*2.3. DPPH Assay*

To a 0.2 mM methanolic solution of DPPH wood or tannin powders were added (final dose 0.03–1.5 mg/mL) and after 10 min under stirring at room temperature the absorbance of the solution at 515 nm was measured [27,28]. Experiments were run in triplicate. Trolox was used as reference antioxidant.

#### *2.4. Ferric Reducing*/*Antioxidant Power (FRAP) Assay*

To 0.3 M acetate bu ffer (pH 3.6) containing 1.7 mM FeCl3 and 0.83 mM TPTZ, wood or tannin powders (final dose 0.00625–0.3 mg/mL) were added and after 10 min under stirring at room temperature the absorbance of the solution at 593 nm was measured [29]. Results were expressed as Trolox equivalents. Experiments were run in triplicate.

#### *2.5. Superoxide Scavenging Assay*

Wood or tannin powders (final dose 0.0625 mg/mL) were added to 0.05 M ammonium hydrogen carbonate bu ffer (pH 9.3) containing 0.4 mM EDTA and 12 μM NBT, followed by a 20 mM pyrogallol solution in 0.05 mM HCl (final pyrogallol concentration 3.3 mM) [4,30]. The mixture was vigorously stirred for 5 min, after that absorbance at 596 nm was measured. Results were expressed as percentage of reduction of the absorbance at 596 nm of a control mixture run in the absence of sample. Experiments were run in triplicate.

#### *2.6. Oxygen Radical Antioxidant Capacity (ORAC Assay)*

Wood or tannin powders (final dose 0.075 mg/mL) were incubated in a 62.7 μM fluorescein solution in 75 mM phosphate bu ffer (pH 7.4) for 30 min, at 37 ◦C. A 153 mM AAPH solution was then added (final APPH concentration 19 mM) and after stirring at 37 ◦C for 45 min fluorescence was measured (λex = 485 nm, λem = 511 nm) [31]. Results were expressed as relative fluorescence intensity with respect to a control mixture run in the absence of APPH. Experiments were run in triplicate.

#### *2.7. MB Adsorption Assay*

Adsorption experiments were performed at room temperature by adding wood samples (0.2 mg/mL) to a 5 or 25 mg/<sup>L</sup> aqueous solution of MB. The mixtures were taken under stirring and after 30 min the absorbance at 654 nm was measured [32]. Activated carbon was used as reference material. Experiments were run in triplicate.

#### *2.8. Nitric oxides (NOx) Scavenging Assay*

A solution of sodium nitrite (1 M) in water was added to 10% sulfuric acid over 10 min [33]. The red orange gas that developed (0.2–0.6 mL) was withdrawn with a syringe and conveyed through a tip containing 5 mg of wood sample into 3 mL of Griess reagen<sup>t</sup> (0.5% sulfanilamide and 0.05% *N*-(1-naphthyl)ethylenediamine dihydrochloride in 1.25% phosphoric acid) and the absorbance at 540 nm was measured. Experiments were run in triplicate.
