Table 3. Effects of stilbenoids 1–3 on inhibition of HaCaT PGE-2 production and COX-2 enzyme activity.

	IC50 (µM)
Compounds	PGE-2	COX-2
Imbricatin (1)	12.2±2.9	12.0±1.2
Methoxycoelonin (2)	19.3±3.8	5.8±1.2
Gigantol (3)	No concentration-dependanteffect	≥100
Indomethacin	2.7±0.7	1.6±0.4

Results are expressed as IC₅₀ (mean ± sd) determined for inhibition of PGE-2 release from UV_B (60 mJ/cm²) irradiated HaCaT and inhibition of human recombinant COX-2 activity. IC₅₀ concentration causing half-maximal inhibition of HaCaT PGE-2 production and concentration causing a half-maximal inhibition of COX-2 control specific activity. Gigantol demonstrated strong inhibition of PGE-2 production but did not display concentration dependent effect at the tested concentrations, thus IC₅₀ could not be calculated. Indomethacin was used as a positive reference.