Passage V

As a person ages, the levels of antioxidants—com­pounds that reduce the number of cell-damaging reactive oxygen molecules (ROM) — may decrease in the body. Tea extracts are a dietary source of antioxidants .

Table 1 shows the percent by mass of each of the 4 major antioxidants (A1-A4) present in 5 tea extracts (T1-T5).

Researchers studied the ability of A1-A4 and of T1-T5 to reduce the number of ROM.

Study 1

Solutions having the same concentration of ROM and various concentrations of A1, A2, A3, or A4 were incubated, each in a separate test tube at 25°C for 30 min. The compound NBT was then added to each tube, where it reacted with all the remaining ROM to form the blue dye formazan. Figure 1 shows, for A1-A4, how the for­mazan concentration varied with the initial antioxidant concentration.

Study 2

Elderly male rats received the same daily dose of T1, T2, T3, T4, or T5, or water only, for 4 weeks. A 1 mg sample of heart tissue was then collected from each rat.

Each sample was placed in a separate test tube con­taining 10 mL of a solution of the compound TBA. Each tube was incubated at 100°C for 1 hr to allow the TBA to react with all the malondialdehyde (a product of ROM cell damage) in the sample to form a pink dye. The concentra­tion of pink dye was measured to determine the malondialdehyde concentration and, thus, the extent of ROM cell damage in the sample.

Figure 2 shows the average malondialdehyde concen­tration of the solutions resulting from each treatment.