Diversity of Sesquiterpenoids from Carpesium cernuum

Abstract

Two new sesquiterpene lactones, 6b-hydroxy-8a-ethoxyeremophil-7(11)-en-12,8b-olide (1) and 4b,10b-dihydroxy-1aH,5aH,11aH-guaian-12,8b-olide (2), together with 22 known sesquiterpenoids with various structural types, were isolated from Carpesium cernuum (Compositae). Their structures and configurations were elucidated by extensive 1D-and 2D-NMR spectroscopic analysis in combination with MS experiments, and comparison with literature data of related compounds.Introduction. -Previous phytochemical studies indicate that sesquiterpene lactones are the most widespread secondary metabolites within the genus Carpesium. Different skeleton types of sesquiterpene lactones, such as eudesmanolides, guaianolides, xanthanolides, germacranolides, and carabranolides have already been isolated from the genus [1 -6]. Noteworthy, some of them showed antifungal, antibacterial, and cytotoxic activities [7 -10]. As a folk medicine with anti-inflammatory, pain-relief, and detoxification effects, Carpesium cernuum from other locations has been previously chemically investigated [11 -14]. To study the influences that C. cernuum imposes on its environment concerning chemical aspects, as well as to search for further biologically active sesquiterpenoids from natural sources, we have reinvestigated the chemical constituents of C. cernuum. Interestingly, in our study, we have not detected germacrane sesquiterpenes, always found in the genus, which play a central role in the biosynthesis of guaiane-and eudesmane-type sesquiterpenes, but isolated a new eremophilenolide, 6b-hydroxy-8a-ethoxyeremophil-7(11)-en-12,8b-olide (1), and a new guaianolide, 4b,10b-dihydroxy-1aH,5aH,11aH-guaian-12,8b-olide (2), along with 22 known sesquiterpenoids, i.e., 4b,10b-dihydroxy-1aH,5aH-guai-11(13)-en-12,8a-olide (3) [6], 4a,10a-dihydroxy-1bH,5bH-guai-11(13)-en-12,8a-olide (4) [6], 1-epiinuviscolide (5) [15], 4a,5a-epoxy-10aH-1-epiinuviscolide (6) [20], and (3S,5R,6S,7E)-5,6-epoxy-3-hydroxymegastigm-7-en-9-one (24) [20]. To the best of our knowledge, among these known sesquiterpenolides, compounds 3 -10 and 19 have

The genus Carpesium: A review of its ethnopharmacology, phytochemistry and pharmacology

“…The pseudoguaianes (44À 48) were only found in Carpesium abrotanoides L., Carpesium faberi C.Winkl. and Carpesium cernuum L. (Wang et al, 2009;Lee et al, 2002aLee et al, , 2002bLiu et al, 2010;Gao and Chen, 2012;Li et al, 2011). These two types of compounds have similar structures; guaianolides and pseudoguaianes differ at Me-15 when comparing their carbon frameworks.…”

“…Until now, Carpesium cernuum L. yielded a series of eudesmanolides including two new eudesmanolides 13-hydroxy-5,7(11)-eudesmadien-12, 8-olide (2) and 6β-hydroxy-8α-ethoxyeremophil-7(11)-en-12, 8β-olide (3) along with several known structures (4 À 11) (Liu et al, 2010;Yang et al, 2002c). In this genus, most of the eudesmanolide structures possess an exocyclic double bond or methyl group at the C-11 position, while the structures of the two new eudesmanolides (2 and 3) have an endocyclic olefin at the C-11 position, which are more rare.…”

“…& Sav., Carpesium triste Maxim., etc. (Lee et al, 2002a(Lee et al, , 2002bWang et al, 2009;Li et al, 2011;Wu et al, 2014;Xie et al, 2012;Liu et al, 2010). The pseudoguaianes (44À 48) were only found in Carpesium abrotanoides L., Carpesium faberi C.Winkl.…”

“…& Sav. and Carpesium cernuum L., respectively (Kim et al, 2004;Liu et al, 2010). The β-sitosterol (142) (Sheng and Chen, 2009), daucosterol (143) (Elyakova et al, 1966), were more common; they were isolated from most of the Carpesium plants.…”

“…3). 4H-xanthalongia (49), xanthalongia (50) (Liu et al, 2010), 11α, 13-dihydro-4H-xanthalongin (51) (Xie et al, 2012), tomentosin (52) and 4H-tomentosin (53) (Kim et al, 2004) were isolated from Carpesium species. These compounds 49 À 53, which are regarded as secoregular bi-cyclic sesquiterpenoids, can be biologically synthesised from the guaiane carbon skeleton by a ring opening at C-4 and C-5.…”