Merck silica gel plates

All reagents were purchased from commercial sources and used without further purification. Substrates which were not commercially available were synthesized according to known literature procedures (see Supporting Information for details). NMR spectra were performed on a Bruker AC-300 or Bruker Avance-400 (Bruker Corporation, Karlsruhe, Germany) using CDCl₃ as solvent and TMS as internal standard unless otherwise stated. Optical rotations were measured on a Jasco P-1030 Polarimeter with a 5 cm cell (c given in g/100 mL). Enantioselectivities were determined by HPLC analysis (Agilent 1100 Series HPLC) equipped with a G1315B diode array detector and a Quat Pump G1311A (Agilent Technologies, Palo Alto, CA, United States) equipped with the corresponding Daicel chiral column; the retention time of the major enantiomer is highlighted in bold. HRMS were measured using HPLC–HRMS (ESI) equipment (Agilent 1100 Series LC/MSD Trap SL, Agilent Technologies). Analytical TLC was performed on Merck silica gel plates and the spots were visualized with UV light at 254 nm (Merck Millipore, Billerica, MA, USA). Flash chromatography employed Merck silica gel 60 (0.040–0.063 mm) (Merck Millipore, Billerica, MA, USA).

Plantain NSP and Q-Sepharose derived neutral and acidic NSP fractions were each hydrolysed with either 0.5% Driselase® (a commercial enzyme mixture of hydrolytic enzymes capable of digesting homogalacturonan and rhamnogalacturonan-I (RG-I) efficiently to galacturonic acid and associated neutral monosaccharides) or 2 M trifluoroacetic acid (TFA) as per [48] (link). Thin-layer chromatography (TLC) was performed on Merck silica-gel plates and on plates pre-washed for in acidified acetone to enhance mobility of the uronic acids. Each loading was derived from 25 µg of plantain NSP or polysaccharide fraction (or contained an equivalent amount of Driselase® or TFA). Plates were run under two solvent conditions, ethyl acetate/pyridine/acetic acid/water (6∶3∶1∶1) and butan-1-ol/acetic acid/water (2∶1∶1), each followed by staining using thymol/H₂SO₄. To better determine galacturonic acid yields, high-voltage paper electrophoresis (HVPE) of plantain fibre samples and their hydrolysis products was also performed as per [49] (link). Briefly, each loading was derived from 200 µg of the fibre or fraction (or contained an equivalent amount of Driselase® or TFA). Electrophoresis was performed using Whatman No. 1 paper in pH 2.0 buffer at 4.7 kV for 80 min, with monosaccharide and oligogalacturonide markers included for reference. Staining was with aniline hydrogen-phthalate [49] (link).