Next Article in Journal
Research on Quantitative Analysis Method of Infrared Spectroscopy for Coal Mine Gases
Previous Article in Journal
Molecular Modification Strategies for Enhancing CO2 Electroreduction
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Molecules
Volume 30
Issue 14
10.3390/molecules30143039
molecules-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Ustisorbicillinols G and H, Two New Antibacterial Sorbicillinoids from the Albino Strain LN02 of Rice False Smut Fungus Villosiclava virens

by
Xuwen Hou
†,
Mengyao Xue
†,
Gan Gu
†,
Dan Xu
,
Daowan Lai
* and
Ligang Zhou
*
Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Molecules 2025, 30(14), 3039; https://doi.org/10.3390/molecules30143039 (registering DOI)
Submission received: 13 June 2025 / Revised: 14 July 2025 / Accepted: 18 July 2025 / Published: 20 July 2025
(This article belongs to the Special Issue Novel Antimicrobial Molecules Derived from Natural Sources)
Browse Figures
Versions Notes

Abstract

Villosiclava virens (anamorph: Ustilaginoidea virens), the causal fungal pathogen of rice false smut, has been found to produce various secondary metabolites. The albino strain LN02 is a natural albino phenotype mutant of V. virens due to its inability to produce ustilaginoidins. The fermentation of V. virens LN02 was performed in solid rice medium to obtain fungal cultures, which were chemically investigated. After removing the known metabolites, two new dimeric sorbicillinoids, namely ustisorbicillinols G (1) and H (2), were isolated from the ethyl acetate extract. Their structures were elucidated using spectroscopic data analyses and quantum chemical calculations. Compounds 1 and 2 displayed antibacterial activity towards Ralstonia solanacearum, Agrobacterium tumefaciens and Bacillus subtilis, with median inhibitory concentration (IC50) values of 19.76–25.43 μg/mL for 1 and 25.35–45.48 μg/mL for 2. The discovery of new sorbicillinoids will increase the diversity of the secondary metabolites of V. virens and provide candidates for the creation of new antimicrobials as well.

1. Introduction

Sorbicillinoids are a group of fungal hexaketide metabolites with a sorbyl side chain [1]. Based on their structural features and biosynthetic pathways, sorbicillinoids are grouped into monomeric, dimeric, trimeric and hybrid ones [2,3]. These sorbicillinoids show important physiological and ecological functions [4,5] and also have various types of biological activity, with potential pharmaceutical and agrochemical applications as antimicrobial, antioxidant, antivirus and anticancer agents [6,7,8,9,10].
Rice false smut (RFS) disease, caused by Villosiclava virens (anamorph: Ustilaginoidea virens), is a serious rice panicle disease in rice-producing areas around the world. In addition, the RFS pathogen V. virens can produce multiple secondary metabolites (SMs), some of which belong to mycotoxins and can be toxic to plants and animals, as well as posing a serious threat to the health of humans and domestic animals [11,12,13,14,15,16,17,18]. These toxic metabolites are involved in the pathogenic process of V. virens on rice plants, resulting in a decrease in the yield and quality of rice grains [19,20,21,22,23].
The albino strain LN02 of V. virens is a natural mutant with a white phenotype due to its inability to synthesize ustilaginoidins [24,25], which are the main SMs in the normal strain of V. virens [12,13,26,27]. Although the albino strain LN02 can produce sorbicillinoids like normal strains P1 and UV-8b [15,28], there are some differences in the types and relative content of sorbicillinoids between albino and normal strains, according to HPLC analysis [24].
In the course of searching for new sorbicillinoids, the albino strain LN02 was cultured in solid rice medium, which led to the separation of two new dimeric sorbicillinoids, namely ustisorbicillinols G (1) and H (2) (Figure 1). Here, we report the isolation, structural characterization and antibacterial activity of these two compounds.

