Development of a GC-MS method and analysis of phenolic acids in fruit and spice matrices and evaluation of their antioxidant capacity

The aim of the present study was to develop a specific and quantitative assay to determine the individual concentrations of naturally occurring phenolic acids and their metabolites in food; then evaluate the antioxidant capacity of the quantified phenolic acids using different assays. A GC/MS method was developed for the quantification of ten commonly present phenolic acids in plant foods. Target analytes were the benzoic acid based phenolic acids - anisic, gallic, p-hydroxy benzoic, o-salicylic, protocatechuic, and vanillic acids, together with the cinnamic acid based phenolic acids - caffeic, p-coumaric, ferulic and sinapinic acids. Deuterated Anisic D7 acid was used as an internal standard to achieve accurate and reliable quantification. Purification was accomplished using C18 solid phase extraction cartridges (ENVI Chrome P, Supelco); sample extracts were derivatized prior to GC-MS analysis using BSTFA and pyridine (4:1 V/V). Resolution and quantification of all compounds were excellent with linear calibration curves over a wide range (0-500 ng/ml) and correlation coefficient (R2) of 0.999. Relative standard deviation (RSD) and response factors (RF) were satisfactory (≥1.1 and >3 respectively) and within the acceptable limits of bioanalytical method validation. The adapted method was applied to different varieties of fresh and sundried Saudi Arabian dates as well as Achacha fruit and eleven selected spices. The results revealed that phenolic acids are present in plant foods mostly in bound form as esters or glycosides. The lipophilic and hydrophilic antioxidant activities of all selected samples were examined using the ORAC assay. In addition, the antioxidant capacity of the identified free and bound phenolic acids was measured by different assays including ORAC, ABTS, DPPH and FCR. The results indicate that hydrophilic antioxidants are higher than lipophilic antioxidants in plant foods and the high phenolic acids content was not correlated with high antioxidant activity. Moreover different antioxidant capacity assays showed different results on the same phenolic acid extracts from different samples (P-value> 0.05). In conclusion the method presented is robust, safe, sensitive and generally applicable to the analysis of free and bound phenolic acids in food samples. The data obtained is sufficiently reliable to be included in food composition databases.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2010

Author dc:creator

• Khojah, Ebtihal

• GC/MS
• Atioxidant capacity
• Phenolic acids metabolites
• Date fruit
• Achacha fruit
• Spices

Statement dc:rights

• open access
• CC BY-NC-ND 3.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by-nc-nd/3.0/au/

Language dc:language

EN

Identifier

https://doi.org/10.26190/unsworks/23607

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/50447