Plant L‐ascorbic acid: chemistry, function, metabolism, bioavailability and effects of processing

Abstract

Humans are unable to synthesise L-ascorbic acid (L-AA, ascorbate, vitamin C), and are thus entirely dependent upon dietary sources to meet needs. In both plant and animal metabolism, the biological functions of L-ascorbic acid are centred around the antioxidant properties of this molecule. Considerable evidence has been accruing in the last two decades of the importance of L-AA in protecting not only the plant from oxidative stress, but also mammals from various chronic diseases that have their origins in oxidative stress. Evidence suggests that the plasma levels of L-AA in large sections of the population are sub-optimal for the health protective effects of this vitamin.Until quite recently, little focus has been given to improving the L-AA content of plant foods, either in terms of the amounts present in commercial crop varieties, or in minimising losses prior to ingestion. Further, while L-AA biosynthesis in animals was elucidated in the 1960s, 1 it is only very recently that a distinct biosynthetic route for plants has been proposed. 2 The characterisation of this new pathway will undoubtedly provide the necessary focus and impetus to enable fundamental questions on plant L-AA metabolism to be resolved.This review focuses on the role of L-AA in metabolism and the latest studies regarding its biosynthesis, tissue compartmentalisation, turnover and catabolism. These inter-relationships are considered in relation to the potential to improve the L-AA content of crops. Methodology for the reliable analysis of L-AA in plant foods is brie¯y reviewed. The concentrations found in common food sources and the effects of processing, or storage prior to consumption are discussed. Finally the factors that determine the bioavailability of L-AA and how it may be improved are considered, as well as the most important future research needs.

An improved and fast UHPLC-PDA methodology for determination of L-ascorbic and dehydroascorbic acids in fruits and vegetables. Evaluation of degradation rate during storage

“…L-ascorbic acid (L-AA) is a water-soluble vitamin widely distributed in plant material. Vegetables and fruits, particularly citrus and tropical fruits, green leafy vegetables, broccoli, and peppers, are important sources of vitamin C [4,[7][8][9]. However, fruits such as pears, apples, and plums contain only a very modest concentration of this vitamin.…”

Exploring alternative germplasm for the development of stable high vitamin C content in tomato varieties

“…In the case of vitamin C, the contents registered in tomato are not especially high (Gould, 1992) and other fruits and vegetables such as orange or broccoli are renowned as more efficient sources of this vitamin (Davey et al, 2000). Nevertheless, despite not having high levels, tomato is still an important source of l-ascorbic acid, as its high volume of consumption all the year round (reaching 40-50 kg per capita and year in countries such as Spain, Italy or USA, source: FAO databases) makes this fruit one of the main sources for this vitamin.…”

“…Nevertheless, their success has been limited. Among other factors, it has to be considered that vitamin C content is highly unstable, as it is very sensitive to environmental conditions (Hamner et al, 1945;Hanson et al, 2004) and as expected considering its antioxidant functions, the levels of ascorbic acid are responsive to stress factors (Davey et al, 2000;Ioannidi et al, 2009). Additionally, a deleterious effect of plant yield has been described for this type of high vitamin C cultivars due primarily to a reduction in fruit size (Stevens and 0304-4238/$ -see front matter © 2011 Elsevier B.V. All rights reserved.…”

Associação de atmosfera modificada e antioxidantes reduz o escurecimento de batatas 'Ágata' minimamente processadas

“…De acordo com Davey et al (2000), batatas apresentam teores de vitamina C que variam entre 100 e 300 mg kg -1 MF. Estes valores podem variar de acor-do com a cultivar, com as práticas agrí-colas, colheita e condições de armazenamento.…”