A cytotoxic triketone–phloroglucinol–bullatenone hybrid from Lophomyrtus bullata

Abstract

Cytotoxic activity against the P388 cell line was seen in a crude extract of the New Zealand shrub Lophomyrtus bullata (Myrtaceae). Bioactivity-guided isolation led to a compound with NMR spectra complicated by the presence of two isomers. These crystallised together and an X-ray structure showed them to be stereoisomeric hybrids of triketone, phloroglucinol and bullatenone units. NMR measurements on the mixed isomers, as well as a cyclic ether produced from them by acid catalysed dehydration, were consistent with these structures. The natural products, named bullataketals A and B, have cytotoxic activity against the P388 cell line (IC₅₀ 1 µg ml⁻¹), and antimicrobial activity against Bacillus subtilis.