Filamentous fungi with high paraquat-degrading activity isolated from contaminated agricultural soils in northern Thailand.

The contamination of paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride) herbicide from the farming area has become a public concern in many countries. This herbicide harms to human health and negatively effects the soil fertility. Several methods have been introduced for the remediation of paraquat. In this study, 20 isolates of the paraquat-tolerant fungi were isolated from the contaminated soil samples in northern Thailand. We found that isolate PRPY-2 and PFCM-1 exhibited the highest degradation activity of paraquat on synthetic liquid medium. About 80 and 68% of paraquat were removed by PRPY-2 and PFCM-1 respectively after 15 days of cultivation. Based on the morphological characteristic and molecular analysis, the fungal isolate PRPY-2 and PFCM-1 were identified as Aspergillus tamarii and Cunninghamella sp. respectively. The biosorption of paraquat on these fungal mycelia was also investigated. It was found that only 8-10% of paraquat could be detected on their mycelia, while 24-46% of paraquat was degraded by fungal mycelia. This is the first report on paraquat degrading ability by A. tamarii and Cunninghamella sp. It is demonstrated that these filamentous fungi are promising microorganisms available for remediation of paraquat contaminated environment.

Bioactive compounds content and their biological properties of acetone extract of Cuscuta reflexa Roxb. grown on various host plants.

The present study is aimed to evaluate the total phenolic and flavonoid contents, and free phenolic compounds of acetone extract of Cuscuta reflexa grown on five different hosts: Coccinia grandis, Ficus racemosa, Samanea saman, Streblus asper and Zollingeria dongnaiensis, and to explore the antioxidant activities, α-glucosidase and tyrosinase inhibitory properties of the extracts. The highest level of total phenolic and flavonoid contents were observed in the extract of C. reflexa that was grown on S. asper (65.45 mg GAE/g extract) and C. grandis (97.83 mg QE/g extract), respectively. According to HPLC results, vanillic acid, rutin and quercetin were found in all extracts of C. reflexa grown on diversified hosts. The extract of C. reflexa grown on C. grandis possessed the greatest antioxidant activities (DPPH; 251.64 µg/mL, FRAP; 26.44 mg GAE/g extract), α-glucosidase inhibition accounted for 84.36 per cent and antityrosinase activity was at 18.29 mg KAE/g sample.