Cultivars, culture conditions and harvest time influence phenolic and ascorbic acid contents and antioxidant capacity of strawberry (Fragaria x ananassa)

in Journal of Food Science (2012), 77

Strawberries are a good source of micronutrients, especially antioxidant phenolics. More information is needed to better exploit the health-promoting effect of such fruits. Several studies focused on the ... [more ▼]

Strawberries are a good source of micronutrients, especially antioxidant phenolics. More information is needed to better exploit the health-promoting effect of such fruits. Several studies focused on the effects of genotype, cultural practices and seasonal variation on the antioxidant potential of strawberries, but often yielding contradictory results and/or focusing on only one source of variability. In the present study, we showed that total phenolic compounds, ascorbic acid and antioxidant capacity strongly differed between genotypes of strawberry. The precise results revealed the importance of genetic background for the antioxidant capacity and for the content of total phenolics (with up to 3.3-fold variations). Other parameters may also influence the antioxidant capacity in strawberry such as harvest time, culture conditions and environmental factors. Moreover, in this study, the harvesting time (at the same ripening stage) appeared to be very important, more important than genotype. Variations of the antioxidant capacity of up to 4.1-folds were observed following the harvesting time of “Elsanta” cultivar. [less ▲]

Do polyamines increase the antioxidant capacity of hyperhydric shoots ?

in 4th international workshop - cost action FA0605 - Book of abstracts - Limassol 17-19 November (2011)

Extraction conditions can greatly influence antioxidant capacity assays in plant food matrices

in Food Chemistry (2011)

The estimated antioxidant capacity of different matrices can vary considerably between research reports. Besides intrinsic factors (not studied here), our work showed that may have various causes. Firstly ... [more ▼]

The estimated antioxidant capacity of different matrices can vary considerably between research reports. Besides intrinsic factors (not studied here), our work showed that may have various causes. Firstly, different methods are used to measure antioxidant capacity. Secondly, the results obtained for a single matrix by one method (such as ORAC) can vary with the extraction conditions. Parameters having a great impact on the amount and composition of antioxidants in extracts, and thus on the measured antioxidant capacity, notably include the extraction solvent composition, temperature, extraction time (duration), solvent-to-solid ratio, and storage conditions. Standardization of the extraction procedure is thus necessary for accurate and reproducible determination of the antioxidant capacity and phenolics in different food matrices by different laboratories. In this study we optimised such a procedure for four fresh plant matrices (orange, apple, leek, and broccoli). The optimised procedure requires extraction in a mixture of acetone/water/acetic acid (70/28/2, v/v/v) for 1 h at 4°C, with a solvent-to-solid ratio of 20 mL per 1 g. Fresh material should be used, but if this is not possible, one may lyophilise the plant matrices or store the extracts for a few days at -20°C before analysis. [less ▲]

Influence of cultivar, harvest time, storage conditions, and peeling on the antioxidant capacity and phenolic and ascorbic acid contents of apples and pears."

in Journal of Agricultural and Food Chemistry (2011), 59

Apple and pear fruits are important sources of secondary plant metabolites and one of the major sources of dietary phenolics consumed all year round. The aim of this work was to identify the main ... [more ▼]

Apple and pear fruits are important sources of secondary plant metabolites and one of the major sources of dietary phenolics consumed all year round. The aim of this work was to identify the main variables influencing phenolic content and antioxidant capacity in apples. Higher phenolic and antioxidant contents were observed in some varieties (such as the Delbar Estival apple and Durondeau pear). Storage conditions were important. Our results also showed that fruits should be consumed rapidly after purchase and with their peel. After one week of domestic storage, the ascorbic acid content was found to decrease by 75%. Peeling led to a more than 25% decrease in total phenolics and ascorbic acid. The harvest time (at normal ripeness) had only a limited impact, but significant year-to-year variations were observed. In conclusion, well-chosen and well-stored apples and pears may contribute to an antioxidant-rich diet if consumed rapidly and with their peel. [less ▲]

In Vitro Preservation of Yam ( Dioscorea cayenensis-D.rotundata complex) for a Better Use of Genetic Resources

in Notulae Botanicae Horti Agrobotanici Cluj-Napoca (2010), 38

Among the food crops, yam takes up quantitatively the first place in the gabonese diet. Unfortunately, it can stay available only 6 to 7 months in the year because of difficulties of harvest and post ... [more ▼]

