Pre-extraction Preparation (Fresh, Frozen, Freeze-Dried, or Acetone Powdered) and Long-Term Storage of Fruit and Vegetable Tissues:  Effects on Antioxidant Enzyme Activity

Abstract

Activities of the antioxidant enzymes ascorbate peroxidase, catalase, dehydroascorbate reductase, glutathione reductase, guaiacol peroxidase, monodehydroascorbate reductase, and superoxide dismutase were assayed in honeydew (Cucumis melo L.) fruit and spinach (Spinacia oleracea L.) leaves either as fresh, frozen to -80 degrees C, frozen in liquid nitrogen, freeze-dried, or acetone powder, representing the various ways tissues are treated prior to enzyme extraction. Treated tissues were analyzed following treatment or stored for up to 8 weeks at -80 degrees C. Enzyme activities in fruit frozen with or without liquid nitrogen and leaves frozen with or without liquid nitrogen or freeze-dried were equal to those of fresh tissue. Enzyme activities in freeze-dried or acetone-powdered fruit and leaves and in acetone-powdered tissues were significantly higher or lower than those in fresh tissue. Enzyme activities in both tissues frozen with or without liquid nitrogen and stored for 8 weeks at -80 degrees C changed little; those in freeze-dried and acetone-powdered tissues, however, significantly increased/decreased over the same period. Fresh tissue should be used in antioxidant enzyme assays, but if storage is necessary, tissues should be placed directly into a -80 degrees C freezer.

Superoxide Dismutase Activity in Mesocarp Tissue from Divergent Cucumis melo L. Genotypes

“…Specific and total SOD activities in C. melo cultivar fruits grown on clay soil were generally higher than similar fruits grown on sandy soil; which paralleled the response found for the non-enzymatic antioxidant β-carotene [12] and ascorbic acid [13] in melons grown on clay vs. sandy soils. A partial explanation for this weak association of soil type with C. melo fruit SOD activities may be due to the soil fertilization during fruit growth and development.…”

“…Extraction and assay of superoxide dismutase (SOD; EC 1.15.1.1) followed the procedure described in Lester et al [13]. SOD activity was monitored at 550 nm as the inhibition of cytochrome c reduction coupled with superoxide generation with and without the protein extract.…”

Impact of Freezing and Freeze-drying Processes on Color, Phytochemical Contents and Antioxidant Capacity of Pomegranate Seeds

“…Anthocyanins content was not stable by the processing techniques. The reduction in total anthocyanins content may be attributed to the presence of oxidative enzymes (Lester et al, 2004). During processing and storage, anthocyanin degradation and polymerization usually lead to its discoloration (Kalt et al, 2000;Yuksel and Koka, 2008).…”

Antioxidative defense mechanism of the ruderal Verbascum olympicum Boiss. against copper (Cu)-induced stress

“…The APX (EC 1.11.1.11) activity was determined according to the method described by Lester et al [22]. This enzyme activity was stated from the decrease in absorbance at 290 nm as ascorbate was oxidised.…”

“…The CAT (EC 1.11.1.6) activity was assayed as described by Lester et al [22] with some modifications. The reaction was initiated by adding 0.1 ml of the enzyme extract to the assay mixture containing 20 mM sodium phosphate buffer (pH 6.8) and 15 mM H 2 O 2 .…”