An Improved Method for Analysis of Polyamines in Plant Tissue by Precolumn Derivatization with o-Phthalaldehyde and Separation by High Performance Liquid Chromatography

An improved high-performance liquid-chromatographic method was developed for estimation of polyamines in crude plant extracts. Polyamines were derivatized with o-phthalaldehyde and mercaptoethanol (OPT). The fluorescent derivatives were eluted from a C(18) column with the dimethylcyclohexylamine-phosphate buffer derived by T. Skaaden and T. Greibrokk ([1982] J Chromatogr 247: 111-122) after treatment to remove impurities in the buffer. The method had a sensitivity of 1-2 picomoles and completely resolved nine polyamines (agmatine, spermine, nor-spermidine, spermidine, 3,5-homospermidine, 4,4-homospermidine, 1,3-diaminopropane, putrescine, and cadaverine) in 12 to 14 minutes. An optional ion-exchange step was used to remove less basic amines (including amino acids) and to concentrate the crude extracts. This method was compared with benzoyl chloride derivatization. Use of the benzoyl chloride method vastly under-estimated the amount of polyamine in some plant extracts, a problem not encountered with the OPT procedure. Additionally, the OPT procedure resolved two isomers of homospermidine found in Azolla caroliniana. These two isomers were not resolved with the benzoylation method. Overall, the OPT method described here requires preparation and analysis time similar to other current methods but provides greater sensitivity and selectivity.