Analysis of the headspace aroma compounds of the seeds of the Cameroonian "garlic plant" Hua gabonii using SPME/GC/FID, SPME/GC/MS and olfactometry

Abstract.

The headspace aroma compounds of the seeds of the "garlic plant" Hua gabonii (Huaceae) from Cameroon were analysed by solid-phase-micro-extraction/gas chromatography/ flame ionization detector (SPME/GC/FID), SPME/GC/mass spectrometry (MS) and olfactoric evaluations. Surprisingly the typical garlic-like aroma of the headspace (SPME) sample is not only the result of well-known disulfides of Allium species, but – in plants with garlic aroma – of hitherto rather rarely identified methyl methylthiomethyl disulfide (2,4,5-trithiahexane) and di-(thiomethylmethyl) disulfide (2,4,5,7-tetrathiaoctane) in concentrations of 23.3% and 21.4% respectively (calculated as percentage peak area of SPME/GC/FID analysis using a non-polar column). As further main compounds (concentrations higher than 1.0%) of this SPME-headspace sample of H. gabonii seeds the monoterpenes p-cymene (1.1%), β-pinene (1.1%), pinocarveol (1.2%), myrtenol (1.3%), 1,8-cineole (1.5%), myrtenal (1.7%), α-terpineol (2.1%), α-pinene (3.6%), α-terpinolene (4.9%), terpinen-4-ol (8.1%) and the sesquiterpenes β-caryophyllene (2.6%) and α-copaene (4.9%) as well as the sulfidic compounds diallyl trisulfide (1.5%), dipropyl trisulfide (1.7%) and methyl propyl tetrasulfide (2.2%), were identified. The characteristic disulfide components of common garlic, like diallyl disulfide, were found only as minor compounds. A correlation of identified volatiles of the H. gaboni seeds responsible for the characteristic garlic aroma with fresh-terpenic notes is additionally given.