## 2 Material and Methods
### Antioxidant Measurements  
Activity of glutathione reductase (GR) and catalase (CAT). The root, leaf, and fruit tissue powder was weighed (200 mg) and suspended in 100 mM of potassium phosphate buffer (5 mL, pH 7.8) containing Triton X-100 (0.5%), insoluble polyvinylpolypyrrolidone (PVPP), and ascorbate (5 mM). The mixture was centrifuged at 48,000\(\times\)_g_ for 20 min at 4 \({}^{\circ}\)C (refrigerated centrifuge 3-30 KS, Sigma, Osteorode, Germany). Enzyme activity (GR: EC 1.6.4.2, CAT: EC 1.11.1.6) was measured spectrophotometrically (HITACHI UV-Vis spectrophotometer, model U2900, Kyoto, Japan) by monitoring the decrease in absorbance at 240 nm and 340 nm for CAT and GR, respectively [31].  
Enzyme activity was expressed in nanokatals per gram fresh weight (nkat g\({}^{-1}\) FW).  
Thiol compounds and ascorbate. Powdered plant tissue was weighed and homogenized in 0.1 M of HCl containing PVPP (refrigerated centrifuge, Micro 22R, Hettich, Tuttlingen, Germany). The content of glutathione and L-cysteine compounds was determined using high-performance liquid chromatography (HPLC) with a Waters 474 Scanning Fluorescence Detector (Waters Co., Milford, MA, USA; System Breeze with a binary solvent delivery system (1525), a degasser, an autosampler with thermostat (M717 PLUS) and the thermostat (Peltier) for the column), using a Luna C18 100 A column (150 \(\times\) 4.6 mm, 5 \(\upmu\)m, Phenomenex, Torrance, CA, USA) for separation [41]. The total glutathione (tGSH: GSH + SSSG, reduced and oxidized forms respectively) and L-cysteine contents were measured in the same supernatant after reduction with dithiothreitol (DTT) and derivatization with monobromobimane. Separation was carried out by applying a solution of 10% methanol (solvent A, pH 4.3) and 90% methanol containing 0.25% (_v/v_) glacial acetic acid (solvent B, pH 3.9). The flow rate was 1 mL min\({}^{-1}\).  
The total concentration of ascorbate (L-AA + DHAA; L-ascorbic and dehydroascorbic acids, respectively) was measured after complete reduction of DHAA with DTT [41]. Separation was carried out using an AtlantisTMdC18 column (250 mm \(\times\) 4.6 mm, 5 \(\upmu\)m, Waters Co., Milford, MA, USA) coupled with a UV-VIS detector (Waters 2487) at 268 nm under isocratic conditions. The mobile phase contained 10% methanol and 2% NH4H2 PO4 with a pH of 2.8. The flow rate was 1 mL min\({}^{-1}\).  
The concentrations of the above compounds were calculated using standard calibration curves.  
Total phenolics content (TPC). TPC was evaluated using the Folin-Ciocalteu method [42] with a two-step extraction with methanol in an ultrasonic bath [43]. The TPC was expressed in gallic acid equivalents (GAE).  
Trolox equivalent antioxidant capacity (TEAC). Three different tests were applied to measure TEAC: FRAP, ABTS, and DPPH assays. These methods have previously been described [41]. The results were calculated using a standard calibration curves and are expressed as mmol TE kg\({}^{-1}\) FW (TE--Trolox equivalents).  
Reagents. GSH, L-AA, DTT, TE, and gallic acid were from Sigma (St. Louis, MO, USA), L-Cysteine was purchased from Fluca (Buchs, Switzerland). Monobromobimane (thiolyte) was from Calbiochem Co. All other chemicals were of analytical or HPLC grapdepurity.