Potential and challenges of tannins as an alternative to in-feed antibiotics for farm animal production

Huang, Qianqian; Liu, Xiuli; Zhao, Guoqi; Hu, Tianming; Wang, Yuxi

Naturally occurring phenolic compounds have long been recognized as effective antioxidants (Rice-Evans et al., 1995 . The antioxidant property of tannins has wide application in food industry and medical field to prevent oxidative stress related diseases such as cardiovascular disease, cancer or osteoporosis (Hollman and Katan, 1999; Scalbert et al., 2005) . It has been shown that CT and HT of relatively high molecular weight exhibited greater antioxidant activities than simple phenolics (Hagerman et al., 1998) . The number of hydroxyl groups and the degree of polymerization of tannins are considered to be correlated with their abilities to scavenge free radicals (Ariga and Hamano, 1990 ). Tannins with the most hydroxyl groups are most easily oxidized (Hodnick et al., 1988) and therefore possess greatest antioxidant activity. Ricci et al. (2016) demonstrated that effectiveness of tannins as natural antioxidants is due to their complex combinations of reducing and redox activities, which also contributes to their abilities to scavenge radicals.