Quantitative analysis of various B-ring unsubstituted and substituted flavonoids in ten Australian species of Eucalyptus

Flavonoids (in particular unsubstituted B ring flavanones) in Eucalyptus foliage play an important role in mediating animal plant interactions, and there is a need for methods to analyse the diverse profiles found in leaves. A simple, high-performance liquid chromatographic (HPLC) method with in-line connected photodiode-array (PDA) detection was developed and validated to identify and quantify nine B-ring unsubstituted and three B-ring substituted flavonoids in ten Australian species of Eucalyptus. Of these, eight compounds were detected and quantified in the crude methanolic extracts of leaves of various Eucalyptus species (E. sieberi, E. rossii, E. fastigata, E. macrorhyncha, E. fraxinoides, E. agglomerata, E. consideniana, E. pauciflora, E. dives and E. obliqua) based on comparison with the retention times and λmax values of pure compounds. This rapid and sensitive HPLC/PDA method was coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) for qualitative analysis to corroborate the identification of compounds by HPLC/PDA analysis.