Anti-inflammatory activity of procyanidins isolated from Tiliae flos.

Tiliae flos is a pharmacopeial plant material used in the form of infusions in the threatmant of feverish colds and upper respiratory tracts irritations. Previous studies have shown that lime flowers contain significant amounts of flavonoids, mucilage and essential olis [1]. Recent research revealed that lime flowers also contain procyanidins from which only few compounds were identified [2]. One kilogram of dried plant material was extracted with acetone:methanol:water (3:1:1) to be next separated by liquid-liquid extraction. Ten flavan-3-ol derivatives were isolated using a combination of column chromatography on Diaion HP-20, Sephadex LH20 or Toyopaerl HW40F as well as preparative HPLC on C-18 column. Compounds were identified using 1D and 2D NMR experiments. One monomer, four dimers, one trimer, two tetramers and two pentamers were isolated. Compounds were identified as epicatechin, procyanidin A2, procyanidins B1, B2 and B5, epicatechin-(4β-> 6)-epicatechin-(4β-> 8)-epicatechin, epicatechin-(4β-> 8)-epicatechin-(4β-> 8)-epicatechin-(4β-> 8-epicatechin, epicatechin-(4β-> 6)-epicatechin-(4β-> 8)-epicatechin-(4β-> 8)-epicatechin, epicatechin-(4b-> 8)-epicatechin-(4β-> 8)-epicatechin-(4β-> 8)-epicatechin-(4β-> 8)-epicatechin and epicatechin-(4β-> 6)-epicatechin-(4β-> 8)-epicatechin-(4β-> 8)-epicatechin-(4β-> 8)-epicatechin. The anti-inflammatory potential, of isolated was evaluated using human neutrophils model. Compounds were tested in the concentration range of 1 – 20µM. The influence on the production of reactive oxygen species, secretion of IL-8, TNF-alpha, MIP-1alpha and MIP-1beta was checked. Compounds (excluding pentameric procyanidnins) were not toxic for neutrophils up to 20µM. All compounds were able to inhibit the production of reactive oxygen species at concentrations of 1, 5 and 20µM. Tertrameric and pentameric procyanidins exhibited the strongest activity. Tested procyanidins were able to decrease the release of IL-8 from stimulated neutrophils but did not influence the secretion of other tested inflammatory mediators. The contribution of procyanidins to the anti-inflammatory potential of Tiliae flos was established.

[1] Wichtl, M. Herbal Drugs and Phytopharmaceuticals. A hand book for practice on a sceintific basis. London, CRC Press, 2004

[2] Karioti, A, Chirabini, L, Fawaz Chehna, M, Vincieri, F.F, Bilia, A.R. J Pharmaceut Biomed Anal 2014, 100: 205 – 214