Endophytic fungi from red ginger (Zingiber officinale var. rubrum) as promising source of antimicrobial and cytotoxic secondary metabolites

In the present study, we reported eight endophytic fungi isolated from stems, rhizomes, and roots of red ginger (Zingiber officinale var. rubrum), collected from Bali, Indonesia. Molecular biology protocol through amplification of internal transcribed spacer and LSU region led to the identification of six fungal isolates as Microdochium colombiense ZOR-S1-1, Phlebiopsis flavidoalba ZOR-S1-3, Penicillium citrinum ZOR-S1-4.1, Dactylonectria anthuriicola ZOR-Rh1-3, Setophoma terrestris ZOR-Br1-1, and Xylaria cubensis ZOR-Rh1-1. Meanwhile, two fungal isolates, ZOR-S1-4 and ZOR-Br1-2, are remain unidentified. Following rice fermentation of all isolated endophytes, all fungal extracts were subjected to antimicrobial, toxicity, and cytotoxicity assays. In the antimicrobial assay, S. terrestris ZOR-Br1-1 extract showed the most pronounced activity against Staphylococcus aureus ATCC 6538 and Candida albicans ATCC 10231, with MIC values of 31.3 and 15.6 µg/ml. Meanwhile, D. anthuriicola ZOR-Rh1-3 extract revealed the most potent activity in toxicity screening employing the brine shrimp lethality test (BSLT), with an LC50 value of 6.8 µg/ml. When tested further for cytotoxicity against breast cancer cells, MCF-7 and 4T1, extracts of D. anthuriicola ZOR-Rh1-3, P. citrinum ZOR-S1-4.1, unidentified isolates ZOR-S1-4 and ZOR-Br1-2, showed strong to moderate inhibition against both tested cell lines with IC50 values ranging from 14 to 74 µg/ml. In light of the bioactivity of endophytic fungal extracts from red ginger found in this study, investigation on secondary metabolites and their pharmacological action on antimicrobial and cytotoxicity of endophytic S. terrestris ZOR-Br1-1, D. anthuriicola ZOR-Rh1-3, and P. citrinum ZOR-S1-4.1 are of scientific interest for further research. Moreover, this result highlights the bioprospecting opportunity of endophytic fungi associated with medicinal plants as a source of bioactive secondary metabolites. © 2024 Ni Putu Ariantari et al.