HPLC for analysis of GL, GAMG, and GA GL, GAMG, and GA concentrations were measured via reverse-phase high performance liquid chromatography (HPLC) on a C18 column (4.6 mm6250 mm, 5 mm particle size, Kromasil) at 40uC. The sample (injection volume, 10 ml) was separated with a mobile phase consisting of 6% acetic acid/ methanol (19:81 v/v), and the elution was monitored via ultraviolet detection at 254 nm. The GL, GAMG, and GA amounts were calculated from the standard curve of the peak area and concentration. Determination of pH and temperature profiles