Background: Endophytic fungi are receiving attention as sources of structurally novel
bioactive secondary metabolites towards drug discovery from natural products. This study reports
the isolation and characterization of secondary metabolites from an endophytic fungus Aspergillus
nidulans, associated with Nyctanthes arbor-tristis Linn., a plant which has a traditional use to
cure many ailments including cancer.
Objective: The objective of this study was to evaluate the antiproliferative activity of the metabolites
of A. nidulans from N. arbor-tristis on three human cancer cell lines, lung (NCI-H460),
breast (MCF-7) and uterine cervix (HeLa), and carry out their characterization.
Methods: The extracts of the endophytic fungus cultured on potato dextrose agar were subjected
to various chromatographic techniques. Structures of pure compounds were determined using
spectroscopic techniques. The non-polar constituents were analyzed by GC-MS. Antiproliferative
activity was determined by sulforhodamine B (SRB) assay.
Results: The extracts and fractions showed moderate to good growth inhibition of the aforementioned
human cancer cell lines. The broth extract was most potent (IC50 = 10 ± 3.1 μg/mL and
LC50= 95 ± 3.9) against HeLa whereas petroleum ether insoluble fraction of mycelium was most
active against NCI-H460 and MCF-7 (IC50 = 10 ± 2.1 μg/mL and 18 ± 3.1 μg/mL respectively).
GC-MS led to identify 12 compounds in mycelium and 19 compounds in broth. Four pure compounds
were isolated and characterized one compound 5, 10-dihydrophenazine-1-carboxylic acid
(1) from broth and three 1-hydroxy-3-methylxanthone (2), ergosterol (3) and sterigmatocystin (4)
from mycelium. 1 has not been reported earlier as a plant/fungal metabolite while 2-4 are new
from this source. Sterigmatocystin exhibited growth inhibitory effect (IC50 = 50 ± 2.5 μM/mL)
against only MCF-7 cell line whereas other compounds had IC50 > 100.
Conclusions: In this paper, the cytotoxicity of mycelium and broth constituents of endophytic
fungus Aspergillus nidulans from Nyctanthes arbor-tristis is reported for the first time. The study
shows that fungus Aspergillus nidulans from Nyctanthes arbor-tristis is capable of producing biologically
active natural compounds and provides a scientific rationale for further chemical investigations
of endophyte-producing natural products.