Harmful and beneficial effects of organic monosulfides, disulfides, and polysulfides in animals and humans

Antibacterial plant combinations prevent postweaning diarrhea in organically raised piglets challenged with enterotoxigenic Escherichia coli F18

Antibiotics and zinc oxide restrictions encourage the search for alternatives to combat intestinal pathogens, including enterotoxigenic Escherichia coli (ETEC), a major cause of postweaning diarrhea (PWD) in pigs. PWD causes important economic losses for conventional and organic farming. This study investigated the effect of dietary supplementation with garlic and apple pomace or blackcurrant on infection indicators and the fecal microbiota of organic-raised piglets challenged with ETEC-F18. For 21 days, 32 piglets (7-weeks-old) were randomly assigned to one of four groups: non-challenge (NC); ETEC-challenged (PC); ETEC-challenged receiving garlic and apple pomace (3 + 3%; GA); ETEC-challenged receiving garlic and blackcurrant (3 + 3%; GB). ETEC-F18 was administered (8 mL; 109 CFU/ml) on days 1 and 2 postweaning. The 1st week, PC had lower average daily gain than those in the NC, GA, and GB groups (P < 0.05). NC pigs showed neither ETEC-F18 shedding nor signs of diarrhea. The PC group had higher diarrhea incidence and lower fecal dry matter than NC (≈5–10 days; 95% sEBCI). The GA and GB groups showed reduced ETEC-F18 and fedA gene shedding, higher fecal dry matter, and lower diarrhea incidence than the PC (≈5–9 days; 95% sEBCI). The NC, GA, and GB had normal hematology values during most of the study, whereas the PC had increased (P < 0.05) red blood cells, hemoglobin, and hematocrit on day 7. Haptoglobin and pig-MAP increased in all groups, peaking on day 7, but PC showed the greatest increase (P < 0.05). The fecal microbiota of PC pigs had reduced α-diversity (day 7; P < 0.05) and higher volatility (days 3–14; P < 0.05). Escherichia, Campylobacter, and Erysipelothrix were more abundant in the PC than in the NC, GB, and GA groups (log2FC > 2; P < 0.05), whereas Catenibacterium, Dialister, and Mitsoukella were more abundant in the NC, GB, and GA than in the PC group (log2FC > 2; P < 0.05). Prevotella and Lactobacillus were more abundant in the GB group (log2FC > 2, P < 0.05). In conclusion, dietary supplementation of GA and GB limited ETEC proliferation, reduced PWD, and beneficially impacted the fecal microbiota's diversity, composition, and stability.

Four organosulfur compounds from the seeds of Capsella bursa-pastoris and their anti-inflammatory activities

Phytochemical investigation of the seeds of Capsella bursa-pastoris led to the isolation of four organosulfur compounds. There were two new compounds, 10-methylsulfinyl-decanamide (1) and 11-methylsulfinyl-undecanamide (2), along with two known compounds (3 - 4), which all have a sulfoxide group and an amide or a nitrile group. Their chemical structures were elucidated by analysing UV, IR, ESI-MS and NMR spectroscopy. In addition, compounds 1 - 4 were evaluated for their anti-inflammatory activities by using LPS-induced RAW 264.7 cells. Compounds 1 - 4 exhibited potential anti-inflammatory activities on NO release characterised by decreasing the mRNA expression levels of inducible NO synthase (iNOS), cytokines cyclooxygenase-2 (COX-2) and interleukin 6 (IL-6).

Role of Sulfur Compounds in Vegetable and Mushroom Aroma

At the base of the food pyramid is vegetables, which should be consumed most often of all food products, especially in raw and unprocessed form. Vegetables and mushrooms are rich sources of bioactive compounds that can fulfill various functions in plants, starting from protection against herbivores and being natural insecticides to pro-health functions in human nutrition. Many of these compounds contain sulfur in their structure. From the point of view of food producers, it is extremely important to know that some of them have flavor properties. Volatile sulfur compounds are often potent odorants, and in many vegetables, belonging mainly to Brassicaeae and Allium (Amaryllidaceae), sulfur compounds determine their specific flavor. Interestingly, some of the pathways that form volatile sulfur compounds in vegetables are also found in selected edible mushrooms. The most important odor-active organosulfur compounds can be divided into isothiocyanates, nitriles, epithionitriles, thiols, sulfides, and polysulfides, as well as others, such as sulfur containing carbonyl compounds and esters, R-L-cysteine sulfoxides, and finally heterocyclic sulfur compounds found in shiitake mushrooms or truffles. This review paper summarizes their precursors and biosynthesis, as well as their sensory properties and changes in selected technological processes.

