Plants remain one of the most useful sources of novel natural products that reveal themselves to have physiological activity and potential applications in medicine. Researchers at the University of Science, Ho Chi Minh City, Viet Nam, and their colleagues have now isolated and studied two new polyisoprenylated acylphloroglucinols, known as thoreliones A and B, as well as a novel tetracyclic xanthone, oxy-thorelione A, from the bark of the tree Calophyllum thorelii.

The team also identified twelve previously known compounds in this species; all identified using proton nuclear magnetic resonance (NMR) spectroscopy. The team explains that this is the first time a 2,2-dimethyl-3-isopropenylcyclopentyl ring has been found in a natural product.

Tests against standard human tumor cell lines, MCF-7, HeLa, and NCI-H460, revealed moderate cytotoxic activity, which might subsequently be optimized in analogs of the compounds.

• Polyisoprenylated acylphloroglucinols and a polyisoprenylated tetracyclic xanthone from the bark of Calophyllum thorelii,
  Le-Thu T. Nguyen, Hieu T. Nguyen, Matej Barbic, Gabi Brunner, Jörg Heilmann, Hung D. Pham, Duc M. Nguyen, Lien-Hoa D. Nguyen,
  Tetrahedron Lett. 2012, 53(34), 4487–4493.
  DOI: 10.1016/j.tetlet.2012.05.096