Changes in phenolic content,composition,and antioxidant activity of blood oranges during cold and on-tree storage

Citrus fruits are rich in phenolic compounds that possess several health benefits.However,few studies have focused on the changes in phenolic compounds in citrus fruits during postharvest storage.This study dynamically monitored the phenolic content,components and antioxidant activity of‘Tarocco’blood oranges during a period of 12-week cold storage and on-tree storage,respectively.We investigated the alteration mechanism of phenolic compounds in blood oranges by evaluating phenylpropanoid pathway-related enzyme activities and gene expression.Results showed that flavanones were the main phenolic compounds in blood oranges.Both storage methods mainly stimulated the accumulation of phenolic acids to improve total phenolic content,which reached the maximum at week 12.Nonetheless,blood oranges had a higher phenolic content and antioxidant activity under on-tree storage than cold storage.Furthermore,the enzyme activities and gene expression of the phenylpropanoid pathway demonstrated that the accumulation of phenolics in blood oranges during storage was highly related to the activation of the phenylpropanoid pathway.These results demonstrate that on-tree storage is a potential approach for extending the supply period of blood orange from the perspective of phenolic compounds.

Polypropylene crisper and 1-MCP delay the softening,lignification and transcription levels of related enzyme genes of golden needle mushrooms(Flammulina velutipes)

The fresh postharvest golden needle mushroom(Flammulina velutipes) sporocarp has a high moisture content and crisp texture, but it still has high physiological activity and respiration, leading to senescence and quality deterioration.Treatments with 1-methylcyclopropene(1-MCP) and polypropylene(PP) crispers were used to study the changes of lignification and softening of F. velutipes during storage. The main findings were as follows: the crisper packaging could effectively prolong the storage time of F. velutipes;either the 1-MCP treatment, crisper packaging or the combination of the two treatments could significantly inhibit the accumulation of lignin and the decreases in the contents of cellulose and pectin, and had certain inhibitory effects on the activities of enzymes involved in lignification and softening including phenylalanine ammonia-lyase(PAL), cinnamyl alcohol dehydrogenase(CAD), cellulase(Cx), pectin methylesterase(PME) and polygalacturonase(PG). Among them, the inhibitory effect of the crisper packaging was higher than the 1-MCP treatment, while the combination of the two treatments was the best. The results of transmission electron microscopy(TEM) and scanning electron microscopy(SEM) showed that the crisper packaging in combination with the 1-MCP treatment could effectively maintain the integrity and stability of the F. velutipes cellular structure and inhibit the emergence of plasmolysis to prevent cell membrane rupture. The transcription levels showed that the crisper packaging and the combination of the 1-MCP treatment and crisper packing could effectively affect the expression of genes for enzymes related to lignification and softening of F. velutipes. In conclusion, 1-MCP and PP crispers could delay the lignification and softening of F. velutipes during storage.

Involvement of CsWRKY70 in salicylic acid-induced citrus fruit resistance against Penicillium digitatum

Penicillium digitatum causes serious losses in postharvest citrus fruit.Exogenous salicylic acid(SA)can induce fruit resistance against various pathogens,but the mechanism remains unclear.Herein,a transcriptome-based approach was used to investigate the underlying mechanism of SA-induced citrus fruit resistance against P.digitatum.We found that CsWRKY70 and genes related to methyl salicylate(MeSA)biosynthesis(salicylate carboxymethyltransferase,SAMT)were induced by exogenous SA.Moreover,significant MeSA accumulation was detected in the SA-treated citrus fruit.The potential involvement of CsWRKY70 in regulating CsSAMT expression in citrus fruit was studied.Subcellular localization,dual luciferase,and electrophoretic mobility shift assays and an analysis of transient expression in fruit peel revealed that the nucleus‐localized transcriptional activator CsWRKY70 can activate the CsSAMT promoter by recognizing the W-box element.Taken together,the findings from this study offer new insights into the transcriptional regulatory mechanism of exogenous SA-induced disease resistance in Citrus sinensis fruit.

Phenolic extract of Morchella angusticeps peck inhibited the proliferation of HepG2 cells in vitro by inducing the signal transduction pathway of p38/MAPK

Morchella angusticeps Peck,one of the most popular edible mushrooms,has attracted great attention due to its delicious taste and healthy properties.However,both its biological effects and the possible mechanism of action have not yet been known.We investigated the anti-proliferative activity of the phenolic extract derived from Morchella angusticeps Peck(MPE)against HepG2 human hepatocellular carcinoma cells.Results showed that MPE at non-cytotoxicity doses significantly inhibited the proliferation of HepG2 cells in a dose-dependent manner with inhibitory rates ranging from 18 to 90%(P<0.01).The possible mechanism might be that MPE induced apoptosis through initiating the mitochondrial death pathway by regulating Bax,Bcl-2 and cleaved caspase-3.On the other hand,MPE might trigger cell cycle arrest at G0/G1/S phases by managing p21,Cyclin D1,cyclin-dependent kinases-4(CDK4)and proliferating cell nuclear antigen(PCNA).Additionally,MPE downregulated TRAF-2 and p-p53,while upregulated p-ASK1 and p-p38.Therefore,it could be inferred that MPE might induce the anti-proliferative function to HepG2 cells through the p38/MAPK signal transduction pathway.