Isolation of iridoids and flavones from the anti-inflammatory, antioxidative and antimicrobial extract of Melampyrum barbatum

The genus Melampyrum, belonging to the Scrophulariaceae family, represents about 25 species of herbaceous annual plants found in the Northern hemisphere. In traditional medicine, aerial parts of Melampyrum species have been used to alleviate rheumatic complaints, symptoms of gout and to treat different skin infections in decoction form [1 – 2]. The aim of the present work was the detailed phytochemical and pharmacological analysis of aboveground parts of Melampyrum barbatum Waldst. & Kit. ex Willd. Previously no data on the chemical constituents of this species have been reported; only antioxidant and free radical scavenging activities of red and yellow forms were investigated [3]. The plant material, collected from wild stock in Hungary, was extracted with methanol-water 7:3, and then liquid-liquid partition was performed with chloroform, ethyl acetate and n-butanol. These fractions were examined for antioxidant activity using DPPH and FRAP methods, and for antimicrobial effect against 6 Gram+ and 4 Gram- bacterial strains by a disc-diffusion method. The in vivo anti-inflammatory activity was studied in rats using the carrageenan-induced paw oedema test after intraperitoneal administration. It was found that the MeOH extract possesses a remarkable antioxidative property, and the EtOAc fraction showed an antibacterial effect against Staphylococcus epidermidis and Moraxella catarrhalis. In the antiphlogistic test the n-butanolic fraction displayed a significant effect (27.3 ± 2.03% inhibition). Isolation was carried out by a combination of different chromatographic methods, including CC, VLC, preparative TLC and HPLC. The structures of the compounds were determined by analysis of their spectroscopic data (1H- and 13C-NMR, 1H,1H-COSY, NOESY, HSQC and HMBC). As a result, apigenin, luteolin, and the iridoid glycosides, mussenoside, 8-epi-loganin, aucubin and loganic acid were identified, besides benzoic acid and galactitol. All compounds were isolated for the first time from this species. References: [1] Gerlach S, Saukel J, Kubelka W. Pflanzen in der osterreichischen Volksmedizin. Sci Pharm 2006; 74Suppl: 36 [2] Mogosan C, Munteanu MF. A comparative study on antiinflammatory effect of the tinctures from Melampyrum bihariense Kern and Melampyrum cristatum. (Scrophulariaceae). Farmacia 2008; 56: 389 – 392 [3] Stajner D, Popovic BM, Boza P, Kapor A. Antioxidant capacity of Melampyrum barbatum - Weed and medicinal plant. Phytother Res 2009; 23: 1006 – 1010