Abstract
Usnic acid, a lichen metabolite, is known to exert antimitotic and antiproliferative activities against normal and malignant human cells. Many chemotherapy agents exert their activities by blocking cell cycle progression, inducing cell death through apoptosis. Microtubules, protein structure involved in the segregation of chromosomes during mitosis, serve as chemotherapeutical targets due to their key role in cellular division as well as apoptosis. The aim of this work was to investigate whether usnic acid affects the formation and/or stabilisation of microtubules by visualising microtubules and determining mitotic indices after treatment. The breast cancer cell line MCF7 and the lung cancer cell line H1299 were treated with usnic acid 29 microM for 24 hours and two positive controls: vincristine (which prevents the formation of microtubules) or taxol (which stabilizes microtubules). Treatment of MCF7 and H1299 cells with usnic acid did not result in any morphological changes in microtubules or increase in the mitotic index. These results suggest that the antineoplastic activity of usnic acid is not related to alterations in the formation and/or stabilisation of microtubules.
Highlights
Lichens synthesize over eight hundred types of metabolites (Müller, 2001)
Cells treated with usnic acid (1b and 2b), were morphologically similar to the cells with no treatment (1a and 2a) even after 24 hours exposure to usnic acid
Treatment with vincristine resulted in accumulation of M phase cells compared to the negative control (Student’s t-test p < 0.05), whereas untreated cells and cells treated with usnic acid showed similar mitotic indices (Student’s t‐test p > 0.05)
Summary
Lichens synthesize over eight hundred types of metabolites (Müller, 2001). Due to their therapeutic properties, many Cultures have utilised these compounds in traditional medicine for centuries (Cocchietto et al, 2002). Depsidones, dibenzofuranes, xanthenes, anthraquinones and usnic acids are amongst the more extensively studied lichen metabolites (Honda and Vilegas, 1998). Usnic acid (2,6-diacetyl-7,9-dihydroxy-8,9bdimethyl-dibenzofuran-1,3[2H,9bH]-dione; C18H16O7) (Figure 1), is one of the most abundant secondary lichen.
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