Sesquiterpenoids from Lactuca tatarica

Chemical characterization by GC/MS analysis of Lactuca tatarica (L.) C.A.Mey. aerial parts and seeds

Lactuca tatarica is a wild species belonging to Asteraceae family omnipresent in Southern Caucasus region including Azerbaijan. Previous studies on the chemical content of some extracts obtained from its different organs have reported the presence of lactone sesquiterpenes, triterpenoids and flavonoids. For the first time, we investigated the volatile composition of L. tatarica aerial parts and seeds by GC/MS technique. The results showed the predominant presence of fatty acids, both saturated and unsaturated. Palmitic acid was prevalent in the aerial parts (up to 89.9%) while linoleic acid (up to 82.6%) was the most abundant component in the seeds. Other minor components were terpene and hydrocarbon derivatives. Some of the detected constituents in L. tatarica have already demonstrated antibacterial, antifungal, anti-inflammatory and antioxidant activity. Therefore, this species could be better studied for its biological properties and considered as a source of active ingredients useful in various fields including the pharmaceutical one.

Phytochemical Characterization of Phitosia crocifolia, a Monotypic Representative of Greek Flora

Within the large Compositae family, Phitosia is considered a monotypic genus of the Greek flora, with its only species P. crocifolia (Boiss. & Heldr.) Kamari & Greuter growing wild with limited distribution, exclusively on the mountains Taigetos and Parnonas in Peloponnese. P. crocifolia's chemical profile was obtained, herein, for the first time and led to the isolation of 20 compounds, thirteen of which were characterized as sesquiterpene lactones and the rest mainly as phenolic derivatives. The isolates 1: -3, 5:  - 7: and 11:  - 13: represent new chemical structures. Compounds 2: and 3: especially are substituted with a pentose moiety, a rare phenomenon in sesquiterpene lactone backbones. A series of spectrometric and spectroscopic techniques were used to elucidate their structures. The relative configurations of the unreported compounds were established via extensive analysis of NMR spectroscopic and HRESIMS data, assisted by CD spectroscopic measurements. Throughout the entire isolation procedure, selected fractions rich in sesquiterpene lactones were tested against HeLa cancerous cell line for their cytotoxic effects with the lowest IC₅₀ values being 18.84 µg/mL. Accordingly, among the tested isolates, compounds 5: and 9: exerted IC₅₀ values of 13.5 µM and 11.4 µM, respectively.

Sesquiterpene lactones and their precursors as chemosystematic markers in the tribe Cichorieae of the Asteraceae revisited: An update (2008-2017)

Ten years after the first overview on sesquiterpene lactones in the Cichorieae tribe of the Asteraceae family, we present an update. This review summarizes all chemosystematically relevant reports on sesquiterpene lactones and their immediate precursors from the Cichorieae (syn.: Lactuceae) tribe of the Asteraceae published between 2008 and 2017 and also includes some corrections to the 2008 review. The number of sesquiterpene lactones and sesquiterpenic acids as immediate precursor of sesquiterpene lactones reported for the Cichorieae has increased from 360 to 475 (+32%) within one decade. The number of known source species increased from 139 to 157 (+13%) and the number of chemosystematic reports (reported compounds per taxon) increased from 838 to 1241 (+48%). Notwithstanding this high interest in sesquiterpene lactones of the Cichorieae, still only from 30 out of 94 currently accepted genera within the Cichorieae at least one sesquiterpene lactone has been reported so far.

Sesquiterpene lactones from Lactuca canadensis and their chemotaxonomic significance

A total of 19 sesquiterpene lactones were isolated from roots of Lactuca canadensis L., of which 10 were reported for the first time from Lactuca species and two were unknown. This is also the first report on the co-occurrence of three pairs of zaluzanin C-type guaianolides, epimeric at C-3, and on the presence of six eudesmanolides, oxygenated at C-1 and C-3, in Lactuca species. The new compounds were characterized as 3-epizaluzanin C-3-O-β-glucopyranoside and 11,13-dehydrolactuside C using 1D and 2D NMR and high resolution mass spectroscopy. The sesquiterpene lactone profile of this species is dominated by zaluzanin C-type guaianolides (9 compounds) and eudesmanolides (8 compounds). The dissimilarity of this profile compared to that of other taxa of the genus is discussed.

A New Eudesmane Sesquiterpenoid Glycoside from Lactuca Sativa L var. Anagustata

Chemical reinvestigation of the methanolic extract of whole plant ofLactuca sativaLvar. anagustatahas now led to the isolation of one new eudesmane sesquiterpenoid glycoside which was elucidated by means of spectroscopic methods, including 2D-NMR experiments (1H-1H COSY, HMQC, HMBC, and NOESY) as 1β-O-β-D-glucopyranosyl-15-O-(p-methoxyphenylacetyl)-5α, 6βH-eudesma-3, 11(13)-dien-12, 6α-olide.