Vitamin C or ascorbic acid (AsA) is a naturally occurring organic compound with antioxidant properties, found in both animals and plants. It functions as a redox buffer which can reduce, and thereby neutralize, reactive oxygen species. It is a cofactor for enzymes involved in regulating photosynthesis, hormone biosynthesis, and regenerating other antioxidants; which also regulates cell division and growth, is involved in signal transduction, and has roles in several physiological processes, such as immune stimulation, synthesis of collagen, hormones, neurotransmitters, and iron absorption, has also roles in detoxifying the body of heavy metals. Severe deficiency of vitamin C causes scurvy, whereas limited vitamin C intake causes symptoms, such as increased susceptibility to infections, loosening of teeth, dryness of the mouth and eyes, loss of hair, dry itchy skin, fatigue, and insomnia. In contrast, vitamin C can also act as a prooxidant, especially in the presence of transition metals, such as iron and copper, starting different hazardous radical reactions. Vitamin C can both act as a strong, efficient, and cheap antioxidant agent and, at the same time, behave as a radical promoter. Further investigations are needed to illuminate the dual roles of vitamin C
Part of the book: Vitamin C
Reactive oxygen species (ROS) are involved in various development stages of seed biology. During seed desiccation, germination and aging, oxidative stress may increase in higher levels, leading to cellular damage and seed deterioration. Plant cells have antioxidant system, detoxifying enzymes and antioxidant compounds, that scavenge ROS, participating in seed survival. This antioxidant system has various roles in desiccation and germination of developing seeds, seed storability, and seed aging. On the other hand, ROS are accepted as molecules involving in cellular signaling, and having regulatory functions in seed development. ROS are also found to have roles in gene expression in early embryogenesis, dormancy and germination. Abscisic acid is a plant hormone and a signaling molecule in seed development and that is reported to have relationships with ROS. The objective of this article is to review the roles of ROS and the importance of antioxidant system in orthodox seeds, and to emphasize the dual effects of ROS in seed biology.
Part of the book: Seed Biology
Vitamin C is an essential micronutrient, a free radical scavenger; while it has functions such as blocking oncogenic transformation induced by carcinogens. A different view of the potential action of vitamin C in cancer came from the discovery of its importance for activation of ten-eleven translocation (TET) enzymes that are involved in demethylation of DNA and histones. Aberrant DNA and histone methylation are hallmarks of all cancers and may result from altered expression or point mutations in the genes encoding these regulatory enzymes. Recent studies have shown that vitamin C potentiates the effects of DNA methyltransferase inhibitors. Epigenetic alterations, along with genetic mutations, are known to contribute to onset of cancer. Vitamin C is found to be a key mediator of the interface between genome and environment, regulating DNA demethylation as a cofactor for TET dioxygenases. It is shown that vitamin C drives active removal of DNA methylation by enhancing TET enzymes, which helps to erase DNA methylation and epigenetic memory encoded by it to improve reprogramming of differentiated cells to an embryonic-like state. Here, an overview of the role of vitamin C as an essential factor for epigenetic regulation and its potential in epigenetic therapy in cancer patients is provided.
Part of the book: Vitamin C