The occurrence of malondialdehyde (MDA), a secondary end product of the oxidation of polyunsatu- rated fatty acids, is considered a useful index of general lipid peroxidation A common method for measuring MDA, referred to as the thiobarbituric acid-reactive- substances (TBARS) assay, is to react it with thiobar- bituric acid (TBA) and record the absorbance at 532 nm However, many plants contain interfering compounds that also absorb at 532 nm, leading to overestimation of MDA values Extracts of plant tissues including purple eggplant (Solanum melongena L) fruit, carrot (Daucus carota L) roots, and spinach (Spinacia oleracea L) leaves were assessed for the presence of MDA and other non-MDA compounds absorbing at 532 nm A method described herein corrects for these interferences by subtracting the absorbance at 532 nm of a solution containing plant extract incubated without TBA from an identical solution containing TBA The reliability and eAciency of this spectrophotometric method was assessed by altering the relative ratios of exogenous MDA additions and/or extracts of red cabbage (Brassica oleracea L) leaves containing inter- fering compounds and then measuring MDA recovery Reliability was also validated through high-performance liquid chromatography and high-performance liquid chromatography-mass spectrometry techniques Results indicated that over 90% of exogenously added MDA could be recovered through the improved protocol If there were no corrections for interfering compounds, MDA equivalents were overestimated by up to 965% Interfering compounds were not detected in vegetables such as lettuce (Lactuca sativa L) and spinach which had low or negligible concentrations of anthocyanidin derivatives Comparisons between the TBARS method presented here and two currently accepted protocols indicated that the new modified method exhibits greater accuracy for quantifying TBA-MDA levels in tissues containing anthocyanins and/or other interfering com- pounds This modified protocol represents a facile and rapid method for assessment of lipid peroxidation in virtually all plant species that contain interfering com- pounds

Improving the thiobarbituric acid-reactive-substances assay for estimating lipid peroxidation in plant tissues containing anthocyanin and other interfering compounds

Antioxidant activity has been assessed in many ways. The limitation of many newer methods is the frequent lack of an actual substrate in the procedure. The combination of all approaches with the many test methods available explains the large variety of ways in which results of antioxidant testing are reported. The measurement of antioxidant activities, especially of antioxidants that are mixtures, multifunctional or are acting in complex multiphase systems, cannot be evaluated satisfactorily by a simple antioxidant test without due regard to the many variables influencing the results. Several test procedures may be required to evaluate such antioxidant activities. A general method of reporting antioxidant activity independent of the test procedure is proposed.

http://ucce.ucdavis.edu/files/datastore/608-46.pdf

Methods for testing antioxidant activity

The use of 1-methylcyclopropene (1-MCP) on fruits and vegetables.

Effects of heat acclimation pretreatment on changes of membrane lipid peroxidation, antioxidant metabolites, and ultrastructure of chloroplasts in two cool-season turfgrass species under heat stress

Analysis of the oxidative processes taking place during fruit ripening in a salad tomato variety (Lycopersicon esculentum Mill. cv. Ailsa Craig) revealed changes in oxidative and antioxidative parameters. Hydrogen peroxide content, lipid peroxidation and protein oxidation were measured as indices of oxidative processes and all were found to increase at the breaker stage. The levels of the aqueous-phase antioxidants, glutathione and ascorbate, increased during the ripening process and these increases were associated with significant changes in their redox status, becoming more reduced as ripening progressed. Changes in the activities of superoxide dismutase, catalase and the enzymes involved in the ascorbate-glutathione cycle during ripening indicated that the antioxidative system plays a fundamental role in the ripening of tomato fruits.

Changes in oxidative processes and components of the antioxidant system during tomato fruit ripening.

Use of the thiobarbituric acid (TBA) assay for thiobarbituric acid-reactive substances (TBARS) of lipid oxidation in extracts of plant materials was examined. Sucrose, fructose, glucose, lactose, citrus pectin, and bovine serum albumin (BSA) interfered with the TBA assay reaction. To correct for the interference caused by sugars (the major interference), a modified procedure was developed using standard curves for both malondialdehyde (MDA) and sucrose. Molar absorbance (MA) of adducts from TBA-MDA and TBA-sucrose reactions increased when the acidity in the reaction mixture increased and the time of heating and the temperature of heating for the reaction increased

Modified thiobarbituric acid assay for measuring lipid oxidation in sugar-rich plant tissue extracts

