Lichen metabolites from the immobilized bionts isolated from Cladonia salzmannii. A study of their antioxidant and antimicrobial activities

Bionts isolated from Cladonia salzmannii, immobilized in calcium alginate, were used to assay their ability to produce barbatic acid and other orcinol derivatives, as well as other active soluble substances, and to test their antioxidant and antimicrobial activities. Immobilisates were supplied with sodium or calcium acetate as precursors for phenol biosynthesis. Barbatic acid was actively produced during incubation of immobilisates, although cell vitality progressively decreased on calcium acetate, producing cell plasmolysis of phycobionts. Thamnolic acid and other orcinol derivates also were secreted to the medium, the concentration of each one depending on the time of immobilization, exogenous acetate supply and the type of biont isolated. The role of lichen algae in phenolic metabolism was also studied. Antioxidant capacity of acetone and chloroform extracts of C. salzmannii was also reported (89.56 and 80.92 % oxidation inhibition, respectively). The soluble extract of the products secreted by lichen immobilisates incubated on sodium acetate during 15 days, contained only proteins and exhibited a potent antioxidant capacity (96.35%). The soluble extract of the products secreted by from fungal immobilisates during 6 and 18 days of incubation showed ranges of 90-94% inhibition. Similar values were found for the soluble extracts of algal immobilisates incubated during 8 and 11 days. On the other hand, the growth of Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae was inhibited by barbatic acid secreted from immobilisates, although organic lichen extracts showed highest antimicrobial activity due to a possible synergism between their different components. Thus, substances produced by immobilized bionts of C. salzmannii are a potential source of different natural antioxidant and antimicrobial compounds.