Formyl Phloroglucinol Meroterpenoids From the Fruits of Eucalyptus globulus

Two formyl phloroglucinol meroterpenoids, namely eurobusone E-F (1 and 2), along with one simple phloroglucinol derivative, 1-(2,4-dihydroxy-6-methoxyphenyl)-2-methyl-1-butanone (3), were isolated from the fruits of Eucalyptus globulus. Their chemical structures were elucidated by comprehensive spectral analysis, and the absolute configurations were established by electronic circular dichroism calculations. Compound 1 features an unusual carbon skeleton, in which a humulane-type sesquiterpene is linked to a phloroglucinol core via a dihydropyran ring. These isolates were evaluated in antimicrobial screening, with compounds 1 and 2 demonstrating moderate antibacterial activities against Staphylococcus aureus, both exhibiting minimum inhibitory concentration values of 16 µg/mL.