ABSTRACT

Two monocyclic sesquiterpene hydrocarbons, zingiberene and curcumene, were found by gas chromatography and mass spectrometry (GC/MS) analysis to be the most abundant sesquiterpenes in the leaf oil of the wild tomato Lycopersicon hiirsutum f. typicum (Solanaceae). Volatile metabolites of Lycopersicon species such as zingiberene and curcumene have a role in tomato flavor, human health-related properties, and host plant defense against arthropod herbivores. Many of these compounds are known for their medicinal and anti-oxidative properties. Zingiberene [5-(1,5-dimethyl-4-hexenyl)-2-methyl-1,3-cyclohexadiene] is known as the main constituent of ginger oil from the rhizomes of Zingiber officinale, Roscoe (Zingiberaceae). An authentic specimen of zingiberene isolated from commercial ginger oil and an authentic specimen isolated from wild tomato leaves of Lycopersicon hirsutum f. typicum (PI-127826 and PI-127827) have identical zingiberene and curcumene GC/MS spectrum. The main sesquiterpene hydrocarbons identified in the leaves of wild tomato species were α-zingiberene, α-curcumene, and trans-caryophyllene. Leaves of six wild tomato accessions of L. hirsutum f. glabratum (Mull), three accessions of L. hirsutum f. typicum (Humb & Bonpl.), two accessions of L. pennellii Corr. (D’ Arcy), one accession of L. pimpinellifolium, and leaves of cultivated tomato L. esculentum cv. Fabulous (Solanaceae) were analyzed for 194chemical composition. Crude extracts of wild tomato leaves were purified using an open glass chromatographic column containing alumina and the contents were separated for GC/MS identification and quantification. Analysis of L. hirsutum f. typicum accessions (PI-127826, PI-127827) indicated the presence of zingiberene, curcumene, and other lipophilic secondary metabolites in their leaves. Zingiberene and curcumene were found mainly in type VI glandular trichomes of typicum accessions. Sesquiterpene content of tomato leaf oil varied considerably among species. Seasonal variation affected the amount of zingiberene and curcumene per unit area of leaves by controlling concentration of zingiberene and curcumene in the glandular tips of type VI trichomes present on the leaves of wild tomato species. Total leaves collected from each plant of accessions PI-127826 and PI-127827 provided 10.7 and 9.8 g of zingiberene, respectively. Wild tomato accessions (PI-127826 and PI-127827) of L. hirsutum f. typicum can be explored as a biorational source of zingiberene.