Tetrahydrocurcuminoids as potential antioxidants for biodiesels

• Tetrahydrocurcuminoids (THCs) as potential antioxidant additives for biodiesels.
• Increase in induction period values of biodiesels with low oxidation stability.
• One THC derivative presented superior performance than curcumin.
• Comparable results with TBHQ as antioxidant for cottonseed oil methyl biodiesels.
• THCs are colorless and thus more attractive for market acceptance.

This work demonstrates the potential use of tetrahydrocurcuminoids (THCs) as natural antioxidants to enhance the oxidation stability of biodiesels. Fatty acid methyl esters produced from cottonseed and residual cooking oils were doped with three different THCs, curcumin and synthetic antioxidants for comparison. The THC derivative with a phenol group in meta-position of the linking chain and a neighboring methoxy group provided higher oxidation stability (induction period values) in both biodiesels in comparison with other THCs and curcumin. Moreover, this THC derivative presented better efficiency than butylated hydroxytoluene in one of the studied biodiesels. This result is in agreement with antioxidant activity data for the three TCHs and curcumin reported in the literature. Additionally, THCs are colorless (instead of curcumin) which increases the market acceptance of such additives for biodiesel.