Enzymatic release of odourant polyfunctional thiols from cysteine conjugates in hop

Polyfunctional thiols are contributors to the hop varietal aroma of beer. Besides free thiols, a cysteine‐S‐conjugate has recently been shown to be an additional component of the thiol potential of hop. Such cysteine adducts investigated here in four hop cultivars and in different hop forms. Hop hydroalcoholic extracts were purified on a cation exchanger and subjected to apotryptophanase β‐lyase activity. The Cascade hop variety exhibited the highest bound 3‐sulphanylhexan‐1‐ol (grapefruit‐like) potential, while both Tomahawk and Nelson Sauvin cultivars were confirmed to be important sources of bound 3‐methyl‐2‐butene‐1‐thiol (skunky‐like), 3‐sulphanylpentan‐1‐ol and 4‐sulphanyl‐4‐methylpentan‐2‐one (box‐tree‐like). Surprisingly, hop CO₂ extracts proved to contain cysteine conjugates. Although related, the concentrations of cysteine‐bound thiols in hop are not strictly correlated to the amounts of free volatiles found in the derived beers. Copyright © 2013 The Institute of Brewing & Distilling     

Metabolism of oligosaccharides and aldehydes and production of organic acids in soymilk by probiotic bifidobacteria

Four strains of Bifidobacterium were assessed for α‐galactosidase activity in MRS broth using p‐nitrophenyl‐α‐d ‐galactopyranoside as substrate. Bifidobacteria were then used to ferment soymilk prepared from soy protein isolate (SPI), with and without d ‐glucose and l ‐cysteine supplementation. Measurements of pH and the quantification of oligosaccharides, organic acids and aldehydes in soymilk were done after 0, 12, 24, 36 and 48 h of incubation. The presence of d ‐raffinose stimulated the α‐galactosidase activity of B. longum BB536 (BB536) and B. pseudolongum 20099 (BP20099). In soymilk, oligosaccharides and aldehydes were effectively metabolized by Bifidobacterium; d ‐glucose and l ‐cysteine supplementation enhanced the hydrolysis of raffinose and stachyose. BB536 and BP20099 degraded a significantly greater level of oligosaccharides and aldehydes than B. animalis Bb‐12 and B. longum 1941 (P < 0.05). Raffinose and stachyose were completely metabolized by BB536 after 48 h. In soymilk without any supplementation, hexanal and pentanal were not detected after 12 h of fermentation with BB536 and BP20099. BB536 was the highest producer of organic acids, with an average acetic acid/l (+)‐lactic acid ratio of 0.7.     

Aminopeptidase from jumbo squid (Dosidicus gigas) hepatopancreas: purification,characterisation, and casein hydrolysis

An aminopeptidase (AP) was partially purified from jumbo squid (Dosidicus gigas) hepatopancreas with 154.24‐fold and yield of 6.15%. The purification procedure consisted of ammonium sulphate fractionation and DEAE‐Sephacel chromatography. The enzyme was approximately 48–53 kDa as estimated by SDS‐PAGE. With l ‐leu‐p‐NA, it had optimum activity at pH 8.0 and 30 °C. The K_m and V_max/K_m values of the enzymes for l ‐leu‐p‐NA were 0.326 mm and 2787 at 37 °C, respectively. Activation energy (E_a) of the enzyme was 53.50 kJ M^?1.The AP showed activity against seven synthetic substrates: l ‐proline>l ‐methionine>Ac. l ‐γ‐glutamic>l ‐glycine>l ‐leucine>l ‐alanine>l ‐lysine‐p‐NA. The enzyme was strongly inhibited by Bestatin, partially inhibited by a metal‐chelating agent and by PCMB, a cystein protease inhibitor. Zn²⁺ and (or) Ca²⁺ seemed to be its metal cofactor(s). Incubation of casein with the partially purified AP resulted in a degree of hydrolysis of 6%.     

Effect of linear density of inlay yarns on the structural characteristics of knitted fabric tube and pressure generation on cylinder

An important step in the digestion of wool by certain insect pests is the reductive cleavage of protein disulphide bonds to open the fibre for protease action. For larvae of the webbing clothes moth, Tineola bisselliella, two enzymes have been suggested as being involved in this process, cystine reductase and cysteine lyase/desulphydrase.

