Overview of antibacterial, antitoxin, antiviral, and antifungal activities of tea flavonoids and teas

Abstract

Tea leaves produce organic compounds that may be involved in the defense of the plants against invading pathogens including insects, bacteria, fungi, and viruses. These metabolites include polyphenolic compounds, the six so-called catechins, and the methyl-xanthine alkaloids caffeine, theobromine, and theophylline. Postharvest inactivation of phenol oxidases in green tea leaves prevents oxidation of the catechins, whereas postharvest enzyme-catalyzed oxidation (fermentation) of catechins in tea leaves results in the formation of four theaflavins as well as polymeric thearubigins. These substances impart the black color to black teas. Black and partly fermented oolong teas contain both classes of phenolic compounds. A need exists to develop a better understanding of the roles of polyphenolic tea compounds in food and medical microbiology. This overview surveys and interprets our present knowledge of activities of tea flavonoids and teas against foodborne and other pathogenic bacteria, virulent protein toxins produced by some of the bacteria, virulent bacteriophages, pathogenic viruses and fungi. Also covered are synergistic, mechanistic, and bioavailability aspects of the antimicrobial effects. Further research is suggested for each of these categories. The herein described findings are not only of fundamental interest, but also have practical implications for nutrition, food safety, and animal and human health.

Amelioration of influenza virus-induced reactive oxygen species formation by epigallocatechin gallate derived from green tea

“…As the most abundant catechin, making up more than half of green www.nature.com/aps Ling JX et al Acta Pharmacologica Sinica npg tea polyphenols, epigallocatechin gallate (EGCG) accounts for the majority of the potential health benefits brought about by green tea consumption. Extensive laboratory and communitybased epidemiological studies have described a wide range of actions of EGCG, including antioxidant, antiallergic, antibacterial, antitumor and antiviral activities [12] . However, the mechanisms of action of EGCG against FluA, such as whether EGCG acts directly on molecular components of the virus or upon cellular events necessary for the viral life cycle, remain incompletely defined.…”

Comparative studies on antioxidant activities of extracts and fractions from the leaves and stem of Epimedium koreanum Nakai

“…Fifty one prenyl flavonoid glycosides and eighteen phenolic acids were identified or tentatively identified using the Q-TOF-MS, and an ethylene glycol (Click OEG) column by Wang (2010). Flavonoids was one of the most important contents of Epimedium and it had been shown to display a number of biological activities such as antioxidant (Giovannini et al 2006;Sang et al 2005) antiviral, antifungal (Friedman 2007), anticancerous (Li et al 2007;Fresco et al 2006) antiangiogenic (Oak et al 2005) and anti-inflammatory activities (Dryden et al 2006). Icariin (C 33 H 40 O 15 ; molecular weight: 676.67, ICA) was one of the main flavonoids of Epimedium koreanum Nakai and it was always used as the standard for the quality control of Epimedium related remedies.…”

Antioxidant mechanisms of Quercetin and Myricetin in the gas phase and in solution – a comparison and validation of semi-empirical methods

“…Moreover, several studies have shown that flavonoids contribute to the overall antioxidant capacity in vivo [4][5]. Besides their antioxidant activity, both flavonoid aglycones and glycosides can act as antifungal, insect antifeedants, antimicrobials and antivirals and anti-inflammatory, and are also of particular importance in chemotaxonomy [6][7][8]. Associated with this, their identification in numerous herbs and infusions has also been the focus of several groups worldwide, particularly from regions where traditional medicine plays an important role [9,10].…”