Effects of watersoluble boron and aluminium compounds on the synthesis of flavanols in grape vine callus

Internode explants of grape vine were used to produce proliferating callus cells in vitro. The tissues were grown on a modified M/S - medium supplemented with different concentrations of boron (H₃BO₃) in the range of 0 to 600 μM and aluminium (AlCl₃) in the range of 0 to 85 μM. With increasing concentrations of boron the content of the following flavanols declined: procyanidin B3 (catechin-(4α → 8) catechin), procyanidin B1 (epicatechin-(4β → 8) catechin), procyanidin B2 (epicatechin-(4β → 8) epicatechin), and B2-3-O-gallate, catechin and epicatechin. ECG (epicatechingallate) showed increased values in dependance on boron supply. Procyanidin B5 (epicatechin-(4β → 6)-epicatechin) showed an indifferent behaviour. In the case of aluminium the concentrations of flavanols were generally increased up to a maximum of 46% with the exception of ECG and B5 where no significant change was observed. While the total sum of flavanols was decreased by boron up to about 30% in comparison to the control (no boron addition) the content of flavanols was basically increased by aluminium up to about 25%. We conclude that the addition of watersoluble boron and aluminium compounds to the culture can significantly modify the synthesis of special monomeric and oligomeric flavanols.