Stereochemical arrangement of hydroxyl groups in sugar and polyalcohol molecules as an important factor in effective cryopreservation

The efficacy of several sugars and polyalcohols in preculture medium was in vestigated using Anigozanthos viridis ssp terraspectans Hopper (Haemodorace ae), a threatened plant species endemic to the south west of Western Austra lia. A vitrification protocol involving preculturing of shoot apices for 3 days on different concentrations of sugars and polyalcohols, followed by in cubation in plant vitrification solution 2 (PVS2) for 25 min, prior to imme rsion in liquid nitrogen (LN) and warming resulted in shoot tip survival ra nging from 34 to 84%. High levels of survival were obtained with polyalcoho ls, compared to sucrose, glucose, trehalose and rafiinose when used at the same molarity (0.4 M) or at the equivalent concentration of total hydroxyl (OH) groups present in molecules. In both cases glycerol proved more effect ive. When polyalcohols (ribitol and erythritol) with similar stereochemical arrangement of OH groups as glycerol were examined, at the same molarity ( 0.4 M) and with equivalent OH numbers, higher survival was achieved when th e total number of OH groups present was the same as glycerol. Additionally, when the structural isomers mannitol/sorbitol and ribitol/xylitol were com pared at the same molarity (0.4 M), the isomer with the higher number of OH groups along the same side resulted in significantly higher levels of post -LN survival. We propose that the mode of action of polyalcohsls is based n ot on molarity, but on the total number of OH groups present in the medium. Furthermore, based on these results we propose that the orientation of OH groups is a determining factor in effective cryopreservation, (C) 2001 Else vier Science Ireland Ltd. All rights reserved.