Malic acid is a tart-tasting organic dicarboxylic acid that plays a role in many sour or tart foods. Apples contain malic acid which contributes to the sourness of a green apple. Malic acid can make a wine taste tart although the amount decreases with increasing fruit ripeness.

Atranorin shows significant antinociceptive and antiinflammatory activities, it has a relevant redox-active action, acting as a pro-oxidant or antioxidant agent depending on the radical.

4-Hydroxynonenal (4-HNE) is an oxidative/nitrosative stress biomarker. It is a substrate and an inhibitor of acetaldehyde dehydrogenase 2 (ALDH2).