Gamma-aminobutyric acid and glutamic acid contents, and the GAD activity in germinated brown rice (Oryza sativa L.): Effect of rice cultivars

Abstract

The γ-aminobutyric acid (GABA) and glutamic acid (Glu) contents, and the glutamate decarboxylase (GAD) activity in brown rice (BR) and germinated BR (GBR) of the 5 Thai rice cultivars KDML105, PT1, CN1, SP1, and PL2 were investigated. BR was soaked at 35°C for 12 h and then germinated for 24 h to produce GBR. Amounts of GABA and Glu, and the GAD activity in samples were determined. The GABA content and GAD activity in GBR samples of all cultivars were increased 7–50× and 10–100× over levels in BR. The GABA content in BR had no effect on GABA accumulation in GBR. There was no trend in changes in the Glu content for different cultivars after soaking and germination. Variation in the GABA amount in GBR was due to both the GAD activity and the amount of Glu. These two parameters affected accumulation of GABA in all cultivars.