Bioautographic profiling of therapeutic metabolites from phytobiologic endosymbionts inhabiting Azadirachta indica L

In the present study, Azadirachta indica L. was evaluated for the presence of bacterial endosymbionts and their capacity to produce antimicrobial metabolites against human pathogens. The active metabolites responsible for activity were characterized via bioautography. Plant materials were surface sterilized, followed by the isolation of endosymbionts, which were screened for antimicrobial activity using agar overlay assays. The potent endosymbionts were cultured, and secondary metabolites were extracted using ethyl acetate. The antimicrobial efficacy of these metabolites was assessed against E. coli and S. aureus using broth dilution and minimum inhibitory concentration (MIC) assays. Partial purification of secondary metabolites was carried out via thin-layer chromatography (TLC) and bioautography-guided fractionation technique which exhibited a prominent band at R f values of 0.6 and 0.8. The Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed the presence of major metabolites such as Oleic acid (C 18 H 34 O 2 ), Pimelic acid, decyl 3-methylbutyl ester (C 22 H 42 O 4 ), Bakuchiol acetate (C 20 H 26 O 2 ), Cis-9-Tetradecenoic acid, isobutyl ester (C 18 H 34 O 2 ), and d-Mannitol, 1-decylsulfonyl (C 16 H 34 O 7 S). The selected endosymbiont was further characterized by biochemical and molecular profiling and the strain was identified as Serratia marcescens and the sequence was deposited in GenBank (Accession Number PQ303445). The extracted secondary metabolites exhibited significant antimicrobial activity, with a MIC of 10 mg/mL. These results highlight the potential of Azadirachta indica L. associated endosymbionts in producing bioactive secondary metabolites with considerable antimicrobial properties which can be good lead to future drug discovery. • Isolation of endosymbionts from Azadirachta indica L. • Extraction of secondary metabolites. • Molecular profiling of the isolated strain • Antimicrobial activity • Partial purification of secondary metabolite via bioassay guided fractionation. • Oleic acid, Pimelic acid, decyl 3-methylbutyl ester, Bakuchiol acetate, Cis-9-Tetradecenoic acid, isobutyl ester, and d-Mannitol, 1-decylsulfonyl.