PubMed · 13513322
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E H MORSE, M POTGIETER, G R WALKER. 1958. Published vs. analyzed values for ascorbic acid.. https://pubmed.ncbi.nlm.nih.gov/13513322/
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Ascorbic acid (AsA) is an essential nutritional component and powerful antioxidant in vegetables, and in plants, AsA levels are regulated by light. AsA levels in the leaves of Chinese chive (Allium tuberosum Rottler ex Spr), a popular vegetable, are poorly understood. Thus, this study was performed to assess the influence of light on AsA biosynthesis in chive and select related genes (AtuGGP1 and AtuGME1); in addition, bioinformatic analyses and gene expression level assays were performed. The biological information obtained for AtuGGP1 and AtuGME1 was analysed with several tools, including NCBI, DNAMAN, and MEGA11. After different light treatments were performed, the Chive AsA content and AtuGGP1 and AtuGME1 expression levels were determined. These results suggest that 1) compared with natural light, continuous darkness inhibited AsA synthesis in chives. 2) The amino acid sequences of AtuGGP1 and AtuGME1 are very similar to those of other plants. 3) The trends observed for the expression levels of AtuGGP1 and AtuGME1 were consistent with the AsA content observed in chives. Hence, we speculated that light controls AsA biosynthesis in chives by regulating AtuGGP1 and AtuGME1 expression. This study provided impactful and informative evidence regarding the functions of GGP and GME in chives.
A short-term pre-exposure to dehydroascorbic acid (DHA) promotes U937 cell death upon exposure to otherwise non-toxic levels of peroxynitrite (ONOO-). Toxicity is mediated by a saturable mechanism and cell death takes place as a consequence of mitochondrial permeability transition. The following lines of evidence are consistent with the notion that the enhancing effects of DHA were related to mitochondrial events resulting in inhibition of complex III upon exposure to otherwise inactive concentrations of ONOO-. First, DHA, as well as bona fide complex III inhibitors, similarly enhanced toxicity and subsequent formation of H2O2 induced by ONOO- via a rotenone- or catalase-sensitive mechanism. Secondly, bona fide complex III inhibitors were ineffective in DHA-pre-loaded cells. In addition, respiration-deficient cells were resistant to toxicity elicited by ONOO- and their supplementation with increasing concentrations of DHA, although resulting in the accumulation of vitamin C levels identical with those observed in respiration-proficient cells, failed to affect ONOO- toxicity. Finally, oxygen-consumption experiments demonstrated that pre-exposure to DHA promotes the ONOO--dependent inhibition of complex III. In conclusion, the above results collectively demonstrate that increasing the intracellular accumulation of vitamin C promotes mitochondrial events leading to ONOO--dependent formation of H2O2 and resulting in a rapid necrotic response.
Broccoli (Brassica oleracea L. var. italica cv. Marathon) inflorescences are a good source of bioactive compounds, such as phenolics (flavonoids and hydroxycinnamoyl derivatives), glucosinolates, and vitamin C. In this work, these health-promoting compounds were submitted to digestion under in vitro gastrointestinal conditions (pH, temperature, enzyme, and chemical conditions). This technique differentiated among the compounds associated with macromolecules in soluble and insoluble form and those that are freely soluble. In addition, it evaluates the chemical stability of the broccoli compounds under simulated physiological conditions. The gastric digestion of broccoli caused high losses in glucosinolates (69% loss), whereas phenolics and vitamin C presented higher stability under these conditions. Thus, there were no losses in flavonoids, a 7% loss of vitamin C, and a variable rate of loss (6-25%) in hydroxycinnamic acid derivatives. The stability of all of the compounds was affected by the in vitro intestinal conditions. Under the in vitro conditions, flavonoids and hydroxycinnamoyl acid derivatives were of low availability, due to their significant losses under these conditions, at the end of the experiment (84 and 80% loss, respectively). Vitamin C was the metabolite that showed the greater decrease after intestinal digestion (91% loss). Regarding the remaining glucosinolates, these compounds presented higher stability under intestinal conditions, rendering an availability similar to that found for phenolics (75% loss). Therefore, broccoli components were affected by gastric and/or intestinal conditions depending on the type of compound. Thus, glucosinolates were mainly degraded by gastric conditions, whereas phenolic compounds and vitamin C were degraded by intestinal conditions.