Sinapaldehyde

HPLC grade methanol, ethanol, and acetonitrile were purchased from Thermo Fisher Scientific (Waltham, MA, USA). Standards of phenolic compounds, including, quinic acid, caffeic acid, vanillic acid, syringic acid, ferulic acid, arbutin, adenosine, tachioside, vanillic alcohol, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillin, p-coumaric acid, coniferol, syringaldehyde, acetovanillone, sinapic acid, coniferylaldehyde, sinapaldehyde, syringaresinol, and balanophonin; standards of furfural (FF) and 5-hydroxymethylfurfural (HMF) were obtained from Sigma-Aldrich (MO, USA) with purity ≥ 98%. Folin–Ciocalteu (FC) reagent, 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) were provided by Yuanye (Shanghai, China). FRAP test kit was purchased from Solibao (Beijing, China). Other chemicals (analytical grade) were supplied by Sinopharm (Beijing, China). Purified water was obtained using a PALL Lab Water Purification System (Port Washington, NY, USA).

The standards
used for the identification of some of the compounds present in the
analyzed fraction were gallic acid (certified reference material);
5-hydroxymethylfurfural (≥99%); furfural (≥98.5%, GC);
vanillic acid (≥97.0%, HPLC); p-hydroxybenzaldehyde
(95.0%, HPLC); 5-hydroxymethylfurfural (≥99%); syringic acid
(≥95.0%, HPLC); vanillin (≥97%); syringaldehyde (≥98%);
coniferaldehyde (≥98%); and sinapaldehyde (≥98%), all
of which were supplied by Sigma-Aldrich (Saint Louis, MO).
The
hydroalcoholic mixtures used for the identifications were made using
99.8% ethanol supplied by Sigma-Aldrich (Saint Louis, MO) and ultrapure
water (EMD-Milipore, Bedford, MA).

Ethanol (99,7%) was purchased from Solveco (Rosersberg, Sweden), acetone (HPLC grade) from VWR (Radnor, PA, USA), ethyl l-lactate (99%) from Alfa Aesar (Haverhill, MA, USA), methanol (LC-MS grade) from J. T. Baker (Philipsburg, NJ, USA) and 2 M ammonia in methanol from Fisher Scientific (Waltham, MA, USA). Water was purified using a Milli-Q purification system. Liquid CO₂ (grade 5.3) was obtained from Linde (Dublin, Ireland). Hardwood (oak, Quercus robur) and softwood (fir, Abies alba) chips were obtained from a local provider in Pisa (Italy). Vanillin, vanillic acid, coniferyl aldehyde, ferulic acid, syringaldehyde, syringic acid, sinapaldehyde, o-Vanillin, and 3-hydroxyacetophenone were purchased from Sigma Aldrich (St. Louis, MO, USA).