In the present study, cystine reductase is shown not to be present in T. bisselliellalarvae. An earlier study, showing that cysteine lyase/desulphydrase is present in these larvae, is confirmed and extended to demonstrate that the activity is localised to the gut of larvae. This activity is also present in the larval gut of another clothes moth, Tinea pellionella, but is absent from the gut of the carpet beetle, Anthrenus flavipes, suggesting that larvae of moths and beetles use different mechanisms to reduce the disulphide bonds of wool.     

In vitro and in vivo antifungal properties of cysteine proteinase inhibitor from green kiwifruit

BACKGROUND: Higher plants possess several mechanisms of defense against plant pathogens. Proteins actively synthesized in response to those stresses are called defense‐related proteins which, among others, include certain protease inhibitors. It is of particular relevance to investigate plant natural defense mechanisms for pathogen control which include cystatins—specific inhibitors of cysteine proteases. RESULTS: In this study, a cysteine proteinase inhibitor (CPI), 11 kDa in size, was purified from green kiwifruit to homogeneity. Immuno‐tissue print results indicated that CPI is most abundant in the outer layer of pericarp, near the peel, and the inner most part of the pulp—sites where it could act as a natural barrier against pathogens entering the fruit. The purified protein (15 µmol L^?1) showed antifungal activity against two phytopathogenic fungi (Alternaria radicina and Botrytis cinerea) by inhibiting fungal spore germination. In vivo, CPI (10 µmol L^?1) was able to prevent artificial infection of apple and carrot with spore suspension of B. cinerea and A. radicina, respectively. It also exerted activity on both intracellular and fermentation fluid proteinases. CONCLUSION: Identification and characterization of plant defense molecules is the first step towards creation of improved methods for pathogen control based on naturally occurring molecules. Copyright © 2012 Society of Chemical Industry     

Efficient production of L‐lactic acid by Crabtree‐negative yeast Candida boidinii

Industrial production of L ‐lactic acid, which in polymerized form as poly‐lactic acid is widely used as a biodegradable plastic, has been attracting world‐wide attention. By genetic engineering we constructed a strain of the Crabtree‐negative yeast Candida boidinii that efficiently produced a large amount of L ‐lactic acid. The alcohol fermentation pathway of C. boidinii was altered by disruption of the PDC1 gene encoding pyruvate decarboxylase, resulting in an ethanol production that was reduced to 17% of the wild‐type strain. The alcohol fermentation pathway of the PDC1 deletion strain was then successfully utilized for the synthesis of L ‐lactic acid by placing the bovine L ‐lactate dehydrogenase‐encoding gene under the control of the PDC1 promoter by targeted integration. Optimizing the conditions for batch culture in a 5 l jar‐fermenter resulted in an L ‐lactic acid production reaching 85.9 g/l within 48 h. This productivity (1.79 g/l/h) is the highest thus far reported for L ‐lactic acid‐producing yeasts. DDBJ/EMBL/GenBank nucleotide database with Accession Nos. AB440630 and AB440631. Copyright © 2009 John Wiley & Sons, Ltd.     

3‐Hydroxypyridinone‐l‐phenylalanine conjugates with antimicrobial and tyrosinase inhibitory activities as potential shrimp preservatives

To explore the potential of novel tyrosinase inhibitors, 3‐hydroxypyridinone‐l ‐phenylalanine conjugates, as shrimp preservatives, compounds 1 and 2 were evaluated for the antimicrobial activity, and compound 2 was investigated for the shrimp preservative efficacy. It was found that they both possess a stronger antibacterial effect than kojic acid against two Gram‐positive bacteria and three Gram‐negative bacteria. The minimum inhibitory concentrations (MICs) of compound 2 against Escherichia coli, Staphylococcous aureus, Salmonella gallinarum, Vibrio parahaemolyticus and Bacillus subtilis were determined as 18.5, 37, 148, 37 and 295 μg mL^?1, respectively, whereas MICs of kojic acid against the same 5 bacterial strains were determined to be 355, 178, 1420, 1420 and 355 μg mL^?1, respectively. It has also been demonstrated that treatment with compound 2 improves the sensory properties, retards the growth of spoilage bacteria, decreases the total volatile basic nitrogen (TVB‐N) and increases the pH of Penaeus vannamei Boone, thereby extending the shelf life to 10 days. In contrast, the shelf life of shrimp treated with kojic acid and the control group was 7 and 6 days, respectively. Clearly, 3‐hydroxypyridinone‐l ‐phenylalanine conjugates could find application as shrimp preservatives by inhibiting melanosis and by preventing the growth of bacteria during the storage.     