2. Results and Discussion

2.1. Structural Identification of Compounds 1 and 2

The EtOAc extract of fungi was successively subjected to repeated column chromatography over a normal-phase silica gel, reversed-phase silica gel (i.e., ODS) and Sephadex LH-20, as well as semi-preparative HPLC, to afford compounds 1 and 2 (Figure 1). The 1D and 2D NMR spectra, UV spectra and HRESIMS spectra of 1 and 2 are shown in Figures S3–S18.
Ustisorbicillinol G (1) was isolated as a yellow amorphous powder that exhibited a prominent pseudomolecular ion peak at m/z 495.2028 [M–H]– (calcd for C28H31O8, 495.2024) in the HRESIMS spectrum (Figure S10), indicating a molecular formula of C28H32O8, with thirteen double-bond equivalents. Its UV spectrum indicated that it was a sorbicillinoid by analogy to the co-isolated trichotetronine (Figure 1).
A detailed analysis of the NMR data (Table 1) revealed that 1 was an analog of trichotetronine [29,30,31], as they showed similar NMR resonances, except for the lack of one olefinic double bond compared to the latter, while containing additionally one oxymethine group (C-19: δC 83.1; δH 4.92) and one methylene group (C-18: δC 42.1; δH 2.90, 2.43 each dd).
Further analysis of the 2D NMR spectra (Figure S1) allowed the establishment of the gross structure of 1. In the 1H−1H COSY spectrum, correlations from Me-22 (δH 1.78, dd) to the olefinic H-21 (δH 5.95, dq), which correlated to another olefinic H-20 (δH 5.78, ddd), were seen. This proton (H-20) was correlated to the oxymethine (H-19), which in turn correlated to the methylene (H2-18), reflecting that one of the sorbyl chains in trichotetronine was modified in 1. The HMBC correlations from H-9 (δH 1.02, s) to C-1 (δC 56.5), C-2 (δC 169.5) and C-7 (δC 209.0); from H-10 (δH 1.29, s) to C-4 (δC 41.2), C-7 and C-8 (δC 73.7); from H-4 (δH 3.57, d) to C-2, C-3 (δC 116.4), C-7 and C-8; from H-18a (δH 2.90, dd) to C-17 (δC 190.8) and C-19 (δC 83.1); and from H-4 to C-17, as well as from H-19 to C-2, suggested the presence of a dihydropyrone ring by linking C2 and C19 via an ether bond in the right part of the structure. Such a pyrone ring connecting the side chain and its cyclohexene ring was seen previously in ustisorbicillinols A–D from U. virens [28]. Hence, the planar structure of 1 was established (Figure 1).
The relative configuration of 1 was established to be the same as for trichotetronine, by comparing the J coupling constants and NOESY correlations, except for C-19. The relative configuration of C-19 was determined by comparing the coupling constants between H-19 and H2-18 (3JH-19/H-18a and 3JH-19/H-18b: 13.8, 3.4 Hz) and the 1H/13C NMR data to those analogs that contained a dihydropyrone moiety [28].
The absolute configuration of 1 was determined by ECD calculation with the calculated ECD curves of 1R, 4S, 5S, 6R, 8S, 11R, 19R-1 at the PBE0/TZVP//B3LYP/6-31g(d) (IEFPCM, MeOH) level of theory, which matched the experimental ECD well (Figure 2). Therefore, compound 1 was elucidated and designated as ustisorbicillinol G (1).
The Michael addition of H2O to the C18/C19 double bond of trichotetronine could yield the corresponding 19-hydroxyl adduct, followed by the intramolecular nucleophilic attack of 19-OH to the keto group (C-2) to generate a semi-ketal, which should give rise to the dihydropyrone structure of 1 after dehydration.
Ustisorbicillinol H (2) was isolated as a yellow amorphous powder that had a prominent pseudomolecular ion peak at m/z 529.2088 [M−H]− (calcd for C28H33O10, 529.2079) in the HRESIMS spectrum. The maximum UV absorptions at 200, 287 and 362 nm were similar to those of previously reported sorbicillinols [28,32].
Extensive analysis of the NMR data (Table 2) revealed that 2 was similar to dihydrotrichodimer ether A [32], except that the signals for one disubstituted double bond in dihydrotrichodimer ether A were replaced by two oxymethines (C11′: δC 67.6/ δH 3.69; C10′: δC 76.7/δH 3.64) in 2. An analysis of the 1H−1H COSY and HMBC spectra revealed that the C-11′-C-10′ double bond was saturated in 2 and substituted with two hydroxyl groups. As in the COSY spectrum, Me-12′ (δH 1.12, d) was correlated to the oxymethine (CH-11′), which in turn was correlated to the second oxymethine (CH-10′), followed by its sequential correlation to the methine (CH-9′) of the pyrone ring. Key HMBC correlations from Me-12′ to C-11′/C-10′ unequivocally supported this assignment (Figure S2).
The similar NOE correlations and coupling constants (3JH-H) to dihydrotrichodimer ether A indicated similar relative stereochemistry in 2, except for C-11′/C-10′. In addition, the CD spectrum of 2 displayed cotton effects at 317, 278, 246, 232 and 216 nm (Figure 3), which were similar to those of dihydrotrichodimer ether A [32], implying the same absolute configuration for the cage structure, except for C-10′ and C-11′. Their configurations were determined by the analysis of the experimental and calculated J values for the model structures (Figure 4). A truncated structure of 2 was used for the calculations, in which both the C5′ and C6′ substituents were replaced by a methyl group. Since the absolute configuration of C9′ has been determined as stated above, only four isomers differing at C-10′/C-11′ were considered (Figure 4A). As shown in Figure 4B, the calculated values for the 10′S,11′S-isomer fitted well with the experimental data. Hence, an S configuration was assigned for both C10′ and C11′. It is possible that the olefinic bond at C10′/C11′ of dihydrotrichodimer ether A was first epoxidized, and then the epoxide ring opened by the nucleophilic attack of water should explain the biosynthesis of 2.

2.2. Antibacterial Activity of Compounds 1 and 2

Compounds 1 and 2 were examined for their antibacterial activity and cytotoxicity in six human cancer cell lines. The positive controls for the antibacterial and cytotoxic activity evaluation were streptomycin sulfate and Taxol, respectively. Compound 1 showed significant antibacterial activity against Ralstonia solanacearum, Agrobacterium tumefaciens and Bacillus subtilis, with IC50 values of 24.33, 19.76 and 25.43 μg/mL, respectively. Compound 2 also had lower or similar antibacterial activity against R. solanacearum, A. tumefaciens and B. subtilis, with IC50 values of 35.42, 45.48 and 25.35 μg/mL, respectively (Table 3). The sorbicillinoids, including ustisorbicillinol B, dihydrotrichodimer ether A, oxosorbicillinol, bisvertinolone and demethyltrichodimerol, isolated from the normal RFS strain UV8b also showed obvious antibacterial activity [28]. This indicates that these sorbicillinoids have protective effects in RFS fungi (V. virens) against bacteria. The ecological significance of sorbicillinoids in V. virens against bacteria need to be further verified and investigated.
Compounds 1 and 2 were also examined for their cytotoxic activity. However, both compounds did not show any cytotoxic activity (Table S1).
Fungi, such as marine fungi [33,34], endophytic fungi [35,36] and pathogenic fungi [37,38], can produce large amounts of SMs, which have been considered a treasure trove of novel bioactive compounds [39].
The potential biosynthetic gene clusters (BGCs) for SMs in V. virens were analyzed by the method of antiSMASH. Nineteen gene clusters for SMs were identified, among which the polyketide BGCs [5] and ribosomal peptide BGCs [40] were well expressed. Many SMs have been identified in V. virens. They mainly include polyketides and cyclopeptides such as ustilaginoidins [12,13], ustiloxins [11,14] and sorbicillinoids [15,28]. In addition to their functions in the development, stress responses and pathogenicity of V. virens [5], these SMs show various types of biological activity, such as cytotoxic, antimicrobial, phytotoxic and antioxidant activity [12,13,14]. Therefore, V. virens has been considered an important SM-producing fungus.
The bioinformatics analysis demonstrated that the number of BGCs encoding SMs in the V. virens genome was much larger than the number of identified SMs, revealing that there were plenty of silent gene clusters in this fungus. In order to either reveal additional quantities of SMs or increase their production in V. virens, the metabolic regulation [41,42,43,44,45,46], metabolic shunting [47,48,49,50,51] or heterologous expression of BGCs [52] and promoter replacement [53,54] for the activation of fungal silent BGCs to mine the chemical diversity of this fungus might be effective strategies.
In this study, the discovery of two new dimeric sorbicillinoids with their antibacterial activity from the albino strain LN02 increased the diversity of SMs in V. virens. Many sorbicillinoids have been screened to show antibacterial and antifungal activity [2,3,7]. Some sorbicillinoids, such as ustisorbicillinol B, dihydrotrichodimer ether A, oxosorbicillinol, bisvertinolone and demethyltrichodimerol, previously isolated from V. virens, have also been screened to show antibacterial activity [28]. These sorbicillinoids might play important roles between V. virens and its surrounding microorganisms.
Some sorbicillinoids, such as trichotetronine (also named bislongiquinolide), have been screened to show cytotoxic activity [20]. Unfortunately, the trichotetronine analogs ustisorbicillinoids G (1) and H (2) reported in this study have not been shown to have cytotoxic activity (Table S1). Possible reasons might be the differences in their structures, the cell lines employed and the experimental conditions between them. The cytotoxic activity of ustisorbicillinoids G (1) and H (2) needs further investigation.
The albino strain LN02 was proven as the natural deletion mutant of ustilaginoidin biosynthesis, which led to the easy recognition and isolation of sorbicillinoids 1 and 2. It is possible that the absence of ustilaginoidins, which were the main metabolites in the normal strain, led to the trace metabolites being detectable in the albino strain. This approach, based on metabolic shunting through genetic dereplication, has been previously reported to discover new SMs (especially trace metabolites) from other fungal species, eliminating the production of the main metabolites and enabling minor metabolites to be detectable and separable [47,48,49,50,51].

