Evaluation of GABA and GA Content in Cereals (Wheat, Spelt, Barley, Millet) Undergoing Germination

Introduction: Gamma-aminobutyric acid (GABA) serves as the primary inhibitory neurotransmitter in the mammalian central nervous system, regulating neuron excitability. GABA is synthesized from glutamic acid (GA) through decarboxylation, catalyzed by the enzyme glutamic acid decarboxylase. Consumption of GABA-enriched foods is related to numerous health benefits and augmenting GABA levels in foods and particularly in seeds is an interesting and challenging task. The aim of this study was to investigate GABA and GA content in cereals (wheat, spelt, barley, millet) during soaking and germination, both with and without the application of cold stress.

Methods: Cereals were purchased from a local market (Plovdiv, Bulgaria) and GABA and GA contents were determined by HPLC after derivatization with dansyl chloride. Germination was followed for 4 days without the application of cold stress or after stress at -18°C.

Results: Wheat accumulated the highest content of GABA on the third day of germination reaching 25.9mg/100g DW, compared to 8.6mg/100g DW in the non-germinated control. Germination increased GABA in all other cereals, reaching 13.9mg/100g DW in spelt, 8.8mg/100g DW in barley and 8.3mg/100g DW in millet. Severe cold stress at -18°C was less conducive to GABA formation and did not result in a further GABA increase. Interestingly, GA levels were notably higher than the GABA content, with wheat containing the highest amount: 130.3mg/100g DW of GA.

Conclusion: The investigated cereals are capable of producing sufficient amounts of GABA after soaking and germination. The data indicate an insignificant difference between the non-stressed and stressed groups, suggesting that the application of cold stress in these cultures may be redundant. These optimistic results inspire further research to enhance GABA yields from natural food sources for nutritional supplements and functional foods.

Acknowledgments: Financial support from the National Science Fund of Bulgaria, Grant № KП-06-Н71/4 from 15.12.2023, is gratefully acknowledged.