Fourteen saxicolous lichens from trans-Himalayan Ladakh region were identified by morpho-anatomical and chemical characteristics. The
n-hexane,
methanol and water extracts of the lichens were evaluated for their
antioxidant capacities. The lichen extracts showing high
antioxidant capacities and rich phenolic content were further investigated to determine their cytotoxic activity on human HepG2 and RKO
carcinoma cell lines. The ferric reducing
antioxidant power (FRAP), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium
salt (
ABTS),
1,1-diphenyl-2-picrylhydrazyl (DPPH) and
nitric oxide (NO) radical scavenging capacities and β-
carotene-
linoleic acid bleaching property exhibited analogous results where the lichen extracts showed high
antioxidant action. The lichen extracts were also found to possess good amount of total
proanthocyanidin,
flavonoid and
polyphenol. The methanolic extract of Lobothallia alphoplaca exhibited highest FRAP value. Methanolic extract of Xanthoparmelia stenophylla showed the highest
ABTS radical scavenging capacity. The
n-hexane extract of Rhizoplaca chrysoleuca exhibited highest DPPH radical scavenging capacity. Highest
antioxidant capacity in terms of β-
carotene linoleic acid bleaching property was observed in the water extract of Xanthoria elegans. Similarly, Melanelia disjuncta water extract showed highest NO scavenging capacity. Among
n-hexane,
methanol and water extracts of all lichens, the methanolic extract of Xanthoparmelia mexicana showed highest total
proanthocyanidin,
flavonoid and
polyphenol content. From cytotoxic assay, it was observed that the methanolic extracts of L. alphoplaca and M. disjuncta were exhibiting high cytotoxic effects against
cancer cell growth. Similarly, the water extract of Dermatocarpon vellereum, Umbilicaria vellea, X. elegans and M. disjuncta and the methanolic extract of M. disjuncta and X. stenophylla were found to possess high
antioxidant capacities and were non-toxic and may be used as natural
antioxidants for stress related problems. Our studies go on to prove that the unique trans-Himalayan lichens are a hitherto untapped bioresource with immense potential for discovery of new chemical entities, and this biodiversity needs to be tapped sustainably.