Antioxidant action of persulfides and polysulfides against free radical-mediated lipid peroxidation

Hydrogen sulfide, hydropersulfides, and hydropolysulfides have been revealed to play important physiological roles such as cell signaling and protection against oxidative stress, but the underlying mechanisms and dynamics of action remain elusive. It is generally accepted that these species act by two-electron redox mechanisms, while the involvement of one-electron redox chemistry has received less attention. In this study, the radical-scavenging activity of hydrogen persulfide, hydrogen polysulfides (HS_nH n = 2-4), and diallyl- or dialkyl-sulfides (RS_nR, n = 1-4) was measured. Furthermore, their antioxidant effects against free radical-mediated human plasma lipid peroxidation were assessed by measuring lipid hydroperoxides. It was found that disodium disulfide, trisulfide, and tetrasulfide acted as potent peroxyl radical scavengers, the rate constant for scavenging peroxyl radical being 3.5 × 10⁵, 4.0 × 10⁵, and 6.0 × 10⁵ M^-1 s^-1 in PBS pH 7.4 at 37 °C respectively and that they inhibited plasma lipid peroxidation efficiently, the efficacy is increased with the catenation number. Disodium tetrasulfide was 1.5 times as reactive as Trolox toward peroxyl radical and inhibited plasma lipid peroxidation more efficiently than ascorbate and Trolox. On the other hand, diallyl- and dialkyl-sulfides did not exert significant radical-scavenging activity, nor did they inhibit lipid peroxidation efficiently, except for diallyl tetrasulfide, which suppressed plasma lipid peroxidation, despite less significantly than disodium tetrasulfide. Collectively, this study shows that hydrogen persulfide and hydrogen polysulfides act as potent radical-scavenging antioxidants and that, in addition to two-electron redox mechanisms, one electron redox reaction may also play important role in the in vivo defense against deleterious oxidative stress.

Role of Sulphur and Heavier Chalcogens on the Antioxidant Power and Bioactivity of Natural Phenolic Compounds

The activity of natural phenols is primarily associated to their antioxidant potential, but is ultimately expressed in a variety of biological effects. Molecular scaffold manipulation of this large variety of compounds is a currently pursued approach to boost or modulate their properties. Insertion of S/Se/Te containing substituents on phenols may increase/decrease their H-donor/acceptor ability by electronic and stereo-electronic effects related to the site of substitution and geometrical constrains. Oxygen to sulphur/selenium isosteric replacement in resveratrol or ferulic acid leads to an increase in the radical scavenging activity with respect to the parent phenol. Several chalcogen-substituted phenols inspired by Vitamin E and flavonoids have been prepared, which in some cases prove to be chain-breaking antioxidants, far better than the natural counterparts. Conjugation of catechols with biological thiols (cysteine, glutathione, dihydrolipoic acid) is easily achieved by addition to the corresponding ortho-quinones. Noticeable examples of compounds with potentiated antioxidant activities are the human metabolite 5-S-cysteinyldopa, with high iron-induced lipid peroxidation inhibitory activity, due to strong iron (III) binding, 5-S-glutathionylpiceatannol a most effective inhibitor of nitrosation processes, and 5-S-lipoylhydroxytyrosol, and its polysulfides that proved valuable oxidative-stress protective agents in various cellular models. Different methodologies have been used for evaluation of the antioxidant power of these compounds against the parent compounds. These include kinetics of inhibition of lipid peroxidation alkylperoxyl radicals, common chemical assays of radical scavenging, inhibition of the OH• mediated hydroxylation/oxidation of model systems, ferric- or copper-reducing power, scavenging of nitrosating species. In addition, computational methods allowed researchers to determine the Bond Dissociation Enthalpy values of the OH groups of chalcogen modified phenolics and predict the best performing derivative. Finally, the activity of Se and Te containing compounds as mimic of glutathione peroxidase has been evaluated, together with other biological activities including anticancer action and (neuro)protective effects in various cellular models. These and other achievements are discussed and rationalized to guide future development in the field.

