GABA Accumulation Research Articles

Effect of pH and chlorine concentration of slightly acidic electrolyzed water on the buckwheat sprouts during germination

Previous research found that slightly acidic electrolyzed water (SAEW) promoted the growth of buckwheat sprouts and the accumulation of bioactive γ-aminobutyric acid (GABA), but mechanisms had not been reported. At present study, the effects of pH and available chlorine concentration (ACC) of SAEW on buckwheat sprouts were investigated. It showed that SAEW1 with moderate pH (5.71 ± 0.03) resulted in the highest accumulation of GABA ((113.5 mg/100 g) in comparison with SAEW 2 (pH 5.01 ± 0.05) and SAEW 3 (pH 6.41 ± 0.04) treatments. Moreover, the higher ACC of SAEW was, the more content of GABA it accumulated, which suggested that ACC played an important role during germination of buckwheat. The above results were demonstrated by the investigation of glutamic acid decarboxylase activity during germination of buckwheat. However, it showed that higher ACC of SAEW had adverse impact on the growth of buckwheat sprouts while pH of SAEW had no adverse impact on the growth of buckwheat sprouts. Generally, appropriate pH and ACC of SAEW should be considered in the application of the production of buckwheat sprouts. Practical applications SAEW that had neutral pH (5.0–6.5) and lower ACC (10–30 mg/L) had been used in the production of sprouts. SAEW could promote the dual accumulation of GABA and rutin in tartary buckwheat sprouts. Obtaining the specific parameters of SAEW would beneficial for the most accumulation of these functional components when it is used for sprouts production.

The Role of IP3 in NO-Enhanced Chilling Tolerance in Peach Fruit.

The role of inositol 1,4,5-trisphosphate (IP3) in nitric oxide (NO)-reduced chilling injury (CI) in peach fruit was investigated. The fruit were immersed in sodium nitroprusside (SNP) (NO donor) and neomycin (IP3 inhibitor). Results showed that chilling tolerance was enhanced upon exogenous SNP in postharvest peach fruit. Further, GABA accumulation was stimulated by SNP. The increase in protein expression and activity for enzymes in GABA biosynthesis, including glutamate decarboxylase (GAD), polyamine oxidase (PAO), and amino aldehyde dehydrogenase (AMADH), upon SNP treatment was also observed. Also, the up-regulation of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and ornithine d-aminotransferase (OAT) and the down-regulation of proline dehydrogenase (PDH) were induced by SNP treatment, thereby accelating proline production. Additionally, SNP treatment elevated protein expression and activity of alternative oxidase (AOX). The above effects induced upon SNP were partly weakened by neomycin. Therefore, IP3 mediated NO-activated GABA and proline accumulation as well as AOX, thus inducing chilling tolerance in postharvest peach fruit.

The role of GAD pathway for regulation of GABA accumulation and C/N balance in Synechocystis sp. PCC6803

Synechocystis sp. PCC6803 was engineered by interrupting the α-ketoglutarate decarboxylase (KGD) and overexpressing the glutamate decarboxylase (GAD) pathways to create ∆Kgd, GADox, and GADox/∆Kgd mutants with the aim to enhance GABA accumulation. Supplementation of 20 mM glutamate or 0.5 mM spermidine increased the GABA contents by several folds in engineered strains. Supplementation of glutamate not only increased the GABA accumulation of cells but also improved the growth rates of engineered strains, signifying that the GAD pathway plays a crucial role in maintaining the intracellular glutamate homeostasis in Synechocystis. The high GABA level was detected in GADox/∆Kgd grown in 0.1% glucose-supplemented medium, ~ 240-folds higher than that in WT grown without glucose. Overall results suggested that the optimization of carbon and nitrogen sources was effective in enhancing the GABA accumulation in Synechocystis overexpressing the GAD and lacking the functional KGD pathway. This work provides an insight into the strategy to improve GABA production in cyanobacteria and possibly in plants as well.

