Bioactive Polyketide Derivatives from the Mangrove-Derived Fungus Daldinia eschscholtzii HJ004

Abstract

Five new tetralones, daldiniones A−E (1−5), three new chromones, 7-hydroxy-5-methoxy-2,3-dimethylchromone (9), 5-methoxy-2-propylchromone (10), and 7ethyl-8-hydroxy-6-methoxy-2,3-dimethylchromone (11), and two new lactones, helicascolides D and E (16 and 17), together with nine known metabolites (6−8, 12−15, and 18− 19) were isolated from the mangrove-derived fungus Daldinia eschscholtzii HJ004. The structures and absolute configurations of the new compounds were determined by analyzing MS and NMR data and utilizing GIAO based 13 C NMR chemical shift calculations and quantum chemical electronic circular dichroism (ECD) calculations. Compounds 9, 13, and 18 showed inhibitory activities against α-glucosidase with IC 50 values of 13, 15, and 16 μM, respectively.

Bioactive Secondary Metabolites from the Culture of the Mangrove-Derived Fungus Daldinia eschscholtzii HJ004

“…Both 1D and 2D NMR spectra were measured on a Bruker AV-400 (Bruker Corporation, Fällanden, Switzerland) instrument by using CDCl 3 as a solvent with TMS as the internal standard. The other experimental procedures were performed as previously described in the literature [9].…”

“…The strain HJ004 was isolated from the stem of mangrove Brguiera sexangula var. rhynchopetala, collected in the South China Sea, and was identified as Daldinia eschscholtzii with the GeneBank (NCBI) accession number MH059553 [9]. This strain was deposited at the Key Laboratory of Tropical Medicinal Resource Chemistry of Ministry of Education, Hainan Normal University, Haikou, China.…”

“…In our ongoing research on mangrove-derived fungi, we have found some new bioactive metabolites (including metabolites with inhibitory activity against α-glucosidase) [9][10][11][12][13][14].…”

“…Mangrove-derived fungi can produce secondary metabolites with novel structures and biological activities [8]. In our ongoing research on mangrove-derived fungi, we have found some new bioactive metabolites (including metabolites with inhibitory activity against α-glucosidase) [9][10][11][12][13][14]. A mangrove-derived fungus Daldinia eschscholtzii HJ004 attracted our attention due to the inhibitory activity against α-glucosidase of its EtOAc extract, and three polyketide derivatives with strong inhibitory activity against α-glucosidase have been isolated [9].…”

“…In our ongoing research on mangrove-derived fungi, we have found some new bioactive metabolites (including metabolites with inhibitory activity against α-glucosidase) [9][10][11][12][13][14]. A mangrove-derived fungus Daldinia eschscholtzii HJ004 attracted our attention due to the inhibitory activity against α-glucosidase of its EtOAc extract, and three polyketide derivatives with strong inhibitory activity against α-glucosidase have been isolated [9]. A further chemical investigation of the fermentation broth resulted in the identification of two new polyketides 8-O-methylnodulisporin F (1) [15] and nodulisporin H (2) [15], two new naphthoquinones 5-hydroxy-2-methoxy-6,7-dimethyl-1,4-naphthoquinone (3), and 5-hydroxy-2-methoxynaphtho [9c]furan-1,4-dione (4), and a new naphthofuran 1,3,8-trimethoxynaphtho [9-c] furan (5), together with five known compounds, 4-O-methyl eleutherol (6) [16], 2-acetyl-7-methoxybenzofuran (7) [17], (-)-orthosporin (8) [18], diaporthin (9) [18], and 6-hydroxymellein (10) [19] (Figure 1).…”