Cytochalasins from the endophytic fungus Phomopsis sp. cib-109

Abstract

Keywords: Phomopsis, secondary metabolite, cytochalasin.Phomopsis sp. is a widely distributed endophytic fungus, some of which can cause serious plant diseases such as leaf blight, twig dieback, fruit rot, and seed decay [1][2][3][4][5][6][7][8]. Cytochalasins were isolated from the genus Phomopsis as the main phytotoxic metabolites, which can inhibit the growth of the plants [9][10][11][12]. In this study, we investigated the secondary metabolites of the plant pathogenic fungus P. sp. cib-109 by chromatographic and spectroscopic methods. As a result, a new compound named cytochalasin R1 (1), along with epoxycytochalasin J, cytochalasin H, cytochalasin J, cytochalasin N, and cytochalasin O [9-13], were isolated and identified from the solid-state fermented rice culture of the fungus P. sp. cib-109. Here we report on the structural elucidation of compound 1.The molecular formula of compound 1 was inferred to be C 30 H 41 NO 6 from the quasi-molecular ion at m/z 534.2815 [M + Na] + in the HR-ESI-MS spectrum and the signals in the 13 C NMR spectrum. The IR spectrum absorption bands at 1680 and 1742 cm -1 and the NMR signals (G C 176.3, G C 170.5, and G H 9.12) suggested the presence of amide and acetyl groups.In the 1 H NMR spectrum, there were signals characteristic of a monosubstituted phenyl at G 7.37 (4H, overlap, H-2c, 3c, 5c, 6c) and 7.28 (1H, t, J = 7.0 Hz, H-4c) and five methyls at G 1.14 (3H, d, J = 6.9 Hz, H-22), 1.18 (3H, d, J = 7.2

Pentacyclic Cytochalasins and Their Derivatives from the Endophytic Fungus Phomopsis sp. xz-18

“…The 1H-NMR spectrum (Table 1) showed the presence of four methyl, three methylene, and fifteen methine (including one olefinic and five phenyl methine) moieties at δ H 7.21-7.36. The 13 C-NMR spectrum (Table 1) showed a total of 26 carbons. Taking into account two methines (δ C 128.8 and δ C 129.4) on the single-substituted phenyl, the total number of carbons conformed to the predicted molecular formula.…”

“…Based on HR-ESI-MS analysis and NMR data (Tables S7 and S8), phomopchalasin C 7 (7) and phomopchalasin C 8 (8) were confirmed as 7-O-acetyl cytochalasin P [3] and 18-O-methyl cytochalasin O [3], respectively. Ten cytochalasin derivatives, cytochalasin J 3 (9) [8], phomopchalasin B (10) [7], cytochalasin H (11), cytochalasin J (12), cytochalasin N (13), cytochalasin O ( 14), cytochalasin P (15), cytochalasin Q ( 16), and cytochalasin R (17) [3] and R1 (18) [13] (Figure 3), were purified from the same strain, and their structures were confirmed by comparison of NMR spectra (Figures S49-S68) and data from the literature. Atipathogenic fungal compounds 9, 11 and 12 were previously reported to have been extracted from Phomopsis sp.…”