Biological and pharmacological aspects of tannins and potential biotechnological applications

•Polyphenols have several applications, such as medical, environmental, and industrial.•Tannins can prevent conditions such as neurodegenerative diseases.•Polyphenols and tannins influence the gut microbiota.•Tannins have several biotechnological applications, such as removing contaminations.•Tannins have direct application in the wine industry. Secondary metabolites are divided into three classes: phenolic, terpenoid, and nitrogenous compounds. Phenolic compounds are also known as polyphenols and include tannins, classified as hydrolysable or condensed. Herein, we explored tannins for their ROS reduction characteristics and role in homeostasis. These activities are associated with the numbers and degree of polymerisation of reactive hydroxyl groups present in the phenolic rings of tannins. These characteristics are associated with anti-inflammatory, anti-aging, and anti-proliferative health benefits. Tannins can reduce the risk of cancer and neurodegenerative diseases, such as cardiovascular diseases and Alzheimer's, respectively. These biomolecules may be used as nutraceuticals to maintain good gut microbiota. Industrial applications include providing durability to leather, anti-corrosive properties to metals, and substrates for 3D printing and in bio-based foam manufacture. This review updates regarding tannin-based research and highlights its biological and pharmacological relevance and potential applications.