Determination of tocopherol and tocotrienol content of Greek barley varieties under conventional and organic cultivation techniques using validated reverse phase high-performance liquid chromatography method

BACKGROUND: Tocotrienols and tocopherols (tocols) are important phytochemical compounds with antioxidant activity and potential benefits for human health. Among cereals, barley is a good source of tocols. In the present study the effect of two cultivation methods, organic and conventional, on the tocol content in 12 Greek barley varieties was investigated. A validated reverse phase high-performance liquid chromatography method (RP-HPLC) with fluorescence detection (excitation at 292 nm, emission at 335 nm) was applied along with direct solvent extraction with acetonitrile at a 1:30 (w/v) sample/solvent ratio for tocol quantification. RESULTS: The results showed statistically significant differences (P < 0.05) between the two cultivation methods (except for delta-tocopherol) as well as among varieties. In the case of organic cultivation the four homologues of tocotrienol (alpha-, beta + gamma- and delta-) increased, by 3.05-37.14% for a-tocotrienol, 15.51-41.09% for (beta + gamma)-tocotrienol and 30.45-196.61% for delta-tocotrienol, while those of tocopherol (alpha- and beta + gamma- but not delta-) decreased, by 5.90-36.34% for alpha-tocopherol and 2.84-46.49% for (beta + gamma)-tocopherol. A simple correlation analysis between tocols revealed a good correlation between (beta + gamma)-tocotrienol and delta-tocotrienol. Although there was a significant decrease in the important alpha-tocopherol in the varieties studied under organic cultivation, there was an overall increase in tocotrienol content. CONCLUSION: The cultivation method (organic or conventional) had an important effect on tocotrienol and tocopherol concentrations in barley. An overall increase in total tocol content and a clear increment in the tocotrienol/tocopherol ratio were observed. (C) 2012 Society of Chemical Industry