3. Materials and Methods

3.1. Fungus and Fermentation

The albino strain LN02 of rice false smut fungus V. virens was stored in a refrigerator at −80 °C before use [24]. Before strain LN02 was cultured on potato dextrose agar medium (200 g/L of potato, 20 g/L of dextrose and 20 g/L of agar, PDA) at 28 °C for 14 days, a few agar plugs (0.3 cm × 0.3 cm) containing mycelia were added into a 250 mL Erlenmeyer flask containing 100 mL of potato dextrose liquid medium, which was PDA without agar. The liquid culture was incubated in a rotatory shaker for 5 days at 180 rpm under 28 °C to produce the seed culture, which was used to inoculate the solid rice medium (1000 mL Erlenmeyer flask containing 100 g rice and 110 mL water). The fermentation was carried out using a total of 10 kg rice at room temperature (RT) under static conditions in darkness for two months.

3.2. Extraction and Separation

The rice cultures, which had been cultivated for two months, were combined, dried and pulverized. The dry materials were extracted with ethyl acetate (EtOAc) three times at room temperature, each for 5 days, which led to 80 g of EtOAc extract after removing the solvent. Then, the extract was subjected to vacuum liquid chromatography (VLC) over silica gel (i.d. 8 cm × 40 cm) by eluting it with a different mixture of petroleum ether (Shanghai Tichem Chemical Co., Ltd., Shanghai, China) and dichloromethane (Shanghai Tichem Chemical Co., Ltd., Shanghai, China) (PE/CH2Cl2), followed by CH2Cl2/EtOAc, EtOAc/MeOH. Fractions were pooled according to TLC analysis, and 14 fractions were obtained (Frs. A–M). Fr. I (5.0 g) was subjected to gel permeation chromatography over a Sephadex LH-20, eluting with CH2Cl2/MeOH (1:1, v/v) to obtain 12 subfractions. Compound 1 (4.5 mg) was purified from subfr. I-3 by semi-preparative HPLC, eluting with 65% MeOH in H2O. Fr. M was chromatographed over RP-18 to afford 25 subfractions. Subfr. M-23 was subjected to gel permeation chromatography over a Sephadex LH-20, eluting with CH2Cl2/MeOH (1:1, v/v) to obtain 14 fractions. Compound 2 (5.5 mg) was further purified from the fifth fraction by semi-preparative HPLC, eluting with 65% MeOH in H2O.
Ustisorbicillinol G (1): yellow amorphous powder; [α]24D +7.33 (c 0.20, MeOH); ECD (c = 0.60 mM, MeOH) λ 216, 258, 286, 319 nm; UV (MeOH) λmax 200, 228, 290 nm; 1H NMR (CD3OD, 500 MHz), 13C NMR (CD3OD, 125 MHz) see Table 1; HRESIMS m/z 495.2028 [M−H]– (calcd for C28H31O8, 495.2024).
Ustisorbicillinol H (2): yellow amorphous powder; [α]24D +9.67 (c 0.20, MeOH); ECD (c = 0.57 mM, MeOH) λ 216, 232, 246, 278, 317 nm; UV (MeOH) λmax 200, 287, 362 nm; 1H NMR (CD3COCD3, 500 MHz), 13C NMR (CD3COCD3, 125 MHz) see Table 2; HRESIMS m/z 529.2088 [M−H]– (calcd for C28H33O10, 529.2079).

3.3. Calculation of ECD

The conformers of compound 1 were generated by Spartan 14 (v1.1.4) using the MMFF94 molecular mechanics force field calculation with 3.0 kcal/mol cutoff energy [55]. The software package Gaussian 09 (E.01) was used to perform DFT calculations. The optimization and frequency calculation of conformers were performed at the B3LYP/6-31G(d) level. The theoretical ECD (TDDFT) of compound 1 was calculated at the PBE0/TZVP level with the IEF-PCM solvent (MeOH) model as well. SpecDis v1.70.1 was used to simulate the ECD curve, with σ/γ value 0.3 eV [56]. The calculated ECD curve of each conformer was Boltzmann-averaged based on their Gibbs free energy. The calculated ECD spectra were UV-shifted by +10 nm for comparison with the measured spectrum. The nuclear spin–spin coupling J (Hz) for the truncated models of 2 was calculated at the mpw1pw91/6-311+g(2d,p) (PCM = acetone) level.

