2.8. Antioxidant Activity Assay of Extracts from Isolated Strains

The qualitative antiradical activity of actinobacteria extracts was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test [31,38]. DPPH (0.0236 g/L) was dissolved in methanol. DPPH and samples were mixed in a 96-well plate. DPPH and samples were mixed in a proportion of 9:1. The plate was incubated for 30 min in darkness. After 30 min, a color change was assessed. A change from pink to yellow indicated the presence of antioxidants in the samples. Spectrophotometric analysis was performed using a microplate reader Infinite M200 (Tecan, Austria, Männedorf), at a wavelength of 517 nm. Dissolved DPPH and methanol were used as a negative control.