Secondary Metabolites from Annulohypoxylon sp. and Structural Revision of Emericellins A and B

Abstract

Seven previously undescribed compounds were isolated from the endophytic fungus Annulohypoxylon sp. KYG-19 (family Xylariaceae), including three gymnomitrane-type sesquiterpenes xylariacinols A, B, and D (1, 2, and 4), one bisabolane-type sesquiterpene annulnol F (6), one phenol derivative lariacinol G (7), and two polyhydroxy compounds hypoxylonols H and I (8 and 9), together with two known gymnomitrane-type sesquiterpenes emericellin A (3) and 3gymnomitren-15-ol (5). The assignments of their structures was determined by extensive spectroscopic and spectrometric analysis, acetonide analysis, Mosher's method, and X-ray crystallography. In addition, the structures of emericellins A and B, which were reported to possess an unprecedented tricyclo[4, 4, 2, 1]hendecane scaffold, were revised by comparing their spectroscopic data with those of 1 and 3. Compounds 1 and 4 exhibited antibacterial activity against Escherichia coli with minimum inhibitory concentrations of 4 and 2 μg/mL, respectively.

A New Highly Oxygenated Polyketide Derivative from Trichoderma sp. and Its Antifungal Activity

“…Antifungal activity assays were performed in sterilized 96‐well microplates using a microdilution method described previously [53–55] . The 24‐h‐old fungal cultures of F. solani , P. cucumerina , A. panax , A. niger , P. herbarum , and F. oxysporum were added to PDA medium (1 L of water, 200 g of potato, 20 g of dextrose and natural pH)) to reach 1×10 5 colony‐forming units/mL.…”

“…Antifungal activity assays were performed in sterilized 96-well microplates using a microdilution method described previously. [53][54][55] The 24-h-old fungal cultures of F. solani, P. cucumerina, A. panax, A. niger, P. herbarum, and F. oxysporum were added to PDA medium (1 L of water, 200 g of potato, 20 g of dextrose and natural pH)) to reach 1 × 10 5 colonyforming units/mL. All compounds and the positive control were dissolved in dimethyl sulfoxide (DMSO), and their final concentrations were ranged from 0.125 to 512 μg/mL as determined by using a 2-fold serial dilution method.…”

Structure Revisions of Phenolic Bisabolane Sesquiterpenes and a Ferroptosis Inhibitor from the Marine-Derived Fungus Aspergillus versicolor YPH93

“…The 13 C NMR spectrum revealed the presence of 15 carbon resonances, which were attributed with the aid of HSQC spectrum to a benzene ring, a carbonyl carbon (δ C 169.6), three methyls, a methylene, two oxygenated methines (δ C 74.3, 64.7), and two oxygenated nonhydrogenated carbons (δ C 80.3, 79.7). The 1 H and 13 C NMR data in association with the 2D NMR correlation established a bisabolane-type sesquiterpene nucleus, structurally related to the known 10-hydroxysydowic acid. 47 The obvious difference between them was owing to the presence of an additional oxygenated methine (δ H 4.06; δ C 64.7) in 1 instead of a C-9 methylene in 10-hydroxysydowic acid, suggesting that 1 was a 9-hydroxylated derivative of 10-hydroxysydowic acid.…”

“…The molecular formula of 3 was established as C 15 H 20 O 6 by HRESIMS, the same as that of 2. Comparison of the 1 H and 13 C NMR spectra of 2 and 3 revealed that the structure of 3 was closely related to 2. The coupling constants showed that the methylene protons H 2 -9 [δ H 2.00 (1H, ddd, J = 13.0, 10.0, 9.8 Hz); 2.10 (1H, ddd, J = 13.1, 4.2, 4.1 Hz)] were coupled to two hydroxymethines, H-8 [δ H 4.08 (1H, dd, J = 9.8, 4.2 Hz)] and H-10 [δ H 3.56 (1H, dd, J = 10.0, 4.1 Hz)], suggesting that the two hydroxy groups of the pyran ring were located at C-8 and C-10, this deduction was confirmed by the COSY relationship from H-8 to H-10 via H 2 -9 (Figure 2).…”

“…In addition, we noticed that some pyrancontaining PBSs (sydowic acid (10) derivatives) reported in the literature that possess similar ECD curves or NMR data were assigned different configurations, indicating the possibility Table 1. NMR Data for 1-3 in Methanol-d 4 ( 1 H NMR at 400 MHz, 13 C NMR at 100 MHz) that some structures were erroneously determined. The above speculations prompted us to explore the antiferroptosis activity and the structures of PBS.…”