Influence of drying mode on iridoid bitter constituent levels in gentian root

Root samples of wild gentian (Gentiana lutea L) were harvested from six localities (altitude 970 m to 1350m) from May to November 2000. Each batch of roots was split into three: fresh roots, naturally dried roots (ambient air) and artificially dried roots (40degreesC). In all the samples, levels of iridoid bitter constituents and of xanthone coloured compounds were determined by HPLC. The mean total iridoid content in the fresh roots was 102.4 g kg(-1) in dry matter (DM). The mean level of the principal bitter compound gentiopicroside was particularly high at 81 g kg(-1) DM. Loganic acid, not previously reported in G lutea, was the second most abundant bitter compound at a mean level of 14.3 g kg(-1) DM. Swertiamarin was present at 5.4gkg(-1), with another minor unidentified iridoid. Levels of iridoid compounds were strongly dependent of the drying mode. These amounts were 88.5 g kg(-1) DM in artificially dried roots and 62.5 g kg(-1) DM in naturally dried roots, mostly owing to a marked decrease in gentiopicroside. The temperature of 40 degreesC preserved the bitter compounds and the bitterness of fresh gentian roots. The amount of coloured xanthones was relatively low at 3.3 g kg(-1) and did not change with the drying mode. (C) 2004 Society of Chemical Industry.