Figure 5: Stepwise conversion of δ-tocotrienol to α-tocopherol: The delta-based δ-tocotrienol 125 mg was administered to well-fed subjects for pharcokinetic study. After 2 h of consumption, δ-tocotrienol was appeared , which gives rise to γ-tocotrienol, β-tocotrienol, α-tocotrienol by successive C-methylation, and further leads to successive reduction to give rise to δ-tocopherol, γ-tocopherol, β-tocopherol and α-tocopherol. The end product is α-tocopherol (vitamin) as reported for biosynthesis of tocotrienols and tocopherols [27].