Production of herbarin and dehydroherbarin by endophytic Chaetosphaeronema sp. (KY321184) isolated from Nepeta septemcrenata and evaluation of their bioactivities

A new endophytic fungal isolate has been isolated from Nepeta septemcrenata growing on Saint-Catherine-South Sinai-Egypt. This isolate has been identified by sequencing the ITS region. It showed 95% similarity with different Chaetosphaeronema species thus this isolate has been suggested as a new undescribed Chaetosphaeronema sp. and released in GenBank under the accession number of KY321184. Herbarin and dehydroherbarin have been isolated as the major bioactive compounds from this isolate when cultivated on potato dextrose broth medium. Herbarin showed weak antimicrobial effect but dehydroherbarin showed moderate antimicrobial effects against gram-negative and gram-positive bacteria. Both compounds showed reduced cytotoxicity against the normal cell line MRC 5 which didn't exceed 45.3% but showed higher toxicity towards the breast cancer cell line MCF 7 where toxicity reaches 95.2% and 94.6% and the estimated IC50 was 811.3 μg/ml and 288 μg/ml for dehydroherbarin and herbarin respectively. On other hand, dehydroherbarin showed higher antiviral activity where it showed 90% protection percentage for Hepatitis A virus. In silico docking study revealed the affinity of dehydroherbarin to bind with human heat shock protein 90 alpha (2K5B) through three hydrogen bonds and the affinity of herbarin to bind with human DNA topoisomerase I (1A35) through five hydrogen bonds which may explain their cytotoxic effects on the tested breast cancer cell line. In silico ADME evaluation of these compounds revealed the possible good druglike nature of herbarin compound.