Fig. 1

The analysis of functional groups in I50 by NMR. The 1H-NMR spectra (top x-axis), the 13C-NMR spectra (left y-axis), and the HSQC spectra of I50 are shown. Peaks and spots representing different carbons, protons, and monosaccharides are labeled. In the 1H-NMR spectrum, the O-acetyl groups of I50 displayed a characteristic signal in the range of 2.03 to 2.13 ppm, considered the fingerprint of A. vera. Three signals correspond to methyl groups at 2.08, 2.10, and 2.13 ppm indicating that O-acetyl groups are located at different positions. These results were further confirmed by the 13C-NMR spectrum which showed the presence of methyl carbon signals at 20.09, 20.30, and 20.57 ppm, as well as the presence of carboxyl carbons at 172.56, 173.38, and 173.91 ppm.