Radical-Scavenging Activity of Orsellinates

Abstract

Lichens produce phenolic compounds, such as depsides, depsidones, dibenzofuranes, usnic acids, depsones and others. Many of them are exclusive of lichens.1) These substances, as well as their derivatives obtained by structural modification, have shown an ample variety of pharmacological activities: antibiotic, antimycobacterial, antiviral, antitumour, analgesic, antipyretic and enzyme inhibitory.2-5) Although these activities continue to be investigated, both in lichen extracts and with pure substances, a number of others have been attributed to the compounds produced by lichens, such as anti-human immunodeficiency virus (anti-HIV) 6) and anti-herpes simplex virus 1 (anti-HSV-1). 7)Numerous studies on the biological activities of phenols have indicated that these substances are also potent antioxidants and free radical scavengers. 8) Although the free radicals perform an important role in the organism, their cumulative effects can promote the initiation and/or progression of several diseases, including atherosclerosis, inflammation, cancer, cardiovascular diseases, ischaemia, aging and other degenerative diseases. [9][10][11] The antioxidants are of interest in the treatment of several cellular degenerations, and they inhibit or delay the oxidation process by blocking the initiation or propagation of oxidizing chain reactions. 12) They are also used to preserve food by retarding rancidity, discoloration, or deterioration due to autoxidation.13) Due to the importance of antioxidants, many researches have been carried out with plants of several families and with simple phenolic substances, like those of the hydroxycinnamates group and the gallic acid derivatives. [14][15][16][17] Although the lichens are an important source of phenolic substances, studies of antioxidant activity with this group are more recent, and they have been performed mainly with extracts of some species. 12,[18][19][20][21] We have investigated lichens from the "cerrado" of the Mato Grosso do Sul State, in Brazil, through the isolation, structural elucidation, structural modifications and evaluation of biological activities of phenolic substances. The lecanoric acid isolated from the lichen Parmotrema tinctorum, and the orsellinates obtained through reactions of this acid with alcohols were evaluated against Artemia salina and microorganisms. [22][23][24] In continuing our investigations, we are relating here the results of the antioxidant activity of the lecanoric acid (1), orsellinic acid (2) and the methyl (3), ethyl (4), n-propyl (5), n-butyl (6), iso-propyl (7), sec-butyl (8) and tert-butyl (9) orsellinates. With the aim of establishing a qualitative correlation structure-activity we have also included the antioxidant activity of orcinol (10), resorcinol (11) and gallic acid (12). Results and Discussion2,2-Diphenyl-1-picrylhydrazyl (DPPH) Radical-Scavenging Activity Antioxidants are closely related to their biofunctionalities, such as the reduction of chronic diseases like DNA damage, mutagenesis, carcinogenesis and inhibition of pathog...

Reducing power and radical scavenging activity of four Parmeliaceae species

“…These values are much lower than results obtained from our samples. For some of the common lichen constituents, such as orcinol and orsellinic acid, EC 50 values were 363 and 841 μg/ml respectively, [7] which is within the range of our results with the exception of the H. physodes extract. Also, our results are in agreement with the reported scavenging ability of Umbilicaria nylanderiana (400.2 μg/ml, the EC 50 values for BHT was the same as in our experiment, 19.8 μg/ml) [13].…”

“…This observation might be attributed to the presence of non-phenolic compounds, antagonistic or synergistic interactions between constituents and also distinct antioxidant activities of individual phenolics. Lopes et al [7], in studying the radical-scavenging activity of common lichen constituents, verified that phenols with hydroxyl groups that established hydrogen bonds with neighboring carbonyl groups were less active than phenols without that possibility (EC 50 for orsellinic acid was 841 μg/ml, EC 50 for orcinol 363 μg/ml, structures of orcinol and orsellinic acid are given in Figure 1). …”

“…Free radicals in the organism can promote the initiation and/or propagation of diseases, including atherosclerosis, inflammation, cancer, cardiovascular diseases, ischemia, aging and other degenerative afflictions [7]. Phenols have been recognized as potent antioxidants [8].…”

“…Phenols have been recognized as potent antioxidants [8]. Even though lichens are an important source of phenolic compounds, the number of studies considering the antioxidant properties of their extracts or isolated pure compounds are relatively rare [7,[9][10][11][12][13]. To the best of our knowledge there is no documentation of the antioxidant activities of methanol extracts of Hypogymnia physodes, Evernia prunastri, Flavoparmelia caperata or Parmelia sulcata.…”

Direct discrimination of Parmotrema tinctorum from various location by Fourier transform infrared spectroscopy

“…Among the features of P. tinctorum are, it has a large thallus, broad lobule and isidium [10]. From the early research on P. tinctorum, lecanoric acid and atranorin were being isolated and purified, and both of these compounds have antioxidant and antibacteria property respectively [11]. Furthermore, lecanoric acid and atranorin also being isolated and purified from the P. tinctorum collected from Bukit Larut, Perak [12].…”