Isothiocyanates as H2S Donors Triggered by Cysteine: Reaction Mechanism and Structure and Activity Relationship

A near-infrared fluorescent probe selectively recognizing cysteine to release H2S and its applications

Cysteine, a pivotal biothiol vital for human health, exhibits strong associations with various diseases, yet its concentration assessment is often confounded by structurally and functionally similar biothiols. Hydrogen sulfide (H2S), an endogenous gasotransmitter with therapeutic potential, faces challenges in achieving pharmacological effects due to the unpredictable presence of inorganic H2S donors. To address these issues, we developed TMN-ONCS, a near-infrared fluorescent probe that integrates a p-tolyl isothiocyanate with a dicyanoisophorone fluorophore through a self-immolative spacer. TMN-ONCS demonstrates high selectivity and analytical performance for cysteine, avoids the generation of multiple fluorophores seen in conventional isothiocyanate probes, and functions as a cysteine-activated fluorescent H2S donor with concurrent visualization. Furthermore, it mitigates lipopolysaccharide-induced inflammation in RAW 264.7 cells, highlighting its potential for treating inflammation.

Self-Assembly of H2S-Generating Photosensitizer for Gas-Assisted Synergistic Photothermal Therapy

Photothermal therapy (PTT) is emerging as a promising cancer treatment, but uneven heat distribution increases side effects and reduces treatment precision, where high-temperature zones risk inducing undesired inflammation, while low-temperature regions are insufficient due to upregulation of heat shock proteins (HSPs). Herein, a gas-assisted PTT strategy is designed to link near-infrared heptamethine cyanine (Cy7) with self-immolative phenyl thiocarbonate (PTC), a hydrogen sulfide (H2S) donor through a disulfide bond, creating a small-molecule photosensitizer (Cy7-SS-PTC) that can self-assemble into nanoparticles (NPs) without stabilizers. Upon internalized by cancer cells, Cy7-SS-PTC NPs respond to elevated glutathione levels, and simultaneously release Cy7 and H2S via a cascade reaction. The released Cy7 reassembles into nanoaggregates, generating hyperthermia under 808 nm light irradiation, and then binds to albumin, producing strong near-infrared fluorescence to track tumors for precise treatment. The released H2S not only disrupts the mitochondrial respiratory chain, blocks ATP production, and suppresses HSP70 overexpression to amplify the efficacy of low-temperature PTT regions but also curbs proinflammatory cytokines in high-temperature PTT zones, delivering powerful tumor ablation with minimal inflammation. This small-molecule-based "H2S-assisted PTT" strategy optimizes the current PTT and validates its potential clinical application.

Evidence-Based Nutraceuticals Derived from Antrodia cinnamomea

Antrodia cinnamomea (A. cinnamomea), a medicinal and edible mushroom endemic to Taiwan, has been traditionally valued as a health tonic. Recent studies have highlighted the diverse specialized metabolites and bioactive potential of this substance, primarily attributed to key secondary metabolites such as benzenoids, maleic and succinic acids, ubiquinone, triterpenoids, and the primary metabolite polysaccharides. These compounds exhibit a broad spectrum of pharmacological properties, including those related to antibacterial, antitumor, anti-inflammation, hepatoprotection, hypoglycaemia, and antioxidant activities, and immunomodulation and gut microbiota regulation. These findings highlight the therapeutic potential of A. cinnamomea and its potential applications in health supplements and functional foods. This review evaluated recent advancements in the cultivation, extraction, and characterization of bioactive compounds from A. cinnamomea, with a particular focus on submerged and solid-state fermentation methods. We hope to provide a comprehensive framework for promoting the efficient and scientific evidence based utilization of A. cinnamomea in novel therapeutic strategies and health-related innovations.

Sulfhydrylation of chlorothalonil in pak choi from cultivation to sample analysis and exposure risk assessment

The rapid sulfhydrylation of chlorothalonil (CHT) in sulfur-rich vegetable matrices was observed in our previous study. However, the formation pathway, residual behavior, and toxicity of sulfhydrylated CHT remain unclear. In this study, we reveal that 4-sulfhydryl chlorothalonil (4-SH-CHT) can be formed by the reaction of CHT with H2S species. CHT sulfhydrylation mainly occurs in tissue-destroyed pak choi, as H2S and various H2S donors are released along with tissue destruction. Over 50 % of CHT was transformed during pak choi homogenization at room temperature (25 °C). Liquid nitrogen with solvent acidification has been proposed to inhibit rapid sulfhydrylation during the analysis of CHT and its degradation products. The analytical method developed to simultaneously detect CHT, 4-SH-CHT, and 4-hydroxy chlorothalonil demonstrated good accuracy, high sensitivity, and satisfactory repeatability. At the maximum recommended dose of CHT, the terminal concentration of CHT in pak choi was higher than the maximum residue level, suggesting a potential chronic risk. The acute toxicity of 4-SH-CHT was higher than that of CHT, and the main target organs were the liver and heart. The consumption of 4-SH-CHT in several tissue-destroyed pak choi samples was higher than the threshold level. This study provides valuable information for further comprehensive safety evaluations of CHT in sulfur-rich vegetables and related foods.

A cysteine-activated fluorescent H2S donor for visualizing H2S release and alleviating cellular inflammation

We developed Bcy-NCS, a Cys-specific fluorescent H2S donor with a self-immolative spacer, overcoming the issue of multiple fluorophore release seen in traditional ICT-based donors. Bcy-NCS selectively responds to Cys, releases H2S, and enables fluorescence-based monitoring. It also reduces LPS-induced inflammation in RAW 264.7 cells, indicating potential for inflammation treatment.

Isothiocyanate-Corticosteroid Conjugates against asthma: Unity makes strength

Asthma is a major noncommunicable disease, affecting both children and adults, and represents one of the major causes leading to high health care costs due to the need for chronic pharmacological treatments. The standard gold therapy of inflammation in asthmatic patients involves the use of glucocorticoids even if their chronic use is often related to serious adverse effects. Growing evidence suggests the biological relevance of hydrogen sulfide (H2S) in the pathogenesis of airway diseases. Hence, aiming to associate the beneficial effects of steroidal anti-inflammatory drugs (SAIDs) to H2S biological activity, we designed and synthesized novel multi-target molecules by chemically combining a group of glucocorticoids, usually employed in asthma treatment, with an isothiocyanate moiety, well-known for its H2S releasing properties. Firstly, the synthesized compounds have been screened for their H2S-releasing profile using an amperometric approach and for their in vitro effects on the degranulation process, using RBL-2H3 cell line. The physicochemical profile, in terms of solubility, chemical and enzymatic stability of the newly hybrid molecules, has been assessed at different physiological pH values and in esterase-rich medium (bovine serum albumin, BSA). The selected compound 5c, through both its corticosteroid and H2S releasing component, has been evaluated in vivo in experimental model of asthma. The compound 5c inhibited in vivo all asthma features with a significative effect on the restoration of pulmonary structure and reduction of lung inflammation.

