He Hypochlorous acid , Also known as monoxocoric acid (I), is a chemical compound of the formula HClO. It is a simple molecule with central oxygen connected to chlorine and hydrogen atoms through simple bonds.
Hypochlorous acid is an oxacid of chlorine, which has valence (I). It is a weak acid that is typically formed when the chlorine dissolves in water. Several other names are referred to, such as: chloric acid, chloranol, hydrogen hypochlorite and chlorine hydroxide.
Figure 1: Hypochlorous acid structure.
Hypochlorous acid is produced in the human body by white blood cells to fight infections, as it acts against a wide range of microorganisms.
Addition of chlorine to water gives hypochlorous acid together with hydrochloric acid (HCl):
Cl2 + H2O ⇌ HOCl + HCl
The above reaction is in equilibrium and it is not easy to isolate HOCl from this mixture. However, stable hypochlorous salts can be obtained by dissolving gaseous chlorine in solution of sodium hydroxide , Or other aqueous basic solutions.
HOCl can also be prepared by dissolving dichlorine monoxide in water (Hypochlorous Acid Uses, Properties, Structure and Formula, S.F.).
Cl2O + H2O → 2HOCl
Physical and chemical properties
Hypochlorous acid only exists as an aqueous solution. It is a colorless solution and its exact physical properties are variable, as they depend on the concentration of the solution. Hypochlorous acid anhydrous or dry is impossible to prepare since the molecule exists in equilibrium with its anhydride (National Center for Biotechnology Information., 2017).
Its molecular weight is 52.46 g / mol and its pKa is 7.53. It is soluble in water.
HOCl is a strong oxidizer and may form explosive mixtures. It is also a reducing agent being able to oxidize to the chloroso, chlorico and perchloric forms of the acid. In aqueous solutions, being a weak acid, it partially dissociates in hypochlorite (OCl-) and H + ion.
HOCl reacts with bases to form salts called hypochlorites. For example, sodium hypochlorite (NaOCl), the active ingredient in the bleach, is formed by reacting hypochlorous acid with sodium hydroxide (Royal Society of Chemistry, 2015).
HOCl + NaOH → NaOCl + H 2 O
Hypochlorous acid also readily reacts with a variety of organic molecules and biomolecules.
Hypochlorous acid is not considered harmful because it occurs in low concentrations in the human body and has antimicrobial action.
Hypochlorous acid reacts slowly with DNA and RNA , As well as all nucleotides in vitro.
GMP is the most reactive because HClO reacts with both the NH group and the amino group.
Similarly, TMP with only one heterocyclic NH group which is reactive with HClO is the second most reactive.
AMP and CMP, which have only a slowly reactive amino group, are less reactive with HClO.
UMP has been reported to be reactive only at a very slow rate. NH heterocyclic groups are more reactive than amino groups, and their secondary chloramines are capable of donating chlorine.
These reactions probably interfere with DNA base pairing, and, accordingly, a decrease in the viscosity of DNA exposed to HClO similar to that observed with heat denaturation has been reported (Prütz, 1996).
The sugar moieties are non-reactive and the DNA backbone does not break. NADH can react with chlorinated TMP and UMP as well as HClO. This reaction can regenerate UMP and TMP and results in the 5-hydroxy derivative of NADH.
The reaction with TMP or UMP is slowly reversible to regenerate HClO. A second slower reaction resulting in cleavage of the pyridine ring occurs when excess HClO is present. NAD + is inert to HClO.
Antimicrobial action
In the last 15 years, the most advanced hypochlorous acid solutions based on electrochemistry have emerged as safe and viable wound cleaning agents as well as complementary therapies for the treatment of infections.
Hypochlorous solution (HOCl) is a strong oxidant and tends to remove electrons from another substance. Its sodium salt, sodium hydroxide (NaClO), or its calcium salt, calcium hydroxide (Ca (ClO) 2) are commonly used in bleaches, deodorants and disinfectants.
HOCl exists as a natural endogenous constituent in humans and animals and is an important part of the innate immune system. HOCl is produced by neutrophil granulocytes, the most abundant type of white blood cells in mammals. He is involved in the last step of the Oxidative Route in the fight against infection and invasion of foreign substances.
When a cell detects the invasion of a foreign substance it undergoes phagocytosis, during which the neutrophil ingests and internalizes microorganisms or foreign particles. This phagocytic event results in the secretion of reactive oxygen species and hydrolytic enzymes (Kavros, S.F.).
Oxygen consumption during the generation of reactive oxygen species, called"reactive explosion", involves the activation of the enzyme NADPH oxidase, which produces large amounts of superoxide.
This highly reactive oxygen species is decomposed into hydrogen peroxide , Which is then converted to HOCl. HOCl exerts bactericidal properties and immediately destroys the bacteria swallowed by neutrophils. Despite the substantial activity of HOCl against microorganisms, it is not cytotoxic to human or animal cells. This is probably related to their endogenous presence in the mammalian cell immune system (Chanson Water Ionizers USA, Inc, 2016).
