Antioxidant Activity of Purified Protein Hydrolysates from Northern Whiting Fish (Sillago sihama) Muscle

In the present study, northern whiting fish (Sillago sihama) muscle was hydrolyzed with gastrointestinal enzymes (pepsin, trypsin and α-chymotrypsin) separately and the resulted protein hydrolysates were tested for antioxidant activities using DPPH radical scavenging activity and reducing power assays. The protein hydrolysate obtained from trypsin exhibited highest antioxidant activity. Further, it was fractionated by consecutive chromatography using anion exchange and gel filtration chromatography; the separated fractions were collected and evaluated for antioxidant activity. The results showed that fraction 2 exhibited high chelating activity (73.15 % at 0.5 mg/mL) and best radical scavenging activity for DPPH radical (55.16 % at 0.5 mg/mL), ABTS radical (57.98 % at 50 μg/mL), superoxide radical (39.55 % at 200 μg/mL) and hydroxyl radical (51.33 % at 100 μg/mL). In addition, the active fraction showed strong antioxidant activity in the inhibition of linoleic acid autooxidation (60 % at 0.5 mg/mL) and also it exhibited significant protective effect on DNA damage caused by hydroxyl radicals. The size of the active fraction was found to be <360.2 Da using mass spectroscopy. These results demonstrate that muscle protein hydrolysate from northern whiting fish could be a best alternative to produce natural antioxidant peptides.     

红托竹荪菌托多糖提取工艺及抗氧化降血糖活性

为利用红托竹荪菌托,采用酶解法提取菌托多糖,优化多糖提取工艺,并测定多糖分子量、单糖组成、抗氧化及降血糖活性。结果表明,最佳酶解法提取工艺为纤维素酶2.5%、果胶酶0.4%、木瓜蛋白酶1.5%,50 ℃酶解1 h,料液比1:60、提取温度80 ℃、时间3 h,该条件下多糖提取率达15.37%,比热水浸提法提高39.60%。酶解法多糖分子量为3 344 Da (Mn)、522 208 Da (Mw)、2 929 Da (Mp),主要由葡萄糖、甘露糖、葡萄糖醛酸、半乳糖和岩藻糖等组成,葡萄糖占最高,达48.82%。菌托多糖为2.0 mg/mL时,DPPH·清除率为93.83%,Fe³⁺还原能力为0.140 7,α-葡萄糖苷酶活性抑制率为54.62%、α-淀粉酶活性抑制率为56.45%,与热水浸提法相比差异极显著或显著。酶解法提取红托竹荪菌托多糖,提取率较高,具有较高的抗氧化、降血糖活性,具有推广应用价值。     

Protein hydrolysates from Bluefin Tuna (Thunnus thynnus) heads as influenced by the extent of enzymatic hydrolysis

Functional properties and antioxidant activities of protein hydrolysates from tuna (Thunnus thynnus) heads (THPHs), with different degrees of hydrolysis, obtained by treatment with Bacillus mojavensis A21 alkaline proteases and Alcalase, were investigated. Protein content of all freeze-dried THPHs ranged from 73.74 ± 0.5 to 78.56 ± 1.2%. The THPHs had excellent solubility, compared to untreated tuna head proteins and possessed interfacial properties, which were governed by their concentrations. Similarly, at a degree of hydrolysis (DH) of 12 and 15%, > 90% nitrogen solubility was observed at all experimental pH values tested. The emulsifying activity index (EAI) and emulsion stability index (ESI) of both hydrolysates at different DHs decreased (p < 0.05) with increasing DH. At low DH (5%), hydrolysates exhibited strong emulsifying properties. All THPHs produced by the A21 proteases generally showed higher antioxidative activity than that of the Alcalase protein hydrolysates. The highest DPPH radical-scavenging activity (78 ± 2.1% at 3 mg/mL) was obtained with a DH of 15%. The IC₅₀ value for the β-carotene bleaching assay was 0.5 ± 0.03 mg/mL. Alcalase (DH = 12%) and A21 (DH = 15%) protein hydrolysates contained glutamic acid/glutamine and arginine as the major amino acids, followed by lysine, aspartic acid/ asparagine, histidine, valine, phenylalanine, and leucine. In addition, the THPHs had a high percentage of essential amino acids, which made up 50.52 and 50.47%, of the protein hydrolysates obtained by the Alcalase and A21 proteases, respectively. Therefore, THPHs can be used as a promising source of functional peptides with antioxidant properties.     

