High Performance Thin Layer Chromatography (HPTLC) to profile lichen metabolites

Lichens produce a large collection of secondary metabolites, mainly phenolic and terpene compounds. Since their discovery, they have been analysed by different techniques such as color tests, crystallisation, separative techniques, and informative physico-chemical techniques for structure elucidation. Thin Layer Chromatography is the most used approach by lichenologists and the current work aims at developing standardised methods for phenolic and terpene compounds analysis. We also compare analytical techniques, such as High Performance TLC (HPTLC) and High Performance Liquid Chromatography (HPLC) with regard to the qualitative and quantitative characterisation of secondary metabolites in lichen extracts. A variety of parameters have been optimised for HPTLC, monitored by a software in a semi-automatic mode. Thanks to pure available lichen compounds, databases were constituted in order to analyse complex lichen extracts.

HPTLC data is mainly based on Rf, absorbances (254 nm, 366 nm, white light), spot colors after derivatisation, KUV test (KOH 10%, 366 nm) and mass data (ESI- for phenols, APCI+for terpenoids). For terpenoid compounds, HPLC data resulted from ELSD detector and an APCI ionisation mode because the major part of them was not visible in UV and show difficulties for ionisation (ESI+/-). Hence, these techniques can be compared and afford additional or complementary results for an accurate profiling of lichen extracts. Results are expected to be useful not only for chemotaxonomic approaches but also to identify new or valuable lichen compounds. With HPTLC, a rapid and convenient identification of bioactive compounds is expected as the technique is suitable for bioautographic assays (antibiotic screening).

 

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Publication History

Article published online:
16 November 2023