Stabilization of papain from papaya peels / Estabilización de la papaína de la cáscara de papaya

1998 ◽  
Vol 4 (3) ◽  
pp. 179-187 ◽  
Author(s):  
N. Espin ◽  
M.N. Islam
Keyword(s):  
Ascorbic Acid ◽  
Enzyme Activity ◽  
Protective Effect ◽  
Total Concentration ◽  
Sodium Ascorbate ◽  
Sodium Metabisulfite ◽  
Appreciable Effect ◽  
Original Activity ◽  
Before And After ◽  
Erythorbic Acid

Crude papain in papaya peels was stabilized before drying by the addition of various chemicals (ascorbic acid, sodium ascorbate, erythorbic acid, sodium erythorbate, sodium metabisulfite, sodium tetrathionate, 4-hexylresorcinol, t-butyl hydroquinone [TBHQ], rutin, α-tocopherol, trehalose, and sucrose). Chemicals were added to the ground papaya peels at 0, 0.12, 0.25, 0.5, 0.75, 1, 1.25, and 1.5% (w /w). Drying temperatures were 40, 55 and 60 °C. Enzyme activity was measured before and after drying by the casein digestion method. Percentage of enzyme activity retained (% EAR) was calculated by assigning a value of 100% EAR to fresh peels. Possible synergism between chemicals was also studied for a 1:1 ratio chemical/chemical at 1% total concentration. The highest % EAR was obtained at 55 °C for all chemicals except for sucrose and trehalose which showed their best effect at 40 °C. TBHQ rutin, α-tocopherol and 4-hexylresorcinol showed a destabilizing effect. Maximum protective effect occurred at 1% concentration. At this concentration sodium tetrathionate showed the best protective effect (90% EAR) followed by sodium metabisulfite (85% EAR), while both sodium ascorbate and sodium erythorbate retained 75% of the original activity. Ascorbic acid and erythorbic acid were 10% less effective than their corresponding sodium salts, possibly due to lower pH. Trehalose showed only 57 % EAR while sucrose failed to produce any appreciable effect. No synergistic effect was shown by any combination of chemicals.

scholarly journals The role of histidine residues in glutamate dehydrogenase

1972 ◽  
Vol 129 (2) ◽  
pp. 419-425 ◽  
Author(s):  
N. Tudball ◽  
R. Bailey-Wood ◽  
P. Thomas
Keyword(s):  
Enzyme Activity ◽  
Glutamate Dehydrogenase ◽  
Rose Bengal ◽  
Marked Decrease ◽  
Total Loss ◽  
Appreciable Effect ◽  
Normal Response ◽  
Original Activity ◽  
Histidine Residues

1. Glutamate dehydrogenase was subject to rapid inactivation when irradiated in the presence of Rose Bengal or incubated in the presence of ethoxyformic anhydride. 2. Inactivation in the presence of Rose Bengal led to the photo-oxidation of four histidine residues. Oxidation of three histidine residues had little effect on enzyme activity, but oxidation of the fourth residue led to the almost total loss of activity. 3. Acylation of glutamate dehydrogenase with ethoxyformic anhydride at pH6.1 led to the modification of three histidine residues with a corresponding loss of half the original activity. Acylation at pH7.5 led to the modification of two histidine residues and a total loss of enzyme activity. 4. One of the histidine residues undergoing reaction at pH6.1 also undergoes reaction at pH7.5. 5. The presence of either glutamate or NAD+in the reaction mixtures at pH6.1 had no appreciable effect. At pH7.5 glutamate caused a marked decrease in both the degree of alkylation and degree of inactivation. NAD+had no effect on the degree of inactivation at pH7.5 but did modify the extent of acylation. 6. The normal response of the enzyme towards ADP was unaffected by acylation at pH6.1 or 7.5. 7. The normal response of the enzyme towards GTP was altered by treatment at both pH6.1 and 7.5.

Sorbitol enhances the physicochemical stability of B12 vitamers

2020 ◽  
Vol 90 (5-6) ◽  
pp. 439-447 ◽  
Author(s):  
Andrew Hadinata Lie ◽  
Maria V Chandra-Hioe ◽  
Jayashree Arcot
Keyword(s):  
Ascorbic Acid ◽  
Uv Light ◽  
Heat Exposure ◽  
Water Soluble ◽  
Uv Exposure ◽  
Physicochemical Stability ◽  
Before And After ◽  
The Stability