Isolation, structural characterization and antioxidant activity of a new water-soluble polysaccharide from Acanthophyllum bracteatum roots

ABPS-1, a new water-soluble polysaccharide with molecular weight of 26 kDa and a specific optical rotation of +170° (c 1.0, H₂O), was extracted from the roots of Acanthophyllum bracteatum by warm water and further successively purified through DEAE-cellulose A52 and Sephadex G-100 columns. Monosaccharide analysis revealed that the ABPS-1 was composed of Glc, Gal and Ara with a relative molar ratio of 1.4:5.2:1.0. Its structural features were elucidated by a combination of FT-IR, methylation and GC-MS analysis, periodate oxidation and Smith degradation, partial acid hydrolysis and ¹³C and ¹H NMR spectroscopy. The data obtained indicate that ABPS-1 possessed a backbone of α-(1 → 6)-linked Gal with branches attached to O-2 by α-1 → linked Glc and at O-3 by α-1 → linked Gal and by α-(1 → 3)-linked Ara. The in vitro antioxidant activity showed that ABPS-1 possesses DPPH radical-scavenging activity in a concentration-dependent manner with an EC₅₀ value of 2.6 mg/ml.     

Total phenolic and flavonoid contents and antioxidant activity of ginger (Zingiber officinale Rosc.) rhizome,callus and callus treated with some elicitors

The present study was aimed at determining total phenolic and flavonoid contents and studying the antioxidant activity of ginger (Zingiber officinale Rosc.) rhizome and callus, 6-gingerol and 6-shogaol and callus treated with elicitors. Petroleum ether (PE) and chloroform: methanol (1:1, v/v) (CM) extracts were prepared by maceration. Highest total phenolic content was obtained from the CM extract (60.34?±?0.43?mg gallic acid/g) of rhizome while callus showed lower content detected in the CM extract (33.6?±?0.07?mg gallic acid/g). Flavonoids were only detected in rhizome (CM extract 40.25?±?0.21?mg quercetin/g). Both rhizome extracts exhibited good antioxidant activity with higher activity recorded in PE extract (IC₅₀ value 8.29?±?1.73?μg/mL). Callus extracts revealed lower antioxidant activity (IC₅₀ value 1265.49?±?59.9?μg/mL obtained from CM extract). 6-gingerol and 6-shogaol displayed high antioxidant activity in both assays with IC₅₀ 4.85?+?0.58_DPPH and 5.35?±?0.33_ABTS μg/mL for the former and IC₅₀ 7.61?±?0.81_DPPH and IC₅₀ 7.05?±?0.23_ABTS μg/mL for the latter. Treatment of callus with elicitors showed significant (p?<?0.05) effects in enhancing phenolic content and related antioxidant activity. The highest significant increase in phenolic content (37% and 34%) and antioxidant activity in DPPH assay (34% and 30%) was observed in callus treated with 100?mg/L yeast extract and 50?mg/L salicylic acid respectively. Therefore, studying the effect of the elicitation of ginger cultured tissues in phenolic accumulation would be of immense importance for pharmacological, cosmetic and agronomic industries.     

In-vitro antioxidative,antiinflammatory properties of Aurea helianthus leaf extract a Korean traditional medicinal plant

The leaf of Aurea helianthus (A. helianthus Jinhuakui) is popularly used in China traditional medicine, however, scientific evidence on its antioxidant properties rarely studied. In this study, biological activities of A. helianthus leave’s 80% ethanol extract (AHL) were investigated. The measured total polyphenol and flavonoid content of AHL was 184.24 ± 5.01 mg GAE/g and 102.53 ± 0.98 mg NAR/g. AHL showed the highest α, α-diphenyl-β-picrylhydrazyl (DPPH) and 2,2′-azino-bis-3-ethylbenzo-thiazoline-6-sulfonic acid (ABTS) radical scavenging activities of 98.30 ± 0.18% at 1000 µg/mL. DPPH and ABTS radical scavenging activities significantly increased in a AHL concentration-dependent manner. AHL treatment significantly suppressed the generation of pro-inflammatory mediators, including nitric oxide (NO), in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. AHL demonstrated strong anti-inflammatory activity that reduced NO production in LPS-stimulated RAW 264.7 cells. To test the potential protective effect of AHL, the antioxidant capacity, on the cell growth, viability of a human hepatoma cell (HepG2) and Raw 264.7 cell were investigated. AHL also enhanced cytotoxicity on the proliferation of HepG2 cells and was capable of inhibiting 56% against LPS at 400 µg/mL. The results of this study the potential of AHL as an excellent antioxidant substance for inhibiting inflammatory mediators. Therefore, AHL may be used as a therapeutic approach to various inflammatory diseases.     

