The endophytic fungi of Salvia miltiorrhiza Bge.f. alba are a potential source of natural antioxidants

Background: Salvia miltiorrhiza Bge. f. alba is a traditional Chinese herbal drug with special pharmacological effect on thromboangiitis obliterans. However, the nature source of S. miltiorrhiza Bge. f. alba is now in short supply because of the over-collection of the wild plant. To better utilize this resource, the diversity and antioxidant activity of endophytic fungi isolated from S. miltiorrhiza Bge. f. alba were investigated. Results: A total of 14 endophytic fungi were isolated from different parts of S. miltiorrhiza Bge. f. alba. Based on morphological and molecular identification, the endophytic fungi isolated were classified into four genera (Alternaria sp., Fusarium sp., Schizophyllum sp. and Trametes sp.). These fungal extracts were prepared using ethanol and evaluated for their phytochemical compounds and antioxidant activity. Alternaria alternata SaF-2 and Fusarium proliferatum SaR-2 are of particular interest because they yielded all of nine phytochemicals including saponins, phenol, flavonoids, cardiac glycosides, steroids, tannins, alkaloids, anthroquinone and terpenoids. F. proliferatum SaR-2 and A. alternata SaF-2 also exhibited stronger antioxidant activities by FRAP and DPPH method, having the higher levels of phenol and flavonoid than those of plant root. The total amount of phenol and flavonoid quantified were of 21.75, 20.53 gallic acid equivalent per gram and 8.27 and 7.36 mu g/mg of quercetin equivalent respectively. These two endophytic fungi (SaR-2 and SaF-2) were found to have comparable scavenging abilities on both FRAP (1682.21 and 1659.05 mu mol/mg, respectively) and DPPH-free radicals (90.14% and 83.25%, respectively, at 0.1 mg/mL). This is the first report about isolation of endophytic fungi from S. miltiorrhiza Bge. f. alba and their antioxidant activities. Conclusions: These results indicate that the endophytic fungi associated with S. miltiorrhiza Bge.f. alba can be a potential source of novel natural antioxidants.