Quantitative variation in the camptothecin produced by diverse endophytic microorganisms of Ophiorrhiza mungos L.

Endophytic microorganisms (EMs) residing in medicinal plants form a promising resource of anticancer compounds such as camptothecin (CPT). Given the increasing therapeutic demand for CPT, its sustainable production is of high significance. This study has investigated the EMs isolated from different parts of Ophiorrhiza mungos for the CPT biosynthetic potential. Preliminary screening of EMs for the CPT synthesis was carried out by HPLC analysis of culture extracts, and the HPLC-positive extracts were further confirmed via LC-MS/MS. From a total of 175 EMs screened in the study, 17 strains (14 bacterial and 3 fungal) were found to be CPT producing, with most of them being sourced from the root tissues. Among the bacterial strains, Alcaligenes faecalis subsp. phenolicus S18 exhibited the highest CPT yield (1294.52 μg/L) followed by Bacillus tequilensis (309.02 μg/L). From the fungal strains, Aspergillus sp., S109, S42, and S111 yielded CPT of 22.07, 18.98, and 13.26 μg/L, respectively. Overall, CPT yield among the bacterial producers ranged from 1294.52 to 5.16 μg/L, predominantly from the Bacillus, Acinetobacter, Alcaligenes, and Pseudomonas genera. This study provides the first report on the CPT production by A. faecalis and Aspergillus sp. isolated from O. mungos, and also the first documentation of CPT synthesis in Stenotrophomonas, Fictibacillus, Acinetobacter, and Pseudomonas genera. These findings highlight the potential of novel microbial sources as high-yielding, reliable, and cost-effective alternatives to support commercial CPT production.