Hyaluronic Acid-Based Nanocapsules as Efficient Delivery Systems of Garlic Oil Active Components with Anticancer Activity

Diallyl disulfide (DADS) and diallyl trisulfide (DATS) are garlic oil compounds exhibiting beneficial healthy properties including anticancer action. However, these compounds are sparingly water-soluble with a limited stability that may imply damage to blood vessels or cells after administration. Thus, their encapsulation in the oil-core nanocapsules based on a derivative of hyaluronic acid was investigated here as a way of protecting against oxidation and undesired interactions with blood and digestive track components. The nuclear magnetic resonance (¹H NMR) technique was used to follow the oxidation processes. It was proved that the shell of the capsule acts as a barrier limiting the sulfur oxidation, enhancing the stability of C=C bonds in DADS and DATS. Moreover, it was shown that the encapsulation inhibited the lysis of the red blood cell membrane (mainly for DADS) and interactions with serum or digestive track components. Importantly, the biological functions and anticancer activity of DADS and DATS were preserved after encapsulation. Additionally, the nanocapsule formulations affected the migration of neoplastic cells—a desirable preliminary observation concerning the inhibition of migration. The proposed route of administration of these garlic extract components would enable reaching their higher concentrations in blood, longer circulation in a bloodstream, and thus, imply a better therapeutic effect.

Targeting the tumor immune microenvironment with "nutraceuticals": From bench to clinical trials

The occurrence of immune effector cells in the tissue microenvironment during neoplastic progression is critical in determining tumor growth outcomes. On the other hand, tumors may also avoid immune system-mediated elimination by recruiting immunosuppressive leukocytes and soluble factors, which coordinate a tumor microenvironment that counteracts the efficiency of the antitumor immune response. Checkpoint inhibitor therapy results have indicated a way forward via activation of the immune system against cancer. Widespread evidence has shown that different compounds in foods, when administered as purified substances, can act as immunomodulators in humans and animals. Although there is no universally accepted definition of nutraceuticals, the term identifies a wide category of natural compounds that may impact health and disease statuses and includes purified substances from natural sources, plant extracts, dietary supplements, vitamins, phytonutrients, and various products with combinations of functional ingredients. In this review, we summarize the current knowledge on the immunomodulatory effects of nutraceuticals with a special focus on the cancer microenvironment, highlighting the conceptual benefits or drawbacks and subtle cell-specific effects of nutraceuticals for envisioning future therapies employing nutraceuticals as chemoadjuvants.

Characterization of the peroxiredoxin 1 subfamily from Tetrahymena thermophila

Peroxiredoxins are antioxidant enzymes that use redox active Cys residues to reduce H2O2 and various organic hydroperoxides to less reactive products, and thereby protect cells against oxidative stress. In yeasts and mammals, the Prx1 proteins are sensitive to hyperoxidation and consequent loss of their peroxidase activity whereas in most bacteria they are not. In this paper we report the characterization of the Prx1 family in the non-parasitic protist Tetrahymena thermophila. In this organism, four genes potentially encoding Prx1 have been identified. In particular, we show that the mitochondrial Prx1 protein (Prx1m) from T. thermophila is relatively robust to hyperoxidation. This is surprising given that T. thermophila is a eukaryote like yeasts and mammals. In addition, the proliferation of the T. thermophila cells was relatively robust to inhibition by H2O2, cumene hydroperoxide and plant natural products that are known to promote the production of H2O2. In the presence of these agents, the abundance of the T. thermophila Prx1m protein was shown to increase. This suggested that the Prx1m protein may be protecting the cells against oxidative stress. There was no evidence for any increase in Prx1m gene expression in the stressed cells. Thus, increasing protein stability rather than increasing gene expression may explain the increasing Prx1m protein abundance we observed.

Natural Hydrogen Sulfide Donors from Allium sp. as a Nutraceutical Approach in Type 2 Diabetes Prevention and Therapy

