Contribution of C-glucosidic ellagitannins to Lythrum salicaria L. influence on pro-inflammatory functions of human neutrophils.

The herb Lythrum salicaria L. (Lythraceae) is used in traditional medicine to treat diseases with an inflammatory background, such as haemorrhoidal disease, dysentery, chronic intestinal catarrh, eczema, varicose veins, periodontosis and gingivitis. Because these diseases are closely associated with an excessive inflammatory response of stimulated neutrophils, the influence of aqueous extract and isolated C-glucosidic ellagitannins (dimeric salicarinins A, B and C, vescalagin, castalagin) on their pro-inflammatory functions was examined. Lythrum salicaria aqueous extract was shown to modulate lipopolysaccharide (LPS)-triggered production of IL-8 (at 20 μg/mL, 16.6 ± 4.2 % inhibition) but had no influence on MMP-9 production. It was active towards cytochalasin A/f-MLP- stimulated elastase release (at 20 μg/mL, 21.5 ± 3.9 % inhibition), myeloperoxidase release (at 1 μg/mL, 26.5 ± 5.4 % inhibition) and f-MLP- and PMA-induced reactive oxygen species production (at 20 μg/mL, 67.0 ± 3.9 and 66.5 ± 1.9 % inhibition, respectively). The extract was also shown to inhibit expression of integrin CD11b on the neutrophil surface without influencing selectin CD62L shedding. Dose-dependent inhibition of hyaluronidase activity was observed with IC50 = 10.1 ± 1.2 μg/mL. The main C-glucosidic ellagitannins were shown to be responsible for all these activities with more significant participation attributable to dimeric salicarinins A, B, C. This study has demonstrated potent activity of aqueous extract on stimulated neutrophils; this enhanced response is known to cause pathological changes in skin and mucosa tissues. These observations support and explain the traditional use of the herb Lythrum salicaria to treat certain diseases with an inflammatory background. C-glucosidic ellagitannins, especially dimeric salicarinins, are the factors responsible for these effects.