Synthesis And Bioactivity Evaluation Of Curcumin-phenyldrazone Derivatives

The plant polyphenolic compounds, curcumin, is a major pigment in turmeric,a yellow spice extracted from the rhizome of the Chinese medicine Curcuma longa L.(Zingiberaceae),that is widely used as a food flavoring and coloring agent. Researchers are paying increasing attention to the medicine because of its multiple pharmacological functions including anti-oxidative, anti-inflammatory, anti-tumor and anti-HFV. Using curcumin as a lead compound for designing new analogues, a series of structurally related compounds had been reported, with a majority of that mainly focused on the medical realm ,in comparison with the agricultural application.Our initial studies have indicated that curcumin is effective against Tetranychus cinnabrinus.So we choose the curcumin as a lead compound to optimize structure, and expect to find some one with higher acaricidal, ultimately provide theoretical foundation for developing new acaricides. Through work of almost two years, the main results are listed below.1 Synthesis of curcumin-diphenylhydrazoneBased on the character of curcumin molecule structure, the derivative, curcumin-diphenylhydrazone,was designed and synthesised. It' s structure was confirmed by 'HNMR,IR,spectra and elemental analysis (EA).We have simplified the synthetic route and optimized synthetic condition, as that, curcumin and phenylhydrazine (1:2.25) were dissolved in dry methanol, acetic acid as a catalyzer was added dropwise to the above solution for 40min. The reaction mixture was further stirred for 30 h at 40℃Under these conditions, the productivity of curcumin-diphenyldrazone would be the highest, about 36.2%.2 Isolation and purification of curcumin-diphenylhydrazoneThe column chromatography on silica gel was used to isolate and purify the target compound. The effect of different product model of silica gel,flow rate and eluting agent on the isolation and purification of curcumin-diphenyldrazone were investigated. Silica gel 100～200 mesh was chosen to separate the curcumin-diphenydrazone; The optimal flow rate was 1ml/2min;and eluting agent was ethyl acetate/petroleun ether mixture (v/v=3:4).The washing out process was repeated two or three times and the compound was recrystallized from ethyl acetate with little ether to give a red needle crystal.3 Evaluation of the bioactivity of the curcumin-diphenyldrazone against Panonychus citri,Tetranychus cinnabarinus, Tyrophgus putrescentiae (Schrank)and Petrobia hartiThe paper evaluated the acaridal bioactivity of the curcumin-diphenyldrazone and curcumin against Panonychus citri, Tetranychus cinnabarinus, Tyrophgus putrescentiae (Schrank)and Petrobia harti,in comparison with 95% pyridaben.The acaridal activity of curcumin and curcumin-diphenyldrazone followed the general trend:Panonychus citri>Petrobia harti>Tetranychus cinnabarinus>Tyrophgus putrescentiae (Schrank) Panonychus citri were treated with Curcumin-diphenyldrazone,curcumin and pyridaben. for 24h> 48h and 72h,and LC50 were measured. It was found that curcumin-diphenyldrazone showed roughly similar activity aganinst Tetranychus cinnabarinus with curcumin, not significantly different from pyridaben , and its LC₅₀ of 24h,48h and 72h were 0.5236 mg/mL,0.3025 mg/ml,0.2064 mg/mL, respectively; Petrobia harti was treated with Curcumin-diphenyldrazone,curcumin and pyridaben for 24h,48h and 72h,and LC₅₀ were measured.It was found that curcumin-diphenyldrazone showed slightly higher toxic to Petrobia harti compared with curcumin, but their activity were lower than pyridaben. Tetranychus cinnabarinus was treated with curcumin-diphenyldrazone,curcumin and pyridaben.for 24h,48h and 72h,and LC₅₀ were measured. It was found that curcumin-diphenyldrazone showed significantly highter toxity than curcumin when treated for 24h, its LC₅₀ was 3.3755 mg/mL, with the toxicity increase by 8 times compared with curcumin, but the two showed similar activity after treated for 48h,72h respectively; Tyrophgus putrescentiae (Schrank) were treated with curcumin-diphenyldrazone,curcumin for 24h,48h and 72h,and LC₅₀ were measured. The results showed that curcumin-diphenyldrazone had lightly higher toxic to Tyrophgus putrescentiae (Schrank) at all three stages, it's LC₅₀ of 24h,48h and72h were 14.0553 mg/mL , 9.3302 mg/mL and 4.2647 mg/mL.In conclusion, the structure change of curcumin molecule seemed to bring some-physiological effect to some mites. But we don't know what changes happened when curcumn-diphenyldrazone bind to the targets, and need a further study.