Metabolites from Combretum dolichopetalum and its associated endophytic fungus Nigrospora oryzae — Evidence for a metabolic partnership
Graphical abstract
Introduction
It is well known that many endophytic fungi are capable of generating the same secondary metabolites as their host plants [1] with some notable examples being paclitaxel [2], camptothecin [3], podophyllotoxin [4], or hypericin [5]. In fact, since the bioactive compound paclitaxel (taxol) was discovered from the endophytic fungus Taxomyces andreanae in 1993, scientists have increasingly paid closer attention to relationships between endophytic fungi and their host plants in search for novel and biologically active compounds [6].
In the course of our ongoing research on bioactive natural products from endophytic fungi and their associated host plants [7], [8], [9], [10], we became interested in the African rain forest tree Combretum dolichopetalum Engl. and Diels (Combretaceae), a plant which is hitherto chemically unexplored but is reported to posses hepatoprotective [11], antiulcer [12] and antidiabetic activities [13] and is used traditionally for the treatment of gastrointestinal disorders [14]. Furthermore, in order to examine whether endophytic fungi from C. dolichopetalum were capable of producing the same or similar bioactive compounds as those present in their host plant, endophytic fungi from the plant were explored, resulting in the isolation of Nigrospora oryzae from leaves of C. dolichopetalum.
Herein we report the isolation, structural elucidation of nine compounds including one new natural product 4-dehydroxyaltersolanol A (9) from the endophytic fungus and its host plant as well as their cytotoxicity. Possible biogenetic relationships among some of the isolated compounds are also discussed. To the best of our knowledge, this is the first report of secondary metabolites from C. dolichopetalum and also the first report on endophytic fungi from this plant.
Section snippets
Results and discussion
Our chemical examination of the roots of C. dolichopetalum led to the isolation of six known compounds including ellagic acid (1) [15], 3,3′,4-tri-O-methylellagic acid (2) [16], arjunolic acid (3) [17], 4′-dihydrophaseic acid (4) [18], echinulin (5) [19] and arestrictin B (6) [20]. Investigation of the EtOAc extract of the endophytic fungus N. oryzae yielded the new altersolanol derivative, 4-dehydroxyaltersolanol A (9), in addition to two known sesquiterpenoids, (S)-7′-hydroxyabscisic acid (7)
General experimental procedures
1H and 13C NMR spectra were recorded on Bruker ARX 300 or AVANCE DMX 600 NMR spectrometers. ESI-MS spectra were measured on a Finnigan LCQ-Deca mass spectrometer and HRESI-MS spectra were recorded with a FTHRMS-Orbitrap (Thermo Finnigan) mass spectrometer. Optical rotations were recorded on a Perkin-Elmer-241 MC polarimeter. Solvents were refined before utilization, and spectroscopic-grade solvents were utilized for spectroscopic measurements. HPLC investigation was performed utilizing a HPLC
Acknowledgments
Financial support by a grant from BMBF (16GW0107K) to P. P. is gratefully acknowledged.
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2019, Journal of Water Process EngineeringCitation Excerpt :In addition, the composition of cell–wall biomass, mainly from fungi (chitin, glucan, mannan, proteins, amino and hydroxyl groups), make this residue attractive for biosorption [21]. Species of fungus of the genus Nigrospora sp. are widely studied in the literature for the production of a wide range of bioactive secondary metabolites [22,23]. Moreover, this genus of fungus is also studied as a potential microorganism in the production of microbial oil by solid–state fermentation [24] and submerged fermentation [25].