Abstract
N-chlorotaurine (NCT) and hydrogen peroxide are powerful endogenous antiseptics. In vivo, the reaction between hydrogen peroxide and metal ions leads to the formation of free hydroxyl radicals, which have an increased bactericidal activity. This study examined whether there is an additive antimicrobial effect of NCT combined with hydrogen peroxide. Additionally, it was tested if the additive effect is based on the formation of free radicals. We found by luminometry that, in the presence of H2O2, NCT caused a slow and long-lasting production of singlet oxygen in contrast to HOCl, where this burst occurred instantaneously. Both NCT and hydrogen peroxide (1.0 and 0.1%) demonstrated bactericidal and fungicidal activity. At pH 7.1 and 37 °C, hydrogen peroxide (1%, 294 mM) showed a stronger bactericidal and particularly fungicidal activity than NCT (1%, 55 mM), whereas at pH 4.0 and also in the presence of 5.0% peptone NCT revealed a stronger bactericidal activity. A combination of NCT and hydrogen peroxide led to an increased bactericidal but no increased fungicidal activity compared to both substances alone. The additive effect against bacteria was not removed in the presence of the radical scavengers NaN3, DMSO, or peptone. As a conclusion, NCT and hydrogen peroxide used concurrently interact additive against a range of microorganisms. However, the results of this study suggest that the additive effect of NCT combined with hydrogen peroxide is rather not based on the formation of free radicals.
Highlights
Human phagocytes are activated by invading microorganisms and produce several reactive oxygen species (ROS) by an enzymatic cascade called oxidative burst (Klebanoff 1968)
Corroborating with the results obtained by monitoring the consumption of NCT, the production of 1O2 took place in more than 30 min, which is an evidence of the slow, but efficient reactivity of this chloramine with H2O2
A slow and long-lasting production of singlet oxygen by NCT plus H2O2 was characterized for the first time in this study
Summary
Human phagocytes are activated by invading microorganisms and produce several reactive oxygen species (ROS) by an enzymatic cascade called oxidative burst (Klebanoff 1968). N-chlorotaurine (Cl–HN–CH2–CH2–SO3−, NCT) is the most abundant representative of this class of compounds (Grisham et al 1984). All these oxidants are thought to be. The mentioned oxidants may react among one another, whereby further microbicidal ROS are formed. The reaction between HOCl and H2O2 to form singlet oxygen (1O2) (Eq 1) was discovered by Khan and Kasha in (1963), and it was studied in details due to its physiological and pathological relevance, including its involvement in signaling and microbicidal
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