Anti-obesity effects of Beta vulgaris and Eruca sativa-based extracts

Obesity is a major source of morbidity worldwide with more than 2 billion adults being overweight or obese. The incidence of obesity has tripled in the last 50 years, leading to an increased risk for a variety of noncommunicable diseases. Previous studies have demonstrated the positive effects of green leafy vegetables on weight gain and obesity and have attributed these beneficial properties, at least in part, to nitrates and isothiocyanates. Nitrates are converted to nitric oxide (NO) and isothiocyanates are known to release hydrogen sulfide (H2S). Herein, we investigated the effect of extracts and fractions produced from Beta vulgaris and Eruca sativa for their ability to limit lipid accumulation, regulate glucose homeostasis, and reduce body weight. Extracts from the different vegetables were screened for their ability to limit lipid accumulation in adipocytes and hepatocytes and for their ability to promote glucose uptake in skeletal muscle cultures; the most effective extracts were next tested in vivo. Wild type mice were placed on high-fat diet for 8 weeks to promote weight gain; animals receiving the selected B. vulgaris and E. sativa extracts exhibited attenuated body weight. Treatment with extracts also led to reduced white adipose tissue depot mass, attenuated adipocyte size, reduced expression of Dgat2 and PPARγ expression, and improved liver steatosis. In contrast, the extracts failed to improve glucose tolerance in obese animals and did not affect blood pressure. Taken together, our data indicate that extracts produced from B. vulgaris and E. sativa exhibit anti-obesity effects, suggesting that dietary supplements containing nitrates and sulfide-releasing compounds might be useful in limiting weight gain.

Natural H2S-donors: A new pharmacological opportunity for the management of overweight and obesity

The prevalence of overweight and obesity has progressively increased in the last few years, becoming a real threat to healthcare systems. To date, the clinical management of body weight gain is an unmet medical need, as there are few approved anti-obesity drugs and most require an extensive monitoring and vigilance due to risk of adverse effects and poor patient adherence/persistence. Growing evidence has shown that the gasotransmitter hydrogen sulfide (H2S) and, therefore, H2S-donors could have a central role in the prevention and treatment of overweight/obesity. The main natural sources of H2S-donors are plants from the Alliaceae (garlic and onion), Brassicaceae (e.g., broccoli, cabbage, and wasabi), and Moringaceae botanical families. In particular, polysulfides and isothiocyanates, which slowly release H2S, derive from the hydrolysis of alliin from Alliaceae and glucosinolates from Brassicaceae/Moringaceae, respectively. In this review, we describe the emerging role of endogenous H2S in regulating adipose tissue function and the potential efficacy of natural H2S-donors in animal models of overweight/obesity, with a final focus on the preliminary results from clinical trials. We conclude that organosulfur-containing plants and their extracts could be used before or in combination with conventional anti-obesity agents to improve treatment efficacy and reduce inflammation in obesogenic conditions. However, further high-quality studies are needed to firmly establish their clinical efficacy.

Activity-Based Fluorescent Probes for Hydrogen Sulfide and Related Reactive Sulfur Species

Hydrogen sulfide (H2S) is not only a well-established toxic gas but also an important small molecule bioregulator in all kingdoms of life. In contemporary biology, H2S is often classified as a "gasotransmitter," meaning that it is an endogenously produced membrane permeable gas that carries out essential cellular processes. Fluorescent probes for H2S and related reactive sulfur species (RSS) detection provide an important cornerstone for investigating the multifaceted roles of these important small molecules in complex biological systems. A now common approach to develop such tools is to develop "activity-based probes" that couple a specific H2S-mediated chemical reaction to a fluorescent output. This Review covers the different types of such probes and also highlights the chemical mechanisms by which each probe type is activated by specific RSS. Common examples include reduction of oxidized nitrogen motifs, disulfide exchange, electrophilic reactions, metal precipitation, and metal coordination. In addition, we also outline complementary activity-based probes for imaging reductant-labile and sulfane sulfur species, including persulfides and polysulfides. For probes highlighted in this Review, we focus on small molecule systems with demonstrated compatibility in cellular systems or related applications. Building from breadth of reported activity-based strategies and application, we also highlight key unmet challenges and future opportunities for advancing activity-based probes for H2S and related RSS.

Synthesis of sinomenine derivatives with potential anti-leukemia activity

In recent years, with sinomenine hydrochloride as the main ingredient, Qingfengteng had been formulated as various dosage forms for clinical treatment. Subsequent findings confirmed a variety of biological roles for sinomenine. Here, 15 H2S-donating sinomenine derivatives were synthesized. Target hybrids a11 displayed substantial cytotoxic effects on cancer cell lines, particularly against K562 cells, with an IC50 value of 1.36 μM. In-depth studies demonstrated that a11 arrested cell cycle at G1 phase, induced apoptosis via both morphological changes in nucleus and membrane potential collapse in mitochondria. These results indicated a11 exerted an antiproliferative effect through apoptosis induction via mitochondrial pathway.

Elemental Sulfur Promoted Cyclization of Aryl Hydrazones and Aryl Isothiocyanates Yielding 2-Imino-1,3,4-thiadiazoles

We report a method for using elemental sulfur to facilitate the cyclization of aryl hydrazones and aryl isothiocyanates, affording biorelated 2-imino-1,3,4-thiadiazoles. Reactions progressed in the presence of elemental sulfur, N-methylmorpholine base, and DMSO solvent, while were tolerant of a wide range of functionalities including halogen, nitro, cyano, methylsulfonyl, and heterocyclic groups. The method appears to offer a general pathway for using simple, cheap, and stable reagents to afford triaryl-substituted 2-imino-1,3,4-thiadiazoles under relatively mild conditions.

The Antioxidant Properties of Glucosinolates in Cardiac Cells Are Independent of H2S Signaling

The organic sulfur-containing compounds glucosinolates (GSLs) and the novel gasotransmitter H2S are known to have cardioprotective effects. This study investigated the antioxidant effects and H2S-releasing potential of three GSLs ((3E)-4-(methylsulfanyl)but-3-enyl GSL or glucoraphasatin, 4-hydroxybenzyl GSL or glucosinalbin, and (RS)-6-(methylsulfinyl)hexyl GSL or glucohesperin) in rat cardiac cells. It was found that all three GSLs had no effect on cardiac cell viability but were able to protect against H2O2-induced oxidative stress and cell death. NaHS, a H2S donor, also protected the cells from H2O2-stimulated oxidative stress and cell death. The GSLs alone or mixed with cysteine, N-acetylcysteine, glutathione, H2O2, iron and pyridoxal-5'-phosphate, or mouse liver lysates did not induce H2S release. The addition of GSLs also did not alter endogenous H2S levels in cardiac cells. H2O2 significantly induced cysteine oxidation in the cystathionine gamma-lyase (CSE) protein and inhibited the H2S production rate. In conclusion, this study found that the three tested GSLs protect cardiomyocytes from oxidative stress and cell death but independently of H2S signaling.

