Stability and transformation of products formed from dimeric dehydroascorbic acid at low pH

Advancements in Nano-Mandoor Bhasma: Unravelling the Particle Size-Ascorbic Acid Synergy for Enhanced Iron Bioavailability for Anemia Treatment

Mandoor Bhasma (MB) medicine, based on classical Indian Ayurveda, was size- and surface-modified to improve its therapeutic efficiency for treating iron-deficient anemia. Physical grinding reduced the size of MB to the nanoparticle (nano-MB) range without changing its chemical composition, as measured by particle size distribution. The surface of nano-MB was modified with ascorbic acid (nano-AA-MB) and confirmed using scanning electron microscopy and Fourier transformed infrared spectroscopy. Enhanced iron dissolution from the surface-modified nano-AA-MB under neutral-to-alkaline pH conditions, and in the intestinal region of the simulated gastrointestinal tract (GIT) digestion model was determined using inductively coupled plasma mass spectroscopy. GIT digestae of MB microparticles and nano-AA-MB were found to be biocompatible in human colon epithelial (Caco-2) cells, with the latter showing threefold higher iron uptake. Subsequently, a dose-dependent increase in cellular ferritin protein was observed in the nano-AA-MB digestae-treated Caco-2 cells, indicating the enhanced bioavailability and storage of dissolved iron. Overall, the study showed that reducing the size of centuries-old traditional Mandoor Bhasma medicine to nanoscale, and its surface-modification with ascorbic acid would help in enhancing its therapeutic abilities for treating iron-deficient anemia.

Unveiling the Reduction Process of Graphene Oxide by Ascorbic Acid: Grafting and Reduction Sequences for High Surface Area Graphene Materials

This work reports the synthesis of high surface area reduced graphene oxides using L-ascorbic acid as a reducing agent by precisely controlling the interaction between graphene oxide and L-ascorbic acid. Based on the structural characterization, such as textural properties (specific surface area, pore structure), crystallinity, and carbon chemical state, we identified that the temperature and reaction time are critical parameters to control the stacking degree of the final reduced product. Besides, by performing a time course analysis of the reaction, we identified the side products of the reducing agent by LC-MS and verified the reduction mechanism. Following our results, we proposed an optimum condition for producing a graphene derivative adsorbent with a high surface area. This graphene derivative was tested in an aqueous solution with organic and inorganic pollutants such as methylene blue, methyl orange, and cadmium.

Spray Drying and Spout-Fluid Bed Drying Microencapsulation of Mexican Plum Fruit (Spondias purpurea L.) Extract and Its Effect on In Vitro Gastrointestinal Bioaccessibility

The Mexican plum (Spondias purpurea L.) is a source of phenolic compounds; however, these compounds are susceptible to various factors (humidity, temperature, light, oxygen), as well as the digestion process, which can modify their bioaccessibility. This study aimed to extract and microencapsulate the phenolic compounds (PC), total anthocyanins (TA), ascorbic acid (AA), dehydroascorbic acid (DHA) and total vitamin C (AA+DHA) from Mexican plum ecotype “Cuernavaqueña” by spray drying (SD) and spout-fluid bed drying (SFB) and evaluate the bioaccessibility of these compounds by in vitro digestion. Optimal extraction conditions for bioactive compounds (BC) and antioxidant capacity (AC) were: three consecutive extractions at 40 °C, for 90 min each, with 1/5 solid-solvent ratio (4 g/20 mL), and 40% v/v aqueous ethanol. The extract without the encapsulation process suffered a significant (p ≤ 0.05) decrease in bioactive compounds and antioxidant capacity after in vitro digestion. Microcapsules obtained by SFB showed better retention and encapsulation efficiencies coupled with better protection against the digestion process. Microencapsulation by SFB protects the BC of Mexican plum, and it could be used in the food industry as ingredient to develop functional foods.

Enhanced Resorption of Liposomal Packed Vitamin C Monitored by Ultrasound

Vitamin C is an essential nutrient for humans and is involved in a plethora of health-related functions. Several studies have shown a connection between vitamin C intake and an improved resistance to infections that involves the immune system. However, the body cannot store vitamin C and both the elevated oral intake, and the intravenous application have certain disadvantages. In this study, we wanted to show a new formulation for the liposomal packaging of vitamin C. Using freeze etching electron microscopy, we show the formed liposomes. With a novel approach of post-processing procedures of real-time sonography that combines enhancement effects by contrast-like ultrasound with a transducer, we wanted to demonstrate the elevated intestinal vitamin C resorption on four participants. With the method presented in this study, it is possible to make use of the liposomal packaging of vitamin C with simple household materials and equipment for intake elevation. For the first time, we show the enhanced resorption of ingested liposomes using microbubble enhanced ultrasound imaging.

