Abstract
Objective: Endophytes are widely spread in the plant kingdom and represent a very promising source of biologically active natural products. The medicinal plant Bidens bipinnata Lin. (Asteraceae) which is known for its anti-inflammatory, antifungal and antitumor effects has been chosen for the investigation of its endophyte to search for bioactive metabolites.
 Methods: An endophytic Alternaria alternata species was isolated from the leaves of the plant B. bipinnata Lin. To investigate the metabolic profile of this endophytic fungus it was cultivated in several culture media as static and shaken culture. The antimicrobial and cytotoxic activities of the ethyl acetate extracts of the fungus were examined. Extracts exhibiting highest antimicrobial activities in agar diffusion assay and cytotoxicity against HeLa cancer cell line were subjected to activity-guided chromatographic fractionation for the identification of bioactive metabolites. A cytotoxic assay was performed on the isolated compounds against HeLa cancer cell lines as well as cytostatic activity tests against HUVEC and K-562 cell lines.
 Results: Chromatographic fractionation resulted in the isolation and identification of alternariol and tentoxin from the extract of the fungus cultivated in medium M5 while sterigmatocystin was isolated in addition to alternariol and tentoxin from the extract of the fungus grown in medium M25. Both alternariol and sterigmatocystin proved to be of moderate cytotoxicity and weak cytostatic activity with alternariol showing higher cytotoxic activity than sterigmatocystin. Highest cytotoxicity against HeLa cell lines was observed for tentoxin with a CC50 of 22.5 µg/ml.
 Conclusion: This study presents the isolation and identification of the bioactive metabolites alternariol, sterigmatocystin and tentoxin from the endophyte A. alternata in addition to the antifungal activity of the strain extract as well as the cytotoxic and cytostatic activities of the isolated metabolites against HeLa, HUVEC and K-562 cell lines, respectively.
Highlights
Endophytes are considered as a promising source for bioactive metabolites and only few plant species of the entire plant kingdom on earth have been examined so far [1,2,3].Plants having special uses and biological activities are considered as a promising source for study [4]
A study has been conducted to investigate the role of total flavonoids of B. bipinnata in suppressing tumor necrosis factor-alpha (TNF-α) and nitric oxide (NO) release in HUVECs cultured with sera from active Henoch-Schonlein purpura (HSP) patients
This study presents the isolation and identification of biologically active metabolites of another endophytic fungus, Alternaria alternata from the leaves of B. bipinnata
Summary
Plants having special uses and biological activities are considered as a promising source for study [4]. The medicinal plant Bidens bipinnata has been chosen for the investigation of its endophytic content. A study has been conducted to investigate the role of total flavonoids of B. bipinnata in suppressing tumor necrosis factor-alpha (TNF-α) and nitric oxide (NO) release in HUVECs cultured with sera from active Henoch-Schonlein purpura (HSP) patients. Results showed that total flavonoids of the plant may inhibit the inflammatory mediators in HUVECs induced by sera from active HSP patients [5]. Polyacetylenes from B. bipinnata were reported to exert antiinflammatory activities on lipopolysaccharide (LPS)-induced interleukin 1 and tumor necrosis factor (TNF-α) production in macrophage (RAW264.7) cells [6]. The plant extract exerted inhibitory effects on human HepG2 cell lines and Hela cell lines with IC50 values of 14.80 μg/ml and 13.50 μg/ml respectively [7]
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