Genomic insights into a robust gamma-aminobutyric acid-producer Lactobacillus brevis CD0817

Lactobacillus brevis CD0817, a strain isolated from a healthy adult gut, was currently the most efficient lactic acid bacterial cell factory for gamma-aminobutyric acid. In this study, the complete genome sequence of CD0817 was determined and compared with some related L. brevis genomes. The CD0817 genome consists of one 2,990,570-bp chromosome and four plasmids. The comparative genomic and phylogenetic analysis revealed that L. brevis CD0817 was not very conserved with low GABA-producing L. brevis strains. A significant divergence was that CD0817 harbors only the gadCA operon whereas the low GABA-producing L. brevis strains contain the operon and gadB. The gadB seemed to only marginally contribute to the accumulation of GABA. The high GABA production ability of CD0817 may be associated with its extraordinary genome.

Clinical diagnosis and mutation analysis of four Chinese families with succinic semialdehyde dehydrogenase deficiency

BackgroundSuccinic semialdehyde dehydrogenase (SSADH) deficiency is a rare autosomal recessively-inherited defect of γ-aminobutyric acid (GABA) metabolism. The absence of SSADH, which is encoded by aldehyde dehydrogenase family 5 member A1 (ALDH5A1) gene, leads to the accumulation of GABA and γ-hydroxybutyric acid (GHB). Few cases with SSADH deficiency were reported in China.Case presentationIn this study, four Chinese patients were diagnosed with SSADH deficiency in Tianjin Children’s Hospital. We conducted a multidimensional analysis with magnetic resonance imaging (MRI) of the head, semi quantitative detection of urine organic acid using gas chromatography-mass spectrometry, and analysis of ALDH5A1 gene mutations.Two of the patients were admitted to the hospital due to convulsions, and all patients were associated with developmental delay. Cerebral MRI showed symmetrical hyperintense signal of bilateral globus pallidus and basal ganglia in patient 1; hyperintensity of bilateral frontal-parietal lobe, widened ventricle and sulci in patient 2; and widened ventricle and sulci in patient 4. Electroencephalogram (EEG) revealed the background activity of epilepsy in patient 1 and the disappearance of sleep spindle in patient 2. Urine organic acid analysis revealed elevated GHB in all the patients. Mutational analysis, which was performed by sequencing the 10 exons and flanking the intronic regions of ALDH5A1 gene for all the patients, revealed mutations at five sites. Two cases had homozygous mutations with c.1529C > T and c.800 T > G respectively, whereas the remaining two had different compound heterozygous mutations including c.527G > A/c.691G > A and c.1344-2delA/c.1529C > T. Although these four mutations have been described previously, the homozygous mutation of c.800 T > G in ALDH5A1 gene is a novel discovery.ConclusionSSADH deficiency is diagnosed based on the elevated GHB and 4, 5DHHA by urinary organic acid analysis. We describe a novel mutation p.V267G (c.800 T > G) located in the NAD binding domain, which is possibly crucial for this disease’s severity. Our study expands the mutation spectrum of ALDH5A1 and highlights the importance of molecular genetic evaluation in patients with SSADH deficiency.

24-epibrassinolide pre-treatment alleviates the salt-induced deleterious effects in medicinal pumpkin (Cucurbita pepo) by enhancement of GABA content and enzymatic antioxidants

