'Antioxidant' berries, anthocyanins, resveratrol and rosmarinic acid oxidize hydrogen sulfide to polysulfides and thiosulfate: A novel mechanism underlying their biological actions.

Nutraceutical polyphenol catechins in green tea oxidize HS to polysulfides (PS) in buffer and in cells thereby conveying their cytoprotective effects. Here we measure HS oxidation in buffer and HEK293 cells by over-the-counter nutraceuticals, blueberry, bilberry and cranberry, and by polyphenols, cyanadin (Cya), quercetin (Que), rosmarinic acid (RA) and resveratrol (Res). HS and PS were measured with specific fluorophores, AzMc and SSP4 respectively, and thiosulfate (TS) production was measured in buffer using silver nanoparticles (AgNPs).

Green tea polyphenolic antioxidants oxidize hydrogen sulfide to thiosulfate and polysulfides: A possible new mechanism underpinning their biological action.

Matcha and green tea catechins such as (-)-epicatechin (EC), (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) have long been studied for their antioxidant and health-promoting effects. Using specific fluorophores for HS (AzMC) and polysulfides (SSP4) as well as IC-MS and UPLC-MS/MS-based techniques we here show that popular Japanese and Chinese green teas and select catechins all catalytically oxidize hydrogen sulfide (HS) to polysulfides with the potency of EGC > EGCG >> EG. This reaction is accompanied by the formation of sulfite, thiosulfate and sulfate, consumes oxygen and is partially inhibited by the superoxide scavenger, tempol, and superoxide dismutase but not mannitol, trolox, DMPO, or the iron chelator, desferrioxamine.

Are the beneficial effects of 'antioxidant' lipoic acid mediated through metabolism of reactive sulfur species?

The health benefits of lipoic acid (LA) are generally attributed to mitigating the harmful effects of reactive oxygen species (ROS). ROS are chemically similar to reactive sulfur species (RSS) and signal through identical mechanisms. Here we examined the effects of LA on RSS in HEK293 cells using HS and polysulfide (PS) specific fluorophores, AzMC and SSP4.