Sunflower roots, stem, leaves and receptacles were extracted with ethanol, and the oily ethanol extracts were partitioned into chloroform-methanol-water (2:2:1.8, by final vol.) by the Bligh-Dyer method to obtain the lipidic fraction in the organic phase. The antimicrobial activity of lipidic fractions were examined by the paper disk method, using
E. coil and
C. herbarum. The results showed that the lipidic fraction of receptacles contained the strongest antimicrobial activities against these two microorganisms. Four antimicrobial compounds were isolated and purified by silicic acid column chromatography, thin layer chromatography and 15% AgNO
3-thin layer chromatography. The structures of the antimicrobial compounds were determined by spectroscopic analysis, IR, MS,
1H-NMR and
13C-NMR. The molecular weights and molecular formulas of the four compounds (1, 2, 3 and 4) were all 302 and C
20H
30O
2, respectively, on the basis of the EI-high resolution MS. Examination of the IR and NMR spectra and degree of unsaturation suggested that these compounds were diterpenoic acids. By using
1H-NMR,
13C-NMR, DEPT,
1H-
1H-NMR and
1H-
13C-NMR spectra, the chemical structure of 1 was determined to be trachyroban-19-oic acid. Similarly, the chemical structure of 2 was determined to be kaur-16-en-19-oic acid. The chemical structure of 4 was postulated to be beyer-15-en-19-oic acid on the basis of the NMR spectra.
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