It is known that epibrassinolide (EBL) plays an important role in the variety of plant developmental processes and adaptation to various environmental stresses. Salt stress is one of the most important environmental problems which limit crop growth and productivity. Here, the effects of EBL pretreatment on amelioration of the adverse effects of salinity were investigated in pumpkin, especially at the establishment stage. For this purpose, uniform-sized seedlings were transplanted to plastic containers containing one-half-strength Hoagland's nutrient solution. EBL was added at 0.1 and 0.01 μM to the hydroponic medium for 5 days before stress. The plants were treated with 40 and 80 mM NaCl for inducing salinity stress. Salt stress reduced the plant growth, calcium and potassium content in leaves and roots, and these detrimental effects were alleviated when plants were pretreated with EBL. Salinity stress caused a significant increase in lipid peroxidation, sodium, and γ-amino butyric acid (GABA) content. EBL pretreatment ameliorated these effects by reducing lipid peroxidation, sodium content and increasing GABA content. The increase in activities of guaiacol peroxidase, catalase, ascorbate peroxidase, and superoxide dismutase was observed under salinity stress. Application of exogenous EBL pretreatment further increased antioxidant enzymes activities. The present work emphasizes the protective role of EBL in the regulation of antioxidant enzymes and GABA accumulation and its possible link in amelioration of stress in plants. This is the first report dealing with EBL effect on GABA content under salt stress.

Nitric oxide, γ-aminobutyric acid, and mannose pretreatment influence metabolic profiles in white clover under water stress.

Nitric oxide (NO), γ-aminobutyric acid (GABA), and mannose (MAS) could be important regulators of plant growth and adaptation to water stress. The application of sodium nitroprusside (SNP, a NO donor), GABA, and MAS improved plant growth under water-sufficient conditions and effectively mitigated water stress damage to white clover. The metabonomic analysis showed that both SNP and GABA application resulted in a significant increase in myo-inositol content; the accumulation of mannose was commonly regulated by SNP and MAS; GABA and MAS induced the accumulation of aspartic acid, quinic acid, trehalose, and glycerol under water deficit. In addition, citric acid was uniquely up-regulated by SNP associated with tricarboxylic acid (TCA) cycle under water stress. GABA specially induced the accumulation of GABA, glycine, methionine, and aconitic acid related to GABA shunt, amino acids metabolism, and TCA cycle in response to water stress. MAS uniquely enhanced the accumulation of asparagine, galactose, and D-pinitol in association with amino acids and sugars metabolism under water stress. SNP-, GABA-, and MAS-induced changes of metabolic profiles and associated metabolic pathways could contribute to enhanced stress tolerance via involvement in the TCA cycle for energy supply, osmotic adjustment, antioxidant defense, and signal transduction for stress defense in white clover.

2-Pyrrolidinone and Succinimide as Clinical Screening Biomarkers for GABA-Transaminase Deficiency: Anti-seizure Medications Impact Accurate Diagnosis

Broad-scale untargeted biochemical phenotyping is a technology that supplements widely accepted assays, such as organic acid, amino acid, and acylcarnitine analyses typically utilized for the diagnosis of inborn errors of metabolism. In this study, we investigate the analyte changes associated with 4-aminobutyrate aminotransferase (ABAT, GABA transaminase) deficiency and treatments that affect GABA metabolism. GABA-transaminase deficiency is a rare neurodevelopmental and neurometabolic disorder caused by mutations in ABAT and resulting in accumulation of GABA in the cerebrospinal fluid (CSF). For that reason, measurement of GABA in CSF is currently the primary approach to diagnosis. GABA-transaminase deficiency results in severe developmental delay with intellectual disability, seizures, and movement disorder, and is often associated with death in childhood. Using an untargeted metabolomics platform, we analyzed EDTA plasma, urine, and CSF specimens from four individuals with GABA-transaminase deficiency to identify biomarkers by comparing the biochemical profile of individual patient samples to a pediatric-centric population cohort. Metabolomic analyses of over 1,000 clinical plasma samples revealed a rich source of biochemical information. Three out of four patients showed significantly elevated levels of the molecule 2-pyrrolidinone (Z-score ≥ 2) in plasma, and whole exome sequencing revealed variants of uncertain significance in ABAT. Additionally, these same patients also had elevated levels of succinimide or its ring-opened form, succinamic acid, in plasma, urine, and CSF and/or homocarnosine in urine and CSF. In the analysis of clinical EDTA plasma samples, the levels of succinamic acid and 2-pyrrolidinone showed a high level of correlation (R = 0.72), indicating impairment in GABA metabolism and further supporting the association with GABA-transaminase deficiency and the pathogenicity of the ABAT variants. Further analysis of metabolomic data across our patient population revealed the association of elevated levels of 2-pyrrolidinone with administration of vigabatrin, a commonly used anti-seizure medication and a known inhibitor of GABA-transaminase. These data indicate that anti-seizure medications may alter the biochemical and metabolomic data, potentially impacting the interpretation and diagnosis for the patient. Further, these data demonstrate the power of combining broad scale genotyping and phenotyping technologies to diagnose inherited neurometabolic disorders and support the use of metabolic phenotyping of plasma to screen for GABA-transaminase deficiency.

