Figure 1.

Enzymatic conversion of (±)-catechin to colored products by extracellular lettuce root enzymes. A 2-day-old lettuce seedling root tip (5 mm) was placed on top of a 1 mM (±)-catechin solution in 5 mM MES buffer (see arrow at 15 min on the time course ——). Absorbance was measured at 440 nm over 1 h in a cuvette at 25°C. The base line is the catechin solution without the root tip (……). The upper left inset shows the absorption spectrum of the solution before (……) and after (——) incubation with the root tip. The lower right inset shows 1 mM (±)-catechin after incubation for 1 h with (right) or without (left) a lettuce root tip in test tubes (notice the root floating on top of the solution). Without the root material, (±)-catechin will also oxidize, but over a much longer period of time. Similar results were obtained when an intact seedling was placed in the solution.