Food Chemistry 129 (2011) 291–296
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Food Chemistry
journal homepage: www.elsevier.com/locate/foodchem
Oleuropein/ligstroside isomers and their derivatives in Portuguese
olive mill wastewaters
Susana M. Cardoso a,b,⇑, Soraia I. Falcão b, António M. Peres b,c, Maria R.M. Domingues d
a
CERNAS – Escola Superior Agrária, Instituto Politécnico de Coimbra, Bencanta, 3040-316 Coimbra, Portugal
CIMO – Escola Superior Agrária, Instituto Politécnico de Bragança, Campus de Sta. Apolónia, 5301-855 Bragança, Portugal
c
LSRE – Escola Superior Agrária, Instituto Politécnico de Bragança, Campus de Sta. Apolónia, 5301-855 Bragança, Portugal
d
Centro de Espectrometria de Massa, QOPNA, Departamento de Química, Universidade de Aveiro, 3810-193 Aveiro, Portugal
b
a r t i c l e
i n f o
Article history:
Received 19 September 2010
Received in revised form 7 March 2011
Accepted 18 April 2011
Available online 24 April 2011
Keywords:
Phenolic compounds
Biophenols
Olive mill wastewaters
Oleuropein
Ligstroside
a b s t r a c t
Olive mill wastewaters (OMW) are a potential source of biophenols, but they have a complex composition
with many unknown phenolics. The analysis of purified methanol extracts from two Portuguese OMW by
electrospray mass spectrometry in the negative mode showed [MH] ions at m/z 539 and m/z 523, corresponding respectively to oleuropein and ligstroside isomers which contain the glucose unit linked to its
aromatic moiety. Also, the fragmentation pathway of the [MH] ions at m/z 863, 685 and 847 indicated
the presence of a diglucoside derivative of the oleuropein isomer and of mono- and diglucosides of the
ligstroside isomer, respectively. Moreover, the two OMW samples contained an elenoic derivative of
the ion at m/z 685 and a degradation product (m/z 453) of the [MH] ion at m/z 523. Future studies
focusing on the abundance of these compounds on OMW, as well as their bioactivities, will determine
their possible industrial exploitation.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
Olea europaea L. is known to contain phenolic compounds
which exhibit important biological properties including antioxidant, anti-inflammatory, antimicrobial, cardioprotective, hypoglycemic and anticarcinogenic (Obied, Bedgood, Prenzler, & Robards,
2007). In particular, the olive fruit is rich in the secoiridoids oleuropein, demethyloleuropein, ligstroside, and in their hydrolytic
derivatives, such as oleuropein aglycones, oleoside-11-methyl ester, elenoic acid, hydroxytyrosol and tyrosol (Fig. 1) (Esti, Cinquanta, & La Notte, 1998; Mulinacci et al., 2001; Romani,
Mulinacci, Pinelli, Vincieri, & Cimato, 1999; Savarese, De Marco,
& Sacchi, 2007). It also contains appreciable amounts of flavonol
glucosides, such as rutin and luteolin-O-7-glucoside and of some
hydroxycinnamic acids derivatives, with the predominance of verbascoside (Esti et al., 1998; Mulinacci et al., 2001; Romani et al.,
1999; Savarese et al., 2007).
Abbreviations: OMW, olive mill wastewaters; MS, mass spectrometry; ESI,
electrospray ionization; HPLC, high-performance liquid chromatography; ESI-MSn,
electrospray ionization-tandem mass spectrometry; CID, collision-induced dissociation; PME, purified methanol extract.
⇑ Corresponding author at: CERNAS – Escola Superior Agrária, Instituto Politécnico de Coimbra, Bencanta, 3040-316 Coimbra, Portugal. Tel.: +351 239 802940;
fax: +351 273 239 802979.
E-mail address: [email protected] (S.M. Cardoso).
0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.foodchem.2011.04.049
Enzymatic and/or chemical reactions occurring along the olive
oil extraction process result in several modifications of the phenolic compounds. The hydrolysis of the glycosidic bonds and the
opening of secoiridoids ring are commonly reported (Caruso,
Colombo, Patelli, Giavarini, & Galli, 2000; Obied, Bedgood, et al.,
2007). Also, as the partition coefficient (oil/water) of most of these
phenolic compounds are in favour of the water phase (Rodis,
Karathanos, & Mantzavinou, 2002), only 2% of the total phenolic
content of the olive fruit passes to the oil phase, while the remaining 98% is lost in the olive mill waste (Rodis et al., 2002).
Olive mill wastewaters (OMW) are the effluent generated in
the olive oil extraction industry operating in three-phases mode.
This by-product is produced in huge amounts (6–7 million tons/
year) and it is characterized by a strong olive oil smell, an intense
brown to dark colour, a pH between 3 and 6 and a strong organic
pollutant load due to the presence of biodegradable and recalcitrant compounds (Ginos, Manios, & Mantzavinos, 2006; Paredes,
Cegarra, Roig, Sanchez-Monedero, & Bernal, 1999). The phytotoxicity of the olive mill wastewaters is mainly attributed to their
high phenolic content (0.5–24 g/l) (Casa et al., 2003; Lanciotti
et al., 2005). On the other hand, attending to the potential
health-benefits of these phenolic compounds, OMW are now regarded as a potent source of natural antioxidants (FernándezBolaños, Rodríguez, Rodríguez, Guillén, & Jiménez, 2006; Obied,
Prenzler, & Robards, 2008).