The dichapetalins—A new class of triterpenoids

Cytotoxic and natural killer cell stimulatory constituents of Phyllanthus songboiensis

“…The 13 C NMR spectrum of 1 showed 40 signals (Table 1), which supported the presence of a triterpene unit connected with a methylenedioxyphenethyl group through a pyran ring system and a C-26 methoxy group. These spectroscopic characteristics were consistent with 1 being a dichapetalin-type triterpene, based on a 13,30-cyclo-dammarane skeleton, containing a five-membered lactone ring (C-20-C-23) and a phenethyl group linked through a pyran ring at the C-3, C-4, and C-29 positions (Achenbach et al, 1995; Addae-Mensah et al, 1996; Fang et al, 2006; Tuchinda et al, 2008; Weckert et al, 1996). …”

“…A signal for a tertiary spiro carbon at δ 113.3 (C-23) of (+)-acutissimatriterpene A was absent in the 13 C NMR spectrum of 1 , indicating the latter compound to be a non-spiro dichapetalin-type triterpene containing a methylenedioxyphenyl group linked at the C-7′ position, as implied by the HMBC correlations observed between H 2 -29/C-7′, H-2′/C-7′, and H-6′/C-7′ (Figure 2). Comparison of the NMR spectroscopic data of 1 with those of (+)-dichapetalin B (Addae-Mensah et al, 1996) showed the two substances to be structurally similar, except that compound 1 exhibited signals for a methylenedioxyphenyl residue while (+)-dichapetalin B contained a benzene group. In addition, resonances for a methoxy group ( δ C 58.4 and δ H 3.36 s) observed in the NMR spectra of 1 were not apparent in analogous data of (+)-dichapetalin B (Addae-Mensah et al, 1996).…”

“…Comparison of the NMR spectroscopic data of 1 with those of (+)-dichapetalin B (Addae-Mensah et al, 1996) showed the two substances to be structurally similar, except that compound 1 exhibited signals for a methylenedioxyphenyl residue while (+)-dichapetalin B contained a benzene group. In addition, resonances for a methoxy group ( δ C 58.4 and δ H 3.36 s) observed in the NMR spectra of 1 were not apparent in analogous data of (+)-dichapetalin B (Addae-Mensah et al, 1996). This methoxy group was assigned at the C-26 position, as evidenced by the different C-26 chemical shifts for 1 ( δ C 77.2, δ H 3.85 overlapped) and (+)-dichapetalin B ( δ C 67.1, δ H 4.11 m) (Addae-Mensah et al, 1996), and the HMBC correlations observed between the protons of this methoxy group and C-26, H-24/C-26, and H 2 -26/C-27 of 1 (Figure 2).…”

The Dichapetalins - Unique Cytotoxic Constituents of the Dichapetalaceae

“…Chromatographic separation of the acetone extract of the whole roots of D. madagascariensis collected in Ghana afforded dichapetalin A as the major constituent, together with the minor components dichapetalins B -H (Achenbach et al, 1995;Addae-Mensah et al, 1996). A separate collection from the same locality gave dichapetalin A and yet another member of the series, dichapetalin M. The absolute configuration of dichapetalin A (Figure 2), the first in the series to be isolated, was determined by single-crystal X-ray diffraction analysis, and has been established to be 4R,5R,7R,8R,9R,10S,13R,14S,17S,20S,23R,6′S.…”

“…L1210 murine leukaemia cells were extremely sensitive (EC 90 <0.0001µg/ml) while human KB carcinoma and murine bone marrow stimulated with GM-CSF were affected by concentrations four orders of magnitude higher. In vivo tests were also not encouraging (Achenbach et al, 1995;Addae-Mensah et al, 1996). Fang and co-workers further demonstrated selective and significant cytotoxicity in dichapetalins A, I and J (IC 50 = 0.2 -0.5 μg/mL) against the SW626 human ovarian cancer cell line.…”