Antioxidant Activity of the Extracts and Their
Constituents. Figure 1 shows antioxidant activity of the
extracts from the plant samples examined by the aldehydes/
carboxylic acid assay at various concentrations at the fourth
week. Values are mean ± standard deviation (SD) (n = 3). The
aldehydes/carboxylic acid assay is convenient for evaluating the
effects of antioxidants against slow oxidation phenomena
occurring over prolonged periods of time, such as the shelf
life of foods.3 Moreover, the matrix of the assay consists of an
organic solvent, dichloromethane, that is easy to apply for water
nonsoluble organic compounds, such as volatile chemicals. All
extracts exhibited antioxidant activity with dose response.
Antioxidant activity at 500 μg/mL ranged from 77.02 ± 0.51%
(tea from the stems of Burea plant) to 52.57 ± 0.92%
(fermented tea of Camellia). The extracts from the stems and
roots of the Burea plant showed antioxidant activity comparable
to that of BHT at the level of 100 μg/mL. At the level of 50 μg/
mL, all extracts exhibited moderate antioxidant activity ranging
from 42.85 ± 0.79% stems of Mulberry tea) to 31.13 ± 0.83%