Syringa oblata Lindl var. alba as a source of oleuropein and related compounds

The leaf methanol extract of Syringa oblata Lindl var. alba was investigated as a source of oleuropein and related compounds. The extract had a high total phenol content and a radical scavenging activity similar to that of the respective extract from Olea europaea leaves. HPLC-DAD characterisation of the two most abundant phenolic compounds in the extract of S. oblata indicated that both had UV spectra matching that of oleuropein. The presence of oleuropein was verified by using LC-MS. Identification of the second compound was only feasible after isolation (preparative HPLC) and spectroscopic characterisation [LC-MS, 1H NMR and homonuclear two-dimensional correlated spectroscopy (COSY)]. The compound identified was the known bioactive syringopicroside. On the basis of MS data other peaks were assigned to oleuropein aglycone, verbascoside, ligstroside and syringopicroside derivatives, as well as to a luteolin rutinoside. The findings are promising for the potential exploitation of S. oblata leaf extract as a source for oleuropein and other bioactive ingredients