Guided isolation of secondary metabolites from Nectria sp. MHHJ-3 by molecular network strategy.

The fungus Nectria sp. MHHJ-3 was isolated from Illigera rhodantha. A molecular networking-guided the secondary metabolites investigation of Nectria sp. MHHJ-3 led to the isolation of ten metabolites (1-10), including two new naphthalenone derivatives, nectrianaphthalenones A (1) and B (2), and two new steroids, nectriasteroids A (3) and B (4). Their structures were elucidated by extensive spectroscopic analysis including the HRESIMS, 1D/2D NMR and electronic circular dichroism (ECD) spectra. A plausible biosynthetic pathway for 1-2 was proposed. Compounds 1 and 2 exhibited moderate acetylcholinesterase (AChE) inhibitory activities. Compounds 3 and 4 showed significant cytotoxic activity against selected tumor cells. Particularly, compound 3 exhibited the strongest activity against A549 cells with an IC50 value of 13.73 ± 0.03 µM, which was at the same grade with that of positive control cisplatin.

A new cyclopentenone derivative from Trichoderma atroviride HH-01.

A new cyclopentenone derivative, atrovinol (1), together with ten known compounds (2-11) were isolated from Trichoderma atroviride HH-01, an endophytic fungus from Illigera rhodantha (Hernandiaceae). Their structures were identified by HRESIMS, 1 D/2D NMR, and electronic circular dichroism (ECD) spectra. Compound 1 exhibited moderate inhibitory activity against Staphylococcus aureus and Bacillus subtilis with MIC values of 8.0 µg/mL and 16.0 µg/mL, respectively.

Phytotoxic meroterpenoids with herbicidal activities from the phytopathogenic fungus Pseudopestalotiopsis theae.

The fungus Pseudopestalotiopsis theae isolated from the fresh leaves of Illigera celebica, has been reported to be a pathogenic fungus that can cause gray blight on tea leaves, a disease characterized by the appearance of necrotic lesions on tea leaves. The pathogenic substances in this fungus have not been clearly identified. Considering the possible involvement of specialized metabolites in symptom appearance, a chemical investigation of specialized metabolites on P. theae was conducted, resulting in the isolation of eight meroterpenoids, including six undescribed biscognienynes G-L and two known ones (biscognienynes B and D). The structures of these new compounds were characterized by extensive NMR spectroscopic and HR-ESI-MS data, and their absolute configurations were elucidated by ECD calculations. Except for biscogniyne L, all the isolated biscognienynes showed different degrees of phytotoxicity to tea in vivo, thereby revealing for the first time the substances in P. theae that cause tea gray blight. Inspired by the fact that phytotoxins produced by pathogenic fungus are an effective resource for designing natural and safe bioherbicides, when assayed the herbicidal activity through Petri dish bioassays, biscognienynes G-J showed phytotoxic effects against seed germination and seedling growth of Setaria viridis, strongly inhibiting seed germination percentage and radicle and germ lengths of seedlings. The results of this study demonstrated the great potential of biscognienynes G-J to be proposed and developed as ecofriendly herbicides.

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

A new highly oxygenated polyketide derivative, trichodersine (1), together with fourteen known compounds (2-15) were isolated from Trichoderma sp. MWTGP-04. The structure of trichodersine (1) was established based on comprehensive spectroscopic data analysis, and biogenesis argument. The results of double culture experiments indicated that the strain exhibited potential antifungal activity. The antifungal activities of all isolated compounds were evaluated, among them compound 1 exhibited remarkable antifungal activities against Fusarium solani, Plectosphaerella cucumerina, Alternaria panax, and Aspergillus niger, with minimum inhibitory concentrations (MICs) of 4, 4, 16, and 32 µg/mL, respectively. In addition, the antifungal experiments of polyketide derivatives (1-3) disclosed that their degree of oxidation was a key factor affecting the antifungal activity.

A new cyclohexenone derivative from phomopsis sp. XM-01.

A new cyclohexenone derivative, phomopine (1), together with five known compounds (2-6) were isolated from Phomopsis sp. XM-01. The structure of 1 was determined by extensive spectroscopic analyses and electronic circular dichroism (ECD) calculation. In vitro bioassays, compounds 1 and 2 exhibited potent antimicrobial activities against Candida albicans and Staphylococcus aureus with their corresponding minimum inhibitory concentrations (MICs) of 64 µg/mL and 16 µg/mL, respectively.

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

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 3-gymnomitren-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.