LC-MS based metabolic profiling of Cetraria islandica and quantification of aliphatic secondary metabolites by LC-MS

C. islandica is one of the most studied lichen species within the cetrarioid species and belongs to the Parmeliaceae family [1]. C. islandica is widely used in folk European medicine for the treatment of respiratory diseases and cough and has been listed in European pharmacopoeias since the 17th century. In addition, an HMPC monograph of the European Medicines Agency (EMA) is also available (EMA/HMPC/678891/2013) [2] [3] [4].

Lichens produce unique profiles of secondary metabolites due to the genetic diversity of the symbiotic partners and the interaction with their environment [4]. In the present project, LC-MS analysis was employed for metabolic profiling of petroleum ether extracts of seven C. islandica samples from different locations, but also including two batches, which were collected about 40 years ago. PCA analysis of the LC-MS data obtained in negative mode revealed paraconic acids as major discriminators in the investigated samples. Paraconic acids are a group of secondary metabolites mainly found in lichens and selected fungi. From C. islandica, compounds such as, lichesterinic, protolichesterinic, dihydroprotolichesterinic and roccellaric acids have shown antitumor, antiproliferative, antiviral and anti-inflammatory activities [5], which makes this compound class of special interest.

Consequently, LC-MS analysis was also employed for the quantification of the four major paraconic acids. Ricinoleic acid was used as an internal standard and lichesterinic acid, isolated by CPC [6], as a calibrator. Among the quantified compounds, lichesterinic acid is the most abundant in all samples ranging from 0.03 to 0.11% w. The content of the major discriminator, protolichesterinic acid, ranges from 0.002 to 0.048% w.

Publication History

Article published online:
16 November 2023

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