Partial purification and characterisation of cysteine protease in wheat germ

BACKGROUND: Proteases have become an essential part of the modern food and feed industry, being incorporated in a large and diversified range of products for human and animal consumption. The objective of this study was to purify and characterise a protease from wheat germ. RESULTS: After purification a single protease of molecular weight 61–63 kDa (determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis) was obtained. The purified protease had optimal activity at 50 °C and maintained its activity completely after incubation at 30 °C for 30 min, while over 47% of the activity was lost after incubation at 80 °C for 30 min. The purified protease had optimal activity and maintained maximum stability at pH 5.5, while the activity decreased after incubation for 30 min at other pH values. The protease was inhibited by Mg²⁺, Mn²⁺, Ba²⁺ and iodacetic acid and stimulated by Li⁺, Ca²⁺, Cu²⁺, β‐mercaptoethanol and dithiothreitol, while Zn²⁺, L ‐cysteine and glutathione had no significant effect on its activity. At pH 5.5 the enzyme had a K_m of 0.562 mg mL^?1 with casein as substrate and showed higher affinity to casein than to bovine serum albumin, ovalbumin and gelatin. CONCLUSION: The purified enzyme from wheat germ was identified as a cysteine protease. Copyright © 2011 Society of Chemical Industry     

Purification and functional characterisation of an α‐l‐rhamnosidase from Penicillium citrinum MTCC‐3565

An extracellular α‐l ‐rhamnosidase from Penicillium citrinum MTCC‐3565 has purified to homogeneity from its culture filtrate using ethanol precipitation and cation‐exchange chromatography on carboxymethyl cellulose. The purified enzyme gave a single protein band corresponding to molecular mass of 45.0 kDa in SDS‐PAGE analysis showing the purity of the enzyme preparation. The native PAGE analysis showed the monomeric nature of the purified enzyme. Using p‐nitrophenyl α‐l ‐rhamnopyranoside as substrate, K_m and V_max values of the enzyme were 0.30 mm and 27.0 μm min mg^?1, respectively. The k_cat value was 20.1 s giving k_cat/K_m value of 67.0 mm s^?1 for the same substrate. The pH and temperature optima of the enzyme were 8.5 and 50 °C, respectively. The activation energy for the thermal denaturation of the enzyme was 29.9 KJ mol^?1. The α‐l ‐rhamnosidase was able to hydrolyse naringin, rutin and hesperidin and liberated l ‐rhamnose, indicating that the purified enzyme can be used for the preparation of α‐l ‐rhamnose and pharmaceutically important compounds by derhamnosylation of natural glycosides containing terminal α‐l ‐rhamnose. The α‐l ‐rhamnosidase was active at the level of ethanol concentration present in wine, indicating that it can be used for improving wine aroma.     

Production of bacteriocin‐like inhibitory substances (BLIS) by Bifidobacterium lactis using whey as a substrate

The objective of this work was to evaluate the production of bacteriocin‐like inhibitory substances (BLIS) by Bifidobacterium animalis subsp. lactis in whey supplemented with yeast extract, inulin, Tween‐80 or l ‐cysteine. Cell growth, acidification, glucose and lactose consumption as well as BLIS production were measured during fermentations carried out in shake flasks. The best additive for both cell growth and BLIS production was shown to be yeast extract, which gave the highest concentrations of biomass (9.9 log cfu/mL) and BLIS (800 AU/mL). In a bench‐scale fermentor, B. lactis growth and BLIS production were between 6% and 25% higher than in flasks depending on the conditions assayed.     

Purification of polyphenol oxidase and the browning control of litchi fruit by glutathione and citric acid

Polyphenol oxidase (PPO, EC 1.10.3.2) was purified to homogeneity from litchi peel yielding a single protein with a molecular weight of about 75.6 kD by Sephadex G‐100 gel filtration, and a 108‐fold purification of PPO achieved. The enzyme was determined to be composed of two similar subunits. Glutathione, L ‐cysteine and citric acid suppressed PPO activity markedly, whereas ascorbic acid and n‐propyl gallate showed a little inhibition. Moreover, the effect was enhanced by the addition of citric acid. On the basis of the inhibition of PPO activity in vitro, the use of 10 mmol l ⁻¹ glutathione and 100 mmol⁻¹ l citric acid was found to give good control of the browning of litchi fruit, and an 80–85% inhibition of PPO activity was observed. It is suggested that application of glutathione in combination with citric acid may slow down the browning of litchi fruit. © 1999 Society of Chemical Industry     

