You-Wei Chen

Chemical Constituents and Bioactivities of Plants from the Genus Paeonia

National Natural Science Foundation of China [20772105]; Fund of Yunnan Province for Young and Middle-aged Talents in Science and Technology [2008PY028]

Ten-Membered Lactones from Phomopsis sp., an Endophytic Fungus of Azadirachta indica

Four new 10-membered lactones ( 1- 4) and one known one ( 5) were isolated from the broth extract of an endophytic fungus, Phomopsis sp., obtained from the stem of Azadirachta indica. Their structures were assigned by analysis of spectroscopic data, and the structures of 1 and 4 were also confirmed by X-ray analysis. Compounds 1- 5 were tested for antifungal activity against several plant pathogens. Compound 4 demonstrated antifungal activity in the MIC value range 31.25-500 microg/mL.

Two New Solanapyrone Analogues from the Endophytic Fungus Nigrospora sp. YB-141 of Azadirachta indica

Two new solanapyrone analogues, solanapyrones N and O (1 and 2, resp.), and three known compounds, solanapyrone C (3), nigrosporalactone (4), and phomalactone (5), were isolated from the fermentation culture of Nigrospora sp. YB-141, an endophytic fungus isolated from Azadirachta indica A. Juss. The structures of the new compounds were elucidated on the basis of spectroscopic analysis. The antifungal activities of 1-5 towards seven phytopathogenic fungi were tested. Most of the compounds exhibited no or only weak antifungal activities.

Rhizospheric fungi of Panax notoginseng: diversity and antagonism to host phytopathogens.

Background Rhizospheric fungi play an essential role in the plant–soil ecosystem, affecting plant growth and health. In this study, we evaluated the fungal diversity in the rhizosphere soil of 2-yr-old healthy Panax notoginseng cultivated in Wenshan, China. Methods Culture-independent Illumina MiSeq and culture-dependent techniques, combining molecular and morphological characteristics, were used to analyze the rhizospheric fungal diversity. A diffusion test was used to challenge the phytopathogens of P. notoginseng. Results A total of 16,130 paired-end reads of the nuclear ribosomal internal transcribed spacer 2 were generated and clustered into 860 operational taxonomic units at 97% sequence similarity. All the operational taxonomic units were assigned to five phyla and 79 genera. Zygomycota (46.2%) and Ascomycota (37.8%) were the dominant taxa; Mortierella and unclassified Mortierellales accounted for a large proportion (44.9%) at genus level. The relative abundance of Fusarium and Phoma sequences was high, accounting for 12.9% and 5.5%, respectively. In total, 113 fungal isolates were isolated from rhizosphere soil. They were assigned to five classes, eight orders (except for an Incertae sedis), 26 genera, and 43 species based on morphological characteristics and phylogenetic analysis of the internal transcribed spacer. Fusarium was the most isolated genus with six species (24 isolates, 21.2%). The abundance of Phoma was also relatively high (8.0%). Thirteen isolates displayed antimicrobial activity against at least one test fungus. Conclusion Our results suggest that diverse fungi including potential pathogenic ones exist in the rhizosphere soil of 2-yr-old P. notoginseng and that antagonistic isolates may be useful for biological control of pathogens.

Diversity, distribution, and antagonistic activities of rhizobacteria of Panax notoginseng

Background Rhizobacteria play an important role in plant defense and could be promising sources of biocontrol agents. This study aimed to screen antagonistic bacteria and develop a biocontrol system for root rot complex of Panax notoginseng. Methods Pure-culture methods were used to isolate bacteria from the rhizosphere soil of notoginseng plants. The identification of isolates was based on the analysis of 16S ribosomal RNA (rRNA) sequences. Results A total of 279 bacteria were obtained from rhizosphere soils of healthy and root-rot notoginseng plants, and uncultivated soil. Among all the isolates, 88 showed antagonistic activity to at least one of three phytopathogenic fungi, Fusarium oxysporum, Fusarium solani, and Phoma herbarum mainly causing root rot disease of P. notoginseng. Based on the 16S rRNA sequencing, the antagonistic bacteria were characterized into four clusters, Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetesi. The genus Bacillus was the most frequently isolated, and Bacillus siamensis (Hs02), Bacillus atrophaeus (Hs09) showed strong antagonistic activity to the three pathogens. The distribution pattern differed in soil types, genera Achromobacter, Acidovorax, Brevibacterium, Brevundimonas, Flavimonas, and Streptomyces were only found in rhizosphere of healthy plants, while Delftia, Leclercia, Brevibacillus, Microbacterium, Pantoea, Rhizobium, and Stenotrophomonas only exist in soil of diseased plant, and Acinetobacter only exist in uncultivated soil. Conclusion The results suggest that diverse bacteria exist in the P. notoginseng rhizosphere soil, with differences in community in the same field, and antagonistic isolates may be good potential biological control agent for the notoginseng root-rot diseases caused by F. oxysporum, Fusarium solani, and Panax herbarum.

