Ascorbic acid was extracted and determined essentially as described in [9]. Briefly, 0.5 g of tissue were homogenized for 1 min using a Polytron homogenizer with 0.1% metaphosphoric acid
(4 mL). The homogenate was centrifuged for 10 min at 4500 rpm at 4 ◦C. The supernatant was filtered through a C18 cartridge (SepPak,Waters, Spain), previously activated with 4 mL of methanol, 4 mL of water and 4 mL of 2% metaphosphoric acid. The extract was subsequently filtered through a 0.45 m nylon filter (25 mm diameter, Análisis Vínicos, Spain). The filtrate was injected in the HPLC-PDA system for AsA determination.