Page 418 - Biosystems Engineering

Phenolic Substances fr om Olives & Olive Mill Pr oducts 395

– caffeic Alcohol phenols – tyrosol
– cinnamic – hydroxytyrosol
– p-coumaric
– o-coumaric
– 3, 4-di-hydroxyphenylacetic
Acid phenols – ferulic – apigenin
– gallic – cyanidin flavone
– p-hydroxyphenylacetic – anthocyanin
– 4-hydroxybenzoic Flavonoids – luteolin
– protocatechuic – luteolin-7-glucoside
– vanillic – quercetin

– catechol
– oleuropein
– demethyloleuropein – 4-methyl-catechol
Secoiridoids Others – p-cresol
– verbascoside – resorcinol
– ligustroside
– nüzhenide
FIGURE 14.2 Major phenol substances present in the olives and relative olive mill
products.

Polyphenols present in the olives are generally water soluble. Due
to their chemical characteristics and partition coefficients, higher quan-
tities of polyphenols are found in the aqueous phase than in the oil. In
addition, olive phenol substances are numerous and variable and can
be free or bound to other substance to form complex molecules.
The major olive polyphenols are listed in Fig. 14.2, and their for-
mulas appear in Figs. 14.3 and 14.4.
It is known from long time that the principal phenolic compound
present in the green parts of the olive tree, including the fruit and the
leaves, is oleuropein (Panizzi et al. 1960).
Oleuropein belongs to a specific group of complex molecules
called secoiridoids.
Olive tree secoiridoids are typically composed of a glycoside,
phenol, and elenolic acid. Similar oleuropein secoiridoids are abun-
dant also in other Oleaceaes, Gentianales and Cornales, and in many
other plants. In the plant, generally, secoiridoids are produced from
the secondary metabolism of terpenes, as a precursor of various alka-
loids (Soler-Rivas et al. 2000).
The glycoside bound to the elenolic acid forms the oleoside, while
the elenolic acid bound with a phenol forms the aglycone. Oleuropein
is an ester of the 3’,4’-dihydroxyphenyl-ethanol (hydroxytyrosol)
with the oleoside formed by elenolic acid and glucose.
Other important secoiridoids are demethyloleuropein and ligus-
troside, containing tyrosol, and verbascoside, containing hydroxyty-
rosol and caffeic acid (Ragazzi et al. 1973; Bianchi and Pozzi 1994).
Recently, a new complex phenolic compound, called nüzhenide, was