Among the food crops, yam takes up quantitatively the first place in the gabonese diet. Unfortunately, it can stay available only 6 to 7 months in the year because of difficulties of harvest and post- harvest. This problem is little studied in the case of Dioscorea cayenensis-D. rotundata complex. In order to optimize the use of micro tubers for the growing in green house or field, it is important to control the duration of storage before the germination. The present study concerns microtubers obtained by in vitro culture. When microtubers were harvested (after 9 months of culture) and directly transferred on a new medium without hormone, the tubers rapidly sprouted in in vitro conditions. Harvested microtubers were also stored dry in jars in sterile conditions during 2 to 18 weeks before in vitro sprouting. In this case, microtubers stored during 18 weeks sprouted more rapidly than those stored 8 weeks. The size of the tubers used for the storage had great influence on further sprouting. The upper microtubers in 25 mm can be kept to the darkness, under 50% of relative humidity, in 25°C during at least 18 weeks. Sprouting is 100% whatever the substrate of culture. The plant tissue culture technique constitutes a serious alternative for the preservation of plant kinds and for the production of planting material. These techniques allow multiplying in a short time of thousands of copies of new varieties of newly created plants. These in vitro plants can be used on one hand, for the production planting material, and on the other hand for ex vitro storage of breeding grounds with decelerated growth, to struggle against genetic erosion. These results should allow improving in practice the multiplication of yam, while guaranteeing phytosanitary qualities. [less ▲]

Effects of storage conditions on sprouting of microtubers of yam (Dioscorea cayenensis-D. rotundata complex).

in Comptes Rendus des Séances de l'Académie des Sciences. Série III, Sciences de la Vie (2010)

The control of field tuber dormancy in yam (Dioscorea cayenensis- D.rotundata complex) is poorly understood. Although studies have examined single environmental factors and chemical treatments that might ... [more ▼]

The control of field tuber dormancy in yam (Dioscorea cayenensis- D.rotundata complex) is poorly understood. Although studies have examined single environmental factors and chemical treatments that might prolong tuber dormancy and storage, only a few were focused on further tuber sprouting. The present study concerns microtubers obtained by in vitro culture. When microtubers were harvested (after 9 months of culture) and directly transferred on a new medium without hormone, the tubers rapidly sprouted in in vitro conditions. No dormancy was observed in this case. Harvested microtubers were also stored dry in jars in sterile conditions during 2 to 18 weeks before in vitro sprouting. In this case, microtubers stored during 18 weeks sprouted more rapidly than those stored 8 weeks. A constant “dormancy-like period” (storage duration + sprouting delay) was observed, between 20 and 28 weeks respectively for the more rapid and the slower microtubers. The size of the tubers used for the storage had great influence on further sprouting. The larger they were, the better they sprouted. Light during storage had no effect on the sprouting delay while a temperature of 25 °C permit a quicker sprouting than 18 °C. The medium used to obtain microtubers could also have an effect on sprouting rate. Ex vitro sprouting was not a problem. There was a delay in sprouting in contrast to in vitro conditions but the rate of 100% was kept. This fact was very important for an agronomical application of this technique to the production of “seeds” directly usable in the field or after culture in greenhouse. [less ▲]

Tuber formation and development of Dioscorea cayenensis-D. rotundata complex in vitro. Effect of polyamines.

in In Vitro Cellular & Developmental Biology-Plant (2009)

Tuberisation was obtained in vitro on yam (Dioscorea cayenensis-D.rotundata complex). The effect of exogenous polyamines on tuber formation and development (length and weight of microtubers) were ... [more ▼]

Tuberisation was obtained in vitro on yam (Dioscorea cayenensis-D.rotundata complex). The effect of exogenous polyamines on tuber formation and development (length and weight of microtubers) were investigated and discussed in relation with changes in endogenous polyamines. Application of exogenous polyamines, inhibitors of their metabolism and polyamines precursors in various concentrations positively affected microtuber formation by yam nodal cuttings and their further development. In control conditions, three weeks are needed to obtain 100% of tuberisation. With low concentrations of putrescine (10 5 or 10 6 M), tuber formation occurred earlier. Polyamine endogenous level and metabolism can be significantly affected by exogenous polyamines but modifications of endogenous free polyamines could not be directly correlated to the tuber formation process. Increases in endogenous putrescine and auxins were observed in tubers showing a better development in the presence of putrescine. These results can be used for optimising in vitro conditions for mass production of larger microtubers of the Dioscorea cayenensis-D. rotundata complex. [less ▲]

Adventitious rooting and xylogenesis are enhanced by methyl jasmonate in tobacco thin cell layers

in Planta (2009), 231

Adventitious roots (ARs) are induced by auxins. Jasmonic acid (JA) and methyl jasmonate (MeJA) are also plant growth regulators with many effects on development, but their role on ARs needs investigation ... [more ▼]