3.4. Antibacterial Assay

The antibacterial activity of compounds 1 and 2 was evaluated on three bacterial strains, namely Ralstonia solanacearum (R. solanacearum), Agrobacterium tumefaciens (A. tumefaciens) and Bacillus subtilis (B. subtilis), which were kindly provided by the Plant Pathology Department of the Plant Protection College, China Agricultural University (CAU). Streptomycin sulfate (Sigma, Shanghai, China) with purity greater than 95% was used as the positive control. Dimethyl sulfoxide (DMSO) for dissolving compounds was used as the blank control. Both the minimum inhibitory concentration (MIC) values and median inhibitory concentration (IC50) values of the compounds and the positive control were obtained in sterile microplates with 96 wells by the modified broth dilution test, as described previously [28].

3.5. Cytotoxic Activity Assay

The cytotoxicity of the compounds was evaluated on human carcinoma cells using the microculture methyl thiazolyl tetrazolium (MTT) assay, as described previously [12]. The tested human cell lines included human colon cancer (HCT116), human breast cancer (MDA-MB-231), human gastric cancer (BGC823), human hepatoma (Huh-7), human non-small cell lung cancer (PC9) and human pancreatic cancer (PANC-1) cell lines, which were provided by the Institute of Materia Medica, Chinese Academy of Medical Sciences. The positive control was Taxol. DMSO, which was used to dilute the compounds, served as the blank control.

4. Conclusions

In summary, two novel dimeric sorbicillinoids, namely ustisorbicillinols G (1) and H (2), were isolated from albino strain LN02 cultures of rice false smut fungus V. virens. The structures of 1 and 2 were elucidated by comprehensive spectroscopic analysis, together with quantum-chemical calculations. Both compounds showed antibacterial activity and could represent candidates for the creation of new antimicrobials. Furthermore, the discovery of new sorbicillinoids will increase the diversity of the secondary metabolites of V. virens. In order to increase the production of ustisorbicillinols G (1) and H (2), it is necessary to optimize the culture conditions to enhance their biosynthesis. In addition, the biosynthesis regulation mechanisms and the physiological and ecological functions of 1 and 2 in V. virens, as well as their potential application as antimicrobial agents, need further investigation.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/molecules30143039/s1. General experimental procedures; Figure S1: Key 2D NMR correlations of 1; Figure S2: Key 2D NMR correlations of 2; Figure S3: 1H NMR spectrum of 1 (CD3OD, 500 MHz); Figure S4: 13C NMR spectrum of 1 (CD3OD, 125 MHz); Figure S5: HSQC spectrum of 1; Figure S6: 1H–1H COSY spectrum of 1; Figure S7: HMBC spectrum of 1; Figure S8: NOESY spectrum of 1; Figure S9: UV spectrum of 1 (100% MeOH/H2O, extracted from HPLC-DAD data); Figure S10: HRESIMS spectrum of 1; Figure S11: 1H NMR spectrum of 2 (CD3COCD3, 500 MHz); Figure S12: 13C NMR spectrum of 2 (CD3COCD3, 125 MHz); Figure S13: HSQC spectrum of 2; Figure S14: 1H–1H COSY spectrum of 2; Figure S15: HMBC spectrum of 2; Figure S16: NOESY spectrum of 2; Figure S17: UV spectrum of 2 (100% MeOH/H2O, extracted from HPLC-DAD data); Figure S18: HRESIMS spectrum of 2; Table S1: Cytotoxic activity of compounds 1 and 2.

Author Contributions

Conceptualization, supervision and funding acquisition, L.Z.; investigation, X.H., M.X., G.G., D.L. and L.Z.; methodology, formal analysis and data curation, M.X., G.G. and X.H.; writing—original draft preparation, X.H., M.X. and G.G.; writing—revision and editing, L.Z.; writing—review, D.L. and D.X. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China (32072373 and 31471729).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data are contained within the article or Supplementary Materials.

