Li, H., Tsao, R. and Deng, Z. 2012. Factors affecting the antioxidant potential and health benefits of plant foods. Can. J. Plant Sci. 92: 1101–1111. Phytochemicals, such as carotenoids, phenolics and glucosinolates, in plants and plant-based foods are able to reduce the incidence of non-communicable diseases such as cardiovascular diseases, diabetes, stroke and different types of cancer due to their antioxidant potential. A brief summary of the in vitro and in vivo evidence and how post-harvest storage and processing conditions can affect the health benefits is presented in this review. Genetic, environmental conditions and physiological factors may modify the composition and amounts of these compounds present in plants, thus affecting the in vitro antioxidant activities. Such changes in combination with degradations after digestion can significantly affect the bioaccessibility and bioavailability of phytochemicals. The main objective of this review is to provide updated information on the effects of various factors such as genetics, environment, post-harvest storage and processing on the bioactive components, and knowledge of these factors can lead to multidisciplinary strategies to maximise the bioavailability and health potential of foods.

Hu, C., Tsao, R., Liu, R., Sullivan, J. A. and McDonald, M. R. 2012. Influence of cultivar and year on phytochemical and antioxidant activity of potato (Solanum tuberosum L.) in Ontario. Can. J. Plant Sci. 92: 485–493. Phytochemicals in coloured vegetables are responsible not only for the colour, but also for nutritional quality. In this study 11 cultivars of potato, with a wide range of skin and flesh colours, grown over two years were tested for the total phenolic content (TPC), total anthocyanin-content (TAC) and total antioxidant activity (TAA). Results showed significant variations among cultivars for both years. TPC was 1.2–3.6 mg gallic acid equivalent (GAE) g−1 dry weight (DW) in 2008 and 0.98–2.81 mg GAE g−1 DW in 2009. Total anthocyanin content was 0.70–1.92 mg cyanidin-3-glucoside equivalent (Cy3g E) in 2008 and 0.05 –1.52 mg Cy3g E g−1 DW in 2009, respectively. The TAA also varied among different potato cultivars, with values of 12 to 64 and 6.3 to 20 µmol ascorbic acid equivalents (AAE) g−1 DW in 2008 and 2009, respectively for the FRAP (ferric reducing/antioxidant power) assay, and from 42 to 168 and 75 to 174 µmol trolox equivalents (TE) g−1 DW in 2008 and 2009 in the ORAC (oxygen radical absorption capacity) assay, respectively. The purple fleshed tubers, such as ‘Mackintosh Black’, demonstrated the highest antioxidant activities, indicating that anthocyanins are important antioxidants. Our results suggest that purple/red potato cultivars have a greater potential as functional foods for enhanced human health benefits.

Stoffyn, O. M., Tsao, R., Liu, R. and Wolyn, D. J. 2012. The effects of environment and storage on rutin concentration in two asparagus cultivars grown in southern Ontario. Can. J. Plant Sci. 92: 901–912. Flavonoids have been shown to have many human health benefits due to their antioxidant activity. Concentration of rutin, the primary antioxidant in asparagus spears, can vary significantly with cultivar, location and season. Assessment of rutin in cultivars across locations throughout the harvest season in Southern Ontario, as well as in stored asparagus, is important for defining the potential benefits of consuming local asparagus. The objectives of this research were to determine the effects of cultivar, harvest time, location, spear diameter and part, and storage of fresh spears and freeze-dried flour on rutin concentration. Sampling date over the 6-wk harvest season and location did not significantly affect rutin concentration in either of the two cultivars tested. Rutin concentration was inversely related to air temperature before harvest and spear diameter, and for any given diameter, was highest in the tops of spears and decreased towards the bottom, in both cultivars. Soil temperatures before harvest were not correlated with rutin concentrations. Storage of fresh spears at 4°C, or freeze-dried flour at varying temperatures, did not affect concentration. The stability of rutin concentration throughout the harvest season, across locations and in stored products suggests predictable antioxidant levels in Ontario-grown asparagus.

2014. Genetic variation and heritability of rutin and glutathione concentrations in asparagus spears. Can. J. Plant Sci. 94: 1355Á1362. Asparagus (Asparagus officinalis L.) spears contain numerous phytochemicals, including rutin (a flavonoid) and glutathione (a biothiol), that are beneficial to human health due to antioxidant or other activities. To assess the potential to increase phytochemical content through breeding, genetic variability was surveyed in diverse germplasm adapted to southern Ontario. Selected female and supermale genotypes were also hybridized in a partial diallel to estimate heritability and identify parents with good combining ability. Genetic variation for rutin (3.30 to 8.14 mg g (1 dry weight) was observed, while glutathione concentrations (5.37 to 7.86 mmol g (1 dry weight) did not differ significantly among tested genotypes. Combining ability effects were significant for rutin concentration and heritability was also moderate. From these results, breeding to improve the concentration of rutin, rather than that of glutathione, is most achievable in the germplasm tested. Drinkwater, J. M., Tsao, R., Liu, R. et Wolyn, D. J. 2014. Variation ge´ne´tique et he´ritabilite´de la concentration de rutine et de glutathion dans les turions d'asperge. Can. J. Plant Sci. 94: 1355Á1362. Les turions d'asperge (Asparagus officinalis L.) renferment de nombreux compose´s phytochimiques be´ne´fiques pour la sante´humaine en raison de leur pouvoir antioxydant et d'autres proprie´te´s. La rutine (un flavonoı¨de) et le glutathion (un biothiol) en sont deux exemples.Pour de´terminer si on pourrait accroıˆtre la concentration de ces compose´s par l'hybridation, les auteurs en ont examine´la variabilite´ge´ne´tique chez des varie´te´s acclimate´es au sud de l'Ontario. Ils ont aussi hybride´quelques ge´notypes femelles et super maˆles dans le cadre d'un croisement dialle`le partiel et identifie´les parents qui pre´sentaient une bonne aptitude a`la combinaison. La concentration de rutine varie ge´ne´tiquement (de 3,30 a`8,14 mg par gramme de poids sec), mais celle de glutathion (de 5,37 a`7,86 mmol par gramme de poids sec) ne diffe`re pas de manie`re significative entre les ge´notypes teste´s. L'aptitude a`la combinaison a des effets significatifs sur la concentration de rutine, dont l'he´ritabilite´est moyenne. D'apre`s ces re´sultats, on conclut que l'hybridation du mate´riel ge´ne´tique teste´se preˆte mieux a`une ame´lioration de la concentration de rutine que de celle du glutathion.