Isolation and structure determination of piptocarphins A-F, cytotoxic germacranolide lactones from Piptocarpha chontalensis

Abstract

Six novel sesquiterpenes, piptocarphins A-F, were isolated from Piptocarpha chontalensis Pall Their structures were elucidated as a series of closely related germacranolide sesquiterpene lactones possessing an unusual conjugated enol lactone and an intramolecular hemiketal functionality on the basis of an extensive spectral analysis. All compounds exhibited cytotoxic activity against the 9KB human nasopharynx carcinoma cells. Piptocarphins A and C also showed borderline activity in the P-388 lymphoid leukemia system.

Chemical Constituents, Antiproliferative and Antioxidant Activities of Vernonanthura nudiflora (Less.) H. Rob. Aerial Parts

“…Structural elucidation of 8α-tigloyloxy-10α-hydroxyhirsutinolide (9) (Table 1) were very similar to those reported for piptocarphins A (6), B (7) and D (8) 40 and as it is characteristic for hirsutinolides derivatives, the 1 H NMR spectrum exhibited broad signals. 41 The 13 , all these signals corroborate the skeleton of a hirsutinolide-type sesquiterpene.…”

“…41 The 13 , all these signals corroborate the skeleton of a hirsutinolide-type sesquiterpene. 40,42,51 In addition, the 1 H and 13 C NMR spectra showed an olefinic signal at d H 7.06 (q, J 7. (Figure 2).…”

“…Compounds 1 to 5 were identified as the pentacyclic triterpenes, lupeol (1), α-amyrin (2), β-amyrin (3), taraxasterol (4) and pseudotaraxasterol (5). 39 Compounds 6 to 8 were identified as the known hirsutinolide sesquiterpene lactones, piptocarphins A (6), B 7, D (8) 40 (Table 1), while compound 9 was identified as the new hirsutinolide derivative, 8α-tigloyloxy-10α hydroxy-hirsutinolide ( Table 1). The configuration for these hirsutinolides was established by comparing the chemical shifts and the coupling constants.…”

Analysis and fragmentation mechanisms of hirsutinolide‐type sesquiterpene lactones by ultra‐high‐performance liquid chromatography/electrospray ionization linear ion trap Orbitrap mass spectrometry

“…[37] Following the same rationale, the MS/MS spectrum of compound C ([M+Na] + at m/z 459) lost mainly a C 5 H 8 O 2 molecule from the R 2 position then an acetyl group, giving rise to an ion at m/z 299. This peak could correspond to two previously isolated compounds, the hirsutinolide piptocarphin B bearing a tiglate ester at C-8 [38] or its C-1 epimer isolated from Vernonanthura squamulosa (see proposed structures in Fig. 3).…”

Antimalarial Activity of Sesquiterpene Lactones from Vernonia cinerea

“…Three further known lactones: 8a-epoxymethacryloyloxy-hirsutinolide-13-O-acetate 2, hirsutinolide-13-O-acetate 5 and piptocarphin D 6, described here for the first time in this plant, have been identified by comparison of their spectroscopic data with those published in the literature. [8][9][10][11][12][13][14] Vernolide C 4 was shown to be a chlorinated compound according to the typical cluster of ions in the mass spectrum at m/z 481 and 483; high resolution analysis of these ions as well as matching of isotopes allowed the composition to be determined as C 21 15) Detailed examination of the chemical shifts and long range CH correlations confirmed that the compound belonged to the hirsutinolide series with a proton onto C-10. That the hydrochlorination had taken place on the epoxide was shown by the presence of an AB quartet featuring H-3Ј of the ester side chain; all of the expected CH couplings be- Two new sesquiterpene lactones, vernolides C and D as well as six known ones were isolated from the dichloromethane fraction of an aqueous extract from Vernonia cinerea.…”