An Unknown Acid from Brain Extracts chromatographed on Silica Gel

Abstract

SINCE partition chromatography on silica gel allows the simultaneous quantitative determination of the individual acids of the polycarboxylic acid cycle^1,2, it became of interest to apply this technique to the measurement of the organic acids in brain tissues. Fig. 1 shows the chromatographic pattern of the tertiary amyl alcohol – chloroform (50 per cent v/v) extract of human brain. (Identical patterns were found for these extracts from guinea pigs, mice, rabbits, turtles and chickens.) The first peak of the chromatogram (fractions 15–25), composed of a mixture of free and esterified fatty acids³, was followed by a smaller peak (fractions 40–50) for fumaric acid. Then, there is a large peak (fractions 60–80) representing mainly lactic acid but also small amounts of succinic acid. The lactic acid was identified by measuring the colour produced when concentrated sulphuric acid and P-hydroxydiphenyl were added⁴. The presence of alpha ketoglutarate is often indicated by the presence of a shoulder to the right of this curve.