Yoshihara, T., et al. 1989. Structure of a tuber-inducing stimulus from potato leaves (Solanum tuberosum L.). Agr. Biol. Chem. 53:2835–2837. Zeringue, Jr., H.J. and S.P. McCormick. 1989. Relationships between cotton leaf-derived volatiles and growth of Aspergillus flavus. J. Amer. Oil Chem. Soc. 66:581–585. Zeringue, Jr., H.J. and S.P. McCormick. 1990. Aflatoxin production in cultures of Aspergillus flavus incubated in atmospheres containing selected cotton leaf-derived volatiles. Toxicon 28:445–448. Zimmerman, D.C. 1966. A new product of linoleic acid oxidation by a flaxseed enzyme. Biochem. Biophys. Res. Commun. 23:398–402. Zimmerman, D.C. and C.A. Coudron. 1979. Identification of traumatin, a wound hormone, as 12-oxo-trans-10-dodecenoic acid. Plant Physiol. 63:536–541. Zimmerman, D.C. and P. Feng. 1978. Characterization of a prostaglandin-like metabolite of linolenic acid produced by a flaxseed extract. Lipids 13:313–316.

/pdf/peroxidative-activity-of-apple-peel-in-relation-to-28q1dbqlfk.pdf

Peroxidative Activity of Apple Peel in Relation to Development of Poststorage Disorders

Total superoxide dismutase (SOD:superoxide: superoxide oxidoreductase; EC 1.15.1.1) activity and individual activities of its three different metalloenzymes, CuZn-SOD, Fe-SOD, and Mn-SOD, were investigated during senescence of apples (Malus domestica Borkh.). Total SOD activity and relative activities of its three forms varied greatly among cultivars. Activities underwent considerable change during senescence of fruit, but changes were different among cultivars. Whether fruit senesced at 0 degrees C or 20 degrees C had little effect on SOD activities, and application of the antioxidant diphenylamine (DPA) did not alter activities. SOD activities increased with occurrence of the physiological disorder "senescent breakdown," but did not increase with occurrence of the disorder "superficial scald." In a given apple cultivar, changes in total SOD activity generally paralleled activities of the different SOD forms. Such activity may reflect changes affecting food and nutritive quality of the fruit.

Superoxide Dismutase Activities in Senescing Apple Fruit (Malus domestica Borkh.)

Ethephon and diphenylamine (DPA) were used to examine the role of ethylene production in biochemical changes that precede development of superficial scald on 'Cortland' apples ( Malus domestica Borkh.) after cold storage. Treatments modified α-farnesene and conjugated triene (CT) accumulations in fruit peel, and their effects on CTs differed depending on whether CTs were measured at 258 nm (CT258) or 281 nm (CT281). Ethephon induced rapid and delayed effects on fruit, the former being stimulation of ethylene production and α-farnesene and CT accumulation in fruit peel, which could increase scald development, and the latter being a disproportionately higher accumulation of CT258 than of CT281 during prolonged cold storage, which was associated with reduced scald development. DPA treatment at harvest also produced rapid and delayed effects. It immediately reduced ethylene synthesis and α-farnesene and CT accumulation. In addition, during fruit storage at 0C, DPA reduced accumulation of CT281 more than that of CT258. The rapid and delayed effects of DPA should contribute to less scald development. These results showed that ethylene probably was involved in effects of ethephon and DPA on scald development and suggest that ethylene has a fundamental role in changes associated with superficial scald development.

/pdf/roles-of-ethylene-in-the-development-of-superficial-scald-in-4knythb7q9.pdf

Roles of Ethylene in the Development of Superficial Scald in 'Cortland' Apples

Three experiments were conducted using 'Cortland' and 'Delicious' apples (Malus domestica Borkh.). Fruit varying widely in superficial scald susceptibility, because of either endogenous or experimentall y induced conditions, were stored for various intervals at 0C and evaluated for scald development at 20C. Samples were extracted periodically in hexane, and ultraviolet absorption spectra of the extracts were used to evaluate α- farnesene and conjugated triene (CT) relationships to scald development. CT concentration s were calculated using each of the three CT absorption maxima (258 - 290 nm, 269 - 290 nm, and 281- 290 nm) and expressed accordingly as CT258, CT269, and CT281. The poor association of CT281 concentrations with scald development led us to propose that metabolic products of CT281 species are more likely to be associated with scald development than the species themselves.

/pdf/a-modified-hypothesis-on-the-role-of-conjugated-trienes-in-46t7slbzxw.pdf

Zhanyuan Du

Papers

Modified thiobarbituric acid assay for measuring lipid oxidation in sugar-rich plant tissue extracts

Peroxidative Activity of Apple Peel in Relation to Development of Poststorage Disorders

Superoxide Dismutase Activities in Senescing Apple Fruit (Malus domestica Borkh.)

Roles of Ethylene in the Development of Superficial Scald in 'Cortland' Apples

A Modified Hypothesis on the Role of Conjugated Trienes in Superficial Scald Development on Stored Apples