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Fhatuwani N. Mudau, Puffy Soundy, and Elsa S. du Toit

Herbal teas have high concentrations of total polyphenols ( Owour et al., 2000 ; Venkatesan et al., 2004 ). Polyphenols are known to posses a wide range of beneficial biochemical and physiological properties ( Hirasawa et al., 2002 ). The major

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Fhatuwani N. Mudau, Puffy Soundy, and Elsa S. du Toit

, 2006) found that single applications of 300 kg·ha −1 N, 300 kg·ha −1 P, and 200 kg·ha −1 K maximized bush tea growth and leaf total polyphenols in all four seasons. According to Hirasawa et al. (2002) , total polyphenols are the primary indicator

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Au Trung Vo, Imane Haddidi, Hussein Daood, Zoltan Mayer, and Katalin Posta

promote the accumulation of some secondary metabolites, including beta-carotene and lycopine in tomato ( Ulrichs et al., 2008 ), or carotenoid and anthocyanins in Lactuca sativa ( Baslam et al., 2013 ). However, opposite results (no change in polyphenol

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Juran C. Goyali, Abir U. Igamberdiev, and Samir C. Debnath

countries in Europe and in South America, Asia, Australia, and New Zealand ( Strik, 2005 ; Strik and Yarborough, 2005 ). They contain higher dietary phytochemicals like polyphenols, anthocyanins, and proanthocyanidins compared with other fruits and

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Arnon Dag, Smadar Boim, Yulya Sobotin, and Isaac Zipori

) ‘Picual’, and (C) ‘Koroneiki’. Data points represent means of four replicates ± sd . An arrow line is inserted at 0.8% to indicate the maximal accepted level for extravirgin olive oil; (1.8 × °C) + 32 = °F. Fig. 2. Changes in polyphenol content of oils

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Robyn McConchie, N. Suzanne Lang, Alan R. Lax, and Gregory A. Lang

Premature leaf blackening in Protea severely reduces vase life and market value. The current hypothesis suggests that leaf blackening is induced by a sequence of events related to metabolic reactions associated with senescence, beginning with total depletion of leaf carbohydrates. It is thought that this carbohydrate depletion may induce hydrolysis of intercellular membranes to supply respiratory substrate, and subsequently allow vacuole-sequestered phenols to be oxidized by polyphenol oxidase (PPO) and peroxidase (POD) (Whitehead and de Swardt, 1982). To more thoroughly examine this hypothesis, leaf carbohydrate depletion and the activities of PPO and POD in cut flower Protea susannae × P. compacta stems held under light and dark conditions were examined in relationship to postharvest leaf blackening. Leaf blackening proceeded rapidly on dark-held stems, approaching 100% by day 8, and was temporally coincident with a rapid decline in starch concentration. Blackening of leaves on light-held stems did not occur until after day 7, and a higher concentration of starch was maintained earlier in the postharvest period for stems held in light than those held in dark. A large concentration of the sugar alcohol, polygalatol, was maintained in dark- and light-held stems over the postharvest period, suggesting that it is not involved in growth or maintenance metabolism. Polyphenol oxidase activity in light- and dark-held stems was not related to appearance of blackening symptoms. Activity of PPO at pH 7.2 in light-held stems resulted in a 10-fold increase over the 8-day period. Activity in dark-held stems increased initially, but declined at the onset of leaf blackening. There was no significant difference in POD activity for dark- or light-held stems during the postharvest period. Total chlorophyll and protein concentrations did not decline over the 8-day period or differ between light- and dark-held stems. Total phenolics in the dark-held stems increased to concentrations ≈30% higher than light-held stems. Consequently, the lack of association between membrane collapse, leaf senescence, or activities of oxidative enzymes (PPO or POD) with leaf blackening does not support the hypothesis currently accepted by many Protea researchers. An alternative scenario may be that the rapid rate of leaf starch hydrolysis imposes an osmotic stress resulting in cleavage of glycosylated phenolic compounds to release glucose for carbohydrate metabolism and coincidentally increase the pool of free phenolics available for nonenzymatic oxidation. The physiology of such a carbohydrate-related cellular stress and its manifestation in cellular blackening remains to be elucidated.

