A review on bacteria-derived antioxidant metabolites: their production, purification, characterization, potential applications, and limitations

Abstract

Antioxidants are organic molecules that scavenge reactive oxygen species (ROS) and reactive nitrogen species (RNS), thereby maintaining cellular redox balance in living organisms. The human body synthesizes endogenous antioxidants, whereas humans obtain exogenous antioxidants from other organisms such as plants, animals, fungi, and bacteria. This review primarily focuses on the antioxidant potential of natural metabolites and extracts from five major bacterial phyla, including the well-studied Actinobacteria and Cyanobacteria, as well as less-studied Bacteroides, Firmicutes, and Proteobacteria. The literature survey revealed that the metabolites and the extracts with antioxidant activity can be obtained from bacterial cells and their culture supernatants. The metabolites with antioxidant activity include pigments, phycobiliproteins, polysaccharides, mycosporins-like amino acids, peptides, phenolic compounds, and alkaloids. Both metabolites and extracts demonstrate in vitro antioxidant capacity through radical-scavenging, metal-reducing, and metal-chelating activity assays. In in vivo models, they can scavenge ROS and RNS directly and/or indirectly eliminate them by enhancing the activities of antioxidant enzymes, such as catalase, superoxide dismutase, and glutathione peroxidase. Due to their antioxidant activities, they may find applications in the cosmetic industry as anti-aging agents for the skin and in medicine as drugs or supplements for combating oxidative stress-related disorders, such as neurodegenerative diseases and diabetes. The literature survey also elucidated that some metabolites and extracts with antioxidant activity also exhibited strong antimicrobial properties. Therefore, we consider that they may have future applications in the treatment of infectious diseases, the preparation of pathogen-free healthy foods, and the extension of food shelf life.

Keywords: Actinobacteria; Cyanobacteria; Proteobacteria; Exogenous antioxidants; Natural metabolites; Oxidative stress.

Fig. 1

The role of antioxidants against oxidative stress. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are produced endogenously by various cellular organelles, including mitochondria, chloroplasts, endoplasmic reticulum, lysosomes, cytoplasm, and plasma membranes, as well as by external factors such as ionizing radiation, smoking, drugs, and heavy metals. An adequate level of ROS and RNS, namely a good redox balance, is essential for various cellular mechanisms. On the contrary, the excess accumulation of ROS and RNS, namely oxidative stress, damages cellular molecules (nucleic acids, membranes, proteins, carbohydrates, and lipids) and tissues. In humans, endogenous and exogenous antioxidants scavenge ROS and RNS molecules, thereby maintaining cellular redox homeostasis

Fig. 2

Production, extraction, purification, characterization, and biological activities of bacterial metabolites. Some bioactive metabolites are extracted from bacterial cells, while others are extracted from culture supernatants of bacteria. The chemical characterization of the purified metabolites or the extracts containing these metabolites was performed using the apparatus such as high-performance liquid chromatograph (HPLC), ultraviolet–visible spectrophotometry (UV–VIS), fourier transform infrared spectroscopy (FTIR), gas chromatography–mass spectrometry (GC–MS), and liquid chromatography–mass spectrometry (LC–MS). The culture supernatants, extracts, and purified metabolites of bacteria exhibit diverse bioactive properties, including antioxidant, anticancer, antibacterial, antiviral, and wound-healing activities

Fig. 3

Chemical structures of bacteria-derived metabolites with antioxidant activity

Fig. 4

In vitro and in vivo antioxidant activities of bacteria-derived metabolites and extracts. Species belonging to different bacterial phyla, including Actinobacteria, Proteobacteria, Bacteroidetes, Firmicutes, and Cyanobacteria, produce various metabolites with antioxidant activity, such as pigments, polysaccharides, peptides, phycobiliproteins, mycosporine-like amino acids, phenolic compounds, alkaloids, and benzoic acid esters. The purified metabolites or extracts containing these metabolites exhibit in vitro antioxidant activities in radical scavenging, metal-reducing, and metal-chelating assays. They show in vivo antioxidant activities by scavenging directly reactive oxygen species (ROS) and reactive nitrogen species (RNS), and/or by indirectly eliminating ROS and RNS via the enhancement of antioxidant enzyme activities