Eurobusones A-D, four antibacterial formyl phloroglucinol meoterpenoids from Eucalyptus robusta

Camaldulensals A–C, the First Meroterpenoids Possessing Two Spatially Separated Formyl Phloroglucinols Conjugated to a Terpene Core from the Leaves of Eucalyptus camaldulensis Dehnh

“…A small number of FPCs have previously been tested at independent laboratories and shown to possess comparable antibacterial activities (for example macrocarpals A and C/G). However, a recent study has reported antibacterial activities as MIC 50 (in μg/mL) and this resulted in macrocarpals A and B and eucalyptal A and the positive control caiprofloxacin being reported with activities 10 to 100-fold more potent than the those reported using the more generally accepted measure of MIC. ,,, Consequently, the activities of all compounds reported by Liu et al 2022 have been shifted by an order of magnitude to make for more meaningful comparisons . Furthermore, we have recently developed a tool to check the validity of NMR assignments for FPCs and the structures of the four new compounds eurobusones A–D, reported by Liu et al 2022 are questionable since their NMR data poorly matches with that predicted for their substructure classes .…”

“…18,20,31,32 Consequently, the activities of all compounds reported by Liu et al 2022 have been shifted by an order of magnitude to make for more meaningful comparisons. 18 Furthermore, we have recently developed a tool to check the validity of NMR assignments for FPCs 33 and the structures of the four new compounds eurobusones A−D, reported by Liu et al 2022 are questionable since their NMR data poorly matches with that predicted for their substructure classes. 18 Unfortunately, this article provided no supporting NMR spectra.…”

“…Over 200 FPCs have been reported to date. , FPCs exhibit a wide range of biological activities, including granulation inhibition, combating bacterial, fungal, protozoan, , and viral infections, binding to TRH receptors-2 in rats, and cell toxicity properties. , Additionally, FPCs also act as feeding deterrents for both mammals and insects. , The majority of FPCs are phloroglucinol–meroterpenoids containing formyl or acyl moieties attached to the phloroglucinol core and conjugated to either mono- or sesquiterpenes. Most FPCs have been reported from Eucalyptus species with smaller numbers reported from Psidium , Rhodomyrtus , and Eugenia species. − Eucalyptus species are dominant features of the Australian landscape and are found across all habitat zones. Eucalypt forests cover 101 million hectares of the Australian landscape.…”

“…18 Furthermore, we have recently developed a tool to check the validity of NMR assignments for FPCs 33 and the structures of the four new compounds eurobusones A−D, reported by Liu et al 2022 are questionable since their NMR data poorly matches with that predicted for their substructure classes. 18 Unfortunately, this article provided no supporting NMR spectra. This makes it impossible to assess the validity of the authors interpretation of their NMR data, and so the structures of these compounds and their activities must be interpreted with caution.…”