Objective: Lichens are emerging as a promising natural source of bioactivities of pharmaceutical interest. The present study aims to contribute to the knowledge of the lichen Umbilicaria muhlenbergii as a potential source of pharmaceutically relevant anticancer and antibiotic lichen chemicals.

Methods: The crude acetone extract of U. muhlenbergii exhibited 13.3 μg mL-1 cytotoxic activity (EC50) against breast cancer cells (MCF-7), as compared to a cisplatin positive control with EC50 of 5.8 μg mL-1. The antibiotic activity of the crude extract against a gram-positive Staphylococcus aureus was 22.5 μg mL-1 as MIC. Using silica gel 60 (SG60) column chromatography, the crude extract was then separated into eight fractions, which were further evaluated for their anticancer activities against MCF-7 cells. By means of propidium iodide flow cytometry, two of the eight SG60 fractions were found to cause cell cycle arrest in MCF-7 cells (73.14% of cells) at the G2 phase, which is indicative of apoptosis and inhibition of cellular proliferation.

Results: Identification of chemical constituents present in these two SG60 fractions was carried out with Thin-Layer Chromatography (TLC) and a lichen metabolite database (Wintabolites). The two fractions (SG60-5 and SG60-6) were found to contain compounds belonging to the chemical families depsides, depsidones, anthraquinones, and xanthones.

Discussion: The SG60-5 and SG60-6 fractions were further fractionated with Sephadex LH-20. Over 15% of the 46 LH-20 fractions obtained from the SG60-5 fraction caused 100% cell death, whereas 32% of the LH-20 fractions derived from SG60 6 fraction reduced cell survival to below 20%.

Conclusion: This work extends the evaluation of the cytotoxic and antibiotic activities of lichen secondary metabolites to the species U. muhlenbergii. It presents encouraging results of pharmaceutical interest that set up lichens as an effective source of new bioactive natural products. Further investigations are underway to reveal the full biopharmaceutical potential of U. muhlenbergii.

目的：地衣正在成为一种有前途的天然生物活性药物来源。本研究旨在为了解地衣脐带作为药物相关抗癌和抗生素地衣化学物质的潜在来源做出贡献。

方法：穆罕默德氏菌粗丙酮提取物对乳腺癌细胞（MCF-7）表现出13.3μgmL-1的细胞毒活性（EC50），而EC50为5.8μgmL-1的顺铂阳性对照。粗提取物对革兰氏阳性金黄色葡萄球菌的抗菌活性为MIC为22.5μgmL-1。然后使用硅胶60（SG60）柱色谱法，将粗提取物分离成8个馏分，进一步评估其对MCF-7细胞的抗癌活性。通过碘化丙啶流式细胞术，发现八个SG60馏分中的两个在G2期引起MCF-7细胞（占细胞的73.14％）的细胞周期停滞，这表明细胞凋亡和抑制细胞增殖。

结果：使用薄层色谱（TLC）和地衣代谢物数据库（Wintabolites）鉴定了这两个SG60馏分中存在的化学成分。发现这两个馏分（SG60-5和SG60-6）含有属于以下两个化学家族的化合物：双侧孢子虫，双侧孢菌烯酮，蒽醌和氧杂蒽酮。

讨论：SG60-5和SG60-6馏分用Sephadex LH-20进一步分馏。从SG60-5馏分获得的46个LH-20馏分中，超过15％导致100％的细胞死亡，而从SG60 6馏分衍生的LH-20馏分中有32％将细胞存活率降低至20％以下。

结论：这项工作扩展了地衣次级代谢产物对U. muhlenbergii物种的细胞毒性和抗生素活性的评估。它呈现出令人鼓舞的药物兴趣成果，使地衣成为新型生物活性天然产物的有效来源。正在进行进一步的研究，以揭示美伦氏假单胞菌的全部生物制药潜力。