Phosphonate-substituted Pyrazinoporphyrin - a General Photocatalyst for Efficient Sulfoxidation.

An exceptional efficiency of pyrazine-annelated porphyrin as a general photocatalyst for the oxidation of organic sulfides is demonstrated. It is shown that phosphonate-substituted pyrazinoporphyrin 2H-1 brings together sufficient photostability and high efficiency in the aerobic photooxidation of a series of various sulfides. The influence of the reaction conditions onto the efficiency of homogeneous sulfide photooxidation in the presence of the PS was investigated and strong dependence on the solvent system was observed. The use of methanol is required for the photocatalytic sulfoxidation and the ratio of the alcohol/other solvent can significantly affect the conversion and selectivity of the reaction. The application of the prepared photosensitizer (PS) in 0.001 mol% loading allowed achieving complete conversion (97-100%, turnover number up to 100000, turnover frequency up to 6250 h-1) of substrates bearing substituents of different nature, namely aromatic and aliphatic sulfides with donor or acceptor substituents and substituents prone to oxidation, as well as cyclic sulfides. The selectivity of the of the corresponding sulfoxides formation of 96-100% was revealed. Finally, a gram-scale synthesis of several sulfoxides was successfully performed with the PS under investigation, providing desired products in 66-96% yield with over 98% purity.

Cooperative photocatalysis of dye-Ti-MCM-41 with trimethylamine for selective aerobic oxidation of sulfides illuminated by blue light.

Ti-incorporated mesoporous materials have widespread applications in photocatalysis. Their adjustable pores could accommodate dyes like alizarin red S (ARS) to circumvent the lack of visible light response. Herein, Ti-MCM-41 was obtained to anchor visible light-capturing ARS, forming ARS-Ti-MCM-41. The ARS-Ti-MCM-41 was screened for the selective photocatalytic oxidation of organic sulfides. To improve the stability of the anchored ARS, electron transfer was orchestrated by a mediator trimethylamine (TMA, 2 mol%) illuminated by blue LEDs. Phenyl methyl sulfide could be almost entirely converted into phenyl methyl sulfoxide with 99% of selectivity within 18 min. In addition, Ti-MCM-41 was beneficial for the anchored ARS, which in turn guaranteed good recycling performance of ARS-Ti-MCM-41. The solvent trifluoroethanol enabled the stability of TMA and facilitated the highly selective formation of the target sulfoxides. This work sheds light on the vast possibility for visible light photocatalysis of dye-mesoporous materials.

Rapid Assessment of Meat Freshness by the Differential Sensing of Organic Sulfides Emitted during Spoilage.

In this work, we report the fabrication of a two-member fluorescence sensor array that enables the assessment of three stages (fresh, slightly spoiled, and moderately or severely spoiled) of meat spoilage. The first member of the array, which has strong chalcogen bonding and sulfur-π interactions with organic sulfides, exhibits very high sensitivity, while the second member of the array, which has weak chalcogen bonding and sulfur-π interactions with organic sulfides, exhibits lower sensitivity. On the basis of the combined fluorescence responses of the two members, three stages of meat spoilage, including fresh, slightly spoiled, and moderately or severely spoiled, can be monitored. Notably, using the volatiles collected from 5 g of meat products over a short period of time (1 min), this two-member sensor array achieves sensitive responses to the organic sulfides emitted from the meats. The capacity of this method to rapidly assess meat freshness facilitates its practical application, as illustrated by the monitoring of the freshness of chicken and pork products in the real world.

Recent Advances in Catalytic Oxidation of Organic Sulfides: Applications of Metal-Ionic Liquid Catalytic Systems.

