Discriminative analysis of free and esterified gallic acids in acorn shells by thermochemolysis-gas chromatography/mass spectrometry in the presence of organic alkalis

作者：Ishida Yasuyuki^*; Hirota Tetsuya; Sato Shiho; Kamegai Masayuki; Kim Si Kyung; Park Song Yi; Koo Da Hee; Shon Myung Soo; Kim Gyo Nam; Park Hae Ryong; Lee Seung Cheol

来源：Journal of Analytical and Applied Pyrolysis, 2015, 116: 114-119.

DOI：10.1016/j.jaap.2015.09.019

• Acorn shell
• Gallic acid
• Thermochemolysis
• Tetramethylammonium hydroxide
• Tetramethylammonium acetate
• Antioxidant activity

The presence of phenolic compounds, possessing outstanding antioxidant activity corresponding to ascorbic acid, in wasted acorn shells was revealed by means of thermochemolysis-gas chromatography/mass spectrometry (thermochemolysis-GC/MS) in the presence of organic alkalis. The chromatogram of intact acorn shell samples obtained by thermochemolysis-GC/MS using tetramethylammonium hydroxide (TMAH) showed a strong peak of 3,4,5-trimethoxybenzoic acid methyl ester. This product was also clearly observed on the chromatograms of the methanol and water extracts from the acorn shells, indicating that 3,4,5-trimethoxybenzoic acid methyl ester was derived from free and/or esterified gallic acids through the thermochemolysis reaction. Based on the peak intensities, the contents of gallic acid components were determined as ca. 27 wt% for the both extracts. Furthermore, the content of free gallic acid was selectively estimated with discriminating from its esterified counterpart by using tetramethylammonium acetate (TMAAc) as a methylating reagent. These results were also correlated with high antioxidant activity of the acorn shell extracts evaluated by a DPPH radical scavenging method.

• 出版日期2015-11