AMADH inhibitor optimization and its effects on GABA accumulation in soybean sprouts under NaCl-CaCl2 treatment.

1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide (EDC) was the suitable inhibitor for aminoaldehyde dehydrogenase (AMADH) compared with N-ethylmaleimide (NEE) and iodoacetamide (IAM). EDC exhibited the most obvious inhibition effect on AMADH activity, while its inhibition on glutamate decarboxylase (GAD) was insignificant. Compared with the control, AMADH activity reduced by 70.4% with 0.5mM EDC, and γ-aminobutyric acid (GABA) content declined by 44.3% in soybean sprouts at 4days of germination. AMADH activity reduced by 80.62, 67.61 and 72.02% in the 4-day sprouts with 1mM EDC under NaCl, CaCl2 and NaCl + CaCl2 treatment, respectively, and GABA content decreased by 43.56, 38.84 and 35.53%, respectively. EDC is a proper inhibitor for AMADH and it could be used to quantify the contribution of polyamine degradation pathway on GABA formation. In soybean sprouts, the presence of CaCl2 under NaCl stress decreased the contribution of polyamine degradation pathway on GABA accumulation.

Enhancing Haematococcus pluvialis biomass and γ-aminobutyric acid accumulation by two-step cultivation and salt supplementation

The primary goal of this study was to assess the roles of chemical factors and bioprocess strategies on a mixotrophic culture of the microalga Haematococcus pluvialis during γ-aminobutyric acid (GABA) production. A two-stage strategy was used to increase the biomass and GABA accumulation of H. pluvialis. In stage I, mixotrophic growth of H. pluvialis in the presence of fulvic acid (FA) produced a high biomass (1.84 g L−1) with a GABA content of 25.45 mg g−1. Furthermore, a maximum GABA content of 38.57 mg g−1 was obtained when cells were cultured with 0.4 g L−1 NaCl under photoautotrophic conditions in stage II, whereas the carbohydrate content of cells sharply decreased from 26.68 to 18.22%. In addition, salt stress upregulated the expression of the gad and cam genes. The results of this study demonstrate an efficient strategy to produce GABA from the microalga H. pluvialis.

ITRAQ-based proteomic analysis reveals the accumulation of bioactive compounds in Chinese wild rice (Zizania latifolia) during germination

Polyphenols and γ-aminobutyric acid (GABA) accumulate during seed germination, but the mechanisms involved are poorly understood. The objective of this study was to elucidate the accumulation of these bioactive compounds in Chinese wild rice during germination. The greatest differences in the phenolic content were at 36-h (G36) and 120-h germination (G120) stages. An iTRAQ-based proteomic analysis revealed 7031 proteins, and a comparison of the G120 and G36 stages revealed 956 upregulated and 188 downregulated proteins. The KEGG analysis revealed significant protein enrichment in the “metabolic pathways”, “biosynthesis of secondary metabolites” and “phenylpropanoid biosynthesis”. Four phenylalanine ammonia-lyases, one 4-coumarate-CoA ligase, one cinnamoyl-CoA reductase, two cinnamyl alcohol dehydrogenases, and four glutamate decarboxylases exhibited higher expression at the G120 than at the G36 stage and promoted phenolics and GABA accumulation. This study revealed bioactive compound accumulation in germinating Chinese wild rice, and the finding may help develop functional foods derived from this cereal.

