Endolichenic fungi (ELF) serve as a novel source of natural products with distinctive bioactivities. A total of 58 ELF isolated from 29 lichens collected from mangrove and mangrove-associated plants of Negombo lagoon, Sri Lanka were identified using morphological and DNA barcoding techniques. Ethyl acetate extracts of 18 such identified ELF isolates were subjected to in vitro assays to determine antioxidant, anti-inflammatory, tyrosinase inhibitory and antibacterial potency. Liquid chromatography–mass spectrometry (LC–MS) dereplication was conducted on the crude extracts in order to detect the secondary metabolites present. The extracts of Daldinia eschscholtzii and Hypoxylon lividipigmentum had the highest radical scavenging activity with SC50 values 14.27 ± 0.24 µg/mL and 18.34 ± 1.37 µg/mL, respectively. D. eschscholtzii also exhibited remarkable anti-inflammatory activity (IC50 7.97 ± 0.09 µg/mL). Tyrosinase inhibitory activity was highest in Cytospora xylocarpi (IC50 68.50 ± 0.34 µg/mL), while the highest activity against aerobic bacterial species Escherichia coli, Bacillus subtilis, Staphylococcus aureus and the anaerobic bacterial strain Streptococcus mutans was observed in the extracts of Xylaria feegenesis and Curvularia lunata. After a thorough study of the LC–MS profiles, it was found that the chemical profiles of Neofusicoccum occulatum, H. lividipigmentum and Myramaececium rubricosum were previously poorly explored in the literature.
Endolichenic fungi (ELF) have been recognized as a promising source of bioactive secondary
metabolites. Sri Lanka, a biodiversity hotspot, harbours a remarkable diversity in mangrove ecosystems.
In the present study, endolichenic fungi obtained from mangrove lichens of Puttalam lagoon were
studied for their secondary metabolites. An endolichenic fungus, Neurospora ugadawe, isolated from
the lichen host Graphis tsunodae Zahlbr. was identified up to the species level. Secondary metabolites
of N. ugadawe were extracted into ethyl acetate and crude extract showed promising antioxidant and
anti-inflammatory activities. Bioassay guided separation on silica gel column chromatography and
preparative TLC were performed to isolate the bioactive pure compounds. Two novel bioactive pure
compounds were identified as Neurosporalol 1 and Neurosporalol 2. Neurosporalol 1 showed the
highest antioxidant activity compared with the positive control BHT. Further, this compound showed
very low anti-inflammatory activity compared to that of the positive control aspirin. Neurosporalol 2
showed comparable antioxidant and moderate anti-inflammatory activities.
Bioassay-guided fractionation of the ethyl acetate extract of Phanerochaete sordida, an endolichenic fungus (ELF) isolated from the host lichen Bactrospora myriadea, collected from Negombo lagoon, Sri Lanka, led to the isolation of a bioactive compound. Following the identification of the fungus using morphological and DNA barcoding techniques, the pure compound was isolated using column chromatography, preparative TLC, and semipreparative HPLC. The structure elucidation was carried out using IR, HR-ESI-MS and 1H, 13C & 2D NMR spectroscopic methods. The in vitro bioassays conducted revealed that compound 1 has a high antioxidant activity with ABTS•+ (IC50
58.91
±
1.35
μ
M
), moderate anti-inflammatory activity (IC50
254.79
±
1.41
μ
M
), comparable antibacterial activity against the oral-bacterial strain Streptococcus mutans (MIC 898.79 μM and MLC 1797.58 μM), moderate tyrosinase inhibition (IC50
1713.69
±
8.65
μ
M
), and moderate cytotoxicity against oral cancer (IC50
13.65
±
0.02
μ
M
), in comparison with respective positive controls. The in silico experiments conducted for tyrosinase inhibition and cytotoxicity using Schrödinger revealed results in line with the in vitro results, thus confirming the bioactivities. The molecule also satisfies the key features of drug likeliness according to pharmacokinetic studies.
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