H-1 NMR study of phenolics in the vegetation water of three cultivars of Olea europaea: Similarities and differences

In this work free phenolics and phenolic glucosides present in the water content (vegetation water, VW) of olive fruits of the three Italian cultivars (cvs.) Cipressino, Dritta, and Leccino were identified by H-1 NMR. The phenolic metabolite content of the three cultivars was studied at three fruit growth stages. The major phenolic compounds, common to all three cultivars, were 4-hydroxyphenylethanol (tyrosol) (1), 4-hydroxyphenylethanol glucoside (2), and oleuropein (3). Considerable differences in the content of compounds (1-3) were found to occur in the fruits during growth and maturation of the drupe. Glucoside (4), a major component of the low molecular weight solutes of Dritta and Leccino cvs., was not detected in Cipressino fruits. The quinol glucoside (4) was thought to derive from oxidation of the glucoside of 4-hydroxyphenylethanol (2). Hydrolysis of (4) followed by cyclization yielded the bicyclic compound halleridone (5).