Acknowledgments

We would like to acknowledge Jiankun Miao from the Institute of Plant Protection, Liaoning Academy of Agricultural Science of China, for providing the white RFS balls to obtain the pure culture of albino strain LN02 of V. virens. We would also like to thank the core facility platform of the College of Plant Protection at China Agricultural University for the assistance with the LC-MS analysis.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Harned, A.M.; Volp, K.A. The sorbicillinoid family of natural products: Isolation, biosynthesis and synthetic studies. Nat. Prod. Rep. 2011, 28, 1790–1810. [Google Scholar] [CrossRef] [PubMed]
  2. Meng, J.; Wang, X.; Xu, D.; Fu, X.; Zhang, X.; Lai, D.; Zhou, L.; Zhang, G. Sorbicillinoids from fungi and their bioactivities. Molecules 2016, 21, 715. [Google Scholar] [CrossRef] [PubMed]
  3. Milzarek, T.M.; Gulder, T.A.M. The fungal natural product class of the sorbicillinoids: Structures, bioactivities, biosynthesis, and synthesis. Nat. Prod. Rep. 2025, 42, 482–500. [Google Scholar] [CrossRef] [PubMed]
  4. Zhang, W.; An, N.; Guo, J.; Wang, Z.; Meng, X.; Liu, W. Influences of genetically perturbing synthesis of the typical yellow pigment on conidiation, cell wall integrity, stress tolerance, and cellulase production in Trichoderma reesei. J. Microbiol. 2021, 59, 426–434. [Google Scholar] [CrossRef] [PubMed]
  5. Zhang, X.; Xu, D.; Hou, X.; Wei, P.; Fu, J.; Zhao, Z.; Jing, M.; Lai, D.; Yin, W.; Zhou, L. UvSorA and UvSorB involved in sorbicillinoid biosynthesis contribute to fungal development, stress response and phytotoxicity in Ustilaginoidea virens. Int. J. Mol. Sci. 2022, 23, 11056. [Google Scholar] [CrossRef] [PubMed]
  6. Lee, D.; Kim, J.; Choi, S.; Choi, J.; Lee, J.W.; Kang, K.S.; Shim, S.H. 2,3-Dihydrosorbicillin and chrysopanol stimulate insulin secretion in INS-1 cells. Bioorg. Med. Chem. Lett. 2023, 83, 129186. [Google Scholar] [CrossRef] [PubMed]
  7. Hou, X.; Zhang, X.; Xue, M.; Zhao, Z.; Zhang, H.; Xu, D.; Lai, D.; Zhou, L. Recent advances in sorbicillinoids from fungi and their bioactivities (covering 2016–2021). J. Fungi 2022, 8, 62. [Google Scholar] [CrossRef] [PubMed]
  8. Duan, C.; Wang, S.; Huo, R.; Li, E.; Wang, M.; Ren, J.; Pan, Y.; Liu, L.; Liu, G. Sorbicillinoid derivatives with the radical scavenging activities from the marine-derived fungus Acremonium chrysogenum C10. J. Fungi 2022, 8, 530. [Google Scholar] [CrossRef] [PubMed]
  9. Liu, J.; Gao, S.; Zhou, W.; Chen, Y.; Wang, Z.; Zeng, Z.; Zhou, H.; Lin, T. Dihydrotrichodimerol Purified from the Marine Fungus Acremonium citrinum prevents NAFLD by targeting PPARα. J. Nat. Prod. 2023, 86, 1189–1201. [Google Scholar] [CrossRef] [PubMed]
  10. Wu, J.; Meng, Q.; Liu, D.; Fan, A.; Huang, J.; Lin, W. Targeted isolation of sorbicilinoids from a deep-sea derived fungus with anti-neuroinffammatory activities. Phytochemistry 2024, 219, 113976. [Google Scholar] [CrossRef] [PubMed]
  11. Koiso, Y.; Li, Y.; Iwasaki, S.; Hanaoka, K.; Kobayashi, T.; Fujita, Y.; Yaegashi, H.; Sato, Z. Ustiloxins, antimitotic cyclic peptides from false smut balls on rice panicles caused by Ustilaginoidea virens. J. Antibiot. 1994, 47, 765–773. [Google Scholar] [CrossRef] [PubMed]
  12. Lu, S.; Sun, W.; Meng, J.; Wang, A.; Wang, X.; Tian, J.; Fu, X.; Dai, J.; Liu, Y.; Lai, D.; et al. Bioactive bis-naphtho-γ-pyrones from rice false smut pathogen Ustilaginoidea virens. J. Agric. Food Chem. 2015, 63, 3501–3508. [Google Scholar] [CrossRef] [PubMed]
  13. Sun, W.; Wang, A.; Xu, D.; Wang, W.; Meng, J.; Dai, J.; Liu, Y.; Lai, D.; Zhou, L. New ustilaginoidins from rice false smut balls caused by Villosiclava virens and their phytotoxic and cytotoxic activities. J. Agric. Food Chem. 2017, 65, 5151–5160. [Google Scholar] [CrossRef] [PubMed]
  14. Wang, X.; Wang, J.; Lai, D.; Wang, W.; Dai, J.; Zhou, L.; Liu, Y. Ustiloxin G, a new cyclopeptide mycotoxin from rice false smut balls. Toxins 2017, 9, 54. [Google Scholar] [CrossRef] [PubMed]
  15. Lai, D.; Meng, J.; Zhang, X.; Xu, D.; Dai, J.; Zhou, L. Ustilobisorbicillinol A, a cytotoxic sorbyl-containing aromatic polyketide from Ustilaginoidea virens. Org. Lett. 2019, 21, 1311–1314. [Google Scholar] [CrossRef] [PubMed]
  16. Sun, Q.; Liu, H.; Zhang, Y.; Yi, X.; Kong, R.; Cheng, S.; Man, J.; Zheng, L.; Huang, J.; Su, G.; et al. Global distribution of ustiloxins in rice and their male-biased hepatotoxicity. Environ. Pollut. 2022, 301, 118992. [Google Scholar] [CrossRef] [PubMed]
  17. Sun, Q.; Qian, Z.; Liu, H.; Zhang, Y.; Yi, X.; Kong, R.; Cheng, S.; Man, J.; Zheng, L.; Huang, J.; et al. Occurrence and translocation of ustiloxins in rice false smut-occurred paddy fields, Hubei, China. Environ. Pollut. 2022, 307, 119460. [Google Scholar] [CrossRef] [PubMed]
