<i>In vitro</i> free radical scavenging and antibacterial activity with plant extracts of ethnobotanical use in banana production

Agricultural productivity is at risk due to the increase in pests and diseases. The most significant losses in plantain and banana crops have been caused by phytopathogenic bacteria such as Ralstonia solanacearum. Even post-harvest, losses are associated with pathogenic microorganisms. New alternatives for controlling pathogenic bacteria in the harvest and post-harvest periods are needed. Plant extracts are of great pharmacological and agricultural interest since they are widely used in the food industry. Colombia is rich in plant diversity, and the Antioquia region is characterized by many traditional medicinal plants. The objective of this study was to determine the antioxidant and antibacterial activity of 13 ethanolic extracts from 12 ethnobotanical species present on the campus of the University of Antioquia. The antioxidant potential of extracts was evaluated by the decolorization test of radical cation α-α-diphenyl-ß-picrylhydrazyl (DPPH), and inhibition of bacterial growth by the disk diffusion method. The latter was performed using a phytopathogenic crop microbial isolate of Ralstonia solanacearum and other pathogenic microbial strains including E. coli, B. subtilis, and B. cereus. It was observed that the plant with the extract having highest radical scavenging capacity was P. niruri with an IC 50 of 3.79 ± 0.4 ppm. The antibacterial activity in vitro for the phytopathogenic strain in R. solanacearum (Banana), inhibition zones were observed between 8 to 25 mm. The inhibition ranges of pathogenic bacteria were between 8-26 mm to 200 and 400 µg/ disc for the 13 extracts evaluated. The most active extract with antibacterial and free radical scavenging was obtained from the G. madruno plant, in which chemical research led to the isolation of a triterpene called friedelan-3-one. This compound was characterized by comparing the spectral signals of nuclear magnetic resonance ( 1 H-NMR). This is the first report of these plants evaluated on R. solanacearum and the first report of the isolation of the compound friedelan-3-one in the species G. madruno.