Characterization of APMCG-1
The chemical composition of APMCG-1 was analyzed and the following contains were observed: 0.85% alkaloids, 25.98% amino acids and peptides, 39.8% carbohydrates, 0.95% flavonoids, 0.3% polyphenols, 1.47% saponins, 15% uronic acids, and 15.63% unknown (Fig. 6A). To identify the presence or absence of glycopeptides in APMCG-1, we used β-elimination reaction. The results showed that the absorption value of the UV spectrum of APMCG-1 significantly increased at 240 nm after alkali treatment, and contained O-linked glycopeptide bonds (Fig. 6B). The results of thin-layer chromatography analysis showed that APMCG-1 also contained sugars and peptides. As revealed by the FT-IR spectrum, the strong and broad absorption peak at around 3400 cm-1 indicated the stretching vibration peak of -OH or -NH on the polysaccharide. The moderate-intensity absorption peak at 2920 cm-1 marked the stretching vibration peak of -CH2 and -CH. The absorption peaks at 1600 cm-1 implied the asymmetric stretching vibration peaks caused by C=O. The above absorption peaks were characteristics of polysaccharides. The absorption peak at 1400 cm-1 was caused by the deprotonated carboxyl group, indicating the presence of a uronic acid structure. The absorption peak at 760 cm-1represented the absorption peak of pyran-ring symmetric ring stretching vibration, revealing the presence of pyran polysaccharide (Fig. 6C). The retention times of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, xylose, galactose, and fucose were observed at 13.120, 16.678, 21.075, 25.187, 30.560, 34.898, 35.640, 38.224 and 42.174 min, respectively. The ratio of monosaccharide of APMCG-1 was mannose, rhamnose, galacturonic acid, glucose, xylose, galactose and arabinose 1:2.57:15:24.54:3.4:28.54:12.38 (Fig. 6D). Amino acid involving cysteic acid, methionine alum, aspartic acid, threonine, serine), glutamate, glycine, alanine, cysteine, valine), methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine, arginine and proline were used as the standard substance, the amino acid composition of APMCG-1 was composed of aspartic acid (2.797%), methionine (3.271%), phenylalanine (6.503%), histidine (4.748%), arginine (2.513%), proline (1.433%), and NH4 (9.086%) (Fig. 6E). These findings denote that APMCG-1 is an active glycopeptide isolated from MCG.