Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system of mammals and plays an important role in the suppression of neurons’ excitability. GABA is formed from the decarboxylation of glutamic acid (Glu), and both GABA and Glu could be considered as important biologically active food components. In the current study, we validated a HPLC method for concomitant detection of GABA and Glu in plant samples after derivatization with dansyl chloride. The validated method had high precision and a high recovery rate and was successfully used for GABA and Glu quantification in 55 plant foods (fruits, vegetables, legumes, cereals, pseudocereals, and nuts) and 19 medicinal plants. Vegetables were the most important dietary source of these amino acids, with the highest quantity of GABA found in potatoes—44.86 mg/100 g fresh weight (FW) and yellow cherry tomatoes—36.82 mg/100 g FW. The highest amount of Glu (53.58 mg/100 g FW) was found in red cherry tomatoes. Analyzed fruits were relatively poor in GABA and Glu, and European gooseberry was the richest fruit with 13.18 mg/100 g FW GABA and 10.95 mg/100 g FW Glu. Cereals, pseudocereals, nuts, and legumes contain much higher amounts of Glu than GABA. The obtained results enrich the available information on the content of gamma-aminobutyric and glutamic acids in plant foods and could be used for the development of GABA-enriched functional foods.

The present study investigates the effect of the addition of medicinal plants, such as lady’s mantle, lavender, rosehip, and meadowsweet, on the chemical composition, antioxidant activity, and color intensity of ready-to-drink aronia nectar during pasteurization and long-term storage. Pasteurization caused a significant decrease in anthocyanin content of aronia nectar, which reduced to 20% of the initial value after four months of storage. Herbs provided different protection to aronia anthocyanins that degraded more slowly during the four-month storage compared to pasteurized control without herbs. The addition of medicinal plants enriched aronia nectar with phenolic compounds and increased its antioxidant activity by up to 52% in meadowsweet-aronia nectar. Moreover, it was accompanied by a color intensity magnification due to co-pigmentation of aronia anthocyanins and herbal phenolics. In contrast to anthocyanins, which constantly degraded during the whole period, color intensity began to stabilize after 30 days, demonstrating that co-pigmentation was progressively established during the time and rosehip provided the best stabilization of aronia nectar color. Current research demonstrates for the first time that medicinal plants such as lady’s mantle, rosehip, and especially meadowsweet can be used to increase antioxidant activity, color, and anthocyanin stability of black chokeberry functional beverages.

This study investigated the effects of germination on gamma-aminobutyric acid (GABA), free sugars, organic acids, polyphenols, protein content, and antioxidant activity in six legumes (mung beans, Dobrudzha beans, white beans, brown lentils, red lentils and chickpeas). Seeds were germinated for 5 days at room temperature, with or without an initial freezing pretreatment at −18 °C for 20 h. Daily analysis revealed significant increases in GABA across all legumes, especially chickpeas, which showed an 18-fold rise to 210.5 mg/100 g dry weight (DW), alongside elevated glutamate decarboxylase activity. Total polyphenols increased 3.4-fold in white beans and chickpeas by day five. Antioxidant activity (ORAC) rose in parallel, reaching 123.8 and 83.3 µmol TE/g DW in germinated white beans and chickpeas, compared to 68.4 and 45.4 µmol TE/g DW in non-germinated controls. While protein content remained stable, levels of free sugars (notably maltose) increased during germination. Organic acids rose across all samples as well, with quinic acid being the most abundant and showing the sharpest increase. Initial freezing had a clear effect on enhancing GABA accumulation compared to non-treated seeds, but generally exerted neutral effects on other bioactive components. Overall, germination triggered biochemical transformations in seeds, enriching them with bioactive compounds and enhancing their nutritional and functional properties, with chickpeas emerging as a particularly rich source of GABA, polyphenols, and organic acids, supporting their potential in functional food development.

Polyphenols and gamma-aminobutyric acid (GABA) are diet-derived bioactive compounds with distinct yet complementary health benefits. Polyphenols exert strong antioxidant and anti-inflammatory effects, whereas GABA serves as an inhibitory neurotransmitter that supports neurological balance. Functional beverages enriched with both compounds based on fruits, vegetables, and herbs, therefore, hold considerable potential for promoting health. However, formulating such products presents substantial challenges. Fruits, vegetables, and herbs are typically rich in polyphenols but low in GABA, while GABA-rich foods often contain minimal polyphenols. Analysis of available data on the polyphenol and GABA content of such beverages revealed substantial variability, underscoring the need for greater standardization. To provide a clearer framework for this review, functional beverages were defined as effective sources of these bioactives if they deliver at least 200 mg of GABA and 500 mg of polyphenols per single daily serving. However, none of the reviewed studies met both criteria, highlighting the need for an integrated approach to develop beverages capable of supplying meaningful amounts of each compound. While fermentation, particularly with lactic acid bacteria, can substantially increase GABA levels, selecting antioxidant-rich fruits and herbs naturally high in polyphenols remains essential. Together, these approaches offer a viable pathway for creating multifunctional beverages with enhanced health value and may help meet the growing demand for natural, functional, health-promoting products.

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the vertebrate central nervous system, known for its role in promoting sleep, reducing anxiety, regulating blood pressure, and modulating stress, cognition, and behavior. Microbial fermentation offers an effective method for GABA production, with certain lactic acid bacteria (LAB) strains recognized as efficient producers. This study assessed the GABA-producing potential of 31 LAB strains, including isolates from traditional Bulgarian foods and plants. The strains were cultivated in an MRS medium supplemented with 1% monosodium glutamate (MSG), and GABA production was quantified using HPLC after derivatization with dansyl chloride. Most strains produced between 200 and 300 mg/L of GABA. However, Levilactobacillus brevis NCTC 13768 showed much higher productivity, reaching 3830.7 mg/L. To further evaluate its capacity, L. brevis NCTC 13768 was cultivated for 168 h in MRS medium with and without MSG. Without MSG, GABA production peaked at 371.0 mg/L during the late exponential phase. In contrast with MSG, GABA levels steadily increased, reaching 3333.6 mg/L after 168 h. RT-qPCR analyses of the glutamic acid decarboxylase (GAD) system showed that the genes of glutamate decarboxylase (gadB), glutamate-GABA antiporter (gadC), and transcriptional regulator (gadR) are significantly overexpressed when the culture reaches the late stationary phase of growth (96 h after the beginning of cultivation). These results identify L. brevis NCTC 13768 as a high-yield GABA producer, with potential applications in the production of fermented functional foods and beverages.