An Evaluation of the Cytotoxicity and Safety Profile of Usnic Acid for a Broad Panel of Human Cancers and Normal Cells with Respect to Its Enantiospecificity

Sep 23, 2026

Uploaded by Stanley

Chirality determines how bioactive compounds act and whether they are toxic. This study evaluated the cytotoxicity and safety profile of usnic acid (UA) enantiomers against colon, prostate, thyroid, brain, and breast cancer cell lines and selected non-cancerous cells. Viability was measured by the MTT assay after 24, 48, and 72 hours. Colon HCT116 cells showed highest sensitivity, with no enantiomeric dominance. Prostate and breast outcomes favored (+)-UA, while brain cells were least affected. UA showed no effect on normal colon epithelial cells but displayed moderate toxicity toward prostate, thyroid, and breast cells. Overall, (+)-UA had stronger cytotoxicity, whereas (−)-UA was more toxic to normal cells, supporting potential advantages for chemopreventive strategies.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages15

Reading Time38 min

AccessFree to download

Abstract

Introduction

Background on chirality and usnic acid

Rationale for enantiospecific comparison

Results and Discussion

Cytotoxic evaluation across cancer cell lines

Article An Evaluation of the Cytotoxicity and Safety Profile of Usnic Acid for a Broad Panel of Human Cancers and Normal Cells with Respect to Its Enantiospecificity Gabriela Siedlarczyk 1, Paweł Pa´sko 2 and Agnieszka Galanty 1, * Academic Editor: Claudio Ferrante Received: 11 June 2025 Revised: 11 July 2025 Accepted: 11 July 2025 Published: 14 July 2025 Citation: Siedlarczyk, G.; Pa´sko, P.; Galanty, A. An Evaluation of the Cytotoxicity and Safety Profile of Usnic Acid for a Broad Panel of Human Cancers and Normal Cells with Respect to Its Enantiospecificity. Molecules 2025, 30, 2964. [https://](https://)[ ](https://)[doi.org/10.3390/molecules30142964](doi.org/10.3390/molecules30142964) [Copyright:](Copyright:) © 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([https://creativecommons.org/](https://creativecommons.org/)[ ](https://creativecommons.org/)[licenses/by/4.0/](licenses/by/4.0/)) . 1 Department of Pharmacognosy, Jagiellonian University Medical College, Medyczna 9, 30-688 Kraków, Poland; [gabriela.siedlarczyk@alumni.uj.edu.pl](gabriela.siedlarczyk@alumni.uj.edu.pl) 2 Department of Food Chemistry and Nutrition, Jagiellonian University Medical College, Medyczna 9, 30-688 Kraków, Poland; [p.pasko@uj.edu.pl](p.pasko@uj.edu.pl) * Correspondence: [agnieszka.galanty@uj.edu.pl](agnieszka.galanty@uj.edu.pl) Abstract Chirality plays a key role in the effectiveness and toxicity of bioactive compounds. Usnic acid (UA), a lichen metabolite, exists as two enantiomers. Despite numerous studies on its biological properties, enantioselective aspects remain poorly recognized. This study assessed the cytotoxicity of UA enantiomers against colon, prostate, thyroid, brain, and breast cancer cell lines, as well as non-cancerous cells. Cell viability was determined by the MTT assay after 24, 48, and 72 h. Colon cancer HCT116 cells were the most sensitive (IC 50 ~10 µg/mL, 72 h), with no enantiomeric dominance. In prostate cancer PC3 cells,(+)-UA was more effective. Moderate cytotoxic effect was noted for thyroid cancer cells; however, this was evaluated for the first time. MDA-MB-231 breast cancer cells were strongly affected (IC 50 15.8 and 20.2 µg/mL for (+)-and (−)-UA, 72 h), as compared to MCF7 cells. Brain cancer cells were the least affected, as so were normal astrocytes. UA had no effect on normal colon epithelial cells but showed moderate toxicity in prostate, thyroid, and breast cells. To conclude, the overall cytotoxicity of (+)-UA was stronger than its (−)-enantiomer, while the latter compound was more toxic to normal cells. These findings highlight the advantage of (+)-UA, especially in chemopreventive strategies. Keywords: UA; cytotoxic; enantiomers; selectivity; toxicity 1. Introduction Chirality plays a crucial role in the effectiveness and toxicity of bioactive compounds. Usnic acid (UA), a dibenzofuran derivative, is synthesized by various lichen species in the form of two enantiomers that differ in the spatial orientation of a methyl group at the chiral center (Figure 1) . The compound is found in high amounts (up to 10%) in several lichen species (e.g., Cladonia, Flavocetraria) and can be isolated relatively easily from the lichen matrix, what, together with its broad spectrum of biological activities, has been attracting significant scientific interest for years. Among the reported biological and pharmacological activities, cytotoxic, anti-inflammatory, and antimicrobial seem to be most promising, and all these aspects have been summarized in detail by a number of recent review articles [1–4] . Despite the large number of publications reporting the biological potential of UA, theenantioselective aspects of its activity and toxicity remain poorly characterized, as most research has focused on the (+)-enantiomer, leaving the biological profile of t

FAQs

What was the main aim of evaluating usnic acid in this study?

To assess the cytotoxicity and safety profile of usnic acid enantiomers and determine how enantiospecificity influences effects in cancer versus non-cancer cells.

How was cell viability measured for UA enantiomers?

Cell viability was determined using the MTT assay at 24, 48, and 72 hours.

Which cancer cell line was reported as most sensitive to UA?

Colon cancer HCT116 cells were described as the most sensitive, with IC50 values around 10 µg/mL at 72 hours.

What overall conclusion was drawn about the (+)-UA and (−)-UA enantiomers?

Overall cytotoxicity was stronger for (+)-UA, while (−)-UA showed greater toxicity to normal cells, suggesting (+)-UA advantages for chemopreventive strategies.

Sep 23, 2026

Uploaded by Stanley