Microtof 2 spectrometer

The peak 2 was characterized based on various physicochemical and spectroscopic properties. Appearance, color, odor, and solubility were determined according to the standard procedures. The UV-Visible spectrum was recorded qualitatively on UV-Visible Spectrophotometer (Shimadzu) in the range of 200–400 nm using acetonitrile as reference solvent.¹H NMR and ¹³C NMR spectra were recorded in chloroform-d [99.8 atom% D, containing 0.1% (v/v) tetramethylsilane (TMS)] at 25°C on 500 MHz AVANCE III Bruker spectrometer equipped with a 5 mm double channel solution state probe. The chemical shifts are reported in parts per million (ppm) relative to TMS (δ0.0) used as internal standard. Mass spectrum (HR-MS) was recorded with Bruker MICROTOF II spectrometer. IR spectrum was recorded with Perkin–Elmer FTIR-C92035 Fourier-Transform spectrophotometer in the range 400–4000 cm^-1 by using CHCl₃ as the medium for the preparation of the samples.

Melting point was measured on a XT4 microscopic melting-point apparatus (Shanghai Jingke Instruments Company, Shanghai, China). Optical rotation was measured with a 241 polarimeter (Perkin-Elmer, Waltham, MA, USA). Electrospray ionization mass spectroscopy (ESIMS) data were recorded with a Micro TOF II spectrometer (Bruker, Bremen, Germany). High-resolution ESIMS data were recorded with an APEX II HR-TOF spectrometer (Bruker). NMR spectra were obtained in DMSO-d₆ on a Bruker Avance DRX 400-MHz spectrometer at 400 MHz for ¹H-NMR and 100 MHz for ¹³C-NMR. Precoated silica gel GF₂₅₄ plates (Merck, Darmstadt, Germany) were used for TLC. For column chromatography, SiO₂ (100–200 mesh, Qingdao Marine Chemical Factory, Qingdao, China) and Rp-C18 (ODS-A, 50 μm, YMC, Yantai, China) were used. HPLC purifications were performed on HPLC columns (YMC-Pack Pro C18, 5 μm, 250 mm × 4.6 mm and 250 mm × 10 mm, YMC, Kyoto, Japan) with a L-2000 HPLC system (Hitachi, Tokyo, Japan).

NMR-spectra were acquired on a Bruker Avance III 400 spectrometer using CDCl₃ or DMSO-d₆ as a solvent. The ESI-MS data were recorded using a Bruker micrOTOF II spectrometer. UV/VIS spectroscopic analysis was performed using an Agilent Cary 60 spectrometer. SEM measurements were performed using a Zeiss FESEM Auriga 40™ Crossbeam and a Hitachi TM3000 Tabletop SEM with a Bruker Quantax EDX Detector for the EDX measurements. EDX line scans were performed at a Zeiss Gemini 500 equipped with an Oxford EDX Ultim Max 100 detector. FT-IR spectra were recorded by using a PerkinElmer Spectrum 100 spectrometer using ATR unit. TGA measurements were measured on a Netzsch STA449 F3 Jupiter. All measurements were performed under oxygen atmosphere with 80 mL min⁻¹ flowrate and a heating rate of 10 K min⁻¹. Fluorescence microscopy was performed at labelled excitation wavelengths using a Zeiss Axio Observer Z1 microscope.

A 45 × 1.5 cm column was packed with amberlite XAD-7 pre-conditioned with acidified water (5% acetic acid) [17 (link)]. The resin was washed with 200 ml of acidified water (5% acetic acid) and 1 mL of the blue corn or tortilla crude extract was added placed and washed with 100 mL of acidified water; the polymer mixture was eluted with 200 mL of acidified ethanol (5% acetic acid). The eluate was concentrated in a rotary evaporator (Heidolph Digital Laborota pump 4011 coupled to V Pimo Vacum Buchi 700) at 28 °C and stored at 4 °C until use. Separation of the compounds was performed using an HPLC equipped with a C-18 ZORBAX eclipse plus column (100 mm × 2.1 mm, 3.5 μm) under isocratic elution with methanol: water (2:8 v:v). The HPLC system was coupled to a Brüker MicrOTOF II spectrometer operating in negative ion mode, scan range: 50–3000 amu, capillary voltage 3.8 kV, dry gas flow at 4.0 L min⁻¹ and heated capillary temperature of 180 °C. Under these conditions an electrospray ionization-mass spectrometry (ESI-MS) analysis of the isolated compounds was performed.

¹H and ¹³C-NMR spectra were recorded on Bruker AVANCE III HD 400 (Billerica, MA, USA) and 500 MHz spectrometer (Billerica, MA, USA) Chemical shift was presented in ppm and referenced by residual solvent peak. Mass spectrometry (MS) was either performed using a Bruker microTOF II spectrometer (Billerica, MA, USA) with electron spray ionization (ESI) or Bruker Autoflex III (Billerica, MA, USA) with matrix-assisted laser desorption/ionization (MALDI). Commercially available solvents and chemicals were used without further purification unless otherwise stated. Water was de-ionized and micro filtered. Flash column chromatography was performed using Biotage flash column chromatography purification system with SNAP Ultra cartridges (Charlotte, NC, USA). All cartridges used silica gel as stationary phase unless otherwise stated.