A new natural product, 2-(a-L-arabinopyranosyloxy)-2-phenylethylglucosinolate, has been isolated from Sesamoides canescens. This glucosinolate together with 2-hydroxy-2-phenylethylglucosinolate and 2 phenethylglucosinolate in a 1: 1: 1 ratio constitutes about 90 % of the total glucosinolate pool in green parts of the plant. Phenethylglucosinolate constitutes about 70 % ofthe total glucosinolate pool in green parts of S. pygmaeu together with minor amounts of the two other glucosinolates. In addition, both plants contain at least seven other glucosinolates. The structure of the new natural product has been confirmed by transformations into D-glucose, L-arabinose, N-(2-(a-Larabinopyranosyloxy)-2_phenylethyl)thiourea, 3-(a-L-arabinopyranosyloxy)-3-phenylpropionitrile and 3-hydroxy-3 phenylpropionic acid, respectively. The significance of this investigation is briefly discussed in relation to the methods used in glucosinolate analysis, chemotaxonomy and possible catabolic transformation of glucosinolates into amines.