Isolation, chemotaxonomic significance and cytotoxic effects of quassinoids from Brucea javanica.

A new quassinoid, bruceene A (1) along with seventeen known quassinoids (2-18) was isolated from the fruits of Brucea javanica. The structure of 1 was elucidated by extensive spectroscopic methods, and was further confirmed by single-crystal X-ray diffraction analysis. Isolation of similar quassinoids 1-3 as those in genus Ailanthus from genus Brucea, indicated the close chemotaxonomic relationship between these two genera, which further supported the phylogenetic study by DNA analysis. Compounds 5, 7, 10 and 12 with a 3-hydroxy-3-en-2-one moiety showed potent inhibitory activities against the MCF-7 and MDA-MB-231 cells with IC50 values in the ranges 0.063-0.182 µM and 0.081-0.238 µM, respectively; while glycosidation at 3-OH significantly decreased the cytotoxicity. It was also found that the most potent compound 7 induced apoptosis in MCF-7 cells via the intrinsic mitochondrial apoptotic pathway.

Brusatol.

The title compound, C(26)H(32)O(11), is composed of an α,ß-unsaturated cyclo-hexa-none ring (A), two cyclo-hexane rings (B and C), a six-membered lactone ring (D) and tetra-hydro-furan ring (E). Ring A exists in a half-chair conformation with a C atom displaced by 0.679 (2) Šfrom the mean plane through the remaining five atoms. Ring B exists in a normal chair conformation. Both rings C and D exist in a twisted-chair conformation due to the O-atom bridge and the carbonyl group in rings C and D, respectively. Ring E shows an envelope conformation with a C atom displaced by 0.761 (1) Šfrom the mean plane through the remaining five atoms. The ring junctions are A/B trans, B/C trans, C/D cis and D/E cis. An intra-molecular O-H⋯O hydrogen bond occurs. In the crystal, O-H⋯O hydrogen bonds involving the hy-droxy, lactone and ester groups and C-H⋯O inter-actions are observed.

14,15-Didehydro-hellebrigenin.

The title compound, C(24)H(30)O(5), is the didehydro product of the steroid hellebrigenin (systematic name: 3ß,5,14-trihy-droxy-19-oxo-5ß-bufa-20,22-dienolide). It consists of three cyclo-hexane rings (A, B and C), a five-membered ring (D) and a six-membered lactone ring (E). The stereochemistry of the ring junctions are A/B cis, B/C trans and C/D cis. Cyclo-hexane rings A, B and C have normal chair conformations. The five-membered ring D with the C=C bond adopts an envelope conformation. Lactone ring E is essentially planar with a mean derivation of 0.006 (4) Šand is ß-oriented at the C atom of ring D to which it is attached. There is an O-H⋯O hydrogen bond in the mol-ecule involving the hy-droxy groups. In the crystal, O-H⋯O hydrogen bonds link the mol-ecules into chains propagating along [010]. The chains are linked by C-H⋯O contacts into a three-dimensional network.