Figure 2: mechanism of antimicrobial action of hypochlorous acid.
It has recently been proposed that bacterial inactivation by HOCl is the result of inhibition of DNA replication. When bacteria are exposed to HOCl, there is an abrupt decline in DNA synthesis that precedes the inhibition of protein synthesis, and is very similar to loss of viability (Davies, 1988).
During replication of the bacterial genome, the origin of replication (oriC in E. coli) binds to proteins that are associated with the cell membrane, and it was observed that HOCl treatment decreases the affinity of membranes extracted for oriC, and This affinity decreases parallel to the loss of viability.
In the work of Henry Rosen (1998), they compared the rate of HOCl inhibition of plasmid DNA replication with different origins of replication and found that certain plasmids exhibited a delay in inhibition of replication when compared to plasmids that Contained oriC. The Rosen group proposed that the inactivation of membrane proteins involved in DNA replication is the mechanism of action of HOCl.
Applications
Formation of chlorohydrins
Hypochlorous acid is used in organic synthesis, converting alkenes to chlorohydrins.
Hypochlorous acid reacts with unsaturated bonds in lipids, but not in saturated bonds, and ClO-ion does not participate in this reaction.
This reaction is produced by hydrolysis with the addition of chlorine to one of the carbons and one hydroxyl to the other. The resulting compound is a chlorohydrin. Polar chlorine disrupts lipid bilayers and may increase permeability.
When chlorohydrin formation occurs in lipid bilayers of red blood cells, permeability increases. Discontinuation may occur if enough chlorohydrin is formed.
The addition of preformed hydrochlorides to Red blood cells May also affect permeability. Cholesterol chlorhydrins have also been observed but do not greatly affect permeability, and it is believed that Cl2 is responsible for this reaction
Cosmetic industry
In the cosmetic industry it is used as a cleansing agent for the skin, which benefits the skin of the body rather than cause drying. It is also used in baby products, because the baby's skin is particularly sensitive and can be irritated easily.
Water treatment
In water treatment, hypochlorous acid is the active disinfectant in hypochlorite-based products (eg used in swimming pools).
In the food and water distribution service, specialized equipment for generating weak solutions of HClO from water and salt is sometimes used to generate adequate amounts of safe (unstable) disinfectant to treat food preparation surfaces and supplies of water.
Pruritus Treatment
Topical hypochlorous acid (HOCl) has recently been proposed as a pruritus treatment. Two mechanisms are proposed by which HOCl can reduce pruritus:
1) HOCl is a microbicide to cutaneous pathogens, especially Staphylococcus aureus In atopic dermatitis.
2) HOCl is anti-inflammatory and reduces the activities of histamine, leukotriene B4 and interleukin-2, all of which are involved in the pathophysiology of itching.
There are conditions under which HOCl can actually cause itching as an adverse effect. For example, HOCl increases the activity of nerve growth factor, which promotes itching. Prolonged or high-dose exposure of HOCl may also cause irritant contact dermatitis, or less commonly, allergic contact dermatitis (Robert Y. Pelgrift, 2013).
References
- Chanson Water Ionizers USA, Inc. (2016). Hypochlorous acid discovery. Retrieved from chansonalkalinewater: chansonalkalinewater.com.
- Davies, S. M. (1988). The inhibition of bacterial growth by hypochlorous acid. Possible role in the bactericidal activity of phagocytes. Biochem. J. 254 (3), 685-692. Ncbi.nlm.nih.gov.
- EMBL-EBI. (2014, March 31). Hypochlorous acid. Retrieved from ebi.ac.uk: ebi.ac.uk.
- Henry Rosen, B. R. (1998). Differential Effects of Myeloperoxidase-Derived Oxidants on Escherichia coli DNA Replication. Infection Immunity. 66 (6), 2655-2659. Ncbi.nlm.nih.gov.
- Hypochlorous Acid Uses, Properties, Structure and Formula. (S.F.). Recovered desoftschools: softschools.com.
- Kavros, S. (S.F.). The Use of Hypochlorous Acid Solution in Wound Management. Retrieved from faim.org.
- National Center for Biotechnology Information. . (2017, March 25). PubChem Compound Database; CID = 24341. Retrieved from PubChem.
- Prütz, W.A. (1996). Hypochlorous Acid Interactions with Thiols, Nucleotides, DNA, and Other Biological Substrates. Archives of Biochemistry and Biophysics Volume 332, Issue 1, 110-120. Retrieved from sciencedirect.com.
- Robert Y. Pelgrift, A.J. (2013). Topical Hypochlorous Acid (HOCl) as a Potential Treatment of Pruritus. Current Dermatology Reports, Volume 2, Number 3, 181. Retrieved from springer.com.
- Royal Society of Chemistry. (2015). Hypochlorous acid. Recovered from chemspider: chemspider.com.