Diaporthe sp. F18; a new source of camptothecin-producing endophytic fungus from Nothapodytes nimmoniana growing in Sri Lanka.

An endophytic fungus producing camptothecin (CPT) was isolated from the leaf of Nothapodytes nimmoniana (Sri Lanka), and culture conditions were optimised to enhance the yield of CPT. The TLC, HPLC-PDA, LC-MS/MS and spectroscopic data were used to identify and quantify CPT. Solvent extraction (chloroform: methanol 4:1 v/v) of submerged cultures in Sabouraud Dextrose Broth (SDB) detected CPT in the mycelial extract but not in the culture broth. The fungus was (KX212080) closely related to Diaporthe guangxiensis (MK335772) with 99% sequence similarity, thus tentatively identified as Diaporthe sp. F18. A significantly high CPT content (72.0 ± 0.2 µg/g) was produced in SDB, pH, 5.6 incubated at 30 °C under shake flask condition (150 rpm) for 14 days. Tryptophan significantly (p > 0.05) enhanced CPT production while ethanol increased it by 8-fold. This endophytic source produced higher CPT content than what has been reported hitherto in the literature, with fairly stable production up to sixth subculture generations.