Catalytic oxidation of organic sulfides is of considerable significance in industrial chemistry and fuel industry. Therefore, numerous methods have been developed for the oxidation. Metal-containing ionic liquid-based catalysts can catalyze the selective oxidation reactions and are highly used in chemical processes, which have also been used as effective solvents, reaction media, extractants, and catalysts for the oxidation of organic sulfides including oxidative desulfurization of fuel oil. Recently, much attention is being drawn to the preparation of heterogenous catalysts based on the immobilization of metal- or nonmetal-containing ILs on diverse solid supports, which can be easily separated after the completion reaction and recycled. Therefore, there is still an increasing interest in developing new and efficient catalytic procedures for the oxidation of organic sulfides. In this review, we have outlined the recent advances in catalytic oxidation of organic sulfides including oxidative desulfurization of fuel oil. The versatilities and adaptabilities of metal-ionic liquid catalytic systems in the selective oxidation of sulfides are considered a powerful research field in these transformations.

Antioxidant activity of organic sulfides from fresh Allium macrostemon Bunge and their protective effects against oxidative stress in Caenorhabditis elegans.

Long-stamen chive (Allium macrostemon Bunge; AMB), which is prevalent in the Wuling Mountain area of China, is a characteristic food of the nation. In the study, we evaluated the as-yet-unknown nutritional value and antioxidant activity of fresh AMB. The free amino acid content, volatile components, and free radical-scavenging capacity of isolated organic sulfides were analyzed to evaluate the qualitative and physiological properties of fresh AMB. The plant was found to be rich in free essential amino acids and contain multiple flavor-imparting amino acids. The organic sulfides showed an apparent free radical-scavenging activity in vitro. Furthermore, these sulfides alleviated oxidative stress in Caenorhabditis elegans. Notably, the organic sulfides isolated from AMB enhanced the activities of superoxide dismutase, catalase, and glutathione peroxidase; improved motility; and extended the lifespan in oxidative stress-affected nematodes. In conclusion, our study indicates that AMB is a nutritious vegetable with potential to be developed as a functional food. PRACTICAL APPLICATIONS: Long-stamen chive is a wild edible vegetable belonging to the genus Allium (A. macrostemon Bunge; AMB). However, its quality and physiological properties have not been comprehensively investigated. Herein, we analyzed the free amino acid content, composition of volatile compounds, and potential antioxidative properties of AMB. Our results indicated that AMB is rich in essential amino acids, making it a highly nutritious food. Further analysis indicated that AMB contains a high proportion of organic sulfides, which have been previously been shown to have antioxidative properties. Together, our findings indicate that AMB contains important bioactive components and can be developed as a functional food or health supplement. Furthermore, our findings will enhance public awareness regarding this wild resource and provide new directions for the research and development of natural products derived from it.

Highly Selective Oxidation of Organic Sulfides by a Conjugated Polymer as the Photosensitizer for Singlet Oxygen Generation.

A cationic conjugated polyelectrolyte PPET3-N2 was used as a photosensitizer for photocatalytic oxidation of organic sulfides, including thioanisole, ethyl phenyl sulfide, 4-methylphenyl methyl sulfide, etc., to form sulfoxides with good yields and high selectivity. Oxidation reactions were performed in both batch and microfluidic reactors, where the microfluidic reactor can significantly promote the conversion of photocatalytic oxidation reaction to over 98% in about 8 min. Further studies of the photocatalytic oxidation of the antitumor drug ricobendazole in the microfluidic reactor demonstrate the potential application of the polymer material in organic reactions given its high selectivity, good efficiency, and operation convenience.

Bioactive Compounds and Biological Functions of Garlic (Allium sativum L.).

Garlic (Allium sativum L.) is a widely consumed spice in the world. Garlic contains diverse bioactive compounds, such as allicin, alliin, diallyl sulfide, diallyl disulfide, diallyl trisulfide, ajoene, and S-allyl-cysteine. Substantial studies have shown that garlic and its bioactive constituents exhibit antioxidant, anti-inflammatory, antibacterial, antifungal, immunomodulatory, cardiovascular protective, anticancer, hepatoprotective, digestive system protective, anti-diabetic, anti-obesity, neuroprotective, and renal protective properties. In this review, the main bioactive compounds and important biological functions of garlic are summarized, highlighting and discussing the relevant mechanisms of actions. Overall, garlic is an excellent natural source of bioactive sulfur-containing compounds and has promising applications in the development of functional foods or nutraceuticals for the prevention and management of certain diseases.