{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T22:26:25Z","timestamp":1789770385972,"version":"4.0.1"},"reference-count":54,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T00:00:00Z","timestamp":1768780800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"crossref","id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/100000057","name":"National Institute of General Medical Sciences","doi-asserted-by":"crossref","id":[{"id":"10.13039\/100000057","id-type":"DOI","asserted-by":"crossref"}]},{"name":"IDeA Networks of Biomedical Research Excellence","award":["P20GM103466"],"award-info":[{"award-number":["P20GM103466"]}]},{"name":"DKICP"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pharmaceuticals"],"abstract":"<jats:p>Background\/Objectives: The global rise in multidrug-resistant (MDR) bacteria, particularly methicillin-resistant and methicillin-susceptible Staphylococcus aureus (MRSA and MSSA), continues to pose a major public health challenge, including in Hawaii. This underscores the need to discover new antimicrobial agents from natural sources. Guided by teachings from a Buddhist master regarding the medicinal value of lichens, we investigated the endemic Hawaiian lichen Cladonia skottsbergii. Methods: Specimens of C. skottsbergii were collected from the Lotus Buddhist Monastery in Mountain View, Hawaii. A methanolic extract was prepared and purified using chromatographic techniques, and compound structures were elucidated through spectroscopic analyses and single-crystal X-ray diffraction. The antibacterial activity of the compounds was assessed against Gram-positive strains (MRSA, MSSA) and Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa). Cytotoxicity was assessed using A549 (non-small cell lung cancer) and Vero E6 (non-tumorigenic) cell lines. Results: Three compounds were isolated: clarosione (1), a newly identified trichlorinated xanthone, and two known metabolites, (S)-usnic acid (2) and perlatolic acid (3). Compounds 2 and 3 demonstrated strong inhibitory effects against MRSA and MSSA. Their minimum inhibitory concentrations (MICs) ranged from 2 to 4 \u00b5g\/mL, compared with vancomycin (0.5\u20131 \u00b5g\/mL). Cytotoxicity testing showed higher sensitivity in A549 cells than in Vero E6 cells, resulting in favorable selectivity indices for the active compounds. Conclusions: In the current study, a new compound, clarosione (1) was discovered. This enhances our understanding of the constituents of C. skottsbergii and its potential antibacterial properties. Lichen-derived compounds may serve as lead candidates for further development, and further study is warranted.<\/jats:p>","DOI":"10.3390\/ph19010174","type":"journal-article","created":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T14:58:54Z","timestamp":1768834734000},"page":"174","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["A New Trichlorinated Xanthone and Compounds Isolated from Cladonia skottsbergii with Antimicrobial Properties"],"prefix":"10.3390","volume":"19","author":[{"given":"Marvin J.","family":"Rositzki","sequence":"first","affiliation":[{"name":"Department of Pharmaceutical Sciences, The Daniel K. Inouye College of Pharmacy, University of Hawai\u2019i at Hilo, Hilo, HI 96720, USA"},{"name":"Department of Pharmacy Practice, The Daniel K. Inouye College of Pharmacy, University of Hawai\u2019i at Hilo, Hilo, HI 96720, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8114-4123","authenticated-orcid":false,"given":"Achara","family":"Raksat","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical Sciences, The Daniel K. Inouye College of Pharmacy, University of Hawai\u2019i at Hilo, Hilo, HI 96720, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Charles J.","family":"Simmons","sequence":"additional","affiliation":[{"name":"X-Ray Diffraction Laboratory, Department of Chemistry, University of Hawai\u2019i at Hilo, Hilo, HI 96720, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Clifford","family":"Smith","sequence":"additional","affiliation":[{"name":"Department of Botany, University of Hawai\u2019i at Manoa, Honolulu, HI 96822, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Reverend Danette V.","family":"Choi","sequence":"additional","affiliation":[{"name":"Bang San Ho Temple Yun Hwa Denomination of World Social Buddhism dba Lotus Buddhist Monastery, Mountain View, HI 96771, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4447-0886","authenticated-orcid":false,"given":"Supakit","family":"Wongwiwatthananukit","sequence":"additional","affiliation":[{"name":"Department of Pharmacy Practice, The Daniel K. Inouye College of Pharmacy, University of Hawai\u2019i at Hilo, Hilo, HI 96720, USA"},{"name":"College of Pharmacy, Rangsit University, Pathum Thani 12000, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9918-5612","authenticated-orcid":false,"given":"Leng Chee","family":"Chang","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical Sciences, The Daniel K. Inouye College of Pharmacy, University of Hawai\u2019i at Hilo, Hilo, HI 96720, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Salam, M.A., Al-Amin, M.Y., Salam, M.T., Pawar, J.S., Akhter, N., Rabaan, A.A., and Alqumber, M.A. (2023). Antimicrobial resistance: A growing serious threat for global public health. 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