Artificial Intelligence (AI) to the Rescue: Deploying Machine Learning to Bridge the Biorelevance Gap in Antioxidant Assays.

Oxidative stress induced by excessive levels of reactive oxygen species (ROS) underlies several diseases. Therapeutic strategies to combat oxidative damage are, therefore, a subject of intense scientific investigation to prevent and treat such diseases, with the use of phytochemical antioxidants, especially polyphenols, being a major part. Polyphenols, however, exhibit structural diversity that determines different mechanisms of antioxidant action, such as hydrogen atom transfer (HAT) and single-electron transfer (SET). They also suffer from inadequate in vivo bioavailability, with their antioxidant bioactivity governed by permeability, gut-wall and first-pass metabolism, and HAT-based ROS trapping. Unfortunately, no current antioxidant assay captures these multiple dimensions to be sufficiently "biorelevant," because the assays tend to be unidimensional, whereas biorelevance requires integration of several inputs. Finding a method to reliably evaluate the antioxidant capacity of these phytochemicals, therefore, remains an unmet need. To address this deficiency, we propose using artificial intelligence (AI)-based machine learning (ML) to relate a polyphenol's antioxidant action as the output variable to molecular descriptors (factors governing in vivo antioxidant activity) as input variables, in the context of a biomarker selectively produced by lipid peroxidation (a consequence of oxidative stress), for example F2-isoprostanes. Support vector machines, artificial neural networks, and Bayesian probabilistic learning are some key algorithms that could be deployed. Such a model will represent a robust predictive tool in assessing biorelevant antioxidant capacity of polyphenols, and thus facilitate the identification or design of antioxidant molecules. The approach will also help to fulfill the principles of the 3Rs (replacement, reduction, and refinement) in using animals in biomedical research.

Oxidative stress in neurodegeneration and available means of protection.

Substantial pieces of direct and indirect evidence have mounted over the years linking the induction of oxidative stress to a plethora of disease conditions, not least those associated with the death of neurons. The causal relationship between oxidative damage and neurodegeneration is, however, not yet clear and still a subject of intense investigation. Nevertheless, the phenomenon of oxidative neuronal death has received considerable attention in a frantic search for efficacious therapies for the management of neurological and neurodegenerative conditions. The redox-active nature of reactive oxygen species (ROS), which in their excessive levels induce oxidative stress, the prevalence of ROS production in biological systems, the complexity of interrelationships among these species, and the context-dependent adequacy and resilience of the antioxidant defense systems are some of the challenges that basic research has to grapple with to advance successfully to the translational stage. Much still has to be understood for research efforts in this field to yield enduring therapies. In this review, we examine the nature (chemistry) of ROS, the relationships between them, their physiological functions, the roles of oxidative stress in neurodegeneration, the mechanisms of cell death induced by oxidant species, and the available means of protecting neurons against oxidative damage.