## 3 Experimental
### Analytical Methods  
The total phenolic content was determined by the Folin-Ciocalteu assay [20], and expressed as Gallic Acid Equivalents (GAE). The total sugar content was determined by the Antrone method [21], and expressed as Glucose Equivalents.  
The phenolic compounds were analysed in an Agilent HPLC 1100 equipped with a Waters Spherisorb ODS-2 column (5 um, 250 mm \(\times\) 4.6 mm) and DAD detector, operating at 30 \({}^{\circ}\)C with a flow rate of 1 mL/min. Gradient elution using solvent A (acetonitrile/water/formic acid, 10:85:5) and solvent B (acetonitrile/water/formic acid, 90:5:5) was performed: 0 min, 100% A, 0% B; 40 min, 85% A, 15% B; 45 min, 0% A, 100% B; 60 min, 100% A, 0% B. Quantification was performed from calibration curves obtained with standard compounds diluted in methanol.  
Samples were conditioned for gas chromatography-mass spectrometry analysis (GC-MS). About 0.25 mL of 3-octanol (10 ppm) was added as internal standard into 25 mL of a diluted extract solution (0.5 g extract/L). This mixture was extracted with dichloromethane (DCM). The organic phase was transferred to a graduate glass tube and concentrated under nitrogen. GC-MS analysis was carried out in splitless mode in a Hewlett-Packard 5890-II gas chromatograph coupled to a mass spectrometer HP-5970 using He as carrier gas. Separation was performed using a 60 m \(\times\) 0.25 mm \(\times\) 0.25 um film thickness HP-Innowax capillary column. The temperature was maintained at 45 \({}^{\circ}\)C for 1 min, increased to 230 \({}^{\circ}\)C at 3 \({}^{\circ}\)C/min, and then held for 30 min. Mass spectrometer was in EI mode (electron energy 70 eV; source temperature 250 \({}^{\circ}\)C), and data acquisition was made in scanning mode from 30 to 300 amu/s and 1.9 spectra/s. Compounds were identified by comparison of the retention time and mass spectra with library data of mass spectra (Wiley 7n) and authentic compounds. Quantification was performed by the internal standard method (using 3-octanol as standard).  
The degree of polymerization of the procyanidins was estimated by RP-HPLC analysis of the depolymerized fractions present in the reaction media after the thiolysis at 65 \({}^{\circ}\)C of the desorbed product diluted in methanol [18]. RP-HPLC analysis were carried out in a Smart (Amersham-Pharmacia Biotech, Uppsala, Sweden) equipment fitted with a C18 Hypersil ODS column (Supelco). Elution was carried out at a flow rate of 1 mL/min of solvent A (0.1% aqueous TFA) and solvent B (0.082% TFA in water/CH\({}_{3}\)CN (1:4)). The gradient, expressed as concentration of B varied as follows: 0-30 min from 12% to 30%, 30-40 min from 30% to 100%, 40-45 min from 100% to 12%.  
The antioxidant activity was evaluated as the radical scavenging using the _TEAC (Trolox Equivalent Antioxidant Capacity)_ assay. A 7 mM ABTS [2,2'-azinobis (3-ethyl-benzothazoline-6-sulfonate)] stock solution was reacted with 2.45 mM potassium persulfate and kept in the dark at room temperature for 12-16 h before use. The formed ABTS\({}^{+}\) solution was diluted with phosphate buffer saline (PBS) (pH 7.4) to an absorbance of 0.700 at 734 nm and equilibrated at 30 \({}^{\circ}\)C. One mL of diluted ABTS\({}^{+}\) solution was mixed with 10 \(\upmu\)L of antioxidant compounds or Trolox standards in ethanol or PBS and the absorbance was read up to 6 min, using appropriate solvent blanks. The percentage inhibition of absorbance at 734 nm was calculated as a function of the concentration of extracts and Trolox.