Bioactive Dibenzo-α-pyrone Derivatives from the Endophytic Fungus Rhizopycnis vagum Nitaf22

Abstract

Six new dibenzo-α-pyrones, rhizopycnolides A (1) and B (2) and rhizopycnins A-D (3-6), together with eight known congeners (7-14), were isolated from the endophytic fungus Rhizopycnis vagum Nitaf22 obtained from Nicotiana tabacum. The structures of the new compounds were unambiguously elucidated using NMR, HRESIMS, TDDFT ECD calculation, and X-ray crystallography data. Rhizopycnolides A (1) and B (2) feature an uncommon γ-butyrolactone-fused dibenzo-α-pyrone tetracyclic skeleton (6/6/6/5), while rhizopycnin B (4) was the first amino group containing dibenzo-α-pyrone. Rhizopycnolides A (1) and B (2) are proposed to be biosynthesized from polyketide and tricarboxylic acid cycle pathways. The isolated compounds were tested for their antibacterial, antifungal, and cytotoxic activities. Among them, rhizopycnolide A (1), rhizopycnins C (5) and D (6), TMC-264 (8), penicilliumolide D (11), and alternariol (12) were active against the tested pathogenic bacteria Agrobacterium tumefaciens, Bacillus subtilis, Pseudomonas lachrymans, Ralstonia solanacearum, Staphylococcus hemolyticus, and Xanthomonas vesicatoria with MIC values in the range 25-100 μg/mL. Rhizopycnin D (6) and TMC-264 (8) strongly inhibited the spore germination of Magnaporthe oryzae with IC50 values of 9.9 and 12.0 μg/mL, respectively. TMC-264 (8) showed potent cytotoxicity against five human cancer cell lines (HCT-116, HepG2, BGC-823, NCI-H1650, and A2780) with IC50 values of 3.2-7.8 μM.

Endophytic Fungi: A Source of Potential Antifungal Compounds

“…Endophytic fungus Rhizopycnis vagum Nitaf 22 obtained from the healthy root of Nicotiana tabacum grown at China Agricultural University Beijing, China was the source of Rhizopycnin D ( 25 ) and TMC-264 ( 26 ) ( Figure 2 ). Compounds 25 and 26 showed strong inhibition of the spore germination of Magnaporthe oryzae with IC 50 values of 9.9 and 12.0 µg/mL, respectively [ 25 ].…”

A Novel Derivative of (-)mycousnine Produced by the Endophytic Fungus Mycosphaerella nawae, Exhibits High and Selective Immunosuppressive Activity on T Cells

“…Because of the unique interaction between the endophytic fungi and their host plants, several efforts have been made to identify bioactive substances produce by these organisms (Kaul et al, 2012; Yuan et al, 2014; Lai et al, 2016). Indeed, endophytic fungi in medicinal plants are potential sources of novel bioactive secondary metabolites, and could contribute to the pharmacological effects of these plants.…”

Lophiostomin A–D: new 3,4-dihydroisocoumarin derivatives from the endophytic fungus Lophiostoma sp. Sigrf10

“…2,3 These microorganisms are also abundant resources for exploring other novel metabolites with interesting bioactivities such as cytotoxic, antitumor, and anti-inammatory activities. 4,5 As part of the continuing interest in searching for bioactive substances from endophytic fungi, [6][7][8] the endophytic fungi from medicinal plants were screened for their antimicrobial-producing potential. As a result, the extract of Lophiostoma sp.…”