Abstract
Four guaianolide type sesquiterpene lactones (SL), namely the new 1,2-dihydro-3-oxo-costic acid guaianyl ester 3β-
O-(1,2-didehydro-3-oxo-costoyloxy)-4β,10β-dihydroxy-guaia-1(2)-en-6β,12-olide (
1) and 3β-
O-(1,2-didehydro-3-oxo-costoyloxy)-4β,10β-dihydroxy-guaia-1(2)-en-6α,12-olide (
2), as well as the known moroccolide A [5αH-2β,4-epoxy-3β-hydroxy-guaia-1(10),11(13)-dien-6β,12-olide,
3] and 3β-
O-(2-methylbutyryl)-moroccolide A [5αH-2β,4-epoxy-3β-(2-methylbutyryloxy)-guaia-1(10),11(13)-dien-6β,12-olide,
4] were examined for their cytotoxic and anti-inflammatory effects in HeLa, Jurkat T and human peripheral blood mononuclear cells. Compounds
1,
2 and
4 were found to exert a strong cytotoxicity similar in potency in all investigated cell types, whereas
3 was significantly less active. Along with the cytotoxic effect compounds
1 and
4 showed a potent and comparable down-regulation of the mRNAs of the house-keeping genes β-actin and GAP-DH in PBMCs after 20 h. In contrast, the down-regulation of the PMA-induced mRNA levels of the NF-κB-driven pro-inflammatory genes IL-2, IL-6, GM-CSF, TNF-α, and IL-1β in PBMCs is significantly stronger with compound
4. Compound
3 did not significantly modulate cytokine mRNAs levels at biochemically relevant concentrations. The electromobility shift assay (EMSA), revealed a stronger inhibition of NF-κB for
1 (IC
50 2.5 μM) than for
4 (IC
50 5 μM). Both compounds were also subjected to an IL-6 luciferase reporter gene assay and showed IC
50 values of 1.0 (
1) and 1.2 μM (
4). Thus, the NF-κB inhibition measured by EMSA, as well as the IL-6 luciferase assay did not reflect the differential modulation of pro-inflammatory genes measured with RT-rt-PCR.
Two new dimeric guaianolide-type sesquiterpene lactones were isolated from
Warionia saharae. Their cytotoxic and anti-inflammatory potential was characterized in different in-vitro test systems, and compared to results obtained for two known monomeric guaianolides. The study revealed that the investigated guaianolides differentially modulate native gene transcription of pro-inflammatory and house-keeping genes despite of similar activity in NF-κB EMSA, IL-6 reporter gene, and cytotoxicity assays.