Inorganic Reactive Sulfur-Nitrogen Species: Intricate Release Mechanisms or Cacophony in Yellow, Blue and Red?

Abstract

Since the heydays of Reactive Sulfur Species (RSS) research during the first decade of the Millennium, numerous sulfur species involved in cellular regulation and signalling have been discovered. Yet despite the general predominance of organic species in organisms, recent years have also seen the emergence of inorganic reactive sulfur species, ranging from inorganic polysulfides (HSx−/Sx2−) to thionitrous acid (HSNO) and nitrosopersulfide (SSNO−). These inorganic species engage in a complex interplay of reactions in vitro and possibly also in vivo. Employing a combination of spectrophotometry and sulfide assays, we have investigated the role of polysulfanes from garlic during the release of nitric oxide (•NO) from S-nitrosoglutathione (GSNO) in the absence and presence of thiol reducing agents. Our studies reveal a distinct enhancement of GSNO decomposition by compounds such as diallyltrisulfane, which is most pronounced in the presence of cysteine and glutathione and presumably proceeds via the initial release of an inorganic mono- or polysulfides, i.e., hydrogen sulfide (H2S) or HSx−, from the organic polysulfane. Albeit being of a preliminary nature, our spectrophotometric data also reveals a complicated underlying mechanism which appears to involve transient species such as SSNO−. Eventually, more in depth studies are required to further explore the underlying chemistry and wider biological and nutritional implications of this interplay between edible garlic compounds, reductive activation, inorganic polysulfides and their interplay with •NO storage and release.

Hydrogen Sulfide in Pharmacotherapy, Beyond the Hydrogen Sulfide-Donors

“…In addition, H 2 S may interact with other reactive species, e.g., oxygen, nitrogen, sulfur and selenium species. These species are produced by various cellular enzymes (NADPH oxidase, xanthine oxidase, uncoupled NOS) and their mutual interaction leads to the formation of numerous products, contributing mostly to the redox biology of the cell [77][78][79][80][81].…”

“…Natural products capable of releasing H 2 S have drawn a lot of attention [149]. Commonly isolated compounds from sulfur natural products are allyl-substituted polysulfides (mainly in form di-, trisulfides and/or tetrasulfides) [79,[150][151][152][153]. The garlic-derived sulfur compounds like the diallyl disulfide (DADS) require the presence of reduced glutathione to release H 2 S. H 2 S generation relies on nucleophilic substitution of GSH at the a-carbon of the allyl substituent to form an allyl perthiol, which further undergoes a thiol/disulfide exchange to release H 2 S. Similarly, red blood cells released H 2 S rapidly from DADS under anoxic conditions and in the presence of glutathione [154].…”

“…Natural products capable of releasing H2S have drawn a lot of attention [149]. Commonly isolated compounds from sulfur natural products are allyl-substituted polysulfides (mainly in form di-, trisulfides and/or tetrasulfides) [79,[150][151][152][153]. The garlic-derived sulfur compounds like the diallyl disulfide (DADS) require the presence of reduced glutathione to release H2S.…”

The Possible Role of the Nitroso-Sulfide Signaling Pathway in the Vasomotoric Effect of Garlic Juice

“…We need to keep in mind that disruption of garlic cloves leads to the activation of enzymes responsible for the formation of thiosulfinates, among which allicin is considered to be the most important biologically active compound, but it is unstable, and a bunch of degradation compounds forms during garlic processing and handling. Thus, the major organosulfur volatiles as diallyl sulfide, diallyl disulfide and diallyl trisulfide ( Figure 1) are formed by the decomposition of allicin and subsequently may play a biological role through H 2 S release with involvement of thiols [25].…”

Inspired by Nature: Redox Modulators and Natural Nanoparticles

“…Compounds such as allicin and polysulfides found in many Allium plants, for instance, can interact with the "cellular thiolstat" [4]. Such agents are moderately reactive, affect numerous cellular processes, exhibit pronounced antioxidant and also cyto-toxic activities and, therefore, have been linked to certain preventive or even therapeutic actions [5][6][7][8][9][10]. Together, a balanced cocktail of such biologically active nutritional components may provide a promising and also more applicable alternative to extensive medication.…”