Study On Antioxidant Activity And Fermentation Products Of Endophytic Fungus

In this paper, endophytic fungi from the medicinal plant Pterocektis tatarinowii Maxim has been selected to be experimental material for looking for a pertential source of natural antioxidants. T-AOC reagent kit was used to screening the antioxidant capacity of the fermentation product of the strain. The strain which showed the highest antioxidant activity has been selected as the tested strain in this study followed by morphological identification. The reducing power, the stability of the antioxidant activity, DPPH radical scavenging activity, superoxide anion radical quenching activity and the hydroxyl radical scavenging capacity of the fermentation products of the tested strain were tested. Furthermore, this study also initially explored the chemical composition of the activity of the fermentation products through separation, purification and characterization. The results were depicted as below:1 T-AOC reagent kit was used to screening the antioxidant capacity of the fermentation product of the strain which was isolated from the medicinal plant Pterocektis tatarinowii Maxim. The results indicated that the active secondary metabolities of the endophtic fungi was mainly distributed in the fermentation broth. Among the 35 tested strains, the strain named No.81 which was isolated from Pterocektis tatarinowii Maxim leaves that grew in Tai’an Shandong province, showed a highest antioxidant activity of which the value was up to 16.12U/mL. As a result, this strain was chosen as the tested strain in this study. The morphological identification demonstrated that the strain was C.globosum.2 The reducing power, stability of the antioxidant activity, DPPH radical scavenging activity, superoxide anion radical quenching capaticy and the hydroxyl radical scavenging activity of the fermentation of No.81 were detected as the index of the antioxidant activity of the strain No.81 after preliminary purification while rutin was chosen as a positive control. The results showed that the fermentation of No.81 had a good reducing power and presented an obvious rising trend which depended on the increasing concentration of the fermentation products. The fermentation of No.81 also showed a good stability of antioxidant activity in this study. The POV value of each concentration in treatment was lower than that of the positive control of rutin which indicated the fermentation of No.81 had a better inhabitation activity of oxide. For the DPPH radical scavenging, the fermentation of No.81 was better than that of rutin in low concentration (0.02 and 0.04mg/mL), and a similar activity in high concentration. The IC50 value of the fermentation of No.81 was 0.023mg/mL while the value of rutin was 0.042mg/mL. The IC50 value of the superoxide anion radical quenching capacity of the fermentation of No.81 was 0.487mg/mL while the value of the positive control rutin was 0.447mg/mL. In general, there was no significant gap between them. The hydroxyl radical scavenging activity of the fermentation of No.81 was lower than that of rutin. However, it could still scavenge the free radicals to a certain degree. And this scavenging activity was increasing with the enhancement of concentration.3 The color reaction indicated that the active compounds in the fermentation of No.81 were polyphenols. Soon afterwards the polyphenols was purified by TLC and column chromatography on silica gel method. Finally, the polyphenols was detected by GC-MS after derivatization. Four compounds were identified as followed: 1,2-Benzenedicarboxylic acid, butyl 2-methylpropyl ester; Tributyl acetylcitrate; 9-Octadecenamide; 1,2-Benzenedicarboxylic acid, mono(2-ethylhexyl) ester respectively.