β ‐Triketone Flavanone Hybrids From Corymbia torelliana and Their Anti‐Inflammatory Activity

A first phytochemical study on the unexplored leaves and twigs of Corymbia torelliana led to the isolation of eight β ‐triketone flavanone hybrids ( 1–8 ) and three C ‐methylflavonoids ( 9–11 ), with the eight hybrids comprising four pairs of 7′′‐epimers. Corytorellin A ( 1 ) is a previously undescribed compound. The stereochemistry of known compounds 2–5 , which had not been previously assigned, was determined in the present study; importantly, the configurations of 3 and 4 correct previously proposed structures. For known compounds 7 and 8 , only relative configurations had been reported earlier, whereas their absolute configurations were elucidated in this work. Their structures were established through comprehensive spectroscopic methods, single‐crystal X‐ray diffraction, and electronic circular dichroism (ECD) calculations. Bioactivity assessment revealed that compound 1 possesses significant inhibition of nitric oxide (NO) production in LPS‐stimulated RAW264.7 macrophages (IC 50 = 10.05 ± 0.66 ε M), with the positive control dexamethasone exhibiting an IC 50 of 0.21 ± 0.03 ε M, whereas none of the isolates showed cytotoxicity against A549, HeLa, and HepG2 human cancer cell lines at a concentration of 20.00 ε M.