Inhibition of COXs and 5-LOX and activation of PPARs by Australian Clematis species (Ranunculaceae)
Li, RW, Lin, GD, Leach, DN, Waterman, PG, Myers, SP 2006, 'Inhibition of COXs and 5-LOX and activation of PPARs by Australian Clematis species (Ranunculaceae)', Journal of Ethnopharmacology, vol. 104, no. 1–2, pp. 138-143.
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The species of Clematis (Ranunculaceae) have been traditionally used for inflammatory conditions by indigenous Australians. We have previously reported that the ethanol extract of Clematis pickeringii inhibited COX-1. In this study, we examined the ethanol extracts and fractions of three Clematis species, Clematis pickeringii, Clematis glycinoides and Clematis microphylla, on cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX). We further examined the activating effects on the protein expression of peroxisome proliferator-activated receptor alpha (PPARα) and gamma (PPARγ) in HepG2 cells. The ethanol extracts of three Clematis species inhibited the activities of COX-1, COX-2 and 5-LOX in the different extents. The stem extract of Clematis pickeringii showed the highest inhibitory activities among the three species on COX-1, COX-2 and 5-LOX with the IC50 values of 73.5, 101.2 and 29.3 μg/mL. One of its fractions also significantly elevated PPARα expression by 173, 280 and 435% and PPARγ expression by 140, 228 and 296% at 4, 8 and 16 μg/mL, respectively.