Peroxidase Inhibition and Antioxidant Activity of Bulk-Marketed Black Tea (<i>Camellia sinensis</i> L.) from the Democratic Republic of the Congo

Abstract

The widely known leaves of Camellia sinensis (L.) derive the most consumed beverage globally. All over the world, like in the Democratic Republic of the Congo (DR Congo), they are marketed in the form of packaged and in bulk black tea. The aim of this study was to report the microscopic botanical features, the chromatographic fingerprints, the antioxidant activities, and the peroxidase inhibition of bulk-marketed black teas consumed in DR Congo. The microscopic analysis of powders from unpackaged black tea marketed in DR Congo allowed the identification of specific microscopical features, which are characteristic to C. sinensis (L.) such as numerous asterosclerites, numerous fragments of unicellular trichomes; fragments of abaxial epidermis consisting of cells with slightly wavy walls, numerous anomocytic stomata, and the detection of biological contaminants, e.g. the dust mites. TLC and HPLC analysis indicated that flavonoids (hyperoside, rutin) and phenolic acids (chlorogenic acid, gallic acid) were major phenolic compounds, along with other secondary metabolites. Aqueous extracts from all bulk-marketed black teas exhibited good antioxidant activities at the concentrations range of 1 - 20 μg·mL-1 using in vitro ABTS and DPPH assays. These extracts showed equally inhibitory effects on myeloperoxidase (MPO) and horseradish peroxidase (HRP) activities at the concentration ranges of 1 - 20 μg·mL-1 and 20 - 100 μg·mL-1 respectively. Bulk-marketed black teas consumed in DR Congo possess antioxidant and anti-inflammatory properties comparable to packaged Ceylon tea largely marketed. The observed bioactivities support the health benefits of the consumed black tea by Congolese people, despite the storage conditions to be improved in order to preserve its nutritional and therapeutic assets.