Distribution of Amygdalin in Apricot (Prunus armeniaca) Seeds Studied by Raman Microscopic Imaging

Amygdalin is a cyanogenic glycoside found in the seeds of several plants belonging to the Rosaceae family. Cyanogenic glycosides can be specifically probed by Raman spectroscopy due to an inherent nitrite group which shows a well-resolved band near 2245 cm(-1). In the current study the subcellular distribution of amygdalin in thin apricot (Prunus armeniaca) seed sections is probed by high-resolution Raman imaging with a step site of 2.5 mu m. Further, Raman images and line maps were collected from four apricot seeds with step sizes between 30 and 70 mu m. The data were processed by functional group mapping and the spectral unmixing algorithm vertex component analysis. Spectral contributions of amygdalin, lipids, and cellulose were identified. One seed had low amygdalin content in its center and higher content toward its epidermis. The other three specimens showed different distributions of amygdalin, with highest concentration in the center and local concentration spots throughout the seed. We conclude from these preliminary results on Raman imaging in apricot seeds that amygdalin is unevenly distributed and its location does not follow the same pattern for all seeds. The observed biological variability of the amygdalin distribution cannot yet be explained satisfactorily and requires further investigation.