NOVEL POLYSULFIDES IDENTIFIED IN THE VOLATILE COMPONENTS FROM WELSH ONIONS (ALLIUM-FISTULOSUM L VAR MAICHUON) AND SCALLIONS (ALLIUM-FISTULOSUM L VAR CAESPITOSUM)

Volatile components were isolated from Welsh onions (Allium fistulosum L. var. maichuon) and scallions (A. fistulosum L. var. caespitosum) by steam distillation and by dichloromethane extraction. The components of distilled oils and solvent extracts were analyzed by gas chromatography and gas chromatography-mass spectrometry (El and Cl). Sulfur-containing compounds accounted for 85% and 77% of the total volatiles in the distilled oils of Welsh onions and scallions, respectively. In addition to the sulfur compounds commonly reported in genus Allium, 25 novel volatile polysulfides were found in the distilled oils from both varieties of green onions. These compounds can be grouped as (a) alk(en)ylthioalkyl alk(en)yl disulfides, (b) alkyl tetraor pentathiaalkanes or -alkene(s), and (c) thiaheterocycles. All these compounds are being reported in Welsh onions and scallions for the first time. Thermal reaction may be responsible for the formation of these volatile polysulfides. © 1990, American Chemical Society. All rights reserved.