Stabilization of stannous pyrophosphate kits with gentisic acid

We evaluated the ability of gentisic acid, an antioxidant, to stabilize stannous pyrophosphate (Sn:PPi) kits and extend the shelf-life of the kit after reconstitution. In vitro studies showed that gentisic acid (0.5 mg/mL) stabilized the stannous ion against oxidation by various levels of exogenous hydrogen peroxide. In patients who received stabilized Sn:PPi for in vivo red blood cell labelling, the left ventricle-to-background activity ratio was significantly higher than that in patients who received a standard formulation of Sn:PPi. Gentisic acid is now used routinely in the Sn:PPi kit formulation in this institution.     

Plantlet regeneration through indirect shoot organogenesis and somatic embryogenesis in Justicia gendarussa Burm. f., a medicinal plant

A protocol for the regeneration of a large number of plantlets via indirect shoot organogenesis and somatic embryogenesis has been developed from the stem and leaf explants of Justicia gendarussa Burm. f. The callus was efficiently induced from the explants using Murashige and Skoog (MS) medium supplemented with α-Naphthalene acetic acid (NAA) + Benzyl amino purine (BAP) (1.0?+?0.1 mg/l). The highest number of plantlets through indirect shoot organogenesis was obtained when the callus was subcultured to MS medium with BAP + NAA (0.1?+?1.0 mg/l). The maximum number of plantlets via somatic embryos was obtained in the medium with BAP + NAA (1.0?+?0.1 mg/l) for stem derived calli and Kinetin (Kn) + NAA (2.0?+?0.1 mg/l) for leaf derived calli. The in vitro developed shoots were rooted well in half strength MS medium supplemented with 0.5 mg/l of Indole-3-acetic acid (IAA). The in vitro regenerated plantlets were hardened using a mixture of sterile sand:soil:manure (1:1:1). The present study is the first report on the regeneration of plants through somatic embryogenesis from stem and leaf derived calli of J. gendarussa.     

狭果茶藨子果实多糖提取及其抗氧化和流变特性

以狭果茶藨子果实为原料,多糖提取量为考察指标,通过单因素试验及响应面试验对多糖提取工艺进行优化,结果表明最佳多糖制备工艺条件为:提取温度40℃,时间30 min,料液比1∶30 g/mL,此时狭果茶藨子中多糖提取量达115.32 mg/g;流变学特性研究表明狭果茶藨子果实多糖溶液属于非牛顿流体,多糖溶液表现出剪切稀化的现象,当多糖质量浓度为1.0%时,其流变学特性与0.1%的羧甲基纤维素钠溶液相似,且过酸、过碱的环境均不会改变狭果茶藨子果实多糖溶液的流变学特性;抗氧化试验结果表明狭果茶藨子果实多糖具有潜在的抗氧化能力,对DPPH自由基的清除能力低于抗坏血酸,而对羟自由基的清除能力显著高于抗坏血酸。本研究结果可为狭果茶藨子果实多糖在食品领域的开发利用提供理论依据。     

Antioxidant and xanthine oxidase inhibitory activities of total polyphenols from onion

Onions (Allium cepa L.) comprise a valuable vegetable crop in many countries. Modern scientific research has shown that onions possess many biological activities, including antibacterial, anticancer, hypoglycemic, hypolipidemic, antiplatelet aggregation, and antioxidant activities. The goal of this study was to investigate the impact of total onion polyphenols on antioxidant and xanthine oxidase (XO) inhibitory activities. Total onion polyphenols showed significant antioxidant activity in DPPH, FRAP, and OH-assays (IC₅₀ [µg/mL]), 43.24, 560.61, and 12.97, respectively). In a X/XO system, antioxidant properties of these polyphenols significantly inhibited XO activity (IC₅₀ [µg/mL], 17.36). These results indicated that total onion polyphenols showed promising antioxidant and anti-gout properties and might be used as potential, natural drugs against oxidative diseases after successful studies in vivo as well as clinical trials.     

