Abstract:

In this study, we reported for the first time an endophytic fungus, named Rb-R-1, with antioxidant activity
isolated and identified from Rhodiola bupleuroides. The isolate Rb-R-1 was affiliated to Neonectria ramulariae
belonging to the order Hypocreales in the phylum Ascomacota. The fungus possessed high scavenging activities against
1,1-diphenyl-2-picrylhydrazyl (DPPH), ·OH, O2-· and NO2- radicals and Fe2+ chelating activity, with half maximal
inhibitory concentration (IC50) of 8.86, 4.40, 9.65, 16.53 and 1.91 mg/mL, respectively. The contents of total phenolics
and total flavonoids in the concentrated culture supernatant of Rb-R-1 were 18.12 and 22.48 mg/g, respectively. The
optimal culture conditions that provided maximal DPPH radical scavenging rate (93.12%) were determined as lactose as
the carbon source, beef extract as the nitrogen source, initial pH 7.0, 90 mL of the medium in a 250-mL flask and 25 ℃.
In the meantime, the maximal contents of total phenolics and total flavonoids of 19.14 and 28.25 mg/g, respectively, were
obtained under these culture conditions.

Key words: Rhodiola bupleuroides, endophytic fungi, antioxidant, fermentation condition optimization