Anti-volatile sulfur compounds (VSC) effect of zinc-chelates with high stability constants

Lozenges containing an amino acid-chelated Zn with a high stability constant (log K1=8) have been shown to inhibit the formation of oral volatile sulfur compounds (VSC). Objectives: To examine the anti-VSC effects of other Zn-chelates. Of four Zn-chelates received as gifts (Albion Laboratory, Utah, USA), two were amino acid-chelates containing 10 and 20% Zn respectively, the third and fourth were arginine- and histidine-chelated, both with 10% Zn. The chelate containing 20% Zn was water soluble, whereas the others had low water solubility. Methods: Addition of small amounts of Zn ions to human saliva incubated overnight at 37 degress C in closed tubes inhibits the copious production of VSC in the headspace. Part A: Zn acetate (ZnAc) and different Zn chelates in dry state (=1mg Zn) were added to test tubes containing one ml of human mixed saliva. After 24 h incubation the amount of headspace VSC was measured in a GC. Part B: 1mg samples of ZnAc or Zn-chelates were added to test tubes containing one ml distilled water saturated with H2S. After 5 min incubation the amount of VSC was measured in the GC. Part C: The clinical anti-VSC effect of a solution containing the soluble Zn-chelate was examined in volunteers and compared with a solution of ZnAc containing the same amount of Zn. Oral VSC formation was enhanced with cysteine as described in previous studies. Results: A) the Zn-chelates inhibited VSC in saliva samples, B) the Zn-chelates inhibited release of Zn from water saturated with H2S, C) the soluble Zn-chelate inhibited oral H2S formation in vivo. All effects were similar to that of ZnAc, which has a very low stability constant. Conclusion: It is suggested that the Zn chelates provide Zn for oral ligands with much higher stability constants. Salivary sulfide anion produced during VSC formation is a likely candidate.