Correlation among suppression of leukotriene B4 release, radical scavenging activity and polyphenol contents of commercial tea extract

Abstract

Anti-allergic effects of 16 commercial available tea extracts were examined by measuring leukotriene B4 (LTB4) release from rat peritoneal cells (PC). LTB4 production is accomplished by oxidative reactions catalyzed by 5-lipoxygenase. As several kinds of tea include polyphenols that have anti-oxidative effects, we also determined the contents of total polyphenol, flavonol and tannin, and examined DPPH radical scavenging activity of the tea extracts. Guava, sweet tea (Rubus suavissimus S. Lee), rooibos, Quercus salicina, green tea, sweet tea (family unknown) and loquat contained large amount of polyphenols. Flavonol was found in guava, and tannin was found in guava and sweet tea (Rubus suavissimus S. Lee). The extracts of green tea and sweet tea (Rubus suavissimus S. Lee) almost completely inhibited LTB4 release from PC, while extracts of ground ivy leaves, guava and Quercus salicina inhibited release by less than 50%. We also examined the correlation between LTB4 release and DPPH radical scavenging activity and between LTB4 release and polyphenol, flavonol, or tannin content. LTB4 release was negatively correlated with DPPH radical scavenging activity and total polyphenol contents, and this correlation was strong among the tea extracts that suppressed LTB4 release. These results suggest that polyphenols in tea extracts may play an important role in the suppression of LTB4 release and may also scavenge arachidonic acid peroxyradicals in the production of LTB4.