Bioactive Metabolites from Manglicolous Lichen Ramalina leiodea (Nyl.) Nyl.

The chemical investigation of acetone extract of manglicolous lichen Ramalina leiodea yielded three known metabolites, methyl 2,6-dihydroxy-4-methyl benzoate (1), haematommic acid (2) and ethyl haematommate (3), which are reported for the first time in this species. The acetone extract and the metabolites (1-3) were screened for antioxidant activity in α,α-diphenyl-β-picrylhydrazyl, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and superoxide free radical assays, for antiinflammatory activity in pretein denaturation assay and for anticancer activity in sulforhodamine B assay on lung, head and neck, and cervical cancer cells. The results showed that compounds 2 and 3 depicted inhibitory profiles against 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) free radical with an IC50 of 40.0 and 40.5 µg/ml, respectively and caused protein denaturation with an IC50 of 435 and 403 µg/ml, respectively. Furthermore, compounds 2 and 3 exhibited a significant degree of specificity against cervical, head and neck, and lung cancer cells, while these compounds showed little toxicity against normal human mammary epithelial cell line. In summary the manglicolous lichen Ramalina leiodea possessed free radical scavenging, antiinflammatory, and anticancer activities and the main metabolites responsible for these activities could be compounds 2 and 3.