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Antioxidant activity of some lichen growing in Serbia
Lichen extracts and metabolites exert a wide variety of biological actions including antibiotic, antiviral, anti-inflammatory, antimycobacterial, analgesic, antiproliferative, antipyretic and cytotoxic effects . In this work, the lichen species namely Caloplaca schaereri (Arnold) Zahlbr, Teloschistaceae and Caloplaca dalmatica (Massal.) H. Olivier, Teloschistaceae were screened for their antioxidant activity using different assay systems . Air-dried powdered materials were successively extracted with chloroform, ethyl acetate, acetone and methanol using Soxhlet extractor for 10h each. After extractions of lichens, the main compounds were identified as 1,8-dihydroxy-6-methoxy-3-methyl-9,10-anthraquinone; 1,8-dihydroxy-3-formyl-6-methoxy-9,10-anthraquinone; 1,8-dihydroxy-3-hydroxymethyl-6-methoxy-9,10-anthraquinone; 1,3,8-trihydroxy-9,10-anthraquinone, etc. The content of anthraquinones in C.schaereri and C.dalmatica were 0.79g/100g and 0.65g/100g dried thallus, respectively. The crude extracts were screened for antioxidant activity. The percentage inhibition of linoleic acid peroxidation was determined by the thiocyanate method, at 37 oC after addition of different extracts . The antioxidant activity of these extracts on the inhibition of peroxidation of linoleic acid were found to be from 24 to 89% compared to BHT. The comparison of scavenging effects of above-mentioned lichen extracts on DPPH radical showed the consistently higher radical-scavenging activity for methanolic extracts. BHT and α-tocopherol were used as positive controls. The results of the reducing powers of different lichen extracts using the potassium ferricyanate method showed that methanol extracts of both lichens had the highest activity. The antioxidant activity of extracts was increased with an increase in concentration. The results suggested that the extracts of lichens Caloplaca schaereri and Caloplaca dalmatica could be of use as an easily accessible source of natural antioxidants in the pharmacy.
Acknowledgements: Ministry of Science and Environment of Serbia, project No 142025.
References: 1. Huneck, S. et al. (1997) Identification of lichen substances. Springer. Berlin.
2. Yen, G.C, et al. (2000) Food Chem. 70: 437–441.