Ods c18 column

¹³C- and ¹H-NMR recorded at 100 MHz and 400 MHz were used for identifying the isolated compounds on an AM-400BB instrument (Bruker, Billerica, MA, USA). Sephadex LH-20 (25–100 mm, Sigma-Aldrich, St. Louis, MO, USA), TLC plates and silica gel (200–300 mesh, Haiyang Chemical Co. Ltd., Qingdao, China) were used for the isolation of the compounds. Spots on the TLC plates were observed under ultraviolet (UV) light and by heating after spraying with 5% (v/v) H₂SO₄ in C₂H₅OH. Reagents used in the isolation and determination were analytical and HPLC grade (Thermo Fisher, Waltham, MA, USA), respectively. A fluorescence microscope (80i, Olympus, Tokyo, Japan) was used for the detection of ROS. Biochemical reagents were purchased from Roche (Basel, Switzerland) and Sigma. A HPLC system equipped with a 2998 UV detector (DAD, Waters 2998, Milford, MA, USA) and a ODS C18 column (250 mm × 4.6 mm × 5 μm, Waters Co., Ltd.) was used for the quantification of the compounds.

The level of glutamate and GABA in the ACM was analyzed by high-performance liquid chromatography (HPLC) using a Waters 2695 liquid chromatograph (Waters, Milford, CT, USA), a Hypersil ODS C18 column (250 by 4.6 mm; particle size, 5 μm), and a Waters 2996 UV/VIS detector. Before injection into the HPLC, the sample was derivatized by incubation with 2,4-dinitrofluorobenzene for 1 h at 60 °C and the reaction was stopped by adding 50 mM potassium dihydrogen phosphate. The mixture was concentrated and filtered using a 0.22 μm filter. The mobile phase consisted of 8% methyl cyanides, 8% ddH₂O, and 84% 40 mM sodium acetate (pH 8.0) at a flow rate of 1.0 mL/min. The UV detector was set to an absorbance of 360 nm. Chromatograms of glutamate and GABA standards yielded respective peaks at 7.968 min and 29.896 min. The concentrations were calculated by LCsolution software (Waters, Milford, CT, USA) based on standard samples.

Inhibitor components were analyzed by HPLC (Waters 1525) equipped with a UV detector (Waters 2489) and a SilGreen ODS C18 column. Furfural and 5-HMF were measured at 280 nm with a flow rate of 1 mL/min, and methanol/water (1:9, v/v) as mobile phase. Formic acid and acetic acid were measured at 210 nm with a flow rate of 0.7 mL/min, KH₂PO₄/methanol (2:8, v/v) as mobile phase (Figure S1).
The content of xylitol, xylose, and glucose was determined using a determined using refractive index detector with an Inertsil Sugarpak1 (6.5 mmid × 300 mm) column and ultra-pure water as the mobile phase. The flow rate was 0.4 mL/min and the detection was carried out at a column temperature of 85 °C. All mobile phases and samples were filtered through a 0.22 μm filter and used in the HPLC analysis (Figure S3). Xylitol yield is calculated by the following equation, calculated according to Equation (1):
$$\mathrm{The} \mathrm{yield} \mathrm{of} \mathrm{xylitol} (\mathrm{g}/\mathrm{g})=\frac{\mathrm{The} \mathrm{concentration} \mathrm{of} \mathrm{xylitol}}{\mathrm{Intial} \mathrm{xylose} \mathrm{concentration}-\mathrm{Residual} \mathrm{xylose} \mathrm{concentration}}$$