Melaleucadines A and B: Two rare benzylic phloroglucinol-terpene hybrids from Melaleuca leucadendron

Abstract Melaleucadines A and B ( 1 and 2 ), two rare benzylic phloroglucinol-terpene hybrids (meroterpenoids), have been isolated and identified from the branches and leaves of the Australian “tea tree” Melaleuca leucadendron L. Their structures including absolute configurations were determined by 1D/2D NMR, HR-MS, and the CD exciton chirality method. Compound 1 was a hybrid of a benzylic phloroglucinol and rearranged β-pinene via a rare 2,3,4,5-tetrahydrooxepine ring, and 2 was the adduct of a benzylic phloroglucinol and a humulene-type sesquiterpene via an oxa-heterocycle. Bioactivity screening revealed that compounds 1 and 2 exhibited neuroprotective effects at a concentration of 50.0 μM.