Cinnamon can deplete gluthatione in a non toxic way. It seems to be a consensus that the toxicity stems from systemically produced gluthatione/thiol metabolites.
http://www.ncbi.nlm.nih.gov/pubmed/12065628?dopt=Abstract
http://www.ncbi.nlm.nih.gov/pubmed/15634943?dopt=Abstract
http://www.ncbi.nlm.nih.gov/pubmed/12065628?dopt=Abstract
http://www.ncbi.nlm.nih.gov/pubmed/15634943?dopt=Abstract
