Essential oil composition of the sub-aerial parts of eight species of Cymbopogon (Poaceae)

The genus Cymbopogon (Poaceae) comprised of many species of grasses that grow in tropical and subtropical regions around the world. Some of the commercially important aromatic species of Cymbopogon are cultivated for the extraction of the essential oils from their aerial-parts. In spite of wide distribution and large scale cultivation, the essential oils of the sub-aerial parts (root/rhizome) of these species have not been systematically studied so far. In this study, the hydro-distilled essential oils from the sub-aerial parts of eight species, including a hybrid of Cymbopogon, namely C. fiexuosus (Nees ex Steud.) W.Watson, C. khasianus (Hack.) Stapf ex Bor, C. pendulus Nees ex Steud., C. khasianus x C. pendulus, C. winterianus Jowitt ex Bor, C. martini (Roxb.) W.Watson, C. distans (Nees ex Steud.) W.Watson, and C. jwarancusa (Jones) Schult. and their varieties/chemotypes were analyzed by gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC MS). A total of thirty-three terpene C-skeleton types (six monoterpene skeletons, twenty-seven sesquiterpene skeletons) were identified. Among these p-menthane, myrcane, elemane, eudesmane, and agarospirane C-skeletons dominated in the examined species of Cymbopogon. A multivariate statistical comparison by principal component analysis and agglomerative hierarchical clustering grouped the examined essential oils in to four clusters (cluster I: geraniol, and piperitone/ geraniol chemotypes; cluster II: high elemol and low elemol chemotypes; cluster III: limonene chemotype; and cluster IV: 5-epi-7-epi-alpha-eudesmol/ eudesmanediol/ hinesol, and cis-p-menth-2-en-1-ol/ trans-p-menth-2-en-1-ol/ eudesmanediol chemotypes). The sub-aerial parts, a waste product of cultivation can serve as good source of valuable and rare lead molecules, such as elemol, 5-epi-7-epi-alpha-eudesmol, beta-eudesmol, eudesmanediol, hinesol, agarospirol, 7-epi-alpha-eudesmol, alpha-eudesmol, gamma-eudesmol, shyobunol, selina-6-en-4-ol, and p-menth-2-en-l-ols.