  18. Han, J.; Wang, G.; Liu, X.; Zhou, Y.; Hu, J.; Wu, Y.; Wang, W.; Shi, J.; Xu, J. Ustiloxin A impairs oocyte quality by disrupting organelles function. Environ. Pollut. 2025, 368, 125733. [Google Scholar] [CrossRef] [PubMed]
  19. Evidente, A.; Andolfi, A.; Cimmino, A.; Ganassi, S.; Altomare, C.; Favilla, M.; De Cristofaro, A.; Vitagliano, S.; Sabatini, M. Bisorbicillinoids produced by the fungus Trichoderma citrinoviride affect feeding preference of the aphid Schizaphis graminum. J. Chem. Ecol. 2009, 35, 533–541. [Google Scholar] [CrossRef] [PubMed]
  20. Balde, E.S.; Andolfi, A.; Bruyere, C.; Cimmino, A.; Lamoral-Theys, D.; Vurro, M.; Damme, M.V.; Altomare, C.; Mathieu, V.; Kiss, R.; et al. Investigations of fungal secondary metabolites with potential anticancer activity. J. Nat. Prod. 2010, 73, 969–971. [Google Scholar] [CrossRef] [PubMed]
  21. Fan, J.; Yang, J.; Wang, Y.-Q.; Li, G.-B.; Li, Y.; Huang, F.; Wang, W.-M. Current understanding on Villosiclava virens, a unique flower-infecting fungus causing rice false smut disease. Mol. Plant Pathol. 2016, 17, 1321–1330. [Google Scholar] [CrossRef] [PubMed]
  22. Sun, W.; Fan, J.; Fang, A.; Li, Y.; Tariqjiaveed, M.; Li, D.; Hu, D.; Wang, W. Ustilaginoidea virens: Inghts into an emerging rice pathogen. Annu. Rev. Phytopathol. 2020, 58, 363–385. [Google Scholar] [CrossRef] [PubMed]
  23. Mishra, A.; Srinivasan, T.S.; Singh, U.M.; Peramaiyan, P. Insights on the genetics, molecular biology and management strategies on emerging false smut pathogenesis in rice. Physiol. Mol. Plant Pathol. 2025, 136, 102552. [Google Scholar] [CrossRef]
  24. Xue, M.; Zhao, S.; Gu, G.; Xu, D.; Zhang, X.; Hou, X.; Miao, J.; Dong, H.; Hu, D.; Lai, D.; et al. A genome-wide comparison of rice false smut fungus Villosiclava virens albino strain LN02 reveals the genetic diversity of secondary metabolites and the cause of albinism. Int. J. Mol. Sci. 2023, 24, 15196. [Google Scholar] [CrossRef] [PubMed]
  25. Xue, M.; Hou, X.; Gu, G.; Dong, J.; Yang, Y.; Pan, X.; Zhang, X.; Xu, D.; Lai, D.; Zhou, L. Activation of ustilaginoidin biosynthesis gene uvpks1 in Villosiclava virens albino strain LN02 influences development, stress responses, and inhibition of rice seed germination. J. Fungi 2024, 10, 31. [Google Scholar] [CrossRef] [PubMed]
  26. Koyama, K.; Natori, S. Further characterization of seven bis(naphtho-γ-pyrone) congeners of ustilaginoidins, coloring matters of Claviceps virens (Ustilaginoidea virens). Chem. Pharm. Bull. 1988, 36, 146–152. [Google Scholar] [CrossRef]
  27. Wen, H.; Shi, H.; Jiang, N.; Qiu, J.; Lin, F.; Kou, Y. Antifungal mechanisms of silver nanoparticles on mycotoxin producing rice false smut fungus. iScience 2023, 26, 105763. [Google Scholar] [CrossRef] [PubMed]
  28. Meng, J.; Gu, G.; Dang, P.; Zhang, X.; Wang, W.; Dai, J.; Liu, Y.; Lai, D.; Zhou, L. Sorbicillinoids from the fungus Ustilaginoidea virens and their phytotoxic, cytotoxic, and antimicrobial activities. Front. Chem. 2019, 7, 435. [Google Scholar] [CrossRef] [PubMed]
  29. Shirota, O.; Pathak, V.; Hossain, C.F.; Sekita, S.; Takatori, K.; Satake, M. Structural elucidation of trichotetronines: Polyketides possessing a bicyclo[2.2.2]octane skeleton with a tetronic acid moiety isolated from Trichoderma sp. J. Chem. Soc. Perkin Trans 1997, 20, 2961–2964. [Google Scholar] [CrossRef]
  30. Andrade, R.; Ayer, W.A.; Trifonov, L.S. The metabolitesof Trichoderma longibrachiatum. III. Two new tetronic acids: 5-hydroxyvertinolide and bislongiquinolide. Aust. J. Chem. 1997, 50, 255–257. [Google Scholar] [CrossRef]
  31. Sperry, S.; Samuels, G.J.; Crews, P. Vertinoid polyketides from the saltwater culture of the fungus Trichoderma longibrachiatum separated from a Haliclona marine sponge. J. Org. Chem. 1998, 63, 10011–10014. [Google Scholar] [CrossRef]
  32. Zhai, M.; Qi, F.; Li, J.; Jiang, C.; Hou, Y.; Shi, Y.; Di, D.; Zhang, J.; Wu, Q. Isolation of secondary metabolites from the soil-derived fungus Clonostachys rosea YRS-06, a biological control agent, and evaluation of antibacterial activity. J. Agric. Food Chem. 2016, 64, 2298–2306. [Google Scholar] [CrossRef] [PubMed]
  33. Elissawy, A.M.; El-Shazly, M.; Ebada, S.S.; Singab, A.B.; Proksch, P. Bioactive terpenes from marine-derived fungi. Mar. Drugs 2015, 13, 1966–1992. [Google Scholar] [CrossRef] [PubMed]
  34. Shabana, S.; Lakshmi, K.R.; Satya, A.K. An updated review of secondary metabolites from marine fungi. Mini-Rev. Med. Chem. 2021, 21, 592–632. [Google Scholar] [CrossRef] [PubMed]
  35. Sonowal, S.; Gogoi, U.; Buragohain, K.; Nath, R. Endophytic fungi as a potential source of anti-cancer drug. Arch. Microbiol. 2024, 206, 122. [Google Scholar] [CrossRef] [PubMed]
