The proposed method, termed the simple flow injection (FI)-spectrophotometric method, was developed by researchers at the Mae Fah Luang University, Thailand, and is based on the DPPH free radical inhibition assay.
Writing in Food Chemistry, the research team said that the new method was simple, rapid, accurate and reproducible – when compared with standard analysis methods such as the full DPPH assay and ORAC analysis.
“The proposed FI method was simple, consumed less reagent and produced less waste. It has shown to overcome the major drawbacks of the batch method and still provide accurate and precise results,” said the researchers, led by Dr Siripat Suteerapataranon from Mae Fah Luang.
“The developed method would be useful in antioxidants screening of large number of samples, and for quality control of antioxidants in raw materials and finished products in a production environment,” they explained.
The research team explained that the flow injection spectrophotometric system was developed based on the colour disappearance due to the scavenging of 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical by antioxidant compounds. The effects of the DPPH concentration, flow rate, and reaction coil length on sensitivity were studied to find optimised conditions for the analysis.
“To determine the accuracy of the proposed method, the optimized FI-spectrophotometric system was employed to determine the antioxidation capacity of the herbal extract samples. The results obtained were compared to those obtained by using the standard batch method,” explained the researchers.
Ascorbic acid was used as the standard antioxidant in the comparisons, and thus the antioxidant capacity was calculated as ascorbic acid equivalent (AAE), they added.
Suteerapataranon and her colleagues noted that the antioxidation capacity obtained by the FI-spectrophotometric method statistically agreed with results obtained by standard methods, “although the batch method gave a bit higher antioxidation capacity in some samples,” they said.
“One of the advantages over the standard batch method was that the antioxidant capacity was calculated through the absorbance decrease so it is independent of initial absorbance of DPPH solution rather than the percentage of consumed radical ... This allowed the use of a higher concentration of DPPH than specified in the manual method and resulted in higher sensitivity than the batch method,” said the team.
Source: Food Chemistry
Published online ahead of print, doi: 10.1016/j.foodchem.2011.10.066
“Rapid antioxidant capacity screening in herbal extracts using a simple flow injection-spectrophotometric system”
Authors: N. Mrazek, K. Watla-iad, S. Deachathai, S. Suteerapataranon