Type 2 diabetes mellitus (DM) is a socially relevant chronic disease with high prevalence worldwide. DM may lead to several vascular, macrovascular, and microvascular complications (cerebrovascular, coronary artery, and peripheral arterial diseases, retinopathy, neuropathy, and nephropathy), often accelerating the progression of atherosclerosis. Dietary therapy is generally considered to be the first step in the treatment of diabetic patients. Among the current therapeutic options, such as insulin therapy and hypoglycemic drugs, in recent years, attention has been shifting to the effects and properties-that are still not completely known-of medicinal plants as valid and inexpensive therapeutic supports with limited side effects. In this review, we report the relevant effects of medicinal plants and nutraceuticals in diabetes. In particular, we paid attention to the organosulfur compounds (OSCs) present in plant extracts that due to their antioxidant, hypoglycemic, anti-inflammatory, and immunomodulatory effects, can contribute as cardioprotective agents in type 2 DM. OSCs derived from garlic (Allium sp.), due to their properties, can represent a valuable support to the diet in type 2 DM, as outlined in this manuscript based on both in vitro and in vivo studies. Moreover, a relevant characteristic of garlic OSCs is their ability to produce the gasotransmitter H₂S, and many of their effects can be explained by this property. Indeed, in recent years, several studies have demonstrated the relevant effects of endogenous and exogenous H₂S in human DM, including by in vitro and in vivo experiments and clinical trials; therefore, here, we summarize the effects and the underlying molecular mechanisms of H₂S and natural H₂S donors.

The mechanisms of pharmacokinetic food-drug interactions - A perspective from the UNGAP group

The simultaneous intake of food and drugs can have a strong impact on drug release, absorption, distribution, metabolism and/or elimination and consequently, on the efficacy and safety of pharmacotherapy. As such, food-drug interactions are one of the main challenges in oral drug administration. Whereas pharmacokinetic (PK) food-drug interactions can have a variety of causes, pharmacodynamic (PD) food-drug interactions occur due to specific pharmacological interactions between a drug and particular drinks or food. In recent years, extensive efforts were made to elucidate the mechanisms that drive pharmacokinetic food-drug interactions. Their occurrence depends mainly on the properties of the drug substance, the formulation and a multitude of physiological factors. Every intake of food or drink changes the physiological conditions in the human gastrointestinal tract. Therefore, a precise understanding of how different foods and drinks affect the processes of drug absorption, distribution, metabolism and/or elimination as well as formulation performance is important in order to be able to predict and avoid such interactions. Furthermore, it must be considered that beverages such as milk, grapefruit juice and alcohol can also lead to specific food-drug interactions. In this regard, the growing use of food supplements and functional food requires urgent attention in oral pharmacotherapy. Recently, a new consortium in Understanding Gastrointestinal Absorption-related Processes (UNGAP) was established through COST, a funding organisation of the European Union supporting translational research across Europe. In this review of the UNGAP Working group "Food-Drug Interface", the different mechanisms that can lead to pharmacokinetic food-drug interactions are discussed and summarised from different expert perspectives.

Absence of adverse effects following the gavage administration of methyl propyl trisulfide to Sprague-Dawley rats for 90 days

Methyl propyl trisulfide is a flavoring substance found in foods such as garlic and onions. At the request of the European Food Safety Authority (EFSA) for additional toxicological data on methyl propyl trisulfide, groups of Sprague-Dawley rats (10/sex/group) were gavaged with 0 (corn oil vehicle control), 0.5, 2, or 6 mg methyl propyl trisulfide/kg bw/day in a 90-day GLP-compliant study. No effects on clinical observations, hematology and clinical chemistry parameters, organ weights, or macroscopic and histopathological examinations were found attributable to ingestion of methyl propyl trisulfide. The oral no-observed-adverse-effect level (NOAEL) for rats of both sexes was the highest dose tested of 6 mg/kg bw/day.

Validation of biomarkers of food intake-critical assessment of candidate biomarkers

Biomarkers of food intake (BFIs) are a promising tool for limiting misclassification in nutrition research where more subjective dietary assessment instruments are used. They may also be used to assess compliance to dietary guidelines or to a dietary intervention. Biomarkers therefore hold promise for direct and objective measurement of food intake. However, the number of comprehensively validated biomarkers of food intake is limited to just a few. Many new candidate biomarkers emerge from metabolic profiling studies and from advances in food chemistry. Furthermore, candidate food intake biomarkers may also be identified based on extensive literature reviews such as described in the guidelines for Biomarker of Food Intake Reviews (BFIRev). To systematically and critically assess the validity of candidate biomarkers of food intake, it is necessary to outline and streamline an optimal and reproducible validation process. A consensus-based procedure was used to provide and evaluate a set of the most important criteria for systematic validation of BFIs. As a result, a validation procedure was developed including eight criteria, plausibility, dose-response, time-response, robustness, reliability, stability, analytical performance, and inter-laboratory reproducibility. The validation has a dual purpose: (1) to estimate the current level of validation of candidate biomarkers of food intake based on an objective and systematic approach and (2) to pinpoint which additional studies are needed to provide full validation of each candidate biomarker of food intake. This position paper on biomarker of food intake validation outlines the second step of the BFIRev procedure but may also be used as such for validation of new candidate biomarkers identified, e.g., in food metabolomic studies.

