500 mhz instrument

The reagents and solvents employed in the existing study were got from commercial dealers. All the reactions were observed by thin-layer chromatography (TLC) on silica gel. Melting points of the synthesized compounds were measured using open capillary tubes and are uncorrected. NMR spectra were recorded on a Jeol 500 MHz instrument (Tokyo, Japan) while the FT-IR spectra were documented on a Perkin Elmer system 2000 FT-IR instrument (KBr) (Shelton, AL, USA). Mass spectra of these compounds were measured on a DART-ToF-MS mass spectrometer (Jeol, MA, USA). Elemental analyses of the synthesized compounds were done on a Perkin Elmer 2400 Series II Elemental CHNS analyzer (Waltham, MA, USA).

The measurement of A. vera components by NMR has been carried out by following the American Herbal Pharmacopoeia guidelines [11 ]. For this, the JEOL 500 MHz instrument using D₂O as a solvent containing 4,4-dimethyl-4-silapentane-1-sulfonic acid (DSS) reference was used.

The NMR spectra were recorded by a 500 MHz instrument (JEOL, Tokyo, Japan) at 25 °C. The chemical shifts (δ) are presented in ppm, and the coupling constants (J) are presented in Hz. The ¹H and ¹³C chemical shifts are referenced to tetramethylsilane using the solvent signals HDO 4.66 ppm, CHCl₃ 7.26 ppm, CHD₂OD 3.31 ppm, and C₆HD₅ 7.16 ppm for ¹H and CDCl₃ 77.16 ppm, CD₃OD 49.00 ppm, and C₆D₆ 128.06 for ¹³C. For the estimation of molecular structures, a series of standard NMR experiments was recorded and analysed, including 2D COSY, HSQC, HMBC, TOCSY, NOESY, ROESY, and selective 1D NOESY, 1D TOCSY, and selective homodecoupled ¹H NMR spectra. For the mass spectrometry (MS) analysis, a Sciex X500R QTOF HR mass spectrometer was used. Fourier-transform infrared analysis (FTIR) was performed using a Nicolet iZ10 from ThermoFisher Scientific (Waltham, MA, USA). The observed pseudo molecular peak [M + Na]⁺ of the studied compounds was usually followed by a less intensive peak of [2M + Na]⁺, which is typical for oxygen compounds [46 (link)]. The peak of [3M + Na]⁺ was not observed. A detailed anomeric composition of the products is given in the Results and Discussion section.