Lichenochemicals: extraction, purification, characterization, and application as potential anticancer agents

ABSTRACT

Introduction: To date, over 1,000 lichen secondary metabolites have been identified. Despite their promising cytotoxic properties, the number of literature reports on anticancer evaluation of lichenochemicals is limited. As cancer prevalence among the human population increases, there is growing interest in lichens as a natural source of secondary metabolites for anti-cancer drug discovery and development.

Areas covered: The lack of significant progress in lichen anticancer research is due to the low levels of cytotoxic compounds contained in lichens, the technical difficulties associated with their isolation and characterization, and the insufficient understanding of their mechanism of action on different cancer cell lines. In this review, the authors discuss these challenges and provide systematically organized information on the limitations and advantages of commonly used and newly developed methods for lichen exploration and screening of lichen secondary metabolites for their anticancer potential.

Expert opinion: Recent research activities have demonstrated that lichen secondary metabolites possess chemotherapeutic properties. A systematic and multidisciplinary approach is required to advance lichen research and improve our understanding of the mechanisms responsible for the potent cytotoxic properties of lichenochemicals. More efforts need to focus on screening and discovery of new lichen-derived compounds with unique anticancer properties.

KEYWORDS:

• Anticancer agents
• antiproliferation
• apoptosis
• cancer cell lines
• cytotoxicity
• DNA fragmentation
• extraction
• lichens
• lichenochemicals
• secondary metabolites

Article Highlights

• Lichens produce diverse bioactive secondary metabolites as a result of their high adaptability to different environments.

• The secondary metabolites are extracted from lichens via a suite of conventional methods, such as maceration and Soxhlet extraction, and non-conventional new techniques like microwave or ultrasound-assisted extraction, and supercritical fluid extraction. Choosing the appropriate extraction method requires prior knowledge of the chemistry and selectivity of the extraction solvents used.

• Lichenochemicals are identified and characterized using an array of analytical chromatography and spectroscopy methods.

• Lichenochemicals can induce intrinsic and extrinsic apoptosis pathways, activate caspases, and inhibit the viability of different cancer cells; however, the mechanism of their action on different cancer cell lines is not well understood. In addition to their cytotoxic properties, lichenochemicals can exhibit a multitude of bioactivities, such as antioxidant, antibiotic, antiviral, anti-inflammatory, and other effects.

• A systematically organized information is provided on the limitations and advantages of commonly used and newly developed methods for lichen exploration and potential for cancer treatment.

Declaration of interest

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer Disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This manuscript was not funded.