Abstract: Two endophytic fungi, Ra-R-32 and ZPRa-S-2, from Rhodiola angusta were isolated and identified.Their fermentation conditions and antioxidant activity were optimized and evaluated,respectively.Fungal identification methods were based on morphological observation and their ITS ribosomal DNA sequences.Orthogonal test was applied to optimize the fermentation conditions based on scavenging DPPH· activity.In addition,the antioxidant activities were subjected to DPPH radical scavenging,hydroxyl radical scavenging,Fe²⁺ chelating,superoxide radical scavenging and nitride clearing assays.The results showed that Ra-R-32 and ZPRa-S-2 belonged to Hypocrea longipilosa and Aspergillus sydowii, respectively.The optimal fermentation conditions for Ra-R-32 were as follows:glucose 35 g/L,peptone 3 g/L,initial pH at 8.0,the loading volume was 100 mL in 250 mL flask,and culture temperature was 35 ℃.The optimal fermentation conditions for ZPRa-S-2 were as follows:sucrose 35 g/L,beef extract 3 g/L,initial pH at 6.0,the loading volume was 150 mL in 250 mL flask,and culture temperature was 30 ℃,and the optimal fermentation time for both fungi were 10 d.Both fungi exhibited excellent scavenging capacities against DPPH,hydroxyl radical and superoxide anion.The EC₅₀ values of Ra-R-32  were 4.72,7.50 and 1.60 mg/mL;and the EC₅₀ values of ZPRa-S-2 were 2.88,8.99 and 4.12 mg/mL,respectively.The results showed that two endophytic fungi from R.angusta have remarkable antioxidant capacity.

Key words: Rhodiola angusta, endophytic fungi, antioxidant, fermentation optimization