A new sesquiterpenoid from Ligusticum chuanxiong Hort

A new sesquiterpenoid named (-)-alloaromadendrane-4β,10α,13,15-tetrol was isolated from the rhizome of Ligusticum chuanxiong Hort., together with two known compounds, campest-4-en-3-one and 3-carboxyethyl-phthalide. Their structures were elucidated on the basis of spectroscopic and chemical analysis. All the compounds showed mild antimicrobial activity.

Sesquiterpenoids from the endophytic fungus Trichoderma sp. PR-35 of Paeonia delavayi.

A new bisabolane‐type sesquiterpene, trichoderic acid (1), and a new acorane‐type sesquiterpene, 2β‐hydroxytrichoacorenol (2), along with three known compounds, cyclonerodiol (3), cyclonerodiol oxide (4), and sorbicillin (5), were isolated from the culture broth of Trichoderma sp. PR‐35, an endophytic fungus isolated from Paeonia delavayi. Their structures were elucidated on the basis of their IR, MS, and 1D‐ and 2D‐NMR analyses. The antibacterial and antifungal activities of 1–5 towards various types of bacteria and fungi were tested. Most of the compounds showed moderate or weak antimicrobial activities in an agar‐diffusion assay.

Diversity, distribution and biotechnological potential of endophytic fungi

Endophytic fungi, living in the inner tissues of living plants, have attracted increasing attention among ecologists, taxonomists, chemists and agronomists. They are ubiquitously associated with almost all plants studied to date. Numerous studies have indicated that these fungi have an impressive array of biotechnological potential, such as enzyme production, biocontrol agents, plant-growth promoting agents, bioremediation, biodegradation, biotransformation, biosynthesis and nutrient cycling. These fungi may represent an underexplored reservoir of novel biological resources for exploitation in the pharmaceutical, industry and agriculture. This review focuses on new findings in isolation methods, biodiversity, ecological distribution and biotechnological potential.

Endophytic fungi harbored in Panax notoginseng: diversity and potential as biological control agents against host plant pathogens of root-rot disease

Background Endophytic fungi play an important role in balancing the ecosystem and boosting host growth. In the present study, we investigated the endophytic fungal diversity of healthy Panax notoginseng and evaluated its potential antimicrobial activity against five major phytopathogens causing root-rot of P. notoginseng. Methods A culture-dependent technique, combining morphological and molecular methods, was used to analyze endophytic fungal diversity. A double-layer agar technique was used to challenge the phytopathogens of P. notoginseng. Results A total of 89 fungi were obtained from the roots, stems, leaves, and seeds of P. notoginseng, and 41 isolates representing different morphotypes were selected for taxonomic characterization. The fungal isolates belonged to Ascomycota (96.6%) and Zygomycota (3.4%). All isolates were classified to 23 genera and an unknown taxon belonging to Sordariomycetes. The number of isolates obtained from different tissues ranged from 12 to 42 for leaves and roots, respectively. The selected endophytic fungal isolates were challenged by the root-rot pathogens Alternaria panax, Fusarium oxysporum, Fusarium solani, Phoma herbarum, and Mycocentrospora acerina. Twenty-six of the 41 isolates (63.4%) exhibited activity against at least one of the pathogens tested. Conclusion Our results suggested that P. notoginseng harbors diversified endophytic fungi that would provide a basis for the identification of new bioactive compounds, and for effective biocontrol of notoginseng root rot.

