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- Shcherbakova, A., et al.
(författare)
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Antimicrobial and antioxidant activity of Evernia prunastri extracts and their isolates
- 2021
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Ingår i: World Journal of Microbiology & Biotechnology. - : Springer. - 0959-3993 .- 1573-0972. ; 37:8
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Tidskriftsartikel (refereegranskat)abstract
- Lichens are symbiotic organisms formed by a fungus and one or more photosynthetic partners which are usually alga or cyanobacterium. Their diverse and scarcely studied metabolites facilitate adaptability to extreme living conditions. We investigated Evernia prunastri (L.) Ach., a widely distributed lichen, for its antimicrobial and antioxidant potential. E. prunastri was sequentially extracted by hexane (Hex), dichloromethane (DCM) and acetonitrile (ACN) that were screened for their antioxidant and antimicrobial (against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans) activities. The Hex extract possessed the highest antioxidant capacity (87 mg ascorbic acid/g extract) corresponding to the highest content of phenols (73 mg gallic acid/g extract). The DCM and Hex extracts were both active against S. aureus (MICs of 4 and 21 mu g/ml, respectively) but were less active against Gram-negative bacteria and yeast. The ACN extract exhibited activity on both S. aureus (MIC 14 mu g/ml) and C. albicans (MIC 38 mu g/ml) and was therefore further fractionated by silica gel column chromatography. The active compound of the most potent fraction was subsequently characterized by H-1 and C-13-NMR spectroscopy and identified as evernic acid. Structural similarity analyses were performed between compounds from E. prunastri and known antibiotics from different classes. The structural similarity was not present. Antioxidant and antimicrobial activities of E. prunastri extracts originate from multiple chemical compounds; besides usnic acid, most notably evernic acid and derivatives thereof. Evernic acid and its derivatives represent possible candidates for a new class of antibiotics.
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- Staples, Richard, et al.
(författare)
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Structure and Chemical Analysis of Major Specialized Metabolites Produced by the Lichen Evernia prunastri
- 2020
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Ingår i: Chemistry and Biodiversity. - : Wiley. - 1612-1872 .- 1612-1880. ; 17:1
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Tidskriftsartikel (refereegranskat)abstract
- We performed comparative profiling of four specialized metabolites in the lichen Evernia prunastri, collected at three different geographic locations, California and Maine, USA, and Yoshkar Ola, Mari El, Russia. Among the compounds produced at high concentrations that were identified in all three specimens, evernic acid, usnic acid, lecanoric acid and chloroatranorin, evernic acid was the most abundant. Two depsidones, salazinic acid and physodic acid, were detected in the Yoshkar‐Ola collection only. The crystalline structure of evernic acid (2‐hydroxy‐4‐[(2‐hydroxy‐4‐methoxy‐6‐methylbenzoyl)oxy]‐6‐methylbenzoate) (hmb) revealed two crystallographically and conformationally distinct hmb anions, along with two monovalent sodium atoms. One hmb moiety contained an exotetradentate binding mode to sodium, whereas the other exhibited an exohexadentate binding mode to sodium. Embedded edge‐sharing {Na2O8}n sodium‐oxygen chains connected the hmb anions into the full three‐dimensional crystal structure of the title compound. The crystal used for single‐crystal X‐ray diffraction exhibited non‐merohedral twinning. The data suggest the importance of the acetyl‐polymalonyl pathway products to processes of maintaining integrity of the lichen holobiont community.
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