Flavonoids with anti-inflammatory and antinociceptive activity from Cistus laurifolius L. leaves through bioassay-guided procedures.

Extracts obtained from the leaves and branches of various Cistus species have been used worldwide as folk remedy for the treatment of various inflammatory ailments including rheumatism and renal inflammations. Effects of the extracts and fractions from the leaves with non-woody branches of Cistus laurifolius L. (Cistaceae) were studied using two in vivo models of inflammation in mice. Model one was based on observed potent inhibitory activity against carrageenan-induced hind paw oedema and the second model used was acetic acid-induced, increased vascular permeability model. Through bioassay-guided fractionation and isolation procedures three flavonoids; 3-O-methylquercetin (1), 3,7-O-dimethylquercetin (2) and 3,7-O-dimethylkaempferol (3) were isolated as the main active ingredients from the ethanol extract. Later on, these flavonoids were shown to possess potent antinociceptive activity, which was assessed through inhibition of p-benzoquinone-induced writhing reflex. Results of the present study have clearly supported the utilization of Cistus laurifolius in Turkish traditional medicine. Subsequently, three flavonoids were shown to have strong antinociceptive and anti-inflammatory activities, per os without inducing any apparent acute toxicity as well as gastric damage.