Small molecular species present in mitochondria as, e.g. quinones and oxygen, can capture cellular electrons thus behaving as electron carriers or reactive species, supporting the fundamental process of respiration, and providing protection from pathogens. When xenobiotics penetrate living cells, their delicate redox balance can be altered by capture of cellular electrons to form temporary negative ions. The latter can give rise to the formation of reactive species via dissociative electron attachment (DEA), as observed under gas-phase or electrochemical conditions. DEA to isolated biorelevant molecules studied in vacuo with the support of in silico methods can serve as a model to predict the behaviour of these species in vivo under conditions of electron ‘leakage’ in the lipid-protein-cytosol media or in enzymatic active centres. The present review summarises the results of studies on the correlation between the biological activity of various classes of compounds and fragment species formed by DEA. The following classes of compounds are included into the present review: chlorinated organic pollutants, brominated ethers, captafol and 2,6-dichloroisonicotinic acid, atrazine and bromoxynil, non-steroidal anti-inflammatory drugs, natural polyphenolic compounds, anthralin, salicylic acid and related compounds, ascorbic acid, melatonin, tryptophan, indole and related compounds and some organic peroxides. Formation of temporary molecular anions and their decay are characterised using electron transmission spectroscopy (ETS) and DEA spectroscopy. Quantum-chemical calculations support the identification of the dissociation products. Cellular electron attachment to unnatural electron acceptors is likely to be the first step of cascade processes which constitute the molecular mechanisms of electron-driven biological processes. The fragment species detected with DEA are of importance for understanding the metabolism of xenobiotics, including side effects produced by drugs.

The electron-attaching properties of polyphenolic compound resveratrol were studied in vacuo by means of dissociative electron attachment (DEA) spectroscopy and in silico using density functional theory calculations. The most intense fragments generated by DEA to isolated resveratrol at thermal electron energy are semiquinone anions and neutral hydrogen molecules. On the basis of the present experimental and theoretical data, a new molecular mechanism for the antioxidant activity of resveratrol is presented. It is suggested that the activity of resveratrol in living cells is driven by dissociative attachment of electrons “leaked” from the respiratory chain to this polyphenolic molecule, followed by the formation of the H2 antioxidant species inside mitochondria and participation in mitochondrial energy biogenesis.