红花桑寄生叶提取物的抗氧化活性及酚类物质分析

采用DPPH法、TEAC法、FRAP法对红花桑寄生叶不同溶剂提取物的抗氧化活性进行体外评价,并测定其总酚、总黄酮含量。结果表明,溶剂种类对红花桑寄生叶提取物的得率、总酚、总黄酮及抗氧化活性影响显著。在3种评价方法中,不同溶剂提取物的抗氧化活性均表现出不同程度的量效依赖关系。3种溶剂提取物的抗氧化活性强弱依次为丙酮提取物 >甲醇提取物 >水提取物,其中80%丙酮提取物(总酚含量最高,达276.83mg/g)抗氧化活性最强,清除DPPH自由基能力EC₅₀值为0.247,FRAP值(FeSO₄ mmol/100g)为115.81,浓度为1.0mg/ml时,TEAC值为2.04。     

Biochemical activities of low molecular weight chitosans derived from squid pens

Chitosans were prepared by H₂O₂ oxidative depolymerization from squid pens with low molecular weights (LMW) of 13,025, 7011, 4169, 2242 and 963 Da. The bile acid binding capacities and antioxidant properties of LMW chitosans were studied in vitro. LMW chitosans exhibited stronger bile acid binding capacities than that of chitosan. The scavenging ability of LMW chitosans against DPPH radicals improved with increasing concentration, and EC₅₀ values were below 1.3 mg/mL. The EC₅₀ values of LMW chitosans against hydroxyl radicals ranged from 0.93 to 3.66 mg/mL. All LMW chitosans exhibited a strong ferrous ion chelating effect and reducing power. At 1 mg/mL, the scavenging ability of chitosan-963 towards superoxide radicals was 67.76%. These results indicated that LMW chitosans which have stronger bile acid binding capacity and antioxidant activities may act as potential antioxidants in vitro.     

Extraction Optimization,Characterization and Bioactivities of a Major Polysaccharide from Sargassum thunbergii

Sargassum thunbergii is a kind of natural edible algae. STP (S. thunbergii polysaccharides) was considered as the main bioactive compounds in S. thunbergii. To obtain the optimal processing conditions for maximum total sugar yield, single factor investigation and response surface methodology (RSM) were employed. The optimal processing conditions were as follows: liquid to solid ratio 120 mL/g, extraction time 210 min, extraction temperature 97°C. The experimental yield 7.53% under optimized conditions was closely agreed with the predicted yield 7.85% of the model. The major polysaccharide fraction from S. thunbergii (named STP-II) was purified by DEAE-Sepharose CL-6B column chromatography. High-performance size-exclusion chromatography (HPSEC), gas chromatography (GC) and high-performance liquid chromatography (HPLC) were used to identify its characterizations, and in vitro antioxidant assays and cytotoxicity assays were used to research its bioactivities. The purified fraction STP-II (63.75%) was a single peak in HPSEC with Sugar KS-804 column, had a molecular weight of 550KD, and comprised mainly of fucose, xylose, galactose, glucose and glucuronic acid. STP-II had higher scavenging activities on hydroxyl radical (76.72% at 0.7 mg/mL) and superoxide radical (95.17% at 2 mg/mL) than Vitamin C (Vc). STP-II also exhibited the capability of anti-proliferation in Caco-2 cells. STP-II possessed good antioxidant and inhibitory activity against human colon cancer Caco-2 cells in vitro and could be explored as novel natural functional food.     

Enzyme inhibition and antioxidant functionality of eleven Inula species based on chemical components and chemometric insights

