A new antifungal dihydroisocoumarin from Xyris pterygoplephara Kunth (Xyridaceae)

Xyris plants are small shrubs, popularly known as „sempre-vivas“ (everlasting plants). Some are collected for ornamental purposes and for medicinal uses, to treat eczemas and dermatitis [1]. Around 90% of the 152 Xyris species found in Brazil are endemic and over harvesting has put some into extinction risk [2]. Both the chemistry and the biological activities of Xyris spp. are poorly studied. We have previously described the isolation of a new anthraquinone from X. pilosa L. with antifungal activity [3]. In the present study, we report the phytochemical study of X. peterygoblephara. The ethanol extract from its aerial parts was evaluated against 9 microorganism strains (Bacillus subtillis, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Aspergillus niger, Epidermophyton floccosum, Mycrosporum canis, Trichophyton mentagrophytes and Trichophyton rubrum) by the microdilution and agar diffusion assays. Fractionation of the extract by silica gel column chromatography and partition between immiscible solvents, following purification by semi preparative NP-HPLC and Sephadex LH20 column chromatography, resulted in the isolation of three compounds. The structures were assigned by spectroscopic data as moronic acid, quercetin and (3R,4R)-(-)-6-methoxy-3,4-dihydro-4-acethoxy-5-n-pentil-1H-2-benzopyran-1-one (1), a new compound. The absolute configuration of 1 was defined using circular dichroism spectroscopy. Assay of 1 (100µg/disc) by the agar diffusion method against isolates of the dermatophytous fungi E. floccossum (inbibition zone, mm±s.d.: 4.5±0.8), T. mentagrophytes (4.8±0.4) and T. rubrum (10.2±0.8) revealed similar activity to the positive control amphotericin B (32µg/disc; 5.0±0.2, 5.0±0.6 and 8.8±1.2, respectively). The obtained data corroborate the ethomedical use of Xyris species to treat dermatitis.

Acknowledgements: CNPq for a research fellowship (FCB), UFMG/PRPq (Projetos Estruturantes) for the financial support, Fundação Zoo-Botânica for collecting the plant material.

References: [1] Pio Corrêa M., Penna L. (1969) Dicionário das plantas úteis do Brasil e das exóticas cultivadas. Ministério da Agricultura. Rio de Janeiro. [2] Sajo, M.G. et al. (1997) Bol. Bot. USP 16: 15–19. [3] Cota et al. (2004) Biochem. Sys. Ecol. 32: 391–397.