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Nixwell Mudau, Puffy Soundy, and Elsa du Toit

Bush tea (Athrixia phylicoides) belongs to the Asteraceae family. It is a popular beverage, commonly used as an herbal tea and for medicinal purposes. In some parts of South Africa, people consume or drink it as an aphrodisiac. Bush tea was grown under varying nitrogen (N), phosphorus (P) and potassium (K) levels in the four seasons to determine the seasonal nutrient requirements for improved quality. Treatment consisted of 0, 100, 200, 300, 400, or 500 kg·ha–1 N, P, or K in a randomized complete-block design under 50% shade nets. Three N, P, and K parallel trials were conducted per season (autumn, winter, spring, and summer). Total polyphenols were extracted using Folin-Ciaocalteau reagents and analyzed in a spectrophotometer. Results for the N trial suggested that total polyphenols increased quadratically in response to N nutrition during summer, winter, and spring, but not in autumn. The optimum N level was 300 kg·ha–1. The highest total polyphenol was 51.1 mg·g–1 in winter. For the P trial, total polyphenols also increased quadratically in response to P nutrition regardless of season. Again winter had the highest total polyphenols (46.8 mg·g–1). The optimum P level was 300 kg·ha–1. In the K trial, regardless of season, total polyphenols plateaued at 200 kg·ha–1 and the highest polyphenols were in winter (43.3 mg·g–1). Therefore, for improved total polyphenol content, 300 kg·ha–1 N and P and 200 kg·ha–1 K are recommended regardless of season.

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Tomoo Maeda, Hideo Kakuta, Takahiro Sonoda, Satoru Motoki, Reiichiro Ueno, Takashi Suzuki, and Katsuji Oosawa

The antioxidation capacities of green `Welcome', green and white `Gijnlim', and purple `Purple passion' asparagus spears were evaluated. Analyses of rutin and total polyphenols, and assays of DPPH radical absorbing and low-density lipoprotein (LDL) antioxidation were conducted. Varietal differences associated with the colors of spears were observed both in the amounts of rutin, total polyphenols and in DPPH radical absorbing activities, although not in LDL antioxidation activities. DPPH radical absorbing activities seemed to be affected by both rutin and other polyphenolic compounds. However, LDL antioxidation activities were likely to be influenced more by other polyphenolic compounds than by rutin. Total polyphenol content showed a fairly close relationship with rutin content, DPPH radical absorbing activity and LDL antioxidation activity. To determinate total polyphenol content using the Folin–Denis' method seemed to be useful for selecting the breeding lines that show high antioxidative capacities.

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Charles L. Rohwer and John E. Erwin

Jasmonates are a class of plant hormones involved in plant defense and stress responses. For example, jasmonate-induced defense responses in Lycopersicon esculentum include increases in activity of proteinase inhibitors, polyphenol oxidases, and peroxidases. As part of our efforts to reduce or control greenhouse pest infestations, we hypothesized that methyl jasmonate (MeJA) could induce these biochemical changes in common greenhouse crops. We studied Impatiens wallerana `Super Elfin Pink', L. esculentum `Big Boy', Petunia ×hybrida `Bravo Lavendar', Viola ×wittrockiana `Imperial Beaconsfield', Coleus ×hybridus `Wizard Jade', Nicotiana alata `Saratoga Lime', Pelargonium ×hortorum `Pinto Pink', and Tagetes erecta `Antigua Primrose'. Polyphenol oxidase and peroxidase activity was studied in the first four species, and proteinase inhibitors were studied in all eight. We sprayed plants with 0, 5 × 10-6, or 10-4 molar MeJA and made measurements after 24 hours. We detected a small increase in polyphenol oxidase activity of plants treated with 10-4 molar MeJA; 5 × 10-6 molar had no effect, and L. esculentum had the highest polyphenol oxidase activity. Peroxidase activity was not affected by MeJA. I. wallerana had the highest peroxidase activity, L. esculentum and V. ×wittrockiana had the lowest. 5 × 10-6 molar MeJA increased proteinase inhibitor activity in most species, and 10-4 molar increased activity in every species except P. ×hortorum.

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M. López-Serrano and A. Ros Barceló

Levels and histochemical localization of peroxidase and polyphenol oxidase, and levels of anthocyanins and (+)-catechin, were studied in fruit of two strawberry (Fragaria ×ananassa Duch.) cultivars (`Oso Grande' and `Chandler'), which show different degrees of susceptibility to enzymatic browning after processing. Although the levels of anthocyanins at the processing-ripe stage may be important in determining pigment stability, and therefore market suitability, the color stability of `Chandler' is apparently determined by the lower endogenous levels of peroxidase and polyphenol oxidase in the processing-ripe stage, which are also accompanied by a lower (+)-catechin content. Polyphenol oxidase was localized almost exclusively in the cortex and to a lesser extent in the pith, showing a complementary pattern to that shown by peroxidase, which was localized in the vascular bundles. Since peroxidase and polyphenol oxidase showed a complementary localization pattern in the fruit, these results strongly suggest a synergic role for these two oxidative enzymes in pigment decay and the associated browning reaction, which occurs in processed strawberry fruit and their derived foods.