Bioassay-Guided Isolation of Iridoids and Phenylpropanoids from Aerial Parts of Lamium album and Their Anti-inflammatory Activity in Human Neutrophils

In traditional medicine, flowers and aerial parts of Lamium album are assigned by their anti-inflammatory, antiseptic, and mucolytic activities, and are used in chronic bronchitis and pharyngitis as well as skin, vaginal, and cervical inflammation.The aim of the present study was to compare effects of ethanolic extracts prepared from flowers and aerial parts of L. album on selected functions of human neutrophils, which are involved in an inflammatory response. In order to identify the compounds engaged in the anti-inflammatory activity of extracts, the bioassay-guided isolation of compounds was performed based on the inhibition of cytokine secretion by stimulated neutrophils.The extracts were phytochemically characterized with the HPLC-DAD-MSn method. The inhibition of reactive oxygen species production by formyl-met-leu-phenylalanine- or phorbol 12-myristate 13-acetate-stimulated neutrophils was determined using luminol- or lucigenin-dependent chemiluminescence. The effect on myeloperoxidase secretion by neutrophils was established spectrophotometrically. The levels of cytokine (interleukin 8, TNF-α) production after extract treatment was measured by ELISA.The most abundant constituents of extracts were phenylpropanoids, iridoids, flavonoids, and phenolic acids. Both extracts at concentrations of 25 and 100 µg/mL significantly inhibited reactive oxygen species production, and myeloperoxidase and interleukin 8 secretion. The phenylethanoid glycosides, such as lamiusides A, B, and C as well as 6″-O-β-D-glucopyranosylmartynoside, were isolated and identified. The cells treated with 6″-O-β-D-glucopyranosylmartynoside and lamiuside B produced 29.47 ± 7.11 % and 64.67 ± 5.25 % of interleukin 8, respectively, compared to non-treated control cells.Our results support the traditional use of L. album and indicate it as a potential source of natural anti-inflammatory constituents, such as phenylpropanoids.