  36. Rustamova, N.; Bozorov, K.; Efferth, T.; Yili, A. Novel secondary metabolites from endophytic fungi: Synthesis and biological properties. Phytochem. Rev. 2020, 19, 425–448. [Google Scholar] [CrossRef]
  37. Moraga, J.; Gomes, W.; Pinedo, C.; Cantoral, J.M.; Hanson, J.R.; Carbu, M.; Carrido, C.; Duran-Patron, R.; Collado, I.G. The current status on secondary metabolites produced by plant pathogenic Colletotrichum species. Phytochem. Rev. 2019, 18, 215–239. [Google Scholar] [CrossRef]
  38. Girimpuhwe, D.; Wu, Q.-X. Plant pathogenic fungi: A treasure trove of bioactive γ-pyrones. J. Agric. Food Chem. 2025, 73, 13229–13262. [Google Scholar] [CrossRef] [PubMed]
  39. Liu, Z.; Zhao, J.; Sun, S.; Li, Y.; Liu, Y. Fungi: Outstanding source of novel chemical scaffolds. J. Asian Nat. Prod. Res. 2020, 22, 99–120. [Google Scholar] [CrossRef] [PubMed]
  40. Tsukui, T.; Nagano, N.; Umemura, M.; Kumagai, T.; Terai, G.; Machida, M.; Asai, K. Ustiloxins, fungal cyclic peptides, are ribosomally synthesized in Ustilaginoidea virens. Bioinformatics 2015, 31, 981–985. [Google Scholar] [CrossRef] [PubMed]
  41. Yang, K.; Tian, J.; Keller, N.P. Post-translational modifications drive secondary metabolite biosynthesis in Aspergillus: A review. Environ. Microbiol. 2022, 24, 2857–2881. [Google Scholar] [CrossRef] [PubMed]
  42. Wang, H.; Ke, X.; Zhou, J.; Liu, Z.; Zheng, Y. Recent advances in metabolic regulation and bioengineering of gibberellic acid biosynthesis in Fusarium fujikuroi. World J. Microbiol. Biotechnol. 2022, 38, 131. [Google Scholar] [CrossRef] [PubMed]
  43. Yu, W.; Pei, R.; Zhou, J.; Zeng, B.; Tu, Y.; He, B. Molecular regulation of fungal secondary metabolism. World J. Microbiol. Biotechnol. 2023, 39, 204. [Google Scholar] [CrossRef] [PubMed]
  44. Verma, A.; Tiwari, H.; Singh, S.; Gupta, P.; Rai, N.; Singh, S.K.; Singh, B.P.; Rao, S.; Gautam, V. Epigenetic manipulation for secondary metabolite activation in endophytic fungi: Current progress and future directions. Mycology 2023, 14, 275–291. [Google Scholar] [CrossRef] [PubMed]
  45. Zhang, Y.; Yu, W.; Lu, Y.; Wu, Y.; Ouyang, Z.; Tu, Y.; He, B. Epigenetic regulation of fungal secondary metabolism. J. Fungi 2024, 10, 648. [Google Scholar] [CrossRef] [PubMed]
  46. Wang, Y.; Guo, J.; Zhong, J.; Xiao, H. Use of epigenetic regulation for the discovery of fungi derived cryptic natural product. Process Biochem. 2024, 145, 32–40. [Google Scholar] [CrossRef]
  47. Chiang, Y.-M.; Ahuja, M.; Oakley, C.E.; Entwistle, R.; Asokan, A.; Zutz, C.; Wang, C.C.; Oakley, B.R. Development of genetic dereplication strains in Aspergillus nidulans results in the discovery of aspercryptin. Angew. Chem. Int. Ed. 2016, 55, 1662–1665. [Google Scholar] [CrossRef] [PubMed]
  48. Chen, L.; Wu, H.; Liu, H.; Li, E.; Ren, J.; Wang, W.; Wang, S.; Yin, W.-B. Genetic dereplication of Trichoderma hypoxylon reveals two novel polycyclic lactones. Bioorg. Chem. 2019, 91, 103185. [Google Scholar] [CrossRef] [PubMed]
  49. Liu, H.; Pu, Y.; Ren, J.; Li, E.; Guo, L.; Yin, W. Genetic dereplication driven discovery of a tricinoloniol acid biosynthetic pathway in Trichoderma hypoxylon. Org. Biomol. Chem. 2020, 18, 5344–5348. [Google Scholar] [CrossRef] [PubMed]
  50. Wei, Q.; Bai, J.; Yan, D.; Bao, X.; Li, W.; Liu, B.; Zhang, D.; Qi, X.; Yu, D.; Hu, Y. Genome mining combined metabolic shunting and OSMAC strategy of an endophytic fungus leads to the production of diverse natural products. Acta Pharm. Sin. B 2021, 11, 572–587. [Google Scholar] [CrossRef] [PubMed]
  51. Yang, L.; Wu, G.; Meng, F.; Ran, H.; Yin, W.; Li, W.; Liu, X. Combination strategy of genetic dereplication and manipulation of epigenetic regulators reveals a novel compound from plant endophytic fungus. Int. J. Mol. Sci. 2022, 23, 3686. [Google Scholar] [CrossRef] [PubMed]
  52. Alberti, F.; Foster, G.D.; Bailey, A.M. Natural products from filamentous fungi and production by heterologous expression. Appl. Microbiol. Biotechnol. 2017, 101, 493–500. [Google Scholar] [CrossRef] [PubMed]
  53. Yeh, H.; Ahuja, M.; Chiang, Y.; Oakley, C.E.; Moore, S.; Yoon, O.; Hajovsky, E.; Bok, J.; Keller, N.P.; Wang, C.C.C.; et al. Resistance gene-guided genome mining: Serial promoter exchanges in Aspergillus nidulans reveal the biosynthetic pathway for fellutamide B, a proteasome inhibitor. ACS Chem. Biol. 2016, 11, 2275–2284. [Google Scholar] [CrossRef] [PubMed]
  54. Lyu, H.; Liu, H.; Keller, N.P.; Yin, W. Harnessing diverse transcriptional regulators for natural product discovery in fungi. Nat. Prod. Rep. 2020, 37, 6–16. [Google Scholar] [CrossRef] [PubMed]
  55. Shao, Y.; Molnar, L.F.; Jung, Y.; Kussmann, J.; Ochsenfeld, C.; Brown, S.T.; Gilbert, A.T.B.; Slipchenko, L.V.; Levchenko, S.V.; O’Neill, D.P.; et al. Advances in methods and algorithms in a modern quantum chemistry program package. Phys. Chem. Chem. Phys. 2006, 8, 3172–3191. [Google Scholar] [CrossRef] [PubMed]