Anti-Proliferative Properties of the Novel Hybrid Drug Met-ITC, Composed of the Native Drug Metformin with the Addition of an Isothiocyanate H2S Donor Moiety, in Different Cancer Cell Lines

Metformin (Met) is the first-line therapy in type 2 diabetes mellitus but, in last few years, it has also been evaluated as anti-cancer agent. Several pathways, such as AMPK or PI3K/Akt/mTOR, are likely to be involved in the anti-cancer Met activity. In addition, hydrogen sulfide (H2S) and H2S donors have been described as anti-cancer agents affecting cell-cycle and inducing apoptosis. Among H2S donors, isothiocyanates are endowed with a further anti-cancer mechanism: the inhibition of the histone deacetylase enzymes. On this basis, a hybrid molecule (Met-ITC) obtained through the addition of an isothiocyanate moiety to the Met molecule was designed and its ability to release Met has been demonstrated. Met-ITC exhibited more efficacy and potency than Met in inhibiting cancer cells (AsPC-1, MIA PaCa-2, MCF-7) viability and it was less effective on non-tumorigenic cells (MCF 10-A). The ability of Met-ITC to release H2S has been recorded both in cell-free and in cancer cells assays. Finally, its ability to affect the cell cycle and to induce both early and late apoptosis has been demonstrated on the most sensitive cell line (MCF-7). These results confirmed that Met-ITC is a new hybrid molecule endowed with potential anti-cancer properties derived both from Met and H2S.

Hydrogen sulfide and sulfaceutic or sulfanutraceutic agents: Classification, differences and relevance in preclinical and clinical studies

Hydrogen sulfide (H2S) has been extensively studied as a signal molecule in the body for the past 30 years. Researchers have conducted studies using both natural and synthetic sources of H2S, known as H2S donors, which have different characteristics in terms of how they release H2S. These donors can be inorganic salts or have various organic structures. In recent years, certain types of sulfur compounds found naturally in foods have been characterized as H2S donors and explored for their potential health benefits. These compounds are referred to as "sulfanutraceuticals," a term that combines "nutrition" and "pharmaceutical". It is used to describe products derived from food sources that offer additional health advantages. By introducing the terms "sulfaceuticals" and "sulfanutraceuticals," we categorize sulfur-containing substances based on their origin and their use in both preclinical and clinical research, as well as in dietary supplements.

Plants and Mushrooms as Possible New Sources of H2S Releasing Sulfur Compounds

Hydrogen sulfide (H2S), known for many decades exclusively for its toxicity and the smell of rotten eggs, has been re-discovered for its pleiotropic effects at the cardiovascular and non-cardiovascular level. Therefore, great attention is being paid to the discovery of molecules able to release H2S in a smart manner, i.e., slowly and for a long time, thus ensuring the maintenance of its physiological levels and preventing "H2S-poor" diseases. Despite the development of numerous synthetically derived molecules, the observation that plants containing sulfur compounds share the same pharmacological properties as H2S led to the characterization of naturally derived compounds as H2S donors. In this regard, polysulfuric compounds occurring in plants belonging to the Alliaceae family were the first characterized as H2S donors, followed by isothiocyanates derived from vegetables belonging to the Brassicaceae family, and this led us to consider these plants as nutraceutical tools and their daily consumption has been demonstrated to prevent the onset of several diseases. Interestingly, sulfur compounds are also contained in many fungi. In this review, we speculate about the possibility that they may be novel sources of H2S-donors, furnishing new data on the release of H2S from several selected extracts from fungi.

H2S Donors with Cytoprotective Effects in Models of MI/R Injury and Chemotherapy-Induced Cardiotoxicity

Hydrogen sulfide (H2S) is an endogenous signaling molecule that greatly influences several important (patho)physiological processes related to cardiovascular health and disease, including vasodilation, angiogenesis, inflammation, and cellular redox homeostasis. Consequently, H2S supplementation is an emerging area of interest, especially for the treatment of cardiovascular-related diseases. To fully unlock the medicinal properties of hydrogen sulfide, however, the development and refinement of H2S releasing compounds (or donors) are required to augment its bioavailability and to better mimic its natural enzymatic production. Categorizing donors by the biological stimulus that triggers their H2S release, this review highlights the fundamental chemistry and releasing mechanisms of a range of H2S donors that have exhibited promising protective effects in models of myocardial ischemia-reperfusion (MI/R) injury and cancer chemotherapy-induced cardiotoxicity, specifically. Thus, in addition to serving as important investigative tools that further advance our knowledge and understanding of H2S chemical biology, the compounds highlighted in this review have the potential to serve as vital therapeutic agents for the treatment (or prevention) of various cardiomyopathies.

Understanding the Therapeutic Approaches for Neuroprotection

The term "neurodegenerative disorders" refers to a group of illnesses in which deterioration of nerve structure and function is a prominent feature. Cognitive capacities such as memory and decision-making deteriorate as a result of neuronal damage. The primary difficulty that remains is safeguarding neurons since they do not proliferate or regenerate spontaneously and are therefore not substituted by the body after they have been damaged. Millions of individuals throughout the world suffer from neurodegenerative diseases. Various pathways lead to neurodegeneration, including endoplasmic reticulum stress, calcium ion overload, mitochondrial dysfunction, reactive oxygen species generation, and apoptosis. Although different treatments and therapies are available for neuroprotection after a brain injury or damage, the obstacles are inextricably connected. Several studies have revealed the pathogenic effects of hypothermia, different breathed gases, stem cell treatments, mitochondrial transplantation, multi-pharmacological therapy, and other therapies that have improved neurological recovery and survival outcomes after brain damage. The present review highlights the use of therapeutic approaches that can be targeted to develop and understand significant therapies for treating neurodegenerative diseases.

Antiproliferative and Proapoptotic Effects of Erucin, a Diet-Derived H2S Donor, on Human Melanoma Cells

Melanoma is the most dangerous form of skin cancer and is characterized by chemotherapy resistance and recurrence despite the new promising therapeutic approaches. In the last years, erucin (ERU), the major isothiocyanate present in Eruca sativa, commonly known as rocket salads, has demonstrated great efficacy as an anticancer agent in different in vitro and in vivo models. More recently, the chemopreventive effects of ERU have been associated with its property of being a H₂S donor in human pancreatic adenocarcinoma. Here, we investigated the effects of ERU in modulating proliferation and inducing human melanoma cell death by using multiple in vitro approaches. ERU significantly reduced the proliferation of different human melanoma cell lines. A flow cytometry analysis with annexin V/PI demonstrated that ERU was able to induce apoptosis and cell cycle arrest in A375 melanoma cells. The proapoptotic effect of ERU was associated with the modulation of the epithelial-to-mesenchymal transition (EMT)-related cadherins and transcription factors. Moreover, ERU thwarted the migration, invasiveness and clonogenic abilities of A375 melanoma cells. These effects were associated with melanogenesis impairment and mitochondrial fitness modulation. Therefore, we demonstrated that ERU plays an important role in inhibiting the progression of melanoma and could represent a novel add-on therapy for the treatment of human melanoma.

