Optimization of the extraction and hydrolysis steps has been described elsewhere (HaÈ kkinen et al., 1998). Ascorbic acid (80 mg) was dissolved in 15 ml of purified water in a 100-ml round-bottom bottle. The sample (0.5 g of freeze-dried berry) was rinsed with 25 ml of methanol into the bottle. To this mixture, 10 ml of 6 M HCl was added by careful mixing (Final HCl concentration 1.2 M) and the solution was sonicated for 2 min. The remaining air in the bottle was replaced by nitrogen gas. The mixture (total volume 50 ml) was shaken in 35°C water bath in dark. After 16 h, the extract was allowed to cool and was then filtered. A 15-ml portion of the filtrate was evaporated to dryness using rotary evaporator and 35°C water bath. The residue was dissolved in 1.5 ml of methanol and filtered through a 0.45 mm filter for organic solvents (Acrodisc LC13 PVDF filter, Gelman Sciences, MI) prior to injection (20 ml) to the HPLC apparatus.