The members of the genus Inula have been widely used in traditional medicinal. In the present study, 11 Inula species were investigated for their phytochemical composition, antioxidant and enzyme inhibitory effects. While quinic acid was the principal compound in I. anatolica, I. britannica, I. inuloides, I. oculus-christi, I. peacockiana, I. sechmenii, I. thapsoides and I. viscidula extracts (22.43–42.02 mg/g dry extract (DE)), I. aucheriana and I. discoidea extracts contained rutin as their most abundant compound (23.28 and 79.10 mg/g extract, respectively). Interestingly, all the Inula extracts were active inhibitors of the five key clinical enzymes (acetylcholinesterase (3.56–5.13 mg galantamine equivalent (GALAE)/g), butyrylcholinesterase (1.49–7.34 mg GALAE/g), tyrosinase (112.31–122.13 mg kojic acid equivalent (KAE)/g), α-glucosidase (0.77–2.08 mmol acarbose equivalent (ACAE)/g) and α-amylase (0.73–0.90 mmol ACAE/g)). Furthermore, the extracts were observed to exhibit substantial antioxidant capacity (1,1-diphenyl-2-picrylhydrazyl (DPPH): 58.99–188.22 mg trolox equivalent (TE)/g); 2,2-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) (ABTS): 90.51–220.97 mg TE/g; cupric reducing antioxidant capacity (CUPRAC): 169.88–460.53 mg TE/g; ferric reducing antioxidant power (FRAP): 81.57–237.99 mg TE/g; metal chelating activity: 8.31–25.39 mg ethylenediamine tetraacetate equivalent (EDTAE)/g; phosphomolybdenum: 1.55–2.49 mmol TE/g). In conclusion, the Inula species studied herein showed promising pharmacological potentials justified by the presence of a panoply of bioactive compounds.     

Synergistic effect of conjugated linolenic acid isomers against induced oxidative stress,inflammation and erythrocyte membrane disintegrity in rat model

Background

α-Eleostearic acid and punicic acid, two typical conjugated linolenic acid (CLnA) isomers present in bitter gourd and snake gourd oil respectively, exhibit contrasting cis-trans configuration which made them biologically important.

Methods

Rats were divided into six groups. Group 1 was control and group 2 was treated control. Rats in the groups 3 and 4 were treated with mixture of α-eleostearic acid and punicic acid (1:1) (0.5% and 1.0% respectively) while rats in the groups 5 and 6 were treated with 0.5% of α-eleostearic acid and 0.5% of punicic acid respectively along with sodium arsenite by oral gavage once per day.

Results

Results showed that increase in nitric oxide synthase (NOS) activity, inflammatory markers expression, platelet aggregation, lipid peroxidation, protein oxidation, DNA damage and altered expression of liver X receptor-α (LXR-α) after arsenite treatment were restored with the supplementation of oils containing CLnA isomers. Altered activities of different antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and ferric reducing ability of plasma (FRAP) also restored after oil supplementation. Altered morphology and fluidity of erythrocyte membrane studied by atomic force and scanning electron microscopy, after stress induction were significantly improved due to amelioration in cholesterol/phospholipid ratio and fatty acid profile of membrane. Oils treatment also improved morphology of liver and fatty acid composition of hepatic lipid.

Conclusions

Overall two isomers showed synergistic antioxidant and anti-inflammatory effect against induced perturbations and membrane disintegrity.

General significance

Synergistic antioxidant and anti-inflammatory role of these CLnA isomers were established by this study.     

Yeast alpha glucosidase inhibitory and antioxidant activities of six medicinal plants collected in Phalaborwa,South Africa

Recent decades have experienced a sharp increase in the incidence and prevalence of diabetes mellitus. One antidiabetic therapeutic approach is to reduce gastrointestinal glucose production and absorption through the inhibition of carbohydrate-digesting enzymes such as α-amylase and α-glucosidase and α-amylase. The aim of the current study was to screen six medicinal plant species, with alleged antidiabetic properties for α-glucosidase inhibitory activities. Powdered plant materials were extracted with acetone, and tested for ability to inhibit baker's yeast α-glucosidase and α-amylase activities. The largest mass (440 mg from 10 g) of the extract was obtained from Cassia abbreviata, while both Senna italica and Mormordica balsamina yielded the lowest mass of the extracts. Extracts of stem bark of C. abbreviata inhibited baker's yeast α-glucosidase activity with an IC₅₀ of 0.6 mg/ml. This plant species had activity at low concentrations, with 1.0 mg/ml and above resulting in inhibition of over 70%. The other five plant extracts investigated had IC₅₀ values of between 1.8 and 3.0 mg/ml. Senna italica only managed to inhibit the activity of enzyme-glucosidase at high concentrations with an IC₅₀ value of 1.8 mg/ml, while Tinospora fragosa extracts resulted in about 55% inhibition of the activity of the enzyme at a concentration of 3.5 mg/ml, with an estimated IC₅₀ value of 2.8 mg/ml. The bark extract of C. abbreviata was the most active inhibitor of the enzyme, based on the IC₅₀ values (0.6 mg/ml). The bark extract of C. abbreviata contains non-competitive inhibitor(s) of α-glucosidase, reducing V_max value of this enzyme from 5 mM·s^–1 to 1.67 mM·s^–1, while K_m remained unchanged at 1.43 mM for para-nitrophenyl glucopyranoside. Antioxidant activity of the extracts was also investigated. The C. abbreviata extract was more active as an antioxidant than the positive control, trolox. The extracts did not inhibit alphaamylase activity more than about 20% at the highest concentration tested.     