Adventitious roots (ARs) are induced by auxins. Jasmonic acid (JA) and methyl jasmonate (MeJA) are also plant growth regulators with many effects on development, but their role on ARs needs investigation. To this aim, we analyzed AR formation in tobacco thin cell layers (TCLs) cultured with 0.01–10 μM MeJA, either under root-inductive conditions, i.e., on medium containing 10 μM indole-3-butyric acid (IBA) and 0.1 μM kinetin, or without hormones. The explants were excised from the cultivars Samsun, Xanthii and Petite Havana, and from genotypes with altered AR-forming ability in response to auxin, namely the non-rooting rac mutant and the over-rooting Agrobacterium rhizogenes rolB transgenic line. Results show that NtRNR1 (G1/S) and Ntcyc29 (G2/M) gene activity, cell proliferation and meristemoid formation were stimulated in hormone-cultured TCLs by submicromolar MeJA concentrations. The meristemoids developed either into ARs and xylogenic nodules, or into xylogenic nodules only (rac TCLs). MeJA-induced meristemoid over-production characterized rolB TCLs. No rooting or xylogenesis occurred under hormone-free conditions, independently of MeJA and genotype. Endogenous JA progressively (days 1–4) increased in hormone-cultured TCLs in the absence of MeJA. JA levels were enhanced by 0.1 μM MeJA, on both days 1 and 4. Endogenous IBA was the only auxin detected, both in the free form and as IBA-glucose. Free IBA increased up to day 2, remaining constant thereafter (day 4). Its level was enhanced by 0.1 μM MeJA only on day 1, while IBA conjugation was not affected by MeJA. Taken together, these results show that an interplay between jasmonates and auxins regulates AR formation and xylogenesis in tobacco TCLs. [less ▲]

Involvement of polyamines in the adventitious rooting of micropropagated shoots of the apple rootstock MM106

in In Vitro Cellular & Developmental Biology-Plant (2009), 45

Apple rootstock MM106 shoots, raised in vitro, rooted at 96.7% after culture on a medium supplemented with an auxin for 5 d in darkness followed by culture on a second medium without growth regulators for ... [more ▼]

Apple rootstock MM106 shoots, raised in vitro, rooted at 96.7% after culture on a medium supplemented with an auxin for 5 d in darkness followed by culture on a second medium without growth regulators for 25 d in light. In control conditions (in absence of auxin in the first medium), these shoots did not root. Putrescine (PUT), spermidine (SPD), cyclohexylamine (CHA), and aminoguanidine (AG) enhanced rooting when applied during the first d of culture in the absence of IBA; on the contrary, α-difluoromethylornithine (DFMO) added to the first medium with IBA inhibited rooting. The endogenous levels of indole 3-acetic acid (IAA) and indole 3-acetylaspartic acid (IAAsp) increased up to a maximum concentration at days 2 and 3, respectively, in initial rooting conditions. PUT, when added with IBA, did not affect the typical IAA and IAAsp increase; when applied alone, it provoked an increase of their levels. Similar results were recorded with CHA. SPD, AG, and DFMO did not induce an increase of IAA and IAAsp in nonrooting conditions. The levels of endogenous PUT increased to a maximum at day 2 in rooting conditions; it was slightly affected by exogenous PUT and CHA application but reduced by SPD, AG, and DFMO. In rooting conditions, if the first medium was supplemented with SPD or AG, a small increase in peroxidase activity was observed, similar to that obtained with PUT treatment. The present work indicates an involvement of polyamines in the control of rooting and an interaction with auxins during the physiological phase of rooting. The consequence of this relationship was a different rooting expression, according especially to the content of these regulators in the culture medium. [less ▲]

An anionic class III peroxidase from zucchini may regulate hypocotyl elongation through its auxin oxidase activity.

in Planta (2009)

The high number of peroxidase genes explains the description of numerous physiological functions and the fact that the in planta function of a single isoform has never been characterized yet. We analyzed ... [more ▼]

The high number of peroxidase genes explains the description of numerous physiological functions and the fact that the in planta function of a single isoform has never been characterized yet. We analyzed in transgenic Arabidopsis thaliana the localization of a zucchini isoperoxidase (APRX), previously purified thanks to its pectin binding ability. We confirmed that the protein is localized near the cell wall, mainly produced in the elongation area of the hypocotyls and respond to exogenous auxin. In addition, the ectopic overexpression of APRX induced changes in growth pattern and a significant reduction of endogenous indole-3-acetic acid (IAA) level. In agreement with these observations APRX showed an elevated in vitro auxin oxidase activity. We propose that APRX participates in the negative feedback regulation of auxin level and consequently terminates the hypocotyl elongation process. [less ▲]