Effects of cyclic cellulase conditioning and germination treatment on the γ-aminobutyric acid content and the cooking and taste qualities of germinated brown rice

A novel method for producing germinated brown rice (GBR) was developed by cyclic cellulase conditioning and germination treatment. Changes in the γ-aminobutyric acid (GABA) content and the cooking and taste qualities of GBR were analysed. The results indicated GABA accumulation reached its highest level under 50 mg/ml cellulase solution treatment for 90 min followed by 32 h germination at 30 °C. The treatment conditions had no significant influence on the cooking or taste qualities of GBR. Correlation analysis showed the taste value of cooked GBR significantly correlated with hardness, springiness, chewiness, and stickiness. The cyclic cellulase conditioning treatment could contribute to improved cooking and taste qualities of GBR and higher GABA content of GBR compared to the soaking treatment. The cooking and taste qualities of GBR were improved by the degradation of the crude fibre of the cortex and the increase in GBR water absorption rate under cyclic cellulase conditioning.

Global Ubiquitome Profiling Revealed the Roles of Ubiquitinated Proteins in Metabolic Pathways of Tea Leaves in Responding to Drought Stress

Drought stress often affects the expression of genes and proteins in tea plants. However, the global profiling of ubiquitinated (Kub) proteins in tea plants remains unearthed. Here, we performed the ubiquitome in tea leaves under drought stress using antibody-based affinity enrichment coupled with LC-MS/MS analysis. In total, 1,409 lysine Kub sites in 781 proteins were identified, of which 14 sites in 12 proteins were up-regulated and 123 sites in 91 proteins down-regulated under drought stress. The identified Kub proteins were mainly located in the cytosol (31%), chloroplast (27%) and nuclear (19%). Moreover, 5 conserved motifs in EKub, EXXXKub, KubD, KubE and KubA were extracted. Several Kub sites in ubiquitin-mediated proteolysis-related proteins, including RGLG2, UBC36, UEV1D, RPN10 and PSMC2, might affect protein degradation and DNA repair. Plenty of Kub proteins related to catechins biosynthesis, including PAL, CHS, CHI and F3H, were positively correlated with each other due to their co-expression and co-localization. Furthermore, some Kub proteins involved in carbohydrate and amino acid metabolism, including FBPase, FBA and GAD1, might promote sucrose, fructose and GABA accumulation in tea leaves under drought stress. Our study preliminarily revealed the global profiling of Kub proteins in metabolic pathways and provided an important resource for further study on the functions of Kub proteins in tea plants.

'Candidatus Liberibacter asiaticus' and Its Vector, Diaphorina citri, Augment the Tricarboxylic Acid Cycle of Their Host via the γ-Aminobutyric Acid Shunt and Polyamines Pathway.

Huanglongbing (HLB), a destructive citrus disease, is associated with 'Candidatus Liberibacter asiaticus', which is transmitted by the Asian citrus psyllid Diaphorina citri. Both 'Ca. L. asiaticus' and its vector manipulate the host metabolism for their benefit, to meet their nutritional needs and neutralize the host defense responses. We used a targeted gas chromatography-mass spectrometry-based method to explore the connection between the tricarboxylic acid (TCA) cycle, γ-aminobutyric acid (GABA) shunt, and polyamines (PAs) pathways in citrus. 'Ca. L. asiaticus' and D. citri accelerated the conversion of α-ketoglutarate to glutamate, then to GABA, causing an accumulation of GABA in the cytosol. In silico analysis showed that the citrus genome possesses a putative GABA permease that connects the GABA shunt with the TCA cycle and supports the accumulation of succinate, fumarate, and citrate. Additionally, the PAs biosynthetic pathway might be connected directly to the TCA cycle, through the production of fumarate, or indirectly, via enhancement of GABA shunt. Taken together, we suggest that GABA shunt and PAs pathways are alternative pathways that contribute to the flux toward succinate rather than an intact TCA cycle in citrus. Both 'Ca. L. asiaticus' and its vector enhance these pathways. This study provides more insights into citrus responses to the HLB pathosystem and could be a further step toward clues for understanding the nutritional needs of 'Ca. L. asiaticus', which could help in culturing 'Ca. L. asiaticus'.

