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 1350 m) from May to November 2000. Each batch of roots was split into three: fresh roots, naturally dried roots (ambient air) and artificially dried roots (40 °C). 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 5.4 g kg −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 °C 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. Copyright © 2004 Society of Chemical Industry