Synthesis of Unsymmetric Trisulfides from 9-Fluorenylmethyl Disulfides

A convenient method for the preparation of unsymmetrical trisulfides using 9-fluorenylmethyl (Fm) disulfide as the precursors is reported. This method gives the desired trisulfides in good yields under mild conditions.

The Oxepane Motif in Marine Drugs

Oceans have shown to be a remarkable source of natural products. The biological properties of many of these compounds have helped to produce great advances in medicinal chemistry. Within them, marine natural products containing an oxepanyl ring are present in a great variety of algae, sponges, fungus and corals and show very important biological activities, many of them possessing remarkable cytotoxic properties against a wide range of cancer cell lines. Their rich chemical structures have attracted the attention of many researchers who have reported interesting synthetic approaches to these targets. This review covers the most prominent examples of these types of compounds, focusing the discussion on the isolation, structure determination, medicinal properties and total synthesis of these products.

Garlic oil polysulfides: H2S- and O2-independent prooxidants in buffer and antioxidants in cells

The health benefits of garlic and other organosulfur-containing foods are well recognized and have been attributed to both prooxidant and antioxidant activities. The effects of garlic are surprisingly similar to those of hydrogen sulfide (H2S), which is also known to be released from garlic under certain conditions. However, recent evidence suggests that polysulfides, not H2S, may be the actual mediator of physiological signaling. In this study, we monitored formation of H2S and polysulfides from garlic oil in buffer and in human embryonic kidney (HEK) 293 cells with fluorescent dyes, 7-azido-4-methylcoumarin and SSP4, respectively and redox activity with two redox indicators redox-sensitive green fluorescent protein (roGFP) and DCF. Our results show that H2S release from garlic oil in buffer requires other low-molecular-weight thiols, such as cysteine (Cys) or glutathione (GSH), whereas polysulfides are readily detected in garlic oil alone. Administration of garlic oil to cells rapidly increases intracellular polysulfide but has minimal effects on H2S unless Cys or GSH are also present in the extracellular medium. We also observed that garlic oil and diallyltrisulfide (DATS) potently oxidized roGFP in buffer but did not affect DCF. This appears to be a direct polysulfide-mediated oxidation that does not require a reactive oxygen species intermediate. Conversely, when applied to cells, garlic oil became a significant intracellular reductant independent of extracellular Cys or GSH. This suggests that intracellular metabolism and further processing of the sulfur moieties are necessary to confer antioxidant properties to garlic oil in vivo.

S-sulfhydration as a cellular redox regulation

This review is focused on formation and biological significance of hydropersulfides, i.e. S-sulfhydration process. Biogenesis and properties of reactive sulfur species and their role in redox signaling are presented. The effect of S-sulfhydration on protein function is discussed.

For many years reactive oxygen and nitrogen species (ROS and RNS) have been recognized as key messengers in the process of thiol-based redox regulation. Relatively recently, literature reports began to mention reactive sulfur species (RSS) and their role in thiol regulation. This review is focused on biogenesis and biological properties of RSS, including: hydropersulfides, polysulfides and hydrogen sulfide (H₂S). Based on the most up-to-date literature data, the paper presents biological significance of S-sulfhydration process. In this reaction, sulfane sulfur is transferred to the–SH groups forming hydropersulfides. Protein cysteine residues, called ‘redox switches’ are susceptible to such reversible modifications. In line with the most recent reports, it was emphasized that sulfane sulfur-containing compounds (mainly hydrogen persulfides and polysulfides) are real and better mediators of S-sulfhydration-based signalling than H₂S. We also overviewed proteins participating in the formation and transport of RSS and in mitochondrial H₂S oxidation. In addition, we reviewed many reports about proteins unrelated to sulfur metabolism which are modified by S-sulfhydration that influences their catalytic activity. We also addressed the problem of the regulatory function of S-sulfhydration reaction in the activation of K_ATP channels (vasorelaxant) and transcription factors (e.g. NF_κB) as well as in the mechanism of therapeutic action of garlic-derived sulfur compounds. Some aspects of comparison between RNS and RSS are also discussed in this review.