α‐l‐Rhamnosidase from Aspergillus flavus MTCC‐9606 isolated from lemon fruit peel

An α‐l ‐rhamnosidase producing fungal strain has been isolated from decaying lemon fruit. The fungal strain has been identified as Aspergillus flavus. The α‐l ‐rhamnosidase has been purified from the culture filtrate of the fungal strain using ultra filtration and cation exchange chromatography on carboxy methyl (CM) cellulose. The molecular mass of the purified enzyme determined by SDS–PAGE analysis was 41 kDa. The K_m values of the enzyme using p‐nitrophenyl‐α‐l ‐rhamnopyranoside and naringin as the substrates were 1.89 and 1.6 mm respectively. The pH and temperature optima of the enzyme were 11.0 and 50 °C respectively. The effects of various chemical species present in grape fruit juice and wine on the activity of the enzyme have been determined.     

Lactic acid fermentation of brewer's spent grain hydrolysate by Lactobacillus rhamnosus with yeast extract addition and pH control

Lactic acid (LA) is a versatile chemical with a wide range of applications in food, pharmaceutical, cosmetic, textile and polymer industries. Brewer's spent grain (BSG) is the most abundant brewing by‐product. In this study BSG hydrolysates were used for LA fermentation by Lactobacillus rhamnosus ATCC 7469. The aim of this study was to evaluate the effects of pH control during fermentation, reducing sugar content and yeast extract content in BSG hydrolysate on LA fermentation parameters. The pH control greatly increased reducing sugar utilization, l ‐(+)‐LA content, yield and volumetric productivity. The highest l ‐(+)‐LA yield and volumetric productivity were achieved with the reducing sugar content of 54 g/L. Yeast extract addition significantly increased reducing sugar utilization, l ‐(+)‐LA content, L. rhamnosus cell viability, l ‐(+)‐LA yield and volumetric productivity. The highest l ‐(+)‐LA content (39.38 g/L), L. rhamnosus cell viability (9.67 log CFU/mL), l ‐(+)‐LA yield (91.29%) and volumetric productivity (1.69 g/L/h) were achieved with the reducing sugar content of 54 g/L and yeast extract content of 50 g/L. Copyright © 2017 The Institute of Brewing & Distilling     

Contribution of cysteine and glutathione conjugates to the formation of the volatile thiols 3‐mercaptohexan‐1‐ol (3MH) and 3‐mercaptohexyl acetate (3MHA) during fermentation by Saccharomyces cerevisiae

Background and Aims: 3‐Mercaptohexan‐1‐ol (3MH) and its ester 3‐mercaptohexyl acetate (3MHA) are potent aromatic thiols that substantially contribute to varietal wine aroma. During fermentation, non‐volatile 3MH conjugates are converted by yeast to volatile 3MH and 3MHA. Two types of 3MH conjugates have been identified, S‐3‐(hexan‐1‐ol)‐L‐cysteine (Cys‐3MH) and S‐3‐(hexan‐1‐ol)‐glutathione (GSH‐3MH). Yeast‐driven formation of 3MH from these precursors has been previously demonstrated, while the relationship between 3MHA and GSH‐3MH remains to be established. This paper aims to investigate yeast conversion of GSH‐3MH to 3MH and 3MHA, and to assess the relative contribution of each individual conjugate to the 3MH/3MHA pool of finished wines. Methods and Results: Fermentation experiments were carried out in model grape juice containing Cys‐3MH and GSH‐3MH. We found 3MH formation from GSH‐3MH to be significantly less efficient than that of Cys‐3MH. Conversely, esterification of 3MH to 3MHA was higher when 3MH was formed from GSH‐3MH. Additional in vitro assays for measuring enzyme cleavage activity suggest the involvement of a different mechanism in 3MH conversion for the two precursors. Conclusions: These results indicate that although both 3MH conjugates can be converted by yeast, the type of precursor affects the rate of formation of 3MH and 3MHA during fermentation. Significance of the Study: Management of the pool of aromatic thiols during fermentation can depend on relative proportions of different 3MH conjugates.     

