Usability of mangrove plant leaves as tea materials: A comparison study on phenolic content and antioxidant capacities with commercial teas

Tea is a beverage that is known to contain polyphenols. Furthermore, the medicinal uses of mangroves have been recognized in tropical and subtropical coastal regions. Several mangroves contain polyphenols in their leaves and bark, and previous studies have demonstrated that plant extracts are effective against many diseases. Moreover, the use of plant leaves as tea materials has been recognized in some regions. However, scientific information on their polyphenol content and antioxidant activities are limited. Trolox equivalent antioxidant capacity (TEAC) based on the 2,2-diphenyl-2-picrylhydrazyl radical scavenging capacity assay and total polyphenol content (TPC) of methanolic and hot water extracts from the leaves of six mangrove species were examined, and the results were compared to those of green, oolong, black, and mate teas. Remarkably high TPC and TEAC were found in three mangrove species belonging to Rhizophoraceae. The highest values among the results were almost the same as or higher than those of the reference tea materials, with few exceptions. Furthermore, as a significant correlation was observed between TPC and TEAC of the respective extracts, the antioxidant properties seemed to originate mainly from polyphenolic compounds. Regarding extractive efficiency, it was found that the polyphenols in the leaves of mangrove species could be extracted by using hot water. Based on the results of this study, we concluded that the leaves of mangrove species belonging to Rhizophoraceae could be used as an important source of water-soluble polyphenols as natural antioxidants.