Anti-Inflammatory Effect of the Natural H2S-Donor Erucin in Vascular Endothelium

Vascular inflammation (VI) represents a pathological condition that progressively affects the integrity and functionality of the vascular wall, thus leading to endothelial dysfunction and the onset of several cardiovascular diseases. Therefore, the research of novel compounds able to prevent VI represents a compelling need. In this study, we tested erucin, the natural isothiocyanate H₂S-donor derived from Eruca sativa Mill. (Brassicaceae), in an in vivo mouse model of lipopolysaccharide (LPS)-induced peritonitis, where it significantly reduced the amount of emigrated CD11b positive neutrophils. We then evaluated the anti-inflammatory effects of erucin in LPS-challenged human umbilical vein endothelial cells (HUVECs). The pre-incubation of erucin, before LPS treatment (1, 6, 24 h), significantly preserved cell viability and prevented the increase of reactive oxygen species (ROS) and tumor necrosis factor alpha (TNF-α) levels. Moreover, erucin downregulated endothelial hyperpermeability and reduced the loss of vascular endothelial (VE)-Cadherin levels. In addition, erucin decreased vascular cell adhesion molecule 1 (VCAM-1), cyclooxygenase-2 (COX-2) and microsomal prostaglandin E-synthase 1 (mPGES-1) expression. Of note, erucin induced eNOS phosphorylation and counteracted LPS-mediated NF-κB nuclear translocation, an effect that was partially abolished in the presence of the eNOS inhibitor L-NAME. Therefore, erucin can control endothelial function through biochemical and genomic positive effects against VI.

Regulation of blood pressure by natural sulfur compounds: Focus on their mechanisms of action

Natural sulfur compounds are emerging as therapeutic options for the management of hypertension and prehypertension. They are mainly represented by polysulfides from Alliaceae (i.e., garlic) and isothiocyanates from Brassicaceae (or crucifers). The beneficial cardiovascular effects of these compounds, especially garlic polysulfides, are well known and widely reported both in preclinical and clinical studies. However, only a few authors have linked the ability of natural sulfur compounds to induce vasorelaxation and subsequent antihypertensive effects with their ability to release hydrogen sulfide (H2S) in biological tissue. H2S is an endogenous gasotransmitter involved in vascular tone regulation. Some cardiovascular diseases, such as hypertension, are associated with lower plasma H2S levels. Consequently, exogenous sources of H2S (H2S donors) have been designed and synthesized or identified among secondary plant metabolites as potential therapeutic options. In addition to antioxidant effects due to its chemical properties as a reducing agent, H2S induces vasorelaxation by interacting with a range of molecular targets. The mechanisms of action accounting for H2S-induced vasodilation include opening of vascular potassium channels (such as ATP-sensitive (KATP) and voltage-operated (Kv7) channels), inhibition of 5-phosphodiesterase (5-PDE), and activation of vascular endothelial growth factor receptor-2 (VEGFR-2). These effects may be attributed to H2S-induced S-persulfidation (or S-sulfhydration), which is a posttranslational modification of cysteine residues of many types of proteins resulting in structural and functional alterations (activation/inhibition). Thus, H2S donors, such as natural sulfur compounds, are promising antihypertensive agents with novel mechanisms of action.

Design, Synthesis and Evaluation of Novel Molecular Hybrids between Antiglaucoma Drugs and H2S Donors

Glaucoma is a group of eye diseases consisting of optic nerve damage with corresponding loss of field vision and blindness. Hydrogen sulfide (H₂S) is a gaseous neurotransmitter implicated in various pathophysiological processes. It is involved in the pathological mechanism of glaucomatous neuropathy and exerts promising effects in the treatment of this disease. In this work, we designed and synthetized new molecular hybrids between antiglaucoma drugs and H₂S donors to combine the pharmacological effect of both moieties, providing a heightened therapy. Brinzolamide, betaxolol and brimonidine were linked to different H₂S donors. The H₂S-releasing properties of the new compounds were evaluated in a phosphate buffer solution by the amperometric approach, and evaluated in human primary corneal epithelial cells (HCEs) by spectrofluorometric measurements. Experimental data showed that compounds 1c, 1d and 3d were the hybrids with the best properties, characterized by a significant and long-lasting production of the gasotransmitter both in the aqueous solution (in the presence of L-cysteine) and in the intracellular environment. Because, to date, the donation of H₂S by antiglaucoma H₂S donor hybrids using non-immortalized corneal cells has never been reported, these results pave the way to further investigation of the potential efficacy of the newly synthesized compounds.

An ESIPT-based fluorescent turn-on probe with isothiocyanate for detecting hydrogen sulfide in environmental and biological systems

A probe with an isothiocyanate group was synthesized and evaluated for its H₂S sensing ability. Upon addition of H₂S, the probe exhibited ratiometric properties during absorption with a red-shift. The probe exhibited fluorescent off-on responses towards H₂S via the ESIPT process, due to the conversion of isocyanate into amine. UV-vis, fluorescence, and ¹H NMR spectroscopic analyses were performed to investigate the sensing mechanism. The probe has a large Stokes shift, short response time, and low detection limit. It can be used to estimate H₂S levels within the range of 0-36 nM. The practical applicability of the probe was demonstrated using water samples and living cells.

Progress and perspective on hydrogen sulfide donors and their biomedical applications

Following the discovery of nitric oxide (NO) and carbon monoxide (CO), hydrogen sulfide (H₂ S) has been identified as the third gasotransmitter in humans. Increasing evidence have shown that H₂ S is of preventive or therapeutic effects on diverse pathological complications. As a consequence, it is of great significance to develop suitable approaches of H₂ S-based therapeutics for biomedical applications. H₂ S-releasing agents (H₂ S donors) play important roles in exploring and understanding the physiological functions of H₂ S. More importantly, accumulating studies have validated the theranostic potential of H₂ S donors in extensive repertoires of in vitro and in vivo disease models. Thus, it is imperative to summarize and update the literatures in this field. In this review, first, the background of H₂ S on its chemical and biological aspects is concisely introduced. Second, the studies regarding the H₂ S-releasing compounds are categorized and described, and accordingly, their H₂ S-donating mechanisms, biological applications, and therapeutic values are also comprehensively delineated and discussed. Necessary comparisons between related H₂ S donors are presented, and the drawbacks of many typical H₂ S donors are analyzed and revealed. Finally, several critical challenges encountered in the development of multifunctional H₂ S donors are discussed, and the direction of their future development as well as their biomedical applications is proposed. We expect that this review will reach extensive audiences across multiple disciplines and promote the innovation of H₂ S biomedicine.