Abstract. The stability of B12 vitamers is affected by interaction with other water-soluble vitamins, UV light, heat, and pH. This study compared the degradation losses in cyanocobalamin, hydroxocobalamin and methylcobalamin due to the physicochemical exposure before and after the addition of sorbitol. The degradation losses of cyanocobalamin in the presence of increasing concentrations of thiamin and niacin ranged between 6%-13% and added sorbitol significantly prevented the loss of cyanocobalamin (p<0.05). Hydroxocobalamin and methylcobalamin exhibited degradation losses ranging from 24%–26% and 48%–76%, respectively; added sorbitol significantly minimised the loss to 10% and 20%, respectively (p < 0.05). Methylcobalamin was the most susceptible to degradation when co-existing with ascorbic acid, followed by hydroxocobalamin and cyanocobalamin. The presence of ascorbic acid caused the greatest degradation loss in methylcobalamin (70%-76%), which was minimised to 16% with added sorbitol (p < 0.05). Heat exposure (100 °C, 60 minutes) caused a greater loss of cyanocobalamin (38%) than UV exposure (4%). However, degradation losses in hydroxocobalamin and methylcobalamin due to UV and heat exposures were comparable (>30%). At pH 3, methylcobalamin was the most unstable showing 79% degradation loss, which was down to 12% after sorbitol was added (p < 0.05). The losses of cyanocobalamin at pH 3 and pH 9 (~15%) were prevented by adding sorbitol. Addition of sorbitol to hydroxocobalamin at pH 3 and pH 9 reduced the loss by only 6%. The results showed that cyanocobalamin was the most stable, followed by hydroxocobalamin and methylcobalamin. Added sorbitol was sufficient to significantly enhance the stability of cobalamins against degradative agents and conditions.

Assessment of Color Stability of Treated Leathers with Silicone Oil and Polyethylene Glycol

2014 ◽  
Vol 1 (1) ◽  
pp. 24-34
Author(s):  
Alireza K. ◽  
Hossein Ahmadi ◽  
Mohsen Mohammadi
Keyword(s):  
Ascorbic Acid ◽  
Polyethylene Glycol ◽  
Treatment Process ◽  
Color Change ◽  
Silicone Oil ◽  
Accelerated Aging ◽  
Color Stability ◽  
Antioxidant Additive ◽  
Before And After ◽  
Aesthetic Values

Lubricants and leather dressings are the most common treatments of dry and water logged historical leathers. Color change has a great importance during the time and treatment process, due to visual and aesthetic values of historic leather relics. Polyethylene glycol (PEG) and silicone oil (SiO) are frequently used leather dressings in the conservation procedures. Therefore, color stability of treated leathers with PEG and SiO were investigated before and after heat accelerated aging. Moreover, application of ascorbic acid was evaluated as an antioxidant additive for PEG (PEG+AA).Color change after treatment and aging were studied by colorimetry technique in the CIE *L*a*b system. Results indicated to severe color alteration in PEG treated and aged leathers with or without ascorbic acid. Whereas, SiO treated samples showed better stability and minimum color shift after aging. Silicone oil was characterized as the best dressing for historical leathers with compared to PEG and PEG+AA, due to its high stability and aesthetical properties.

scholarly journals Light-Induced Byproducts of Vitamin C in Multivitamin Solutions

2004 ◽  
Vol 50 (1) ◽  
pp. 135-140 ◽  
Author(s):  
Jean-Claude Lavoie ◽  
Philippe Chessex ◽  
Thérèse Rouleau ◽  
Diane Migneault ◽  
Blandine Comte
Keyword(s):  
Mass Spectrometry ◽  
Ascorbic Acid ◽  
Vitamin C ◽  
Organic Peroxides ◽  
Ambient Light ◽  
Rapid Loss ◽  
Biological Importance ◽  
Before And After

Abstract Background: When solutions of multivitamin preparations (MVPs) are exposed to light, H2O2 as well as organic peroxides are generated and the concentration of vitamin C decreases. The aim of this study was to determine, using mass spectrometry, whether the generation of oxidative byproducts of vitamin C, such as dehydroascorbate (DHA) and 2,3-diketogulonic acid (DKG), accounted for the reported decrease in ascorbic acid in MVPs exposed to light. Methods: Mass spectrometry was used to document the formation of byproducts of ascorbic acid in solutions containing a MVP, vitamin C + riboflavin, and vitamin C + H2O2 + Fe2+. The involvement of ascorbic acid and H2O2 in the formation of organic peroxides was tested by measuring peroxide concentrations in solutions containing H2O2 with or without ascorbic acid and with or without Fe2+ before and after addition of catalase. Results: The loss of ascorbic acid in photo-exposed MVPs was associated with the concomitant generation of byproducts different from DHA and DKG. Among them, one mass fingerprint was particularly observed with solutions of vitamin C + riboflavin exposed to ambient light as well as with the solution of vitamin C + H2O2 + Fe2+, suggesting a Fenton-like reaction. This fingerprint was associated with the formation of catalase-resistant peroxides. Conclusion: Exposure of MVPs to light leads to the rapid loss of ascorbic acid and generation of specific byproducts that differ from DHA and DKG. The conversion of vitamin C into byproducts could be of biological importance in accounting for the decrease in ascorbic acid concentrations and the generation of organic peroxides in light-exposed MVPs.

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