Synthesis And Preliminary Study On Insecticidal/Acaricidal Activities Of 7?-oxycarbonyl-11,12-dehydro-14-deoxyandrographolide Derivatives

Due to the unreasonable use of chemical pesticides,the serious pests resistance and environmental problems have appeared.The development of green pesticides with high efficiency,low toxicity,and strong selectivity has become one of the research directions.Andrographolide is a labdane diterpenoid isolated from Andrographis paniculata and acts as the major active component,which has good biological activities.In order to further study and expand the application of andrographolide in agriculture,a series of andrographolide derivatives were synthesized,and its insecticidal activity against Mythimna separata Walker,aphicidal activity against Aphis citricola van der Goot and acaricidal activity against Tetranychus cinnabarinus Boisduva were studied.Moreover,the control efficiency of some compounds against A.citricola and T.cinnabarinus was also conducted.The main results of this article are as follows:?1?51 andrographolide derivatives?including 40 target products and 11 intermediates?were designed and synthesized,and 49 compounds are not reported.Their structures were confirmed by ¹H NMR,melting points,high resolution mass spectrometry,and optical rotation.Compound If was further determined by X-single crystal diffraction.?2?Their insecticidal activity against M.separata was determined at 1 mg/m L by the leaf-dipping method.Compounds IIc,IIf,Vb and Vc had good insecticidal activity.Especially compound Vc showed the highest final mortality rate of 57.1%,which was better than those of the precursor andrographolide?32.1%?and the positive control toosendanin?50.0%?.?3?Their aphicidal activity against A.citricola was tested at a dose of 0.04?g/nymph by the topical application.The mortality rates at 48 h of compounds Ic,IIe,Va,Vb and Vc were 52.8%,52.8%,50.0%,55.6%and 51.1%,respectively.And the aphicidal activity of Vb was higher than that of the andrographolide,and its LD₅₀ value was 0.035?g/nymph,which was 5.1 folds of that of andrographolide?0.178?g/nymph?.?4?Their acaricidal activity against T.cinnabarinus was measured at 0.5 mg/m L by the slide dipping method.The acaricidal activity of derivatives were improved.The corrected mortality rates at 72 h of compounds Ic,IIb,IIc,IIIc and IVe were 46.9%,58.0%,56.5%,45.7%and 50.1%,respectively,which were significantly higher than that of andrographolide.Especially the LC₅₀value of compound IIb was 0.406 mg/m L,which was 12.6 folds of that of andrographolide?5.106 mg/m L?.?5?The control efficiency of some compounds was tested against A.citricola and T.cinnabarinus at 0.5 and 0.2 mg/m L,respectively.On the 7th day,the control effects of compounds IIe and Vb against A.citricola were 61.9%and 60.3%,respectively.On the 5th day,the control effects of compounds IIb and IIc against T.cinnabarinus were 47.1%and48.8%,respectively.According to the preliminary structure-activity relationships analysis,introduction of n-butyraldehyde at the C-3 and 19 positions of andrographolide is helpful to improve the insecticidal and acaricidal activities.By introduction of fatty acid or aromatic acid esters at the C-7 position of andrographolide,the insecticidal and acaricidal activities of some compounds were increased.In summary,these results will pave the way for synthesis of andrographolide derivatives as pesticidal agents in the future.