Potential Effects of Natural H2S-Donors in Hypertension Management

After the discovery of hydrogen sulfide (H2S) in the central nervous system by Abe and Kimura in 1996, the physiopathological role of H2S has been widely investigated in several systems such as the cardiovascular. In particular, H2S plays a pivotal role in the control of vascular tone, exhibiting mechanisms of action able to induce vasodilation: for instance, activation of potassium channels (KATP and Kv7) and inhibition of 5-phosphodiesterase (5-PDE). These findings paved the way for the research of natural and synthetic exogenous H2S-donors (i.e., molecules able to release H2S) in order to have new tools for the management of hypertension. In this scenario, some natural molecules derived from Alliaceae (i.e., garlic) and Brassicaceae (i.e., rocket or broccoli) botanical families show the profile of slow H2S-donors able to mimic the endogenous production of this gasotransmitter and therefore can be viewed as interesting potential tools for management of hypertension or pre-hypertension. In this article, the preclinical and clinical impacts of these natural H2S-donors on hypertension and vascular integrity have been reviewed in order to give a complete panorama of their potential use for the management of hypertension and related vascular diseases.

A new isothiocyanate-based Golgi-targeting fluorescent probe for Cys and its bioimaging applications during the Golgi stress response

When the cell environment changes or is stimulated, the Golgi apparatus will respond to the corresponding stress, through the opening of related pathways, the expression of corresponding substances can be promoted or inhibited to achieve the purpose of controlling cell redox homeostasis and reducing cytotoxicity. Intuitive analysis of the changes in the content of various substances in the process of stress has important guiding value for the further study of stress response, drug evaluation and clinical diagnosis. Therefore, for the Cys overexpressed during the oxidative stress of the Golgi apparatus, we developed a specific and sensitive fluorescent probe (Gol-NCS) to visually monitor the biologically important Cys in real time. The probe has low cytotoxicity and shows great potential in cell and zebrafish imaging, it can detect the changes of endogenous and exogenous cysteine. It is important to explore the synthetic pathway of Cys during Golgi stress by using the Golgi targeting performance of the probe Gol-NCS. It is confirmed by fluorescence imaging for the first time that the activity of CSE enzyme plays a decisive role in the formation of Cys. Therefore, probe Gol-NCS with excellent photochemical properties is expected to provide help for the research on the involvement of Cys in Golgi stress.

Cysteine-Activated Small-Molecule H2Se Donors Inspired by Synthetic H2S Donors

The importance of selenium (Se) in biology and health has become increasingly clear. Hydrogen selenide (H₂Se), the biologically available and active form of Se, is suggested to be an emerging nitric oxide (NO)-like signaling molecule. Nevertheless, the research on H₂Se chemical biology has technique difficulties due to the lack of well-characterized and controllable H₂Se donors under physiological conditions, as well as a robust assay for direct H₂Se quantification. Motivated by these needs, here, we demonstrate that selenocyclopropenones and selenoamides are tunable donor motifs that release H₂Se upon reaction with cysteine (Cys) at pH 7.4 and that structural modifications enable the rate of Cys-mediated H₂Se release to be tuned. We monitored the reaction pathways for the H₂Se release and confirmed H₂Se generation qualitatively using different methods. We further developed a quantitative assay for direct H₂Se trapping and quantitation in an aqueous solution, which should also be operative for investigating future H₂Se donor motifs. In addition, we demonstrate that arylselenoamide has the capability of Cys-mediated H₂Se release in cellular environments. Importantly, mechanistic investigations and density functional theory (DFT) calculations illustrate the plausible pathways of Cys-activated H₂Se release from arylselenoamides in detail, which may help understand the mechanistic issues of the H₂S release from pharmacologically important arylthioamides. We anticipate that the well-defined chemistries of Cys-activated H₂Se donor motifs will be useful for studying Se biology and for development of new H₂Se donors and bioconjugate techniques.

Beneficial Health Effects of Glucosinolates-Derived Isothiocyanates on Cardiovascular and Neurodegenerative Diseases

Neurodegenerative diseases (NDDs) and cardiovascular diseases (CVDs) are illnesses that affect the nervous system and heart, all of which are vital to the human body. To maintain health of the human body, vegetable diets serve as a preventive approach and particularly Brassica vegetables have been associated with lower risks of chronic diseases, especially NDDs and CVDs. Interestingly, glucosinolates (GLs) and isothiocyanates (ITCs) are phytochemicals that are mostly found in the Cruciferae family and they have been largely documented as antioxidants contributing to both cardio- and neuroprotective effects. The hydrolytic breakdown of GLs into ITCs such as sulforaphane (SFN), phenylethyl ITC (PEITC), moringin (MG), erucin (ER), and allyl ITC (AITC) has been recognized to exert significant effects with regards to cardio- and neuroprotection. From past in vivo and/or in vitro studies, those phytochemicals have displayed the ability to mitigate the adverse effects of reactive oxidation species (ROS), inflammation, and apoptosis, which are the primary causes of CVDs and NDDs. This review focuses on the protective effects of those GL-derived ITCs, featuring their beneficial effects and the mechanisms behind those effects in CVDs and NDDs.

Dietary Organosulfur-Containing Compounds and Their Health-Promotion Mechanisms

Dietary organosulfur-containing compounds (DOSCs) in fruits, vegetables, and edible mushrooms may hold the key to the health-promotion benefits of these foods. Yet their action mechanisms are not clear, partially due to their high reactivity, which leads to the formation of complex compounds during postharvest processing. Among postharvest processing methods, thermal treatment is the most common way to process these edible plants rich in DOSCs, which undergo complex degradation pathways with the generation of numerous derivatives over a short time. At low temperatures, DOSCs are biotransformed slowly during fermentation to different metabolites (e.g., thiols, sulfides, peptides), whose distinctive biological activity remains largely unexplored. In this review, we discuss the bioavailability of DOSCs in human digestion before illustrating their potential mechanisms for health promotion related to cardiovascular health, cancer chemoprevention, and anti-inflammatory and antimicrobial activities. In particular, it is interesting that different DOSCs react with glutathione or cysteine, leading to the slow release of hydrogen sulfide (H2S), which has broad bioactivity in chronic disease prevention. In addition, DOSCs may interact with protein thiol groups of different protein targets of importance related to inflammation and phase II enzyme upregulation, among other action pathways critical for health promotion.

Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Dietary organosulfur compounds: Emerging players in the regulation of bone homeostasis by plant-derived molecules

The progressive decline of bone mass and the deterioration of bone microarchitecture are hallmarks of the bone aging. The resulting increase in bone fragility is the leading cause of bone fractures, a major cause of disability. As the frontline pharmacological treatments for osteoporosis suffer from low patients' adherence and occasional side effects, the importance of diet regimens for the prevention of excessive bone fragility has been increasingly recognized. Indeed, certain diet components have been already associated to a reduced fracture risk. Organosulfur compounds are a broad class of molecules containing sulfur. Among them, several molecules of potential therapeutic interest are found in edible plants belonging to the Allium and Brassica botanical genera. Polysulfides derived from Alliaceae and isothiocyanates derived from Brassicaceae hold remarkable nutraceutical potential as anti-inflammatory, antioxidants, vasorelaxant and hypolipemic. Some of these effects are linked to the ability to release the gasotrasmitter hydrogen sulfide (H₂S). Recent preclinical studies have investigated the effect of organosulfur compounds in bone wasting and metabolic bone diseases, revealing a strong potential to preserve skeletal health by exerting cytoprotection and stimulating the bone forming activity by osteoblasts and attenuating bone resorption by osteoclasts. This review is intended for revising evidence from preclinical and epidemiological studies on the skeletal effects of organosulfur molecules of dietary origin, with emphasis on the direct regulation of bone cells by plant-derived polysulfides, glucosinolates and isothiocyanates. Moreover, we highlight the potential molecular mechanisms underlying the biological role of these compounds and revise the importance of the so-called 'H₂S-system' on the regulation of bone homeostasis.

Thiobenzophenones: tunable hydrolysis-based donors for intracellular H2S delivery

H2S, the third gasotransmitter, is involved in many physiological and pathological processes. Compounds that can release H2S slowly under physiological conditions are useful chemical tools for studying H2S biology as...

H2S Donors and Their Use in Medicinal Chemistry

Hydrogen sulfide (H2S) is a ubiquitous gaseous signaling molecule that has an important role in many physiological and pathological processes in mammalian tissues, with the same importance as two others endogenous gasotransmitters such as NO (nitric oxide) and CO (carbon monoxide). Endogenous H2S is involved in a broad gamut of processes in mammalian tissues including inflammation, vascular tone, hypertension, gastric mucosal integrity, neuromodulation, and defense mechanisms against viral infections as well as SARS-CoV-2 infection. These results suggest that the modulation of H2S levels has a potential therapeutic value. Consequently, synthetic H2S-releasing agents represent not only important research tools, but also potent therapeutic agents. This review has been designed in order to summarize the currently available H2S donors; furthermore, herein we discuss their preparation, the H2S-releasing mechanisms, and their -biological applications.

Red-emitting fluorescent turn-on probe with specific isothiocyanate recognition site for cysteine imaging in living systems

Cysteine (Cys) is an effective biomarker in life systems and is closely related to a variety of diseases, so developing a specific and efficient detection method for Cys is of great significance. To date, extensive work has been undertaken toward this goal. However, the differentiation of Cys from other biothiols still represents a challenge from an experimental point of view. Toward this end, a selective and sensitive red-emitting probe (TMN-NCS) with an isothiocyanate (ITC)-based structure was proposed in this paper. A large Stokes shift (210 nm) was observed upon addition of Cys to a solution of TMN-NCS. In addition, TMN-NCS showed low toxicity, a low detection limit (120 nM), and excellent cell permeability. The results suggested that TMN-NCS holds great promise for biological applications.

The degradation kinetics and mechanism of moringin in aqueous solution and the cytotoxicity of degraded products

In this work, we investigated the degradation of moringin (4-[(α-l-rhamnosyloxy)benzyl]-isothiocyanate), a major bioactive isothiocyanate (ITC) found in moringa seeds (Moringa oleifera Lam), at various food processing conditions. Moringin degrades rapidly to several water-soluble products via a pseudo-first-order kinetics. By analyzing the reaction products, the degradation mechanism was found to be through hydrolyzing to (A) 1-O-(4-hydroxymethylphenyl) α-l-rhamnopyranoside (rhamnobenzyl alcohol RBA) or (B) rhamnobenzylamine. The formed amine further reacts with moringin to form N,N'-bis{4-[(α-l-rhamnosyloxy)benzyl]}thiourea (di-rhamnobenzyl thiourea, DRBTU). In addition, moringin isomerizes to 4-[(α-l-rhamnosyloxy)benzyl]thiocyanate (RBTC), which further reacts with moringin to form S,N-bis{4-[(α-l-rhamnosyloxy)benzyl]}-dithiocarbamate (DRBDTC). Furthermore, pH was found to have an effect on the degradation of moringin. RBA and RBTC were major degraded products in neutral and acidic conditions while thiourea (DRBTU) was in alkaline condition. Although moringin showed higher cytotoxicity to cancer cells, its degraded products showed very weak or no activities, suggesting that the isothiocyanate group of ITCs is essential for their cancer chemoprevention activities.

The H2S-Donor Erucin Exhibits Protective Effects against Vascular Inflammation in Human Endothelial and Smooth Muscle Cells

Preservation of vascular wall integrity against degenerative processes associated with ageing, fat-rich diet and metabolic diseases is a timely therapeutical challenge. The loss of endothelial function and integrity leads to cardiovascular diseases and multiorgan inflammation. The protective effects of the H₂S-donor erucin, an isothiocyanate purified by Eruca sativa Mill. seeds, were evaluated on human endothelial and vascular smooth muscle cells. In particular, erucin actions were evaluated on cell viability, ROS, caspase 3/7, inflammatory markers levels and the endothelial hyperpermeability in an inflammatory model associated with high glucose concentrations (25 mM, HG). Erucin significantly prevented the HG-induced decrease in cell viability as well as the increase in ROS, caspase 3/7 activation, and TNF-α and IL-6 levels. Similarly, erucin suppressed COX-2 and NF-κB upregulation associated with HG exposure. Erucin also caused a significant inhibition of p22phox subunit expression in endothelial cells. In addition, erucin significantly prevented the HG-induced increase in endothelial permeability as also confirmed by the quantification of the specific markers VE-Cadherin and ZO-1. In conclusion, our results assess anti-inflammatory and antioxidant effects by erucin in vascular cells undergoing HG-induced inflammation and this protection parallels the preservation of endothelial barrier properties.

