Phytochemical Profiling of Sticta caulescens De Not.: Green Extraction and Multiscale Chemotaxonomic Analysis

A Chilean lichen yields a treasure trove of 33 metabolites—and a green chemistry twist that could change how we explore nature's medicine cabinet.

Lichen are nature's chemical factories, and Sticta caulescens from Chile is no exception. Scientists set out to catalog its secondary metabolites using two extraction methods: traditional methanol maceration and microwave-assisted extraction (MAE) with ethyl lactate, a greener solvent. The result? A rich spectrum of compounds—carbohydrates, aromatic acids, depsides, depsidones, dibenzofurans, lipids, anthraquinones, and triterpenes—revealed by UHPLC/ESI-MS/MS analysis.

Maceration with methanol yielded 32 metabolites and a slightly higher extract percentage (6.3% vs 5.0%), but MAE extracted an almost identical set of 33 compounds, including one unique to the microwave method. This highlights the efficiency and selectivity of green extraction—promising for sustainable chemistry.

Beyond the single species, the team compared S. caulescens with 11 other Sticta species using computational tools like Morgan fingerprints and hierarchical clustering. The analysis showed S. caulescens is one of the most chemically diverse, closely related to S. cordillerana, and part of a major lineage rich in scaffolds and shared biosynthetic pathways for aromatics and depsidones.

This study not only enriches our understanding of lichen chemistry but also demonstrates how green chemistry and chemoinformatics can work together to map biodiversity's molecular potential.

Key Points

• 32–33 metabolites identified via UHPLC/ESI-MS/MS.
• Green MAE with ethyl lactate matches methanol extraction.
• S. caulescens is chemically diverse, akin to S. cordillerana.