AACC International - 2009 Meeting Abstract - HPLC determination of insoluble phenolic acids in selected Japanese grains: Comparison of photodiode array detector and electro- chemical detector

Meeting Abstract - Poster Presentation

HPLC determination of insoluble phenolic acids in selected Japanese grains: Comparison of photodiode array detector and electro- chemical detector
A. YOSHIDA (1), K. Miyagi (1), H. Ohta (1), S. Hashimoto (1)
(1) Nakamuragakuen University, Fukuoka, AC, JAPAN
Cereal Foods World 54:A73

Epidemiological studies indicate that a high consumption of whole grain products may reduce the risk of chronic disease. These effects have been ascribed to dietary fiber and other constituent, including phenolic acids. In this study, the photodiode array detector (PDA) and electro- chemical detector (ECD) in the determination of insoluble phenolic acids, including p-coumaric acid, ferulic acid and caffeic acid, by high performance liquid chromatography (HPLC) were compared to develop more sensitive method. The grain samples in Japan were used as follows: reddish rice, black rice, unpolished rice, polished rice, foxtail millet, Japanese barnyard millet, grain amaranth, and three wheat flours (soft, medium and hard). Each sample was lyophilized and ground with an Ultra Centrifugal Mill. The ground powder were sieved, and stored at –20°C until analysis. All samples were discarded to remove fat with n-hexane, then soluble components with 80% ethanol. The residue was hydrolyzed with 1M NaOH at room temperature under nitrogen gas. Phenolic acids were extracted with ethyl acetate, and analyzed by PDA-HPLC or ECD-HPLC. The content of ferulic acid by PDA-HPLC was 21.8~2.5 mg/100 g of powder, while those by ECD-HPLC 76.5~1.9 mg/100 g. The content of ferulic acid in black rice by ECD-HPLC increased to 76.5 mg /100 g compared with 21.8 mg/100 g by PDA-HPLC. No caffeic acid was detected by PDA-HPLC, whereas caffeic acid (0.061 mg~0.002 mg/100 g) in all samples was detected by ECD-HPLC. The content of phenolic acids in rice was larger in unpolished rice than polished ones, showing the high content in the rice bran. Phenolic acids (ferulic, p-coumaric and caffeic acid) in whole black rice were predominant, followed by unpolished rice, reddish and ricefoxtail millet. In conclusion, ECD-HPLC was a useful method to investigate the phenolic acids in the grain samples.