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Although calcium (Ca) concentration in cellular compartments has been suggested to be tightly regulated, Ca deficiency disorders such as blossom-end rot (BER) in tomato (Solanum lycopersicum) fruit may be induced by abnormal regulation of Ca partitioning and distribution in the cell. The objectives of this work were to analyze the effects of high expression of the constitutively functional Arabidopsis (Arabidopsis thaliana) Ca 2+ /H + exchanger (sCAX1) tonoplast protein in tomato fruit on cellular Ca partitioning and distribution, membrane integrity, and the transcriptional profile of genes potentially involved in BER development. Wild-type and sCAX1-expressing tomato plants were grown in a greenhouse. Wild-type plants did not develop BER, whereas sCAX1-expressing plants reached 100% BER incidence at 15 d after pollination. The sCAX1-expressing fruit pericarp had higher total tissue and water-soluble Ca concentrations, lower apoplastic and cytosolic Ca concentrations, higher membrane leakage, and Ca accumulation in the vacuole of sCAX1-expressing cells. Microarray analysis of healthy sCAX1-expressing fruit tissue indicated down-regulation of genes potentially involved in BER development, such as genes involved in membrane structure and repair and cytoskeleton metabolism, as well as up-regulation of genes that may have limited BER damage expansion, such as genes coding for heat shock proteins, glutathione S-transferases, and peroxidases. The results indicate that the high expression of the sCAX1 gene reduces cytosolic and apoplastic Ca concentrations, affecting plasma membrane structure and leading to BER symptom development in the fruit tissue.

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The ratio between MHO-on and MHO-ol might serve as an index of superficial scald severity. Reduction of BP symptoms in LO2-treated fruits could be due to accumulation of volatile alcohols in the peel tissue.

Summary Sweetpotato [Ipomoea batatas (L.) Lam.] cv. ‘Beauregard’ roots were cooked using three different heat‐processing techniques (baked in a conventional oven, baked in a microwave oven, and boiled). Total phenolic content, individual phenolic acids, and antioxidant capacity were determined using Folin‐Denis assay, HPLC (high‐performance liquid chromatography), and DPPH (1,1‐diphenyl‐2‐picrylhydazyl) assay, respectively. The skin tissue (raw or processed) contained the highest concentration of total phenolics. All heat‐processing methods resulted in a significant loss in total phenolic content and antioxidant capacity of the skin tissue. However, compared with the other processing methods, conventional oven baking resulted in greater losses in antioxidant capacity of skin tissue. Total phenolic content ranged from a low of 1.58 mg chlorogenic acid equivalent g−1 dry tissue weight in boiled pith tissue to a high of 17.7 mg chlorogenic acid equivalent g−1 dry tissue weight in raw skin tissue. The antioxidant capacity was highest in raw skin tissue (22.9 mg Trolox equivalent g−1 dry tissue weight). Chlorogenic acid was the principal phenolic acid found in all sweetpotato tissues. Caffeic acid and three isomers of dicaffeoylquinic acid (diCQA) were also identified and quantified.

Phenolic acids are one of the several classes of naturally occurring antioxidant compounds found in sweetpotatoes. Simplified, robust, and rapid methodologies were optimized to quantify total and individual phenolic acids in sweetpotato roots. Total phenolic acid content was quantified spectrophotometrically using both Folin-Denis and Folin-Ciocalteu reagents. The Folin-Ciocalteu reagent gave an overestimation of total phenolic acids due to the absorbance of interfering compounds (that is, reducing sugars and ascorbic acid). Individual phenolic acids were quantified by high-performance liquid chromatography (HPLC) using the latest in column technology. Four reversed-phase C18 analytical columns with different properties (dimensions, particle size, particle shape, pore size, and carbon load) were compared. Three different mobile phases using isocratic conditions were also evaluated. A column (4.6 x 150 mm) packed with 5-microm spherical silica particles of pore size 110 A combined with 14% carbon load provided the best and fast separation of individual phenolic acids (that is, chlorogenic acid, caffeic acid, and 3 isomers of dicaffeoylquinic acid) with a total analysis time of less than 7 min. Among the 3 mobile phases tested, a mobile phase consisting of 1% (v/v) formic acid aqueous solution: acetonitrile: 2-propanol, pH 2.5 (70:22:8, v/v/v) gave adequate separation. Among the solvents tested, aqueous mixtures (80:20, solvent:water) of methanol and ethanol provided higher phenolic acid extraction efficiency than the aqueous mixture of acetone.

Phenolic acids are considered important antioxidants that may help to prevent many human chronic diseases. The antioxidant activity and phenolic content of sweetpotato [Ipomoea batatas (L.) Lam.] roots and leaves of different sizes and ages, respectively, were quantified. Small roots (≈4 g root weight) had a higher antioxidant activity and phenolic content compared with full-sized marketable roots (≈300 g root weight). Phenolic content in marketable roots was significantly higher in the cortex tissue than in the internal pith tissue. The highest total phenolic content [chlorogenic acid equivalents (10.3 mg·g−1 dry weight)] and antioxidant activity [Trolox equivalents (9.7 mg·g−1 dry weight)] was found in cortex tissue of small-sized roots. Sweetpotato leaves had a significantly higher phenolic content and antioxidant activity than roots. Young, immature unfolded leaves had the highest total phenolic content (88.5 mg·g−1 dry weight) and antioxidant activity (99.6 mg·g−1 dry weight). Chlorogenic acid was the major phenolic acid in root and leaf tissues with the exception of young immature leaves in which the predominant phenolic acid was 3,5-dicaffeoylquinic acid. The results suggest that small-sized roots, which are typically discarded in the field, and young immature leaves may be concentrated sources of phenolic antioxidants.