Fifteen alkaloids were isolated from the 95% ethanol extract of the whole plants of Viola yedoensis by various column chromatographic techniques such as silica gel and Sephadex LH-20. Their structures were identified as neoechinulin A（1）,N-benzoyl-L-p-hydroxy-phenylalaninol（2）,aurantiamide acetate（3）,aurantiamide（4）,anabellamide（5）,trichosanatine（6）,indole-3-carboxylic acid methyl ester（7）,3-carboxyindole（8）,N-trans-feruloyl-tyramine（9）,paprazine（10）,7'-（3', 4'-dihydroxyphenyl）-N-[(4-methoxyphenyl)ethyl]propenamide（11）,cannabisin F（12）,N-(4-hydroxyphenethyl)octacosanamide（13）,N-(4-hydroxyphenethyl)hexacosanamide（14）and N-benzoyl-L-phenylalaninol（15）. All the compounds except 3 and 4 were isolated from this plant for the first time. These alkaloids exhibited anti-complement activity against the classical pathway(CP)and the alternative pathway(AP)with the CH50 and AP50 values ranging from 0.12 to 0.33 g•L⁻¹ and 0.22 to 0.50 g•L⁻¹, respectively. Preliminary mechanism study using complement-depleted sera showed that these alkaloids acted on different complement components in the complement activation cascade.
Keywords: Viola yedoensis; alkaloids; amides; anti-complement.
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