Metabolic responses to elevated pCO2 in the gills of the Pacific oyster (Crassostrea gigas) using a GC-TOF-MS-based metabolomics approach

Rising atmospheric carbon dioxide (CO2), primarily from anthropogenic emissions, are resulting in increasing absorption of CO2 by the oceans, leading to a decline in oceanic pH in a process known as ocean acidification (OA). There is a growing body of evidence demonstrating the potential effect of OA on the energetics/physiology and consequently life-history traits of commensally important marine organisms. However, despite this little is known of how fundamental metabolic pathways that underpin changes in organismal physiology are affected by OA. Consequently, a gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) based metabolic profiling approach was applied to examine the metabolic responses of Crassostrea gigas to elevated pCO2 levels, under otherwise natural field conditions. Oysters were exposed natural environmental pCO2 (~625.40 μatm) and elevated pCO2 (~1432.94 μatm) levels for 30 days. Results indicated that 36 differential metabolites were identified. Differential metabolites were mapped in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database to search for the related metabolic pathways. Pathway enrichment analysis indicates that alanine, aspartate and glutamate metabolism and glycine, serine and threonine metabolism were the most statistically enriched pathways. Further analysis suggested that elevated pCO2 disturb the TCA cycle via succinate accumulation and C. gigas most likely adjust their energy metabolic via alanine and GABA accumulation accordingly to cope with elevated pCO2. These findings provide an understanding of the molecular mechanisms involved in modulating C. gigas metabolism under elevated pCO2.

Analysis of metabolic and mineral changes in response to salt stress in durum wheat (Triticum turgidum ssp. durum) genotypes, which differ in salinity tolerance

The key mechanisms of salinity tolerance (ST) in durum wheat were investigated, with five genotypes used to determine changes in morpho-physiological traits and mineral and metabolite contents after exposure to 50, 100 and 200 mM NaCl. Plant growth impairment was evident at the highest salt level. Under this condition, a wide range of shoot Na+ contents and ST were observed within genotypes. However, no significant correlation was seen between ST and Na+ exclusion from the shoots, which indicates that tissue tolerance also has a role. Consistent with this, there was significant correlation between ST and the Na+:K+ ratio in the shoots. Indeed, the maintenance of the shoot Na+ and K+ homeostasis was found to be essential to achieve osmotic adjustment, which relied substantially on inorganic osmolytes, and to avoid toxicity symptoms, such as chlorophyll loss, which appeared only at the highest salinity level. Consistently, the metabolite changes occurred mainly in the shoots, with a dual response to salinity: (i) a conserved response that was common to all the genotypes and resulted in the accumulation of proline and in the depletion of organic acids, including some intermediates of the Krebs cycle; and (ii) a genotype-specific response that involved the accumulation of GABA, threonine, leucine, glutamic acid, glycine, mannose and fructose and appeared related to the different tolerance of genotypes to salinity. The lower magnitude of response to salinity detected in the roots confirmed the major role of the shoots in the determination of ST of durum wheat.