Chemical constituents from the stem bark of Trewia nudiflora

Trewia nudiflora L. is the only member of the genus Trewia (Euphorbiaceae), which is mainly distributed in India, Malaysia, and southwest of China. Previous studies have shown that the seed of T. nudiflora is a rich source of maytansinoid tumor inhibitors [1, 2]. Phytochemical studies are mainly focused on the seed and pericarp of the plant; however, there are only few reports on its stem bark [3, 4]. The air-dried powdered stem bark of T. nudiflora (8.8 kg) was extracted with 95% EtOH three times at room temperature. The EtOH extract was concentrated in vacuum to give a residue. The residue was suspended in water and successively treated with EtOAc. The EtOAc extract (32 g) was subjected to chromatography on silica gel eluting with CHCl3–MeOH gradient (1:0–0:1) to give nine fractions (I–IX). Fraction III was repeatedly subjected to column chromatography on RP-18 silica gel with MeOH-H2O (2:3) and Sephadex LH-20 with MeOH to give compound 1 (9 mg). Repeated chromatography of fraction IV on silica gel with petroleum ether–Me2CO gradient (4:1, 7:3, 6:4) and RP-18 silica gel with MeOH–H2O gradient (2:3, 1:1) afforded compounds 2 (6 mg) and 3 (10 mg). Fraction V was submitted to repeated column chromatography on silica gel with CHCl3–MeOH gradient (15:1, 10:1) and RP-18 silica gel with MeOH–H2O gradient (3:7, 2:3) to afford compounds 4 (13 mg), 5 (18 mg), and 6 (10 mg). Fraction VI was chromatographed on silica gel column with CHCl3–MeOH (8:1) to yield compounds 7 (16 mg) and 8 (13 mg). Trewiasine was isolated from the stem bark of T. nudiflora for the first time. Compounds 2–8 were isolated from this plant for the first time. The structures of these compounds were confirmed using a combination of spectral analyses, including NMR and mass spectrometry, and by comparison with reported spectroscopic data in the literature. Trewiasine (1). C37H52ClN3O11, colorless crystals, mp 180−182°C. ESI-MS m/z: 772 [M+Na]+. 1H NMR (500 MHz, CDCl3, δ, ppm, J/Hz): 2.19 (1H, dd, J = 14.5, 3.1, H-2a), 2.56 (1H, dd, J = 14.5, 12.0, H-2b), 4.77 (1H, dd, J = 12.0, 3.1, H-3), 0.78 (3H, s, 4-CH3), 3.02 (1H, d, J = 9.7, H-5), 1.28 (3H, d, J = 6.3, 6-CH3), 4.29 (1H, m, H-7), 3.53 (1H, d, J = 9.0, H-10), 5.74 (1H, dd, J = 15.1, 9.0, H-11), 6.46 (1H, dd, J = 15.1, 11.2, H-12), 6.99 (1H, d, J = 11.2, H-13), 1.54 (3H, s, 14-CH3), 4.87 (1H, s, H-15), 6.55 (1H, d, J = 1.5, H-17), 7.24 (1H, d, J = 1.4, H-21), 3.35 (3H, s, 10-OCH3), 3.37 (3H, s, 15-OCH3), 4.01 (3H, s, 20-OCH3), 3.18 (3H, s, 18-NCH3), 5.39 (1H, m, H-2′), 1.29 (3H, d, J = 6.8, 2′-CH3), 2.89 (3H, s, 2′-NCH3), 2.79 (1H, m, H-4′), 1.13 (3H, d, J = 6.8, 4′-CH3), 1.08 (3H, d, J = 6.5, 4′-CH3), 6.28 (1H, s, 9-NH). 13C NMR (125 MHz, CDCl3, δ, ppm): 32.3 (C-2), 78.1 (C-3), 59.9 (C-4), 67.4 (C-5), 38.8 (C-6), 74.1 (C-7), 36.0 (C-8), 80.7 (C-9), 85.3 (C-10), 129.6 (C-11), 132.5 (C-12), 127.8 (C-13), 142.0 (C-14), 86.6 (C-15), 141.3 (C-16), 120.2 (C-17), 139.2 (C-18), 119.2 (C-19), 156.2 (C-20), 108.7 (C-21), 176.7, 170.8, 168.7, 152.2 (4 × C=O), 56.3, 56.5, 56.7 (3 × OCH3), 14.5, 13.0, 11.9, 9.9 (4 × CH3), 35.2 (18-NCH3), 30.6 (2′-NCH3), 52.4 (C-2′), 30.4 (C-4′), 19.4, 18.8 (2 × 4′-CH3) [1, 2]. Balanophonin (2). C20H20O6, pale yellow oil. EI-MS (70 eV) m/z (%): 356 [M] + (82), 338 (100), 326 (55), 306 (18), 295 (7), 152 (24), 137 (22), 115 (12), 77 (14). 1H NMR (500 MHz, CD3COCD3, δ, ppm, J/Hz): 7.04 (1H, d, J = 1.9, H-2), 6.81 (1H, d, J = 8.1, H-5), 6.88 (1H, dd, J = 8.1, 1.9, H-6), 5.65 (1H, d, J = 6.7, H-7), 3.64 (1H, m, H-8), 3.85 (2H, d, J = 4.9, H-9), 7.29 (1H, d, J = 1.7, H-2′), 7.31 (1H, d, J = 1.7, H-6′), 7.58 (1H, d, J = 15.8, H-7′), 6.66 (1H, dd, J = 15.8, 7.8, H-8′), 9.63 (1H, d, J = 7.8, H-9′), 3.82 (3H, s, 3-OMe), 3.89 (3H, s, 5′-OMe). 13C NMR (125 MHz, CD3COCD3, δ, ppm): 133.7 (C-1), 110.5 (C-2), 148.4 (C-3), 147.5 (C-4), 115.7 (C-5), 119.7 (C-6), 89.4 (C-7), 54.2 (C-8), 64.1 (C-9), 128.9 (C-1′), 119.6 (C-2′), 131.2 (C-3′), 152.4 (C-4′), 145.6 (C-5′), 113.5 (C-6′), 154.1 (C-7′), 127.1 (C-8′), 193.8 (C-9′), 56.2 (3-OMe), 56.4 (5′-OMe) [5].