Determination of cellular vitamin C dynamics by HPLC-DAD

A redox-sensitive inter-conversion between ascorbic acid (ASC) and its oxidized form dehydroascorbic acid (DHA) in the intracellular environment has been of exceptional interest to recent metabolomics and pharmaceutical research. We developed a chromatographic protocol to instantly determine these vitamers with each identity from cellular extracts, without any labeling and pretreatments. Owing to its simplicity, one can readily continue the assay for hours, an otherwise difficult to cover timescale at which the intracellular DHA-ASC conversion comes into play. The method was validated for the analysis of pancreatic cancer cells, to our knowledge the first-ever study on a nucleated cell type, to trace in detail their kinetics of glucose transporter-dependent DHA uptake and, simultaneously, that for the intracellular ASC conversion. The simplest of all the relevant techniques and yet with the unique ability to provide each vitamer identity on a high-throughput basis, this method should offer the most practical option for VC-involved physiological and pharmaceutical studies including high-dose VC cancer therapy.

The oxidation of dehydroascorbic acid and 2,3-diketogulonate by distinct reactive oxygen species

l-Ascorbate, dehydro-l-ascorbic acid (DHA), and 2,3-diketo-l-gulonate (DKG) can all quench reactive oxygen species (ROS) in plants and animals. The vitamin C oxidation products thereby formed are investigated here. DHA and DKG were incubated aerobically at pH 4.7 with peroxide (H2O2), 'superoxide' (a ∼50 : 50 mixture of [Formula: see text] and [Formula: see text]), hydroxyl radicals (•OH, formed in Fenton mixtures), and illuminated riboflavin (generating singlet oxygen, 1O2). Products were monitored electrophoretically. DHA quenched H2O2 far more effectively than superoxide, but the main products in both cases were 4-O-oxalyl-l-threonate (4-OxT) and smaller amounts of 3-OxT and OxA + threonate. H2O2, but not superoxide, also yielded cyclic-OxT. Dilute Fenton mixture almost completely oxidised a 50-fold excess of DHA, indicating that it generated oxidant(s) greatly exceeding the theoretical •OH yield; it yielded oxalate, threonate, and OxT. 1O2 had no effect on DHA. DKG was oxidatively decarboxylated by H2O2, Fenton mixture, and 1O2, forming a newly characterised product, 2-oxo-l-threo-pentonate (OTP; '2-keto-l-xylonate'). Superoxide yielded negligible OTP. Prolonged H2O2 treatment oxidatively decarboxylated OTP to threonate. Oxidation of DKG by H2O2, Fenton mixture, or 1O2 also gave traces of 4-OxT but no detectable 3-OxT or cyclic-OxT. In conclusion, DHA and DKG yield different oxidation products when attacked by different ROS. DHA is more readily oxidised by H2O2 and superoxide; DKG more readily by 1O2 The diverse products are potential signals, enabling organisms to respond appropriately to diverse stresses. Also, the reaction-product 'fingerprints' are analytically useful, indicating which ROS are acting in vivo.

Metabolites of 2,3-diketogulonate delay peroxidase action and induce non-enzymic H2O2 generation: Potential roles in the plant cell wall

A proportion of the plant's l-ascorbate (vitamin C) occurs in the apoplast, where it and its metabolites may act as pro-oxidants and anti-oxidants. One ascorbate metabolite is 2,3-diketogulonate (DKG), preparations of which can non-enzymically generate H2O2 and delay peroxidase action on aromatic substrates. As DKG itself generates several by-products, we characterised these and their ability to generate H2O2 and delay peroxidase action. DKG preparations rapidly produced a by-product, compound (1), with λmax 271 and 251 nm at neutral and acidic pH respectively. On HPLC, (1) co-eluted with the major H2O2-generating and peroxidase-delaying principle. Compound (1) was slowly destroyed by ascorbate oxidase, and was less stable at pH 6 than at pH 1. Electrophoresis of an HPLC-enriched preparation of (1) suggested a strongly acidic (pKa ≈ 2.3) compound. Mass spectrometry suggested that un-ionised (1) has the formula C6H6O5, i.e. it is a reduction product of DKG (C6H8O7). In conclusion, compound (1) is the major H2O2-generating, peroxidase-delaying principle formed non-enzymically from DKG in the pathway ascorbate → dehydroascorbic acid → DKG → (1). We hypothesise that (1) generates apoplastic H2O2 (and consequently hydroxyl radicals) and delays cell-wall crosslinking - both these effects favouring wall loosening, and possibly playing a role in pathogen defence.