Antioxidant activity and mechanism of commercial Rama Forte persimmon fruits (Diospyros kaki)

Attenuation of Chilling Injury and Improving Antioxidant Capacity of Persimmon Fruit by Arginine Application

Persimmon is a climacteric perishable fruit with a short storage life. In recent years, using natural compounds that are safe for human health and environment have obtained more attention in postharvest investigations. The current research was conducted to study efficacy of postharvest L-arginine treatment at 0, 0.3, and 0.6 mM in improving chilling tolerance and maintaining the nutritional quality of persimmon fruit during low-temperature storage. According to the results, the highest weight loss (4.3%), malondialdehyde (MDA (5.8 nmol g⁻¹ FW)), and hydrogen peroxide (H₂O₂ (22.33 nmol g⁻¹ FW)) was detected in control fruit. Fruit firmness was gradually decreased during storage, but it was slower in L-arginine-treated fruit. The highest tissue firmness (3.8 kg cm⁻²) was noted in fruit treated with 0.6 mM L-arginine. The chilling was gradually increased during storage. Fruits treated with L-arginine showed a lower chilling injury than the control fruit. Total soluble tannin compound and antioxidant enzymes activities in persimmons declined during cold storage. L-arginine treatment significantly maintained antioxidant enzymes activity, antioxidant capacity, and total soluble tannin compounds, while L-arginine had no significant impact on titratable acidity and total soluble solids. It seems that a reduction in oxidative damage and an increase in quality of persimmon during low-temperature storage manifested several defense mechanisms induced by exogenous application of L-arginine. These findings indicated that the application of L-arginine to maintain the quality and increase postharvest life of persimmon is very useful and can be applied during cold storage.

Diospyros kaki extract protects myoblasts from oxidative stress-induced cytotoxicity via secretions derived from intestinal epithelium

Under oxidative stress, reactive oxygen species (ROS) alter signal transduction and induce macromolecular damage in cells. Such oxidative damage can lead to sarcopenia, an age-related syndrome characterized by a progressive loss of mass and strength of skeletal muscles. Because food components do not directly come in contact with muscle cells, we focused on the effects of secretions produced by stimulated intestinal epithelial cells on oxidative stress in myoblast cells. An extract of Diospyros kaki was fractionated using different concentrations of ethanol. Each fraction showed different levels of antioxidant and phenolic compounds. The biological activity was evaluated using a Caco-2 cell coculture system. Secretions from Caco-2 cells exposed to 0.5 mg/mL D. kaki extract attenuated the oxidative stress-induced reduction of C2C12 cell viability, suggesting that the D. kaki extract could stimulate intestinal epithelial cells to produce secretions that reduce oxidative stress in myoblasts in vitro.

Evaluating the In Vitro Potential of Natural Extracts to Protect Lipids from Oxidative Damage

Lipid peroxidation is a chemical reaction known to have negative impacts on living organisms' health and on consumer products' quality and safety. Therefore, it has been the subject of extensive scientific research concerning the possibilities to reduce it, both in vivo and in nonliving organic matrices. It can be started by a variety of oxidants, by both ROS-dependent and -independent pathways, all of them reviewed in this document. Another feature of this reaction is the capacity of lipid peroxyl radicals to react with the non-oxidized lipids, propagating the reaction even in the absence of an external trigger. Due to these specificities of lipid peroxidation, regular antioxidant strategies-although being helpful in controlling oxidative triggers-are not tailored to tackle this challenge. Thus, more suited antioxidant compounds or technologies are required and sought after by researchers, either in the fields of medicine and physiology, or in product development and biotechnology. Despite the existence of several laboratory procedures associated with the study of lipid peroxidation, a methodology to perform bioprospecting of natural products to prevent lipid peroxidation (a Lipid Peroxidation Inhibitory Potential assay, LPIP) is not yet well established. In this review, a critical look into the possibility of testing the capacity of natural products to inhibit lipid peroxidation is presented. In vitro systems used to peroxidize a lipid sample are also reviewed on the basis of lipid substrate origin, and, for each of them, procedural insights, oxidation initiation strategies, and lipid peroxidation extent monitoring are discussed.