Fungal Metabolites in Drug Discovery: Bioactive Secondary Metabolites from Endophytic Fungi Isolated from Plant Hosts Pandanus spp. and Rhizophora spp.

The rising cases of infectious diseases and multidrug resistance remain a global issue thus, the discovery of novel bioactive secondary metabolites from natural products continues. Fungal endophytes are viable sources of secondary metabolites, which have been proven to possess antimicrobial properties. Endophytic fungi were isolated from leaves of plant hosts through surface-sterilization technique. Then, secondary metabolites were mass-produced in potato dextrose broth, and liquid extraction with ethyl acetate was done to obtain the crude culture extracts. Kirby Bauer disc diffusion assay involving ESKAPE bacteria was performed followed by thin layer chromatography (TLC)-bioautography for bioassay-guided screening of secondary metabolites. Antioxidant activities were determined trhough DPPH radical scavenging activity assay. Series of column chromatography and spectroscopic techniques were employed to isolate and identify pure bioactive compounds. Endophytic fungi in family Pandanaceae, specifically Pandanus amaryllifolius and P. dubius, and family Rhizophoraceae specifically Rhizophora mucronata and R. apiculata include Colletotrichum sp., Diaporthe sp., Phyllosticta sp., Ramichloridium sp., Guignardia sp., and Fusarium sp. Their varied secondary metabolites exhibited antibacterial and antioxidant properties. This proves that endophytic fungi are promising sources of a plethora of bioactive compounds.