Diet and Hydrogen Sulfide Production in Mammals

Significance: In recent times, it has emerged that some dietary sulfur compounds can act on mammalian cell signaling systems via their propensity to release hydrogen sulfide (H₂S). H₂S plays important biochemical and physiological roles in the heart, gastrointestinal tract, brain, kidney, and immune systems of mammals. Reduced levels of H₂S in cells and tissues correlate with a spectrum of pathophysiological conditions, including heart disease, diabetes, obesity, and altered immune function. Recent Advances: In the last decade, researchers have now begun to explore the mechanisms by which dietary-derived sulfur compounds, in addition to cysteine, can act as sources of H₂S. This research has led to the identified several compounds, organic sulfides, isothiocyanates, and inorganic sulfur species including sulfate that can act as potential sources of H₂S in mammalian cells and tissues. Critical Issues: We have summarised progress made in the identification of dietary factors that can impact on endogenous H₂S levels in mammals. We also describe current research focused on how some sulfur molecules present in dietary plants, and associated chemical analogues, act as sources of H₂S, and discuss the biological properties of these molecules as studied in a range of in vitro and in vivo systems. Future Directions: The identification of sulfur compounds in edible plants that can act as novel H₂S releasing molecules is intriguing. Research in this area could inform future studies exploring the impact of diet on H₂S levels in mammalian systems. Despite recent progress, additional work is needed to determine the mechanisms by which H₂S is released from these molecules following ingestions of dietary plants in humans, whether the amounts of H₂S produced is of physiological significance following the metabolism of these compounds in vivo, and if diet could be used to manipulated H₂S levels in humans. Importantly, this will lead to a better understanding of the biological significance of H₂S generated from dietary sources, and this information could be used in the development of plant breeding initiatives to increase the levels of H₂S releasing sulfur compounds in crops, or inform dietary intervention strategies that could be used to alter the levels of H₂S in humans.

Hybrids between H2S-donors and betamethasone 17-valerate or triamcinolone acetonide inhibit mast cell degranulation and promote hyperpolarization of bronchial smooth muscle cells

Glucocorticoids represent the standard gold treatment of inflammation in asthmatic patients. More recently, H₂S has been described to exert positive effect on this disease. Bearing in mind that an improved pharmacological activity and a reduced toxicity can be obtained through hybridization of different molecules, simultaneously modulating multiple targets, we designed and synthesized novel betamethasone 17-valerate and triamcinolone acetonide hybrids with well-known H₂S-donor moieties. Synthesized compounds have been evaluated for the potential H₂S-releasing profile both in cell-free environment and into the cytosol of bronchial smooth muscle cells (BSMCs). The two hybrids 4b and 5b were investigated by molecular modelling studies and results indicated that the steric accessibility of the isothiocyanate carbon atom can account for their different H₂S releasing properties. Furthermore, the most promising derivatives 4b and 5b have been tested for inhibitory effect on mast cell degranulation and for the ability to induce cell membrane hyperpolarization in BSMCs. Significant inhibitory effect on mast cell degranulation was assessed, resulting to reduce β-hexosaminidase release more efficiently than the corresponding native drugs. Both compounds determined a massive membrane hyperpolarization of BSMCs and proved to be 4-fold more effective compared to reference compound NS1619. These effects represent an enrichment of the pharmacological activity of the native drugs.

New possible silver lining for pancreatic cancer therapy: Hydrogen sulfide and its donors

As one of the most lethal diseases, pancreatic cancer shows a dismal overall prognosis and high resistance to most treatment modalities. Furthermore, pancreatic cancer escapes early detection during the curable period because early symptoms rarely emerge and specific markers for this disease have not been found. Although combinations of new drugs, multimodal therapies, and adjuvants prolong survival, most patients still relapse after surgery and eventually die. Consequently, the search for more effective treatments for pancreatic cancer is highly relevant and justified. As a newly re-discovered mediator of gasotransmission, hydrogen sulfide (H₂S) undertakes essential functions, encompassing various signaling complexes that occupy key processes in human biology. Accumulating evidence indicates that H₂S exhibits bimodal modulation of cancer development. Thus, endogenous or low levels of exogenous H₂S are thought to promote cancer, whereas high doses of exogenous H₂S suppress tumor proliferation. Similarly, inhibition of endogenous H₂S production also suppresses tumor proliferation. Accordingly, H₂S biosynthesis inhibitors and H₂S supplementation (H₂S donors) are two distinct strategies for the treatment of cancer. Unfortunately, modulation of endogenous H₂S on pancreatic cancer has not been studied so far. However, H₂S donors and their derivatives have been extensively studied as potential therapeutic agents for pancreatic cancer therapy by inhibiting cell proliferation, inducing apoptosis, arresting cell cycle, and suppressing invasion and migration through exploiting multiple signaling pathways. As far as we know, there is no review of the effects of H₂S donors on pancreatic cancer. Based on these concerns, the therapeutic effects of some H₂S donors and NO–H₂S dual donors on pancreatic cancer were summarized in this paper. Exogenous H₂S donors may be promising compounds for pancreatic cancer treatment.

Trends in H2S-Donors Chemistry and Their Effects in Cardiovascular Diseases

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter recently emerged as an important regulatory mediator of numerous human cell functions in health and in disease. In fact, much evidence has suggested that hydrogen sulfide plays a significant role in many physio-pathological processes, such as inflammation, oxidation, neurophysiology, ion channels regulation, cardiovascular protection, endocrine regulation, and tumor progression. Considering the plethora of physiological effects of this gasotransmitter, the protective role of H₂S donors in different disease models has been extensively studied. Based on the growing interest in H₂S-releasing compounds and their importance as tools for biological and pharmacological studies, this review is an exploration of currently available H₂S donors, classifying them by the H₂S-releasing-triggered mechanism and highlighting those potentially useful as promising drugs in the treatment of cardiovascular diseases.

Sulfur-containing therapeutics in the treatment of Alzheimer's disease

Sulfur is widely existent in natural products and synthetic organic compounds as organosulfur, which are often associated with a multitude of biological activities. OBenzothiazole, in which benzene ring is fused to the 4,5-positions of the thiazolerganosulfur compounds continue to garner increasing amounts of attention in the field of medicinal chemistry, especially in the development of therapeutic agents for Alzheimer's disease (AD). AD is a fatal neurodegenerative disease and the primary cause of age-related dementia posing severe societal and economic burdens. Unfortunately, there is no cure for AD. A lot of research has been conducted on sulfur-containing compounds in the context of AD due to their innate antioxidant potential and some are currently being evaluated in clinical trials. In this review, we have described emerging trends in the field, particularly the concept of multi-targeting and formulation of disease-modifying strategies. SAR, pharmacological targets, in vitro/vivo ADMET, efficacy in AD animal models, and applications in clinical trials of such sulfur compounds have also been discussed. This article provides a comprehensive review of organosulfur-based AD therapeutic agents and provides insights into their future development.

