Bioprospecting of endophytic Actinobacteria from selected medicinal Plants

Abstract

Antimicrobial resistance (AMR) within a wide range of contagious microorganisms is newlinea growing public health threat to countries and multiple sectors. It threatens the effective newlineprevention and treatment of an ever-increasing range of infections caused by bacteria, parasites, newlineviruses and fungi. Existing drugs will continue to lose their effectiveness over time, and patients newlinewill continue to need new drugs and therapies. Actinobacteria, mainly Streptomyces are the top newlinereservoir for the biosynthesis of bioactive secondary metabolites and has contributed newlineimmensely to the drug discovery paradigm. In the present study, fifty morphologically different newlineactinobacterial strains were isolated from 11 medicinal plants. Based on their phenotypic newlinecharacteristics all the strains were identified as Streptomyces. All the 50 endophytic newlineactinobacterial strains were screened for their antimicrobial potential against various Gram newlinepositive and Gram-negative pathogens. Out of which 50 strains, 29 endophytic actinobacterial newlinestrains showed activity against minimum of 2 out of 9 pathogens tested whereas two isolates newlinenamely KCA1 and KCA2 showed positive activity against all of the 9 pathogens tested. newlineFermentation strategies were designed for optimization of bioactive molecule and in newlinesubmerged fermentation, 47 mg of crude extract was obtained from 100 mL of ISP2 medium newlineusing ethyl acetate as a solvent. Further, the pure compound purification was initiated with newlinecolumn chromatography and totally 44 fractions were collected, in which the fractions F13- newlineF26 was showed antibacterial activity against E. coli ATCC 25922 and S. aureus ATCC 29213. newlineThese 14 active fractions were concentrated and injected for second round of purification newlinethrough silica gel column chromatography. Here, the fractions F5 and F6 indicated newlineantibacterial activity were pooled again before being subjected to semi- preparative HPLC. newlineSingle active metabolite collected from HPLC based purification showed yellow in color and newlinesoluble in water, chloroform, ethyl acetate and methanol.