Amino acid and water-driven tunable green protocol to access S–S/C–S bonds via aerobic oxidative coupling and hydrothiolation

Arginine in conjunction with water has been employed as an effective and recyclable organocatalyst for oxidative coupling of thiophenols and hydrothiolation of alkynes.

Disulfide Oil Hazard Assessment Using Categorical Analysis and a Mode of Action Determination

Diethyl and diphenyl disulfides, naphtha sweetening (Chemical Abstracts Service [CAS] # 68955-96-4), are primarily composed of low-molecular-weight dialkyl disulfides extracted from C4 to C5 light hydrocarbon streams during the refining of crude oil. The substance, commonly known as disulfide oil (DSO), can be composed of up to 17 different disulfides and trisulfides with monoalkyl chain lengths no greater than C4. The disulfides in DSO constitute a homologous series of chemical constituents that are perfectly suited for a hazard evaluation using a read-across/worst-case approach. The DSO constituents exhibit a common mode of action that is operable at all trophic levels. The observed oxidative stress response is mediated by reactive oxygen species and free radical intermediates generated after disulfide bond cleavage and subsequent redox cycling of the resulting mercaptan. Evidence indicates that the lowest series member, dimethyl disulfide (DMDS), can operate as a worst-case surrogate for other members of the series, since it displays the highest toxicity. Increasing the alkyl chain length or degree of substitution has been shown to serially reduce disulfide toxicity through resonance stabilization of the radical intermediate or steric inhibition of the initial enzymatic step. The following case study examines the mode of action for dialkyl disulfide toxicity and documents the use of read-across information from DMDS to assess the hazards of DSO. The results indicate that DSO possesses high aquatic toxicity, moderate environmental persistence, low to moderate acute toxicity, high repeated dose toxicity, and a low potential for genotoxicity, carcinogenicity, and reproductive/developmental effects.

Synthesis and bioactivity profile of 5-s-lipoylhydroxytyrosol-based multidefense antioxidants with a sizeable (poly)sulfide chain

Novel polyfunctionalized antioxidants, 5-S-lipoylhydroxytyrosol (1) and its disulfide 2, trisulfide 3, and tetrasulfide 4, were prepared from tyrosol and dihydrolipoic acid in the presence, when appropriate, of sulfur. Compound 1 exhibited significant activity in the ferric reducing/antioxidant power (FRAP) assay (1.60 Trolox equiv), whereas polysulfides 2-4 were more efficient in the DPPH reduction assay (88-93% reduction vs 68% by Trolox). At 10 μM concentration, all compounds 1-4 proved to be efficient hydroxyl radical scavengers (56-69% inhibition) in a Fenton reaction assay. When administered to human HepG2 cells, 1-4 proved to be nontoxic and exhibited marked protective effects against reactive oxygen species (ROS) generation (60-84% inhibition at 1 μM concentration) and cell damage induced by 400 μM tert-butylhydroperoxide. All compounds 1-4 exhibited overall greater antioxidant activity than hydroxytyrosol.

Effect of garlic-derived organosulfur compounds on mitochondrial function and integrity in isolated mouse liver mitochondria

The objectives of this work were to evaluate the direct effects of diallysulfide (DAS) and diallyldisulfide (DADS), two major organosulfur compounds of garlic oil, on mitochondrial function and integrity, by using isolated mouse liver mitochondria in a cell-free system. DADS produced concentration-dependent mitochondrial swelling over the range 125-1000μM, while DAS was ineffective. Swelling experiments performed with de-energized or energized mitochondria showed similar maximal swelling amplitudes. Cyclosporin A (1μM), or ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA, 1mM) were ineffective in inhibiting DADS-induced mitochondrial swelling. DADS produced a minor (12%) decrease in mitochondrial membrane protein thiols, but did not induce clustering of mitochondrial membrane proteins. Incubation of mitochondria with DADS (but not DAS) produced an increase in the oxidation rate of 2',7' dichlorofluorescein diacetate (DCFH-DA), together with depletion of reduced glutathione (GSH) and increased lipid peroxidation. DADS (but not DAS) produced a concentration-dependent dissipation of the mitochondrial membrane potential, but did not induce cytochrome c release. DADS-dependent effects, including mitochondrial swelling, DCFH-DA oxidation, lipid peroxidation and loss of mitochondrial membrane potential, were inhibited by antioxidants and iron chelators. These results suggest that DADS causes direct impairment of mitochondrial function as the result of oxidation of the membrane lipid phase initiated by the GSH- and iron-dependent generation of oxidants.