Pharmacological modulation of the hydrogen sulfide (H2 S) system by dietary H2 S-donors: A novel promising strategy in the prevention and treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) represents the most common age-related metabolic disorder, and its management is becoming both a health and economic issue worldwide. Moreover, chronic hyperglycemia represents one of the main risk factors for cardiovascular complications. In the last years, the emerging evidence about the role of the endogenous gasotransmitter hydrogen sulfide (H₂ S) in the pathogenesis and progression of T2DM led to increasing interest in the pharmacological modulation of endogenous "H₂ S-system". Indeed, H₂ S directly contributes to the homeostatic maintenance of blood glucose levels; moreover, it improves impaired angiogenesis and endothelial dysfunction under hyperglycemic conditions. Moreover, H₂ S promotes significant antioxidant, anti-inflammatory, and antiapoptotic effects, thus preventing hyperglycemia-induced vascular damage, diabetic nephropathy, and cardiomyopathy. Therefore, H₂ S-releasing molecules represent a promising strategy in both clinical management of T2DM and prevention of macro- and micro-vascular complications associated to hyperglycemia. Recently, growing attention has been focused on dietary organosulfur compounds. Among them, garlic polysulfides and isothiocyanates deriving from Brassicaceae have been recognized as H₂ S-donors of great pharmacological and nutraceutical interest. Therefore, a better understanding of the therapeutic potential of naturally occurring H₂ S-donors may pave the way to a more rational use of these nutraceuticals in the modulation of H₂ S homeostasis in T2DM.

Moringin and Its Structural Analogues as Slow H2S Donors: Their Mechanisms and Bioactivity

Moringin (rhamnobenzyl isothiocyanate) is a major bioactive compound in moringa seeds, which have been used as a healthy food. However, its bioactivity mechanisms are not well understood. We investigated moringin and its structurally similar analogues, including benzyl isothiocyanate and 4-hydroxylbenzyl isothiocyanate, for their hydrogen sulfide (H₂S)-releasing activity triggered by cysteine. These isothiocyanates rapidly formed cysteine adducts, which underwent intramolecular cyclization followed by slowly releasing (a) organic amine and raphanusamic acid and (b) H₂S and 2-carbylamino-4,5-dihydrothiazole-4-carboxylic acids. The product distributions are highly dependent on para-substituents on the phenyl group. Moringin has higher cytotoxicity to cancer cells and is a more potent anti-inflammatory agent than benzyl and hydroxybenzyl analogues, while benzyl isothiocyanate is a better antibacterial agent. Taken together, their bioactivity may not be directly related to their H₂S donation activity. However, other metabolites alone do not have cytotoxicity and anti-inflammatory activity. These findings indicated that their activity may be the combination effects of different metabolites via competitive pathways as well the para-substituent groups of benzyl ITCs.

Structure-activity relationships study of isothiocyanates for H2S releasing properties: 3-Pyridyl-isothiocyanate as a new promising cardioprotective agent

Introduction

The gasotransmitter hydrogen sulphide (H₂S), an endogenous ubiquitous signalling molecule, is known for its beneficial effects on different mammalian systems. H₂S exhibits cardioprotective activity against ischemia/reperfusion (I/R) or hypoxic injury.

Methods

A library of forty-five isothiocyanates, selected for their different chemical properties, has been evaluated for its hydrogen sulfide (H₂S) releasing capacity. The obtained results allowed to correlate several factors such as steric hindrance, electronic effects and position of the substituents to the observed H₂S production. Moreover, the chemical-physical profiles of the selected compounds have been studied by an in silico approach and from a combination of the obtained results, 3-pyridyl-isothiocyanate (25) has been selected as the most promising one. A detailed pharmacological characterization of its cardioprotective action has been performed.

Results

The results herein obtained strongly indicate 3-pyridyl-isothiocyanate (25) as a suitable pharmacological option in anti-ischemic therapy. The cardioprotective effects of compound 25 were tested in vivo and found to exhibit a positive effect.

Conclusion

Results strongly suggest that isothiocyanate-based H₂S-releasing drugs, such as compound 25, can trigger a ‘‘pharmacological pre-conditioning” and could represent a suitable pharmacological option in antiischemic therapy.

Organic Isothiocyanates as Hydrogen Sulfide Donors

Significance: Hydrogen sulfide (H₂S), the "new entry" in the series of endogenous gasotransmitters, plays a fundamental role in regulating the biological functions of various organs and systems. Consequently, the lack of adequate levels of H₂S may represent the etiopathogenetic factor of multiple pathological alterations. In these diseases, the use of H₂S donors represents a precious and innovative opportunity. Recent Advances: Natural isothiocyanates (ITCs), sulfur compounds typical of some botanical species, have long been investigated because of their intriguing pharmacological profile. Recently, the ITC moiety has been proposed as a new H₂S-donor chemotype (with a l-cysteine-mediated reaction). Based on this recent discovery, we can clearly observe that almost all the effects of natural ITCs can be explained by the H₂S release. Consistently, the ITC function was also used as an original H₂S-releasing moiety for the design of synthetic H₂S donors and original "pharmacological hybrids." Very recently, the chemical mechanism of H₂S release, resulting from the reaction between l-cysteine and some ITCs, has been elucidated. Critical Issues: Available literature gives convincing demonstration that H₂S is the real player in ITC pharmacology. Further, countless studies have been carried out on natural ITCs, but this versatile moiety has been used only rarely for the design of synthetic H₂S donors with optimal drug-like properties. Future Directions: The development of more ITC-based synthetic H₂S donors with optimal drug-like properties and selectivity toward specific tissues/pathologies seem to represent a stimulating and indispensable prospect of future experimental activities.

Activatable Small-Molecule Hydrogen Sulfide Donors

Significance: Hydrogen sulfide (H2S) is an important biological signaling molecule involved in many physiological processes. These diverse roles have led researchers to develop contemporary methods to deliver H2S under physiologically relevant conditions and in response to various stimuli. Recent Advances: Different small-molecule donors have been developed that release H2S under various conditions. Key examples include donors activated in response to hydrolysis, to endogenous species, such as thiols, reactive oxygen species, and enzymes, and to external stimuli, such as photoactivation and bio-orthogonal chemistry. In addition, an alternative approach to release H2S has utilized the catalyzed hydrolysis of carbonyl sulfide (COS) by carbonic anhydrase to generate libraries of activatable COS-based H2S donors. Critical Issues: Small-molecule H2S donors provide important research and pharmacological tools to perturb H2S levels. Key needs, both in the development and in the use of such donors, include access to new donors that respond to specific stimuli as well as donors with well-defined control compounds that allow for clear delineation of the impact of H2S delivery from other donor byproducts. Future Directions: The abundance of reported small-molecule H2S donors provides biologists and physiologists with a chemical toolbox to ask key biological questions and to develop H2S-related therapeutic interventions. Further investigation into different releasing efficiencies in biological contexts and a clear understanding of biological responses to donors that release H2S gradually (e.g., hours to days) versus donors that generate H2S quickly (e.g., seconds to minutes) is needed.

Visualization of the cysteine level during Golgi stress using a novel Golgi-targeting highly specific fluorescent probe

A novel Golgi-targeting highly specific fluorescent probe was developed to visualize the level of cysteine during Golgi stress.