In-Vitro Studies on Biological Activities of Some Lichen Extracts

Abstract

Lichens are unique symbiotic organisms composed of fungal and photosynthetic partners that produce a wide range of bioactive secondary metabolites with significant pharmacological potential. The present study was undertaken to investigate the phytochemical composition and evaluate the biological activities of selected lichen species collected from Ooty, Tamil Nadu. The lichens were identified using morphological, chemical, and chromatographic techniques, followed by extraction using solvents of increasing polarity such as hexane, ethyl acetate, methanol, and ethanol. Qualitative and quantitative phytochemical analyses revealed the presence of various bioactive constituents including alkaloids, flavonoids, phenols, tannins, terpenoids, steroids, carbohydrates, and anthraquinones. Among these, phenolic and flavonoid compounds were found to be predominant, particularly in methanolic extracts. The biological evaluation demonstrated significant antimicrobial, antioxidant, antidiabetic, and anticancer activities. Methanolic extracts exhibited strong antimicrobial activity with low MIC values and effectively altered microbial growth kinetics. The extracts also showed dose-dependent inhibition of α-amylase and β-glucosidase enzymes, indicating antidiabetic potential. Furthermore, cytotoxic studies revealed selective anticancer activity through induction of apoptosis and cell cycle arrest. Isolation and characterization of bioactive compounds confirmed the presence of pharmacologically important metabolites such as stictic acid, constictic acid, and anthraquinone derivatives. Overall, the findings suggest that lichens are a rich and underexplored source of natural bioactive compounds with promising therapeutic applications in modern medicine.