Isolation and Identification of Phenolic Acids from Tobacco Leaf

A new chromatographic method utilizing the hydrogen bonding properties of Sephadex LH-20 gel in methanol / chloroform, was developed for the isolation of phenolic acids. This method was applied to the characterization of phenolic acids in flue-cured tobacco. Gel chromatography successfully isolated and concentrated the phenolic acids from other acidic substances and allowed identification and quantitation of these compounds by GC and GC-MS, as their trimethylsilyl derivatives. Compounds identified included: cis- and trans-isomers of p-coumaric, ferulic, caffeic, and sinapic acids; o-, m-, and p-hydroxybenzoic acids; o-hydroxyphenