Abstract:
Three endophytic yeasts were isolated from the lower stem and roots of Phragmites australis Cav. (Trin) ex Steud., observed to be dominant along the banks of the tailings pond 5A of the Lepanto Consolidated Mining Co. in Mankayan, Benguet. These yeast isolates were tested for their antioxidant properties in vitro to establish the possible contribution of these endophytes to the survival of their hosts in this inhospitable environment. All fungal yeast isolates displayed significantly higher antioxidant activities than the sterile potato dextrose broth that served as the control. Notable isolates were Yph3, which displayed the highest antioxidant activity using the 1,1-diphenyl-2-picrylhydrazyl assay, and C. parapsilosis Yph5, which yielded the highest ascorbic acid equivalent per mg dry weight using the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) assay. C. parapsilosis Yph5 also produced the highest amount of phenolic compounds measured as gallic acid equivalents. All three yeast isolates were observed to exhibit similar ascorbate peroxidase activities. On the other hand, D. hansenii Yph4 showed the highest catalase activity. It is clear from this study that the different endophytic yeasts have different mechanisms for quenching reactive oxygen species. This may be an indication that in situ, they perform synergistic and complementary roles in the antioxidative system of their host plant P. australis.
