Structure of the sesquiterpene lactone artapshinin

Abstract

The new sesquiterpene lactone artapshin isolated from Artemisfragrans Willd., gathered on Apsheron (Azerbaidzhan Republic), has been reported previously [1]. Not one of the sesquiterpene lactones (alchanene, alkhanin, alkhanol, erivanin) characteristic for Artemisia fragrans was detected in this plant material.Continuing the study of the sesquiterpene lactones of this plant material we have isolated a substance with the composition C15H2204 (1), the IR spectrum of which had the absorption band of OH groups (3430 cm -]) of the CO of a 3'-lactone ring (1765 cm-1), and of double bonds (1670, 1640 cm-1). On acetylation, (1) formed a diacetate. The IR spectrum of the diacetate had the bands of a lactone CO (1790 cm-1), of the CO groups of acetyl residues (1735, 1260, 1240 cm-]), and of double bonds (1670, 1650 cm-1). There was no band of hydroxy groups.After having compared the physicochemical properties of the lactone under investigation and its diacetyl derivative, we came to the conclusion that it was new, and for it we have proposed the name artapshinin.In the 1H NMR spectrum of diacetylartapshinin (2) a doublet appeared at 1.18 ppm (J = 7 Hz, 3H, CH3--CH< at I Cll), a broadened singlet at 1.76 ppm (3H, CH3-C=), and singlets at 1.90 and 2.01 ppm (3H each, CH3--C=()). A oneproton broadened singlet at 5.27 ppm and a doublet at 5.36 ppm (J = 2 Hz) showed the presence of an exomethylene group in the molecule of the substance. The signal of a lactone proton was found in the spectrum in the form of a triplet at 4.65 ppm (1H, Jl = J2 = 10 Hz) with a ratio of the intensities of the components of 1:2:1.In view of the presence in the 1H NMR spectrum of signals corresponding to CH 3-CH <, CH 3-C=, and CH2=C-groups, it could be assumed that the compound was based on a germacrane or guaiane carbon skeleton. The choice was made on the basis of the 13C NMR spectrum of the 1diacetate taken with incomplete suppression of spin-spin coupling (offresonance).The spectrum contained 19 signals (Table i), including 4 quartets (CH 3 groups), 4 triplets (CH 2 groups), 6 doublets t I I (CH groups) and 5 singlets (-C-,-C = and-C=()). As can be seen from the .figures given in Table 1, one triplet (at 112.90 I Ippm, JcH = 157.21 Hz) was observed in the spectrum in the region of sp2-hybridized carbon atoms and belonged to the carbon of an exomethylene group. The other triplets, appearing in the region of sp3-hybridized carbon atoms, characterized three ring methylene groups. Thus, with the presence of two double bonds and three cyclic methylene groups, the compound under investigation could only be based on a germacrane carbon skeleton.As we have noted, artapshinin contains two double bonds. One of them is a methylene bond, the second is secondary-tertiary (s, 1.66; 3H and d, 5.3 ppm, J = 10 Hz, 1H). The doublet structure of the signal of the olef'mic proton and the spin-spin coupling constant (SSCC) permitted us to ascribe the C4-C5 position to the secondary-tertiary bond. This point of view was confirmed by the signal of the lactone proton, w...

Cytotoxic Sesquiterpene Lactones of Egyptian Tanacetum santolinoides

“…Nauplii were collected after incubation for 24 h, then kept under the same conditions for another 24 h. Samples (triplicates) were dissolved in DMSO (2 mg /400 μL), then diluted serially and the volume was adjusted to 5 mL with seawater. Nauplii (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) were added to each set of vials containing the samples.…”

“…The present work represents the results of re-investigation of the aerial parts of T. santolinoides. Extraction and subsequent chromatographic fractionation of the chloroform soluble fraction of the methanolic extract yielded a new sesquiterpene lactone (1), isolated for the first time from a natural source, in addition to five known lactones 1α, 3β-dihydroxy-7α,11βH-germacra-4Z,9Z-dien-12,6αolide (2) [5,7], 1α,3β-dihydroxy-9β,10β-epoxy-7α,11βH-germacra-4Z-en-12,6α-olide (3) [5], 1α,3βdihydroxy-7α,11βH-germacra-4Z,10(14)-dien-12,6αolide (4) [5], artapshinin (5) [16][17][18], and 1-epierivainin (6) [19] (for spectral characterization see supplementary data). The sesquiterpene lactones 2-5 were previously isolated from the same plant, while compound 6 from T. santolinoides is reported here for the first time.…”