Antioxidant Defenses Against Air Humidity Stress in Fruit Bodies of Auricularia heimuer (Agaricomycetes).

Air humidity is an important environmental factor restricting the fruit body growth of Auricularia heimuer. Low air humidity causes the fruit body to desiccate and enter dormancy. However, the survival mechanisms to low air humidity for fruit bodies before dormancy remain poorly understood. In the present study, we cultivated A. heimuer in a greenhouse and collected the fruit bodies at different air humidities (90%, 80%, 70%, 60%, and 50%) to determine the contents of malondialdehyde (MDA) and non-enzymatic antioxidants such as ascorbic acid (AsA) and glutathione (GSH); and the activities of enzymatic antioxidants including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX) and glutathione reductase (GR). Results showed that the MDA contents tended to increase with decreasing relative air humidity. Relative air humidity below 90% caused membrane lipid peroxidation and oxidative stress (based on MDA contents) to the fruit body, which we named air humidity stress. In contrast to the control and with the degree of stress, the GSH contents and activities of SOD, CAT, GR, GPX, and APX tended to ascend, whereas AsA showed a declining trend; the POD activity only rose at 50%. The antioxidants favored the fruit body to alleviate oxidative damage and strengthened its tolerance to air humidity stress. The antioxidant defense system could be an important mechanism for the fruit body of A. heimuer in air humidity stress.

A polysaccharide PRCP from Rosa cymosa Tratt fruit: Structural characteristics and immunomodulatory effects via MAPK pathway modulation in vitro.

The Rosa cymosa Tratt, an herbal plant from the Rosaceae family, has historically been valued in China for its medicinal and edible properties. In this study, a novel polysaccharide from R. cymosa fruit, termed PRCP (purified R. cymosa polysaccharide), was isolated using water extraction, decolorization, deproteinization, and ion-exchange chromatography. The structural characteristics of PRCP were investigated using monosaccharide composition analysis, methylation, GPC, FTIR, CD, and NMR spectroscopy. The immunomodulatory effect and potential mechanism of PRCP were evaluated in vitro using a macrophage cell model. Results indicated that PRCP (37.28 kDa) is a highly branched polysaccharide (72.61 %) primarily composed of arabinogalactan, rhamnogalacturonan, and galactoglucan domains with 13 types of glycosidic linkage fragments. Furthermore, PRCP appears to modulate immunomodulatory effects by influencing the phosphorylation of P38 and JNK proteins in the MAPK pathway. Collectively, these findings highlight the potential of PRCP as a promising natural functional food ingredient for immunostimulation.