Sociedade Brasileira de Espectrometria de Massas – BrMASS
Poster
Mass spectrometry (ESI-MS) analysis of the tocopherols, oryzanol and free fatty acids in rice oil
Vanessa A. Santestevan1 (PG), Gabriela H. Hörnke2 (IC), Elina B. Caramão1
(PQ) e Maria Regina A. Rodrigues1,2* (PQ)
*regina.rodrigues@ufpel.edu.br
1
Lab. de Química Analítica Ambiental e Oleoquímica – LAAO/DI/IQ/UFRGS
– Av. Bento Gonçalves, 9500, Porto Alegre/RS - CEP 91501-970
2
Lab. de Oleoquímica e Biodiesel-LOB/DQO/IQ/UFPel – Campus do Capão
do Leão, s/nº, Pelotas/RS – CEP 96010-900
Rice (Oryza sativa L.) contains high levels of phytochemicals, such as vitamins A
(carotenoids) and E, including the four homologs (, ,  and ) of tocopherols and
tocotrienols, and the fraction -orizanol, which consist of a mixture of ferulic acid
esters of triterpenes alcohols and sterols1,2. Vitamin E and -orizanol are present in the
unsaponificable fraction of rice oil, and fatty acids are in the saponificable fraction.
Methods reported for the quantification for these compounds in rice involve extraction
of rice oil as liquid-liquid phase extraction (LLE), solid phase extraction (SPE),
supercritical fluid extraction (SFE) and direct solvent extraction (Soxhlet)2.
Identification of compounds in rice oil obtained is carried out using gas and liquid
chromatography (GC-MS and HPLC) and recently the liquid-chromatography/mass
spectrometry (LC-MS/MS) is the technique more studied1,3. The aim of this study was
to analysis directly the components of -orizanol, tocopherols and free fatty acids in
rice oil using MS/MS. Integral grains rice were submitted to direct solvent extraction in
a Soxhlet apparatus, with petroleum ether as extractor solvent to obtained rice oil.
Identification of these components was made by negative-ion spectra from
electrospray ionization mass spectrometry (ESI-MS), model MS/MS - Bruker, Esquire
6000. For optimum MS analysis, 10 mM ammonium acetate in methanol was used as
ionization reagent. Conditions for ESI-MS analysis included a capillary voltage of 4037
V, a nebulizing pressure of 33.4 psi, a drying gas flow of 8 mL min-1, and temperature
of 250°C. Samples and standards were analyzed by direct infusion at a flow rate of
0.2 mL min-1, in an automatic MS/MS, with width of the isolation of 4.0, fragmentation
amplitude of 0.40 V and number of parents=1. Stock solutions (10 mg mL-1) were
prepared of rice oil and standards (, , -tocopherols; -orizanol and palmitic, oleic
and linoleic acids) in methanol and work solutions (10 g mL-1) were prepared in 10
mM ammonium acetate/methanol. In rice oil, it was possible to observe deprotonated
molecular ions [M-H]- from -orizanol at m/z 561, 587, 601, 615, 617 and 633,
corresponding to campesterol trans-caffeate, cycloartenol trans-caffeate, cycloartenol
trans-ferulate, 24-methylenecycloartanol trans-ferulate, 24-methylcycloartanol transferulate, 24 or 25-hidroxy-24methylcycloartanol trans-ferulate. Collision-induced
decomposition (CID) of these deprotonated product abundant ions of [M-H-Me]-,
resulting from the loss of a methyl group in the ferulic or caffeic acids moiety. The
deprotonated molecular ions [M-H]- from FFA palmitic, oleic and linoleic were m/z 255,
281 and 279, respectively. Tocopherols were detected with low intensity. The proposed
spectrometric method using ESI in negative mode was more sensitive than positive
mode, according to literature4. Based in the results obtained, the technique is fast,
selective and accurate for simultaneous determination of phytochemicals in rice oil. It
is important to salient that there was not necessary previous treatment of the rice oil.
References
[1] Stöggl, W.; Huck, C.; Wongyai, S.; Scherz, H.; Bonn, G. J. Sep. Sci. 2005, 28, 1712-1718.
[2] Lilitchan, S.; Tangprawat, C.; Aryusuk, K.; Krisnangkura, S; Chokmoh, S.; Krissnangkura, K.
Food Chem. 2008, 106, 752-759.
[3] Fang, N.; Yu, S.; Badger, T. J. Agric. Food Chem. 2003, 51, 3260-3267.
[4] Lanina, S. A.; Toledo, P.; Sampels, S.; Eldin, A. K.; Jastrebova, J. A. J. Chromatogr. A
2007, 1157, 159-170.
3º Congresso BrMass – 12 a 15 de Dezembro de 2009