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• Emodin from R. palmatum presented significant insecticidal activities against N. lugens and M. separate. • Emodin could be used as alternative environmentally bio-insecticide. • Plumbagin demonstrated the strong antifungal activity and a wide antifungal spectrum. • Plumbagin could be used as alternative fungicide for crop protection. As a well-known herb worldwide, rhubarb presents a wide range of pharmacological activities. In our studies, Rheum palmatum L. extracts and five isolated anthraquinones possessed insecticidal activity. The acetone extract (yield, 8.84%), which contained the highest amount of compounds (82.87 mg/g), showed stronger insecticidal activity than did the aqueous extract (yield, 37.17%) and the ethanol extract (yield, 36.92%). Notable amounts of compounds were also found in water extract residues (18.2 mg/g). Among the isolated quinones and structurally related compounds, emodin exhibited the highest insecticidal activity (LC 50 = 84.30 μg/mL) against Nilarparvata lugens ; and very moderate activity against Mythimna separata (LC 50 = 548.74 μg/mL). The LC 50 values of positive agent toosendanin against two insects were 89.34 and 418.24 μg/mL, respectively. Moreover, emodin exhibited significant AChE and GST inhibitory activities (with respective IC 50 values of 11.36 and 4.18 μg/mL). Plumbagin exhibited stronger and broader antifungal activity against eight phytopathogenic fungi (with EC 50 values ranging from 2.84 to 10.53 μg/mL) compared to a commercial fungicide, azoxystrobin (EC 50 ranging from 20.40 to >100.00 μg/mL). Plumbagin significantly damaged the cell and mitochondrial membrane systems, changed the morphology, triggered the release of cellular contents and generate reactive oxygen species in Rhizoctonia solani mycelia. This study laid the foundation for the future development of emodin and plumbagin as alternative, environmentally friendly bioinsecticide and biofungicide, respectively. Rhubarb and its residues can be used as renewable sources of anthraquinone-based products. [ABSTRACT FROM AUTHOR]

Magnolia officinalis , as a well-known herb worldwide, has been widely used to treat multiple diseases for a long time. In this study, the petroleum ether extract from M. officinalis showed effective antifungal activity against seven plant pathogens (particularly against R. solani with an inhibition rate of 100.00% at 250 μg/mL). Honokiol and magnolol, isolated by the bioassay-guided method, exhibited greater antifungal activity than tebuconazole (EC 50 = 3.07 μg/mL, p ≤ 0.001) against R. solani , which EC 50 values were 2.18 μg/mL and 3.48 μg/mL, respectively. We used transcriptomics to explore the mechanism of action of honokiol against R. solani. Results indicated that honokiol may exert antifungal effects by blocking the oxidative phosphorylation metabolic pathway. Further studies indicated that honokiol induced ROS overproduction, disrupted the mitochondrial function, affected respiration, and blocked the TCA cycle, which eventually inhibited ATP production. Besides, honokiol also damaged cell membranes and caused morphological changes. This study demonstrated that the lignans isolated from M. officinalis possess the potential to be developed as botanical fungicides. Unlabelled Image • Honokiol strongly suppressed the growth of phytopathogenic fungi in vitro. • Honokiol showed better antifungal activity than tebuconazole against R. solani. • Transcriptomics was used to study mode of action of honokiol against R. solani. • Honokiol possessed the potential to be exploited as botanical fungicides. [ABSTRACT FROM AUTHOR]

• Modified the isocryptolepine and evaluated the antifungal activity for the first time. • This class exhibits good antifungal activity against six plant pathogenic fungi. • The antifungal mechanism of this type of compounds was explored firstly. In this paper, the nitrogen atom was inserted into the anthracycline system of the isocryptolepine nucleus to obtain the "Aza"-type structure benzo[4,5]imidazo[1,2-c] quinazoline. A series of "Aza"-type derivatives were designed, synthesized and evaluated for their antifungal activity against six plant fungi in vitro. Among all derivatives, compounds A-0 , B-1 and B-2 showed significant antifungal activity against B. cinerea with the EC 50 values of 2.72 μg/mL, 5.90 μg/mL and 4.00 μg/mL, respectively. Compound A-2 had the highest activity against M. oryzae with the EC 50 values of 8.81 μg/mL, and compound A-1 demonstrated the most control efficacy against R. solani (EC 50 , 6.27 μg/mL). Moreover, compound A-0 was selected to investigate the in vivo tests against B. cinerea and the results indicated that the preventative efficacy of it up to 72.80% at 100 μg/mL. Preliminary mechanism studies revealed that after treatment with A-0 at 5 µg/mL, the B. cinerea mycelia appeared curved, collapsed and the cell membrane integrity may be damaged. The reactive oxygen species production, mitochondrial membrane potential and nuclear morphometry of mycelia have been changed, and the membrane function and cell proliferation of mycelia were destroyed. Compounds A-0 , A-1 , B-1 and B-2 presented weaker toxicities against two cells lines than isocryptolepine. This study lays the foundation for the future development of isocryptolepine derivatives as environmentally friendly and safe agricultural fungicides. [ABSTRACT FROM AUTHOR]