  56. Bruhn, T.; Schaumloeffel, A.; Hemberger, Y.; Bringmann, G. SpecDis: Quantifying the comparison of calculated and experimental electronic circular dichroism spectra. Chirality 2013, 25, 243–249. [Google Scholar] [CrossRef] [PubMed]
Molecules 30 03039 g001
Figure 1. Structures of ustisorbicillinoids G (1) and H (2).
Figure 1. Structures of ustisorbicillinoids G (1) and H (2).
Molecules 30 03039 g001
Molecules 30 03039 g002
Figure 2. Calculated and experimental ECD spectra of 1.
Figure 2. Calculated and experimental ECD spectra of 1.
Molecules 30 03039 g002
Molecules 30 03039 g003
Figure 3. Experimental ECD spectrum of 2.
Figure 3. Experimental ECD spectrum of 2.
Molecules 30 03039 g003
Molecules 30 03039 g004
Figure 4. The experimental and calculated J values for 2. (A) Four isomers with different C10′/C11′ stereochemistry were used for calculation. (B) A comparison of the J values of H10′/H9′ and H10′/H11′ between the experimental and computed structures at the mpw1pw91/6-311+g(2d,p) (PCM = acetone)// b3lyp/6-31g(d) level of theory.
Figure 4. The experimental and calculated J values for 2. (A) Four isomers with different C10′/C11′ stereochemistry were used for calculation. (B) A comparison of the J values of H10′/H9′ and H10′/H11′ between the experimental and computed structures at the mpw1pw91/6-311+g(2d,p) (PCM = acetone)// b3lyp/6-31g(d) level of theory.
Molecules 30 03039 g004
Table 1. 1H (500 MHz) and 13C (125 MHz) NMR data of 1 (CD3OD)
Table 1. 1H (500 MHz) and 13C (125 MHz) NMR data of 1 (CD3OD)
PositionδC, TypeδH, Mult. (J in Hz)
156.5, C
2169.5, C *
3116.4, C
441.2, CH3.57, d (2.0)
544.5, CH3.03, dd (6.1, 2.0)
653.8, CH2.79, d (6.1)
7209.0, C *
873.7, C
911.2, CH31.02, s
1025.2, CH31.29, s
1185.1, C
12181.6, C *
1395.5, C *
14177.9, C *
1522.0, CH31.45, s
166.3, CH31.56, s
17190.8, C
1842.1, CH22.90, dd (16.7, 13.8); 2.43, dd (16.7, 3.4)
1983.1, CH4.92, m
20129.1, CH5.78, ddd (15.4, 7.4, 1.8)
21132.9, CH5.95, dq (15.4, 6.4)
2217.9, CH31.78, dd (6.4, 1.8)
23203.2, C *
24128.9, CH6.10, d (15.5)
25147.9, CH *7.14, dd (15.5, 10.8)
26131.8, CH6.31, dd (15.1, 10.8)
27145.1, CH6.41,dq (15.1, 6.8)
2819.1, CH31.90, d (6.8)
* The signals were further confirmed through HMBC spectra.
Table 2. 1H (500 MHz) and 13C (125 MHz) NMR data of 2 (CD3COCD3)
Table 2. 1H (500 MHz) and 13C (125 MHz) NMR data of 2 (CD3COCD3)
PositionδC, TypeδH, Mult. (J in Hz)
159.0, CH3.11, d (2.4)
279.6, C
3105.3, C
460.8, C
5202.3, C
6105.5, C
7174.3, C
8120.5, CH6.52, dd (14.8, 4.2)
9143.1, CH7.30, ddd (14.8, 11.0, 7.0)
10132.1, CH6.42, m
11139.8, CH6.26, dqd (15.0, 7.6, 3.8)
1219.0, CH31.88, d (7.6)
1322.2, CH31.34, s
1419.9, CH31.32, s
1′53.9, CH3.19, s
2′79.4, C
3′105.0, C
4′56.4, C
5′173.7, C
6′109.5, C
7′189.8, C
8′36.6, CH22.66, dd (16.9, 14.6); 2.37, dd (16.9, 3.2)
9′81.6, CH4.15, ddd (14.6, 4.43.2)
10′76.7, CH3.64, dd (6.3, 4.5)
11′67.6, CH3.69, dq (6.3, 6.1)
12′19.5, CH31.12, d (6.1)
13′19.5, CH31.41, s
14′21.7, CH31.24, s
Table 3. Antibacterial activity of compounds 1 and 2.
Table 3. Antibacterial activity of compounds 1 and 2.
BacteriumMIC/IC50
(μg/mL)		Compound
12CK+
R. solanacearumMIC32.0064.002.50
IC5024.33 ± 2.0435.42 ± 1.291.15 ± 0.27
A. tumefaciensMIC32.0064.005.00
IC5019.76 ± 2.7745.48 ± 3.221.12 ± 0.17
B. subtilisMIC32.0032.005.00
IC5025.43 ± 2.7425.35 ± 3.981.37 ± 0.51
Note: The positive control was streptomycin sulfate. MIC, minimum inhibitory concentration; IC50, median inhibitory concentration.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Hou, X.; Xue, M.; Gu, G.; Xu, D.; Lai, D.; Zhou, L. Ustisorbicillinols G and H, Two New Antibacterial Sorbicillinoids from the Albino Strain LN02 of Rice False Smut Fungus Villosiclava virens. Molecules 2025, 30, 3039. https://doi.org/10.3390/molecules30143039

AMA Style

Hou X, Xue M, Gu G, Xu D, Lai D, Zhou L. Ustisorbicillinols G and H, Two New Antibacterial Sorbicillinoids from the Albino Strain LN02 of Rice False Smut Fungus Villosiclava virens. Molecules. 2025; 30(14):3039. https://doi.org/10.3390/molecules30143039

Chicago/Turabian Style

Hou, Xuwen, Mengyao Xue, Gan Gu, Dan Xu, Daowan Lai, and Ligang Zhou. 2025. "Ustisorbicillinols G and H, Two New Antibacterial Sorbicillinoids from the Albino Strain LN02 of Rice False Smut Fungus Villosiclava virens" Molecules 30, no. 14: 3039. https://doi.org/10.3390/molecules30143039

APA Style

Hou, X., Xue, M., Gu, G., Xu, D., Lai, D., & Zhou, L. (2025). Ustisorbicillinols G and H, Two New Antibacterial Sorbicillinoids from the Albino Strain LN02 of Rice False Smut Fungus Villosiclava virens. Molecules, 30(14), 3039. https://doi.org/10.3390/molecules30143039

Article Metrics

Back to TopTop