In the search for novel potent fungi-derived bioactive compounds for bioinsecticide applications, crude ethyl acetate culture filtrate extracts from 110 mangrove fungal endophytes were screened for their toxicity. Toxicity tests of all extracts against brine shrimp (Artemia salina) larvae were performed. The extracts with the highest toxicity were further examined for insecticidal activity against Spodoptera litura larvae and acetylcholinesterase (AChE) inhibition activity. The results showed that the extracts of five isolates exhibited the highest toxicity to brine shrimp at 50% lethal concentration (LC50) values of 7.45 to 10.24 ppm. These five fungal isolates that obtained from Rhizophora mucronata were identified based on sequence data analysis of the internal transcribed spacer region of rDNA as Aspergillus oryzae (strain BPPTCC 6036), Emericella nidulans (strains BPPTCC 6035 and BPPTCC 6038), A. tamarii (strain BPPTCC 6037), and A. versicolor (strain BPPTCC 6039). The mean percentage of S. litura larval mortality following topical application of the five extracts ranged from 16.7% to 43.3%. In the AChE inhibition assay, the inhibition rates of the five extracts ranged from 40.7% to 48.9%, while eserine (positive control) had an inhibition rate of 96.8%, at a concentration of 100 ppm. The extracts used were crude extracts, so their potential as sources of AChE inhibition compounds makes them likely candidates as neurotoxins. The high-performance liquid chromatography profiles of the five extracts differed, indicating variations in their chemical constituents. This study highlights the potential of culture filtrate ethyl acetate extracts of mangrove fungal endophytes as a source of new potential bioactive compounds for bioinsecticide applications.

Mangrove fungi are known as the sources of secondary metabolites of active compounds. In the search for novel, potent, fungi-derived bioactive compounds for bioinsecticide applications, crude ethyl acetate culture filtrate extract from Emericella nidulans BPPTCC 6038 was tested for toxic activity using brine shrimp lethality bioassay against Artemia salina larvae; insecticidal activity using indirect contact bioassay against neonate of Spodotera litura larvae; and acetylcholinesterase (AChE) inhibition activity by acethylcholinesterase inhibition assay. The results showed that the extract exhibited toxic activity against A. salina larvae, rated as highly toxic at 80 ppm; exhibited insecticidal activity against S. litura larvae, causing mortality by 66.67% at 5 mg; and acetylcholinesterase inhibition activity by 47.60% at 100 ppm. The fractionation on the E. nidulans BPPTCC 6038 extract produced seven fractions, and the best insecticidal activity against S. litura neonate larvae using feeding dietary bioassay was exhibited by the fraction no. 6, causing 98.33% larval mortality at 2500 ppm. The chemical characterization of the E. nidulans BPPTCC 6038 extracts using thin layer chromatography combined with several reagents showed that the extract contained triterpenoid, saponin and phenolic compounds, and the active fraction (fraction no. 6) from E. nidulans BPPTCC 6038 contained triterpenoid and saponin compounds. Thus, the extract of the E. nidulans BPPTCC 6038 might provide new bioactive compounds to be applied as potential bioinsecticides.

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