Biological Activities of Sesquiterpene Lactones from Helianthus annuus: Antimicrobial and Cytotoxic Properties; Influence on DNA, RNA, and Protein Synthesis

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Abstract
The compounds have an antibiotic effect on gram-negative and gram-positive bacteria and on some fungi. The minimal inhibiting concentration (MIC) of compound II (15-hydroxy-3-dehydrodesoxyfruticin), for example, is 15 .mu.g/ml for Bacillus brevis and 95 .mu.g/ml for the fungus Eremothecium ashbyi. Cytotoxic effects on mouse myeloma cells (NS-1) were also shown. Compound II causes a 50% inhibition of cell proliferation (ED50) at a concentration of 170 nM, compound I (niveusin C, Fig. 1) at 220 mM. The LD50-values were 0.15 .mu.g II/ml and 1.24 .mu.g I/ml, respectively. By measuring 14C-labeled thymidine, uridine and leucine incorporation into murine cells of the ascitic form of Ehrlich carcinoma (EAC), it could be shown that compounds I and II inhibit DNA and RNA synthesis, but do not affect the translation process involved in protein synthesis. The exocyclic methylene group in the molecules of I and II plays an important role in triggering the described inhibitory effects.

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