Purification,characterisation and application of α‐l‐rhamnosidase from Penicillium citrinum MTCC‐8897

An α‐l ‐rhamnosidase secreted by Penicillium citrinum MTCC‐8897 has been purified to homogeneity from the culture filtrate of the fungal strain using ammonium sulphate precipitation and cation‐exchange chromatography on carboxymethyl cellulose. The sodium dodecyl sulphate/polyacrylamide gel electrophoresis analysis of the purified enzyme gave a single protein band corresponding to the molecular mass 51.0 kDa. The native polyacrylamide gel electrophoresis also gave a single protein band confirming the enzyme purity. The K_m and V_max values of the enzyme for p‐nitrophenyl α‐l ‐rhamnopyranoside were 0.36 mm and 22.54 μmole min^?1 mg^?1, respectively, and k_cat value was 17.1 s^?1 giving k_cat/K_m value of 4.75 × 10⁴ m ^?1 s^?1. The pH and temperature optima of the enzyme were 7.0 and 60 °C, respectively. The purified enzyme liberated l ‐rhamnose from naringin, rutin, hesperidin and wine, indicating that it has biotechnological application potential for the preparation of l ‐rhamnose and other pharmaceutically important compounds from natural glycosides containing terminal α‐l ‐rhamnose and also in the enhancement of wine aroma.     

PURIFICATION AND CHARACTERIZATION OF A MYOFIBRIL-BOUND SERINE PROTEINASE FROM THE SKELETAL MUSCLE OF SILVER CARP

Recently, a myofibril‐bound serine proteinase (MBSP) in the skeletal muscle of silver carp was identified. MBSP could be dissociated from myofibrils by treatment at pH 4.0. Following ultrafiltration concentration and chromatography on Sephacryl S‐200, High Q ion‐exchange and affinity column of Arginine Sepharose‐4B, MBSP was partially purified. The enzyme with an estimated molecular weight of 28 kDa cleaves synthetic fluorogenic substrates specifically at the carboxyl sites of arginine and lysine residues. MBSP activity is suppressed by serine proteinase inhibitors such as Pefabloc SC, lima bean trypsin inhibitor and benzamidine; it is insensitive to Pepstatin, l ‐3‐carboxy‐trans‐2, 3‐epoxypropionyl‐l ‐leucine‐4‐guanidinobutylamide and ethylenediaminetetraacetic acid, suggesting MBSP is a trypsin‐like serine proteinase. Optimal profiles of pH and temperature of the enzyme are 8.5 and 55C, respectively. Hydrolysis of myofibrillar proteins such as myosin heavy chain, actin and tropomyosin by purified MBSP occurred especially at around 55C, consistent with our proposal that MBSP plays a significant role in the Modori phenomenon.     

An α‐l‐rhamnosidase from Aspergillus awamori MTCC‐2879 and its role in debittering of orange juice

The extracellular α‐l ‐rhamnosidase has been purified by growing a new fungal strain Aspergillus awamori MTCC‐2879 in the liquid culture growth medium containing orange peel. The purification procedure involved ultrafiltration using PM‐10 membrane and anion‐exchange chromatography on diethyl amino ethyl cellulose. The purified enzyme gave single protein band in SDS‐PAGE analysis corresponding to molecular mass 75.0 kDa. The native PAGE analysis of the purified enzyme also gave a single protein band, confirming the purity of the enzyme. The K_m and V_max values of the enzyme for p‐nitrophenyl‐α‐l ‐rhamnopyranoside were 0.62 mm and 27.06 μmole min^?1 mg^?1, respectively, yielding k_cat and k_cat/k_m values 39.90 s^?1 and 54.70 mm ^?1 s^?1, respectively. The enzyme had an optimum pH of 7.0 and optimum temperature of 60 °C. The activation energy for the thermal denaturation of the enzyme was 35.65 kJ^?1 mol^?1 K^?1. The purified enzyme can be used for specifically cleaving terminal α‐l ‐rhamnose from the natural glycosides, thereby contributing to the preparation of pharmaceutically important compounds like prunin and l ‐rhamnose.     

Ammonium nitrate fertility levels influence flavour development in hydroponically grown ‘Granex 33’ onion

