Indole alkaloids isolated from the Nicotiana tabacum-derived Aspergillus fumigatus 0338 as potential inhibitors for tobacco powdery mildew and their mode of actions.

To explore active natural products against tobacco powdery mildew caused by Golovinomyces cichoracearum, an extract from the fermentation of endophytic Aspergillus fumigatus 0338 was investigated. The mechanisms of action for active compounds were also studied in detail. As a result, 14 indole alkaloid derivatives were isolated, with seven being newly discovered (1-7) and the remaining seven previously described (8-14). Notably, compounds 1-3 are rare linearly fused 6/6/5 tricyclic prenylated indole alkaloids, with asperversiamide J being the only known natural product of this kind. The isopentenyl substitutions at the 5-position in compounds 4 and 5 are also rare, with only compounds 1-(5-prenyl-1H-indol-3-yl)-propan-2-one (8) and 1-(6-methoxy-5-prenyl-1H-indol3-yl)-propan-2-one currently available. In addition, compounds 6 and 7 are new framework indole alkaloid derivatives bearing a 6-methyl-1,7-dihydro-2H-azepin-2-one ring. The purified compounds were evaluated for their activity against G. cichoracearum, and the results revealed that compounds 7 and 9 demonstrated obvious anti-G. cichoracearum activities with an inhibition rate of 82.6% and 85.2%, respectively, at a concentration of 250 µg/mL, these rates were better than that of the positive control agent, carbendazim (78.6%). The protective and curative effects of compounds 7 and 9 were also better than that of positive control, at the same concentration. Moreover, the mechanistic study showed that treatment with compound 9 significantly increased the structural tightness of tobacco leaves and directly affect the conidiospores of G. cichoracearum, thereby enhancing resistance. Compounds 7 and 9 could also induce systemic acquired resistance (SAR), directly regulating the expression of defense enzymes, defense genes, and plant semaphorins, which may further contribute to increased plant resistance. Based on the activity experiments and molecular dockings, the indole core structure may be the foundation of these compounds' anti-G. cichoracearum activity. Among them, the indole derivative parent structures of compounds 6, 7, and 9 exhibit strong effects. Moreover, the methoxy substitution in compound 7 can enhance their activity. By isolating and structurally identifying the above indole alkaloids, new candidates for anti-powdery mildew chemical screening were discovered, which could enhance the utilization of N. tabacum-derived fungi in pesticide development.

C-Alkylated flavonoids from the whole plants of Desmodium caudatum and their anti-TMV activity.

BACKGROUND: Natural products are important sources of biopesticides to control plant virus, and flavonoids are identified as promising anti-tobacco mosaic virus (TMV) agents. Since Desmodium caudatum is a rich source of flavonoids, this study focuses on the discovery of the new anti-TMV active flavonoids from D. caudatum and their possible mode of action. RESULTS: Three new (compounds 1-3) and nine known (compounds 4-12) C-alkylated flavonoids were isolated from D. caudatum. To the best of our knowledge, the framework of 1-3 was reported in natural products for the first time. In addition, 1-3, 5, and 6 showed notable anti-TMV activity with inhibition rates in the range of 35.8-64.3% at a concentration of 50 µg/mL, and these rates are higher than that of positive control (with inhibition rates of 34.6% ± 2.8). In addition, the structure-activity relationship study revealed that the (pyrrol-2-yl)methyl moiety on flavone can significantly increases the activity. This result is helpful to find new anti-TMV inhibitors. CONCLUSION: C-Alkylated flavonoids showed potent activities against TMV with multiple modes of actions. The increase of defense-related enzyme activities, up-regulate the expression of defense related genes, down-regulate the expression of Hsp70 protein by inhibiting the related Hsp genes that are involved in tobacco resistance to TMV. By the actions mentioned earlier, the infection of TMV was influenced, thereby achieving the effects of control of TMV. The successful isolation of the earlier-mentioned flavonoids provide the new source of biopesticides to TMV proliferation, and also contribute to the utilization of D. caudatum. © 2023 Society of Chemical Industry.

[Study of the role of nuclear factor-kappa B in preterm birth with subclinical chorioamnionitis].

OBJECTIVE: To investigate the role of nuclear factor-kappa B (NF-kappaB) in preterm birth with subclinical chorioamnionitis. METHODS: From October 2005 to October 2006, 111 cases including 36 cases of preterm birth in labor, 37 cases of full term gravida with spontaneous labor and 38 cases of full term gravida without threatened labor in the Hunan Province People's Hospital, third Xiangya Hospital of Central South University and Changsha Maternal and Child Care Service Center were enrolled in the study. After delivery, by pathology results of fetal membrane they were divided into two groups: subclinical chorioamnionitis group (subclinical infectious group) and non-infectious group. Immunohistochemical staining and RT-PCR were used to observe the change of the p65 subunit of NF-kappaB family in maternal blood and fetal membrane in subclinical infectious group and non-infectious group. RESULTS: (1) The incidence of subclinical chorioamnionitis: there were 24 cases of subclinical chorioamnionitis in the 36 cases of preterm birth in labor (67%), 7 cases in the 37 cases of full term gravida with spontaneous labor group (19%) and 3 cases in the 38 cases of full term gravida without threatened labor group (8%). There was a significant difference among the three groups (P < 0.01). In the totally 111 cases, 34 cases were classified as subclinical infectious group and 77 cases as non-infectious group. (2) In fetal membrane, the median of the average staining intensity of NF-kappaB p65 protein was higher in the subclinical chorioamnionitis group (8.0) than those in non-infectious group (4.0). Similarly, the average staining intensity of NF-kappaB p65 mRNA was higher in the subclinical infectious group (47.5 +/- 17.2) than those in non-infectious group (31.3 +/- 13.6). There was a significant difference between the two groups (P < 0.01). (3) In maternal blood, the expression of NF-kappaB p65 protein and mRNA was higher in subclinical chorioamnionitis group(8.0 and 42.6)than those in non-infectious group(4.0 and 23.6).There was a significant difference between the two groups (P < 0.01). (4) The concentration of NF-kappaB p65 protein in fetal membrane was positively correlated with that of maternal blood (r = 0.581, P < 0.01) and the concentration of NF-kappaB p65 mRNA in fetal membrane was positively correlated with that of maternal blood (r = 0.571, P < 0.01). CONCLUSION: The expression of NF-kappaB in maternal blood and fetal membrane in preterm birth with subclinical chorioamnionitis is higher and the two are correlated with each other. NF-kappaB p65 could be an accurate biochemical marker in predicting subclinical chorioamnionitis in preterm birth. NF-kappaB p65 plays an important role in the pathogenesis of subclinical chorioamnionitis in preterm birth.