4 protein may be a key element in the apoptotic response to oxidative stress.

The use of nano-quercetin to arrest mitochondrial damage and MMP-9 upregulation during prevention of gastric inflammation induced by ethanol in rat

Gastric ulcer is a multifaceted process that involves reactive oxygen species (ROS) generation, extracellular matrix degradation and mitochondrial damage. Mitochondria play a crucial role for homeostasis of ROS and cell survival. In our study, we investigated the efficacy and mechanism of polymeric nanocapsuled quercetin (NQC) over the free quercetin (QC) molecule in prevention of ethanol-induced gastric ulcer in rat. NQC possessed significantly higher efficacy (~20 fold) than free QC while preventing gastric ulcers. Our data show that prior administration of NQC and/or QC significantly blocked synthesis and secretion of matrix metalloproteinase (MMP)-9 as well as infiltration of inflammatory cells and oxidative damage in rat gastric tissues. As compared to free QC, NQC protected much better the mitochondrial integrity and size along with mitochondrial functions by controlling succinate dehydrogenase and NADH oxidase in rat gastric tissues. In addition, both free QC and NQC down regulated PARP-1 as well as apoptosis during protection against ethanol-induced gastric ulcer. Herein, the effect of NQC was greater than QC on expression of enzymes like cyclooxygenase and nitric oxidase synthase (NOS)-2. We conclude that NQC with greater bioavailability offers significantly higher potency in downregulating MMP-9 and NOS-2 as well as oxidative stress in blocking ethanol-induced gastric ulcer.

Encapsulation of the flavonoid quercetin with an arsenic chelator into nanocapsules enables the simultaneous delivery of hydrophobic and hydrophilic drugs with a synergistic effect against chronic arsenic accumulation and oxidative stress

Chronic arsenic exposure causes oxidative stress and mitochondrial dysfunction in the liver and brain. The ideal treatment would be to chelate arsenic and prevent oxidative stress. meso-2,3-Dimercaptosuccinic acid (DMSA) is used to chelate arsenic but its hydrophilicity makes it membrane-impermeative. Conversely, quercetin (QC) is a good antioxidant with limited clinical application because of its hydrophobic nature and limited bioavailability, and it is not possible to solubilize these two compounds in a single nontoxic solvent. Nanocapsules have emerged as a potent drug delivery system and make it feasible to incorporate both hydrophilic and lipophilic compounds. Nanoencapsulated formulations with QC and DMSA either alone or coencapsulated in polylactide-co-glycolide [N(QC+DMSA)] were synthesized to explore their therapeutic application in a rat model of chronic arsenic toxicity. These treatments were compared to administration of quercetin or DMSA alone using conventional delivery methods. Both nanoencapsulated quercetin and nanoencapsulated DMSA were more effective at decreasing oxidative injury in liver or brain compared to conventional delivery methods, but coencapsulation of quercetin and DMSA into nanoparticles had a marked synergistic effect, decreasing liver and brain arsenic levels from 9.5 and 4.8μg/g to 2.2 and 1.5μg/g, respectively. Likewise, administration of coencapsulated quercetin and DMSA virtually normalized changes in mitochondrial function, formation of reactive oxygen species, and liver injury. We conclude that coencapsulation of quercetin and DMSA may provide a more effective therapeutic strategy in the management of arsenic toxicity and also presents a novel way of combining hydrophilic and hydrophobic drugs into a single delivery system.

Artocarpus Plants as a Potential Source of Skin Whitening Agents

Artocarpus plants have been a focus of constant attention due to the potential for skin whitening agents. In the in vitro experiment, compounds from the Artocarpus plants, such as artocarpanone, norartocarpetin, artocarpesin, artogomezianol, andalasin, artocarbene, and chlorophorin showed tyrosinase inhibitory activity. Structure-activity investigations revealed that the 4-substituted resorcinol moiety in these compounds was responsible for their potent inhibitory activities on tyrosinase. In the in vitro assay, using B16 melanoma cells, the prenylated polyphenols isolated from Artocarpus plants, such as artocarpin, cudraflavone C, 6-prenylapigenin, kuwanon C, norartocarpin, albanin A, cudraflavone B, and brosimone I showed potent inhibitory activity on melanin formation. Structure-activity investigations revealed that the introduction of an isoprenoid moiety to a non-isoprenoid-substituted polyphenol enhanced the inhibitory activity of melanin production in B16 melanoma cells. In the in vivo investigation, the extract of the wood of Artocarpus incisus and a representative isolated compound from it, artocarpin had a lightening effect on the skin of guinea pigs’ backs. Other in vivo experiments using human volunteers have shown that water extract of Artocarpus lakoocha reduced the melanin formation in the skin of volunteers. These results indicate that the extracts of Artocarpus plants are potential sources for skin whitening agents.