MAPK mediates NO/cGMP-induced GABA accumulation in soybean sprouts

The effects of nitric oxide (NO)-guanosine 3‘,5‘-cyclic monophosphate (cGMP) on UV-B stress-induced γ-aminobutiric acid (GABA) accumulation, and the influences of mitogen-activated protein kinase (MAPK) on NO/cGMP-induced GABA accumulation under UV-B stress in soybean sprouts were investigated. The sprouts were treated with donors and inhibitors of NO and cGMP as well as MAPK inhibitor. The results showed that NO, with cGMP/PKG as a second messenger, stimulated GABA accumulation under UV-B treatment. Consistent with the elevation in GABA content, the increment of gene and protein expression and activity of diamine oxidase (DAO) and amino aldehyde dehydrogenase (AMADH) in response to 8-Br-cGMP (cGMP analog) and sodium nitroprusside (SNP) (exogenous NO donor) was also observed. Therefore, NO/cGMP mediates UV-B radiation-induced GABA accumulation in soybean sprouts. What's more, NO, with cGMP/PKG as a second messenger, activated gene and protein expression of MAPK under UV-B treatment. MAPK up-regulated gene and protein expression and activity of DAO and AMADH, and subsequently induced GABA accumulation. Overall, MAPK mediated NO/cGMP/PKG-stimulated GABA biosynthesis in soybean sprouts.

GABA enhances physio-biochemical metabolism and antioxidant capacity of germinated hulless barley under NaCl stress

The effects of exogenous γ-aminobutyric acid (GABA) on the endogenous GABA metabolism and antioxidant capacity of germinated hulless barley (Hordeum vulgare L.) under NaCl stress were investigated. The results showed that all of the GABA treatments could alleviate the growth inhibition and oxidative damage by NaCl stress, with 0.5 mM being the most effective concentration. The GABA-treated barley seedlings exhibited a significantly higher content of endogenous GABA and other free amino acids, especially proline, which resulted from the changes in corresponding enzyme activity. The phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H), and 4-coumarate coenzyme A ligase (4CL) activities also increased in GABA-treated barley, which led to higher total phenolic content and antioxidant capacity than that of the control barley. These results indicate that GABA treatment may be an effective way to relieve salt stress as it induces the accumulation of endogenous GABA and proline and total phenolic content, thus enhancing the antioxidant capacity.

Accumulation of γ‐aminobutyric acid during cold storage in mulberry leaves

SummaryThe γ‐aminobutyric acid (GABA) contained in mulberry leaves has the effect of improving mood. Mulberry leaf cultivars ‘Kangxuan 01‐28’, ‘Lunbai No.1’ and ‘BR 60’ were analysed for GABA accumulation under low temperature storage. The effects of ice temperature storage (ITS), cold acclimation combined with ice‐temperature storage (CACIS) and cold storage (CS) on GABA and associated enzymes, soluble protein and leaf colour were measured. The increase in GABA content differed among varieties. Under different low temperature storage treatments, the GABA concentration increased by 33.93‐fold, 11.75‐fold and 4.28‐fold in mulberry leaves compared with the initial concentration in the three cultivars ‘Kangxuan 01‐28’, ‘Lunbai No.1’ and ‘BR 60’, respectively. GAD activity and soluble protein were positively correlated with GABA concentration, while GABA‐T activity showed an opposite trend to the GABA concentration. After being treated with ITS, ‘Kangxuan 01‐28’ could accumulate higher GABA and should be consumed within 7 days.

Free α-amino acids, γ-Aminobutyric acid (GABA), phenolic compounds and their relationships with antioxidant properties of sorghum malted in different conditions

Two cultivars of sorghum were germinated at 25 or 30°C for 1, 2, or 3days to investigate the evolution of γ-Aminobutyric acid (GABA), total free phenolic compounds (FPC), hydroxycinnamic acid derivatives, free amino acid (FAA) profile, and antioxidant activity during malting. Results showed time-temperature interaction had significant influence on GABA accumulation, increasing over time at 25°C, but keeping constant after first day at 30°C. Free amino acid profile changed during malting with time and temperature, increasing until the third or second day at 25 and 30°C, respectively. Content of hydroxycinnamic acid derivatives depended on time, temperature, and cultivar; ferulic was the phenolic acid found in greater amount. Pearson correlation analysis suggested malting generated not only FPC responsible for antioxidant activity, but also other bioactive compounds like FAA, particularly sulfur-containing ones. Germination for 3days at 25°C was the most suitable condition to obtaining functional sorghum malt.