Enzymatic synthesis of palm-based ascorbyl esters

The synthesis of palm-based ascorbyl esters through transesterification of ascorbic acid and palm oil in tert-amyl alcohol catalyzed by immobilized lipase is described. Highest conversion (70–75%) was determined after 16 h reaction at 40 °C using lipase (Novozyme 435 from Candida antartica) with an ascorbic acid to palm oil mole ratio of 1:8. The purified product was further characterized by ¹³C NMR and GC–MS and the mixture of ascorbyl monoesters obtained were identified as ascorbyl monooleate (61%), ascorbyl monopalmitate (30%) and ascorbyl monostearate (9%). The antioxidant activity of palm-based ascorbyl esters was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) test. The results showed that pure palm-based ascorbyl esters have an antioxidant activity with an IC₅₀ value of 0.1 mg/mL.     

Profiling the phyto-constituents of Punica granatum fruits peel extract and accessing its in-vitro antioxidant,anti-diabetic,anti-obesity,and angiotensin-converting enzyme inhibitory properties

This context was investigated to assess the in vitro antioxidant, anti-diabetic, anti-obesity, and angiotensin-converting enzyme (ACE) inhibition traits of Punica granatum fruits peel extract. Initially, among various extracts tested, aqueous and ethanolic peel extracts depicted the presence of diverse phytoconstituents. In vitro antioxidative properties of peel extracts were determined using standard methodologies. Results showed that aqueous and ethanolic extracts had IC₅₀ values of 471.7 and 509.16 μg/mL, respectively in terms of 1,1,diphenyl 2,2,picrylhydrazyl scavenging. Likewise, IC₅₀ values of aqueous and ethanol extract were obtained as 488.76 and 478.47 μg/mL towards the degradation of hydrogen peroxide. The ethanolic extract exhibited the highest inhibition of α-glucosidase by showing activity of 53.34 ± 2.0 to 15.18 ± 1.4 U/L in a dose dependent manner (100–1000 µg/mL). Ethanolic extract was reported as the most active inhibitor of lipase with an IC₅₀ value of 603.50 µg/mL. Ethanolic extract showed increased inhibition of ACE in a concentration dependent manner (100–1000 µg/mL) with IC₅₀ value of 519.45 µg/mL. Fourier transform-infrared spectrum revealed the availability of various functional groups in the ethanolic extract of peel. Gas chromatography-mass spectrometry chromatogram of peel extract illustrated 23 diversified chemical constituents including 1,2,3,4-butanetetrol, Dimethyl sulfone, 9-octadecenamide, and Pentadecanoic acid as predominant compounds. In summary, P. granatum fruits peel extract revealed promising antioxidant, anti-diabetic, anti-obesity, and anti-hypertensive properties.     

Transport and metabolic effects of α-aminoisobutyric acid in saccharomyces cerevisiae

α-Aminoisobutyric acid is actively transported into yeast cells by the general amino acid transport system. The system exhibits a K_m for α-aminoisobutyric acid of 270 μM, a V_max of 24 nmol/min per mg cells (dry weight), and a pH optimum of 4.1–4.3. α-Aminoisobutyric acid is also transported by a minor system(s) with a V_max of 1.7 nmol/min per mg cells. Transport occurs against a concentration gradient with the concentration ratio reaching over 1000:1 (in/out). The α-aminoisobutyric acid is not significantly metabolized or incorporated into protein after an 18 h incubation. α-Aminoisobutyric acid inhibits cell growth when a poor nitrogen source such as proline is provided but not with good nitrogen sources such as NH₄⁺. During nitrogen starvation α-aminoisobutric acid strongly inhibits the synthesis of the nitrogen catabolite repression sensitive enzyme, asparaginase II. Studies with a mutant yeast strain (GDH-CR) suggest that α-aminoisobutyric acid inhibition of asparaginase II synthesis occurs because α-aminoisobutyric acid is an effective inhibitor of protein synthesis in nitrogen starved cells.