The 8-aminoquinoline analogue sitamaquine causes oxidative stress in Leishmania donovani promastigotes by targeting succinate dehydrogenase

The 8-aminoquinoline analogue sitamaquine (SQ) is an oral antileishmanial drug currently undergoing phase 2b clinical trials for the treatment of visceral leishmaniasis. In the present study, we investigated the mechanism of action of this drug in Leishmania donovani promastigotes. SQ causes a dose-dependent inhibition of complex II (succinate dehydrogenase) of the respiratory chain in digitonin-permeabilized promastigotes, together with a drop in intracellular ATP levels and a decrease of the mitochondrial electrochemical potential. This is associated with increases of reactive oxygen species and intracellular Ca(2+) levels, a higher percentage of the population with sub-G(1) DNA content, and exposure of phosphatidylserine. Taken together, these results support a lethal mechanism for SQ that involves inhibition of the respiratory chain complex II, which in turn triggers oxidative stress and finally leads to an apoptosis-like death of Leishmania parasites.

The protective effect of Malva sylvestris on rat kidney damaged by vanadium

Background

The protective effect of the common mallow (Malva sylvestris) decoction on renal damages in rats induced by ammonium metavanadate poisoning was evaluated. On the one hand, vanadium toxicity is associated to the production of reactive oxygen species, causing a lipid peroxidation and an alteration in the enzymatic antioxidant defence. On the other hand, many medicinal plants are known to possess antioxidant and radical scavenging properties, thanks to the presence of flavonoids. These properties were confirmed in Malva sylvestris by two separate methods; namely, the Diphenyl-2-picrylhydrazyl assay and the Nitroblue Tetrazolium reduction assay.

Results

In 80 rats exposed to ammonium metavanadate (0.24 mmol/kg body weight in drinking water) for 90 days, lipid peroxidation levels and superoxide dismutase, catalase and glutathione peroxidase activities were measured in kidney. A significant increase in the formation of free radicals and antioxidant enzyme activities was noticed. In addition, a histological examination of kidney revealed a structural deterioration of the renal cortical capsules and a shrinking of the Bowman space. In animals intoxicated by metavanadate but also given a Malva sylvestris decoction (0.2 g dry mallow/kg body weight), no such pathologic features were observed: lipid peroxidation levels, antioxidant enzyme activities and histological features appeared normal as compared to control rats.

Conclusion

Malva sylvestris is proved to have a high antioxidative potential thanks to its richness in phenolic compounds.

Prenylated flavanones with anti-tyrosinase activity from Dalea boliviana

Three new prenylated flavanones, (2S)-5,7,2'-trihydroxy-5'-(1''',1'''-dimethylallyl)-8-prenylflavanone (1), (2S)-5,7,2'-trihydroxy-8,3'-diprenylflavanone (2), and (2S)-5,2'-dihydroxy-6'',6''-dimethylchromeno-(7,8:2'',3'')-3'-prenylflavanone (3), and a known chromeno (dimethylpyrano) flavanone, obovatin (4), were isolated from the n-hexane extract of Dalea boliviana roots. The compounds were evaluated in vitro in relation to their inhibitory effect on the tyrosinase activity by using a spectrophotometric method.

Effects of Phyllanthus urinaria extract on HepG2 cell viability and oxidative phosphorylation by isolated rat liver mitochondria

ETHNOPHARMACOLOGICAL RELEVANCE

Phyllanthus urinaria is widely used as anti-inflammatory, anti-diarrheal and hepatoprotective medicines in Asian countries such as India, China and Thailand. In Thailand, Phyllanthus urinaria is traditionally used as an adjuvant or alternative medicine for cancer patients, including liver cancer. However, there is limited scientific evidence supporting its use in cancer particularly hepatocellular carcinoma.

AIM OF THE STUDY

To investigate the cytotoxic effect of Phyllanthus urinaria extract on human hepatocellular carcinoma HepG2 cells and the effect on oxidative phosphorylation by isolated rat liver mitochondria.

MATERIALS AND METHODS

HepG2 cells and isolated rat liver mitochondria were treated with the 50% methanolic extract of Phyllanthus urinaria. Cytotoxicity of the extract was assessed by trypan blue exclusion and MTT assay. Rates of oxygen consumption of isolated mitochondria were determined with a Clark oxygen electrode.

RESULTS

It was found that the hydromethanolic extract induced cell death of HepG2 cells in a dose-dependent fashion. The IC(50) of Phyllanthus urinaria extract measured by trypan blue exclusion and MTT assay were 431+/-65 microg/ml and 445+/-62 microg/ml, respectively. Morphological changes of the cells were also observed. With isolated rat liver mitochondria, the extract slightly stimulated mitochondrial state 4 respiration but profoundly depressed state 3 respiration and respiratory control ratio.

CONCLUSIONS

The extract impairs energy metabolism by acting as inhibitor of oxidative phosphorylation and weak mitochondrial uncoupler. These mitochondrial effects may play a role in the cytotoxic action of Phyllanthus urinaria extract on HepG2 cells. These results provide preliminary experimental evidence supporting the use of Phyllanthus urinaria against hepatocellular carcinoma and open the possibility of considering this plant an adjunctive medicine for the treatment of this deadly disease.