Is lecanoric acid a good antioxidant?

TL;DR: The antioxidant capacity of lecanoric acid remains uncertain due to conflicting experimental findings and the lack of a definitive mechanism. This work provides a detailed mechanistic investigation using DFT calculations and antioxidant assays, suggesting that LA is an efficient scavenger of the HO radical but exhibits weak activity against the HOO radical.

Abstract: Lecanoric acid (LA), an abundant chemical found in lichens, has demonstrated a wide range of biological activities, including anti-cancer cytotoxic, antibiotic, antimycobacterial, antiviral, and anti-hepatocarcinoma properties. The antioxidant capacity of this molecule, while inferred from certain experimental findings, is doubtful based on structural characteristics and therefore remains to be established. DFT calculations are used in this work to conduct a comprehensive evaluation of the mechanism and kinetics governing the antiradical activity of LA in lipidic and aqueous solvent environments. Although the DPPH/ABTS+ assays revealed good antioxidant activity in vitro, the modeling yielded mixed results. The data suggests that LA is an efficient scavenger of the HO radical with rate constants of 2.01 × 1010 and 2.80 × 108 M−1 s−1 in polar and lipid media, respectively, by the FHT and RAF mechanisms. However, the data also suggests that LA exhibits only weak activity against the HOO radical in all physiological environments. This is consistent with structural features that predict low activity.