High levels of nitrogen (N) fertility have been shown to influence bulb flavour characteristics in onion (Allium cepa L). To test the effects of lower levels of N fertility on onion bulb flavour, ‘Granex 33’ onions were grown hydroponically in a greenhouse with varying solution N levels. Eleven levels were tested by increasing the concentration of NH₄NO₃ in solutions from 20 to 140 mg l^?1 N. Mature plants were harvested and evaluated for plant leaf and bulb fresh weights (FWs), bulb soluble solids content (SSC), bulb total pyruvic acid, bulb total sulphur (S), and bulb sulphate (SO₄^2?). To determine the effect of N on the flavour biosynthetic pathway of onion, total and individual S‐alk(en)yl cysteine sulphoxides and related peptide intermediates were also tested. Leaf and bulb FWs responded quadratically to N concentration, as did total bulb S. Bulb SO₄^2? and SSC, though significantly influenced by N concentration, did not respond with a meaningful trend. Bulb pyruvic acid increased linearly with N level increases, as did (+)‐S‐propyl‐L ‐cysteine sulphoxide. Total precursors, (+)‐S‐methyl‐L ‐cysteine sulphoxide, and trans‐(+)‐S‐1‐propenyl‐L ‐cysteine sulphoxide responded quadratically to N levels. At lower N levels, trans‐(+)‐S‐1‐propenyl‐L ‐cysteine sulphoxide content was highest relative to the other precursors. However, at elevated N levels, (+)‐S‐methyl‐L ‐cysteine sulphoxide accumulated in the highest concentrations. Peptide intermediates 2‐carboxypropyl glutathione and γ‐glutamyl propenyl cysteine sulphoxide responded linearly and quadratically respectively to increasing N fertility levels. Nitrogen fertility levels can influence flavour intensity and quality and should be considered when growing onions for flavour attributes. Copyright © 2003 Society of Chemical Industry     

The effect of certain amino acids and browning inhibitors on the ‘black spot’ phenomenon produced by Carnimonas nigrificans

Black spots are sometimes observed in fermented sausages and raw cured meat products, with resultant economic loss. The effect brought about by some amino acids in the development of this browning was evaluated, in aerobiosis at 30 °C and 90–95% RH, in a pork meat mixture with glucose, NaCl and inoculated with Carnimonas nigrificans CTCBS1^T at 1.0 × 10⁷ CFU g⁻¹. Amino acids and alternative substances to bisulphite and nitrite as preventative agents were studied for their effect on the browning reaction. The effect of NaCl concentration on browning and on the growth of Carnimonas nigrificans CTCBS1^T was also evaluated. Glycine, L ‐arginine, L ‐glutamine and L ‐monosodium glutamate were the amino acids that significantly decreased the L values and increased the browning scores in comminuted meat which was mixed with 40 gkg⁻¹ NaCl and 20 gkg⁻¹ D ‐(+)‐, glucose and inoculated with Carnimonas nigrificans CTCBS1^T. N‐acetyl‐L ‐cysteine, L ‐cysteine, potassium metabisulphite and propil‐3, 4, 5‐trihydroxybenzoate prevented browning at 10 and 5 gkg⁻¹. The optimum concentration of NaCl for the growth of Carnimonas nigrificans CTCBS1^T was 40 gkg⁻¹. © 2000 Society of Chemical Industry     

S‐Allyl cysteine,S‐ethyl cysteine and S‐propyl cysteine alleviate oxidative stress‐induced damage within PC12 cells

BACKGROUND: The PC12 cell line is a suitable model for the investigation of neurodegenerative diseases. In this study, PC12 cells were used to examine in vitro antioxidative and antiapoptotic protection by S‐allyl cysteine (SAC), S‐ethyl cysteine (SEC) and S‐propyl cysteine (SPC). PC12 cells were treated with these agents at 5 and 10 µmol L^?1 before exposure to hydrogen peroxide (H₂O₂). RESULTS: H₂O₂ treatment significantly decreased mitochondrial membrane potential (MMP) and cell viability and increased lactate dehydrogenase (LDH) release and DNA fragmentation (P < 0.05). The pre‐treatments with SAC, SEC and SPC significantly and concentration‐dependently elevated cell viability and MMP and lowered LDH release and DNA fragmentation (P < 0.05). H₂O₂ treatment also significantly increased levels of malondialdehyde (MDA), reactive oxygen species (ROS) and oxidised glutathione (GSSG) and decreased glutathione (GSH) content (P < 0.05). The pre‐treatments with SAC, SEC and SPC significantly decreased subsequent H₂O₂‐induced formation of MDA, ROS and GSSG (P < 0.05) and also alleviated H₂O₂‐induced GSH depletion (P < 0.05). Finally, H₂O₂ treatment significantly decreased Na⁺‐K⁺‐ATPase activity and elevated caspase‐3 activity (P < 0.05). The pre‐treatments with SAC, SEC and SPC significantly attenuated H₂O₂‐induced Na⁺‐K⁺‐ATPase activity reduction and caspase‐3 activity elevation (P < 0.05). CONCLUSION: The results obtained support that the three cysteine‐containing compounds studied are potent neuroprotective agents. Copyright © 2008 Society of Chemical Industry