Taylor, Elizabeth Jane; (1999) Evaluation of medicinal plants used in the treatment of psoriasis. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Glycyrrhiza glabra, Galium aparine, Trifolium pratense and Bellis perennis have been used traditionally in the treatment of inflammatory skin diseases including Psoriasis vulgaris. To verify these past claims the plants were extracted with a range of solvents increasing in polarity and the extracts screened using the anti-inflammatory model, inhibition of chemically induced erythema on the mouse ear (CDl). Although activity was observed for some extracts of all herbs the ethyl acetate fraction of G.glabra and the chloroform fraction of G.aparine were most active against chemically induced erythema, with an IC50 of 10 and 5 μg/ear respectively. Inhibition of chemically induced erythema was further employed as a technique for bioactivity guided fractionation of the two extracts, resulting in the isolation of three chalcones, isoliquiritigenin, licochalcone B and echinatin from G.glabra and four carotenoids, lutein, anhydrolutein I, 2',3'-anhydroluteion II and 3-hydoxy-3'-methoxycarotene from G.aparine. Isolation of the compounds was achieved through column and preparative thin layer chromatography and identification achieved by spectroscopic techniques including UV analysis, mass spectrometry and one and two dimensional NMR.The isolated compounds were further examined in a range of biological assay to assess their potential for anti-psoriatic activity and the possible modes of action. The retrochalcone, echinatin, was most active in the inhibition of both normal and TPA induced Swiss 3T3 cell proliferation, at l?g an 82% and 42% inhibition was exhibited respectively. The retrochalcones, echinatin and licochalcone B also proved most active against chemically induced mouse ear erythema (IC50 1-5 ?g). Licochalcone B and the carotenoid, lutein, were most active against physically (UV) induced erythema on the dorsal skin of Wistar rats and were able to inhibit the epidermal proliferation by 81% and 77% respectively. Lutein also exhibited most activity in the inhibition of blood platelet aggregation; at 50?g a 13% and 26% inhibition against TPA and ADP induced aggregation was shown. The chalcones from G.glabra showed little activity against blood platelet aggregation. The results provide some scientific evidence to support the traditional use of the four herbs to treat psoriasis.

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