Toxicity of Carlina Oxide—A Natural Polyacetylene from the Carlina acaulis Roots—In Vitro and in Vivo Study

Abstract

There are several reports indicating that the roots of the Carlina acaulis L. used to be commonly applied as a treatment measure in skin diseases and as an antiparasitic agent, starting from antiquity to the 19th century; however, nowadays, it has lost its importance. Currently, numerous studies are being conducted assessing the possibility of reintroducing C. acaulis-derived extracts to phytotherapy. Determining the safety profile of the main constituents of the plant material is crucial for achieving this goal. Here, we aimed to determine the toxicity profile of carlina oxide, one of the most abundant components of the C. acaulis root extract. We obtained the carlina oxide by distillation of C. acaulis roots in the Deryng apparatus. The purity of the standard was evaluated using GC-MS, and the identity was confirmed by IR, Raman, and NMR spectroscopy. In vitro cytotoxicity was assessed using a panel of human cell lines of skin origin, including BJ normal fibroblasts and UACC-903, UACC-647, and C32 melanoma cells. This was accompanied by an in vivo zebrafish acute toxicity test (ZFET). In vitro studies showed a toxic effect of carlina oxide, as demonstrated by an induction of apoptosis and necrosis in both normal and melanoma cells. Decreased expression of AKT kinase and extracellular signal-regulated kinase 1/2 (ERK1/2) was noted in the UACC-647 melanoma cell line. It was also observed that carlina oxide modified the expression of programmed cell death-ligand 1 (PD-L1) in tested cell lines. Carlina oxide exhibited high in vivo toxicity, with LC50 = 10.13 µg/mL upon the 96 h of exposure in the ZFET test. Here, we demonstrate that carlina oxide displays toxic effects to cells in culture and to living organisms. The data indicate that C. acaulis-based extracts considered for therapeutic use should be completely deprived of carlina oxide.

Back to the Roots—An Overview of the Chemical Composition and Bioactivity of Selected Root-Essential Oils

“…Thus, the treatment of herpetic eruptions and suppurating rashes (pyodermias) was also reported [ 13 , 82 ]. Nowadays, C. acaulis is still recognized as a remedy in the folk medicine of mountainous areas through Europe, although it lost its importance as a medicinal plant at the end of the 19th century for unclear reasons [ 5 ]. Limited effectiveness, undesirable toxicity, or its limited presence in natural habitats due to massive collection might be possible reasons [ 5 , 83 ].…”

“…Nowadays, C. acaulis is still recognized as a remedy in the folk medicine of mountainous areas through Europe, although it lost its importance as a medicinal plant at the end of the 19th century for unclear reasons [ 5 ]. Limited effectiveness, undesirable toxicity, or its limited presence in natural habitats due to massive collection might be possible reasons [ 5 , 83 ]. Along with its medicinal use, C. acaulis is still recognized as a food plant (receptacle and roots) [ 84 ] and—together with its EO—is listed in the BELFRIT botanical list as a botanical food supplement by Italy [ 85 ], Belgium, and France [ 86 ].…”

“…Carlina oxide (2-(3-phenylprop-1-ynyl) furan) Figure 1 (11)—a natural polyacetylene—has been found to be the outstanding principal and bioactive component of the EO through all studied samples (ranging from 91.5% to 99.0%) [ 5 , 10 , 81 , 88 , 91 , 93 , 94 , 95 ]. Apart from varying concentrations, the results obtained were all in accordance.…”

“…Besides carlina oxide as the main component (97.2%), benzaldehyde (0.8%), ar -curcumene (0.6%) Figure 1 (12), heptane (0.5%), 1-phenyl-2-propanone (0.2%), ( Z , E ) α-farnesene (0.2%), and β-sesquiphellandrene (0.2%) Figure 1 (13) were found in amounts < 1% [ 91 ]. Similarly, carlina oxide (96.2%), benzaldehyde (0.6%) Figure 1 (14), ar -curcumene (0.6%), and β-sesquiphellandrene (0.2%) were identified as the main components in the hydrodistilled EO from C. acaulis roots collected in Lublin, Poland [ 5 ].…”

“…They are mainly constituted by terpenoids and phenylpropanoids. However, some EOs are made up of constituents of different chemical structures such as polyacetylenes or even sulfur-containing compounds [ 4 , 5 , 6 ]. In many cases, they can be characterized by up to three major components, at a relatively high concentration compared with other compounds present in trace amounts [ 2 ].…”