Phloroglucinol derivatives from Eucalyptus camaldulensis Dehnh: Quantitative and qualitative analysis by NMR and antibacterial evaluation

Phloroglucinol derivatives constitute an important class of bioactive secondary metabolites found in Eucalyptus species. In the present study, a phloroglucinol-rich fraction was prepared from leaves of Eucalyptus camaldulensis using the hexane fraction of leaves. The enrichment of phloroglucinol derivatives was confirmed by 1H NMR profiling and high-resolution electrospray ionization mass spectrometry (HRESIMS). Quantification of individual phloroglucinol derivatives was achieved using quantitative 1H NMR (qNMR) with 2-ethylphenol as an internal standard. The confirmation of individual compounds was done by HSQC experiment. A total of nine phloroglucinol derivatives were quantitatively analysed in both the enriched fraction and whole leaf material of E. camaldulensis. Furthermore, the crude methanolic extract, hexane fraction, phloroglucinol-rich fraction, and compounds including euglobal Ia2, T1, loxophlebene, and grandinol, were evaluated for their antibacterial activity.