Detection of Heterogeneous Peptides in Tryptic Digests of Ajiao by UPLC -QTOF and RRLC-IT

Donkey-hide gelatin (Ajiao in Chinese) is a gelatin drug, which is the dry glue pieces made from the hide of Equus asinus L. (family Equidae), and used to tone the blood, arrest bleeding, nourish yin and prevent dryness. After a series of processes of the hide: washing, soaking, plucking, rinsing and stewing, the collagen of the donkey hide was hydrolyzed into a mixture of polypeptides. It is used unprepared, or stir-baked with oyster shell powder or cat-tail pollenpowder into small glue balls for use. In China, bovine and porcine hides are also used as the gelatin drug. The similarity between different gelatins makes it difficult to trace their species origin[1].

In our experiment, the gelatins were digested by trypsin, and the zymolytic peptides were analyzed by UPLC-QTOF. Comparative analysis was performed by Biopharmalynx software which indicated that the several extracted ion chromatographic peaks specific for donkey, bovine and porcine were successfully detected in the digested bovine and porcine gelatin, respectively. The above peaks are attributed to specific peptides for donkey, bovine and porcine by RRLC-IT according to the Sequence alignment analysis [2] that provides the different sequences zymolytic peptides of Type I and Type II collagen of donkey, bovine and porcine in theory. The donkey, bovine and porcine hides can be identified by their specific marker peptides.

References: [1] Zhang GF, Sun Aimei, et al. (2006)J of Chrom A, 1114: 274–277. [2] Zhang GF, Liu T, et al. (2009) Food Hydrocolloids, 23: 2001–2007.