Phenolic Compounds of Reynoutria sp. as Modulators of Oral Cavity Lactoperoxidase System

Lactoperoxidase (LPO) together with its (pseudo)halogenation cycle substrates, H2O2 and thiocyanate ions oxidized to hypothiocyanite ions, form one of the main systems involved in antimicrobial defense within the oral cavity. In bacterial diseases such as dental caries, lactoperoxidase is oxidized to a form known as Compound II, which is characterized by its inability to oxidize SCN–, resulting in a decreased generation of antimicrobial products. Reynoutria sp. rizome extracts, due to their high polyphenol content, have been tested as a source of compounds able to regenerate the antimicrobial activity of lactoperoxidase through converting the Compound II to the native LPO state. In the presented study, acetone extracts of R. japonica, R. sachalinensis, and R. x bohemica, together with their five fractions and four selected polyphenols dominating in the studied in extracts, were tested toward lactoperoxidase reactivating potential. For this purpose, IC50, EC50, and activation percentage were determined by Ellman’s method. Furthermore, the rate constants for the conversion of Compound I–Compound II and Compound II–native-LPO in the presence of extracts, extracts fractions, and selected polyphenols were determined. Finally, the ability to enhance the antimicrobial properties of the lactoperoxidase system was tested against Streptococcus mutans. We proved that Reynoutria sp. rhizome is the source of lactoperoxidase peroxidation cycle substrates, which can act as activators and inhibitors of the antimicrobial properties of that system. The presented study shows that the reactivation of lactoperoxidase could become a potential therapeutic target in prevention and treatment support in some infectious oral diseases.

Atmospheric reactive oxygen species and some aspects of the antiviral protection of the respiratory epithelium

The review focuses on molecular and biochemical mechanisms of nonspecific protection of respiratory epithelium. The authors provide a comprehensive analysis of up-to-date data on the activity of the lactoperoxidase system expressed on the surface of the respiratory epithelium which provides the generation of hypothiocyanate and hypoiodite in the presence of locally produced or inhaled hydrogen peroxide. Molecular mechanisms of production of active compounds with antiviral and antibacterial effects, expression profiles of enzymes, transporters and ion channels involved in the generation of hypothiocyanite and hypoiodate in the mucous membrane of the respiratory system in physiological and pathological conditions (inflammation) are discussed. In the context of antibacterial and antiviral defense special attention is paid to recent data confirming the effects of atmospheric air composition on the efficiency of hypothiocyanite and hypoiodate synthesis in the respiratory epithelium. The causes and outcomes of lactoperoxidase system impairment due to the action of atmospheric factors are discussed in the context of controlling the sensitivity of the epithelium to the action of bacterial agents and viruses. Restoration of the lactoperoxidase system activity can be achieved by application of pharmacological agents aimed to compensate for the lack of halides in tissues, and by the control of chemical composition of the inhaled air.

Lactoperoxidase system in the dairy industry: Challenges and opportunities

The objective of this review was to search the literature for studies on the lactoperoxidase system (LPS) as milk natural preservation, action mechanisms, usage methods and perspectives for the dairy industry. A comprehensive literature review approach was conducted for collecting evidence in scientific publications. The biological properties of milk promote the development of microorganisms which compromise its quality, therefore demanding the use of techniques for preserving the milk matrix from its collection until processing. Within this context, LPS could represent an alternative to guarantee the safety of this food in are as where refrigeration is not possible; in addition, studies on applying this system in the dairy industry have been explored, as is the case in the test for verifying pasteurisation efficiency according to determining the lactoperoxidase enzyme activity. Natural antimicrobial properties of LPS make it a promising alternative for the industrial preservation and processing of milk, especially when considering the current quality standard demanded by the market. However, the potential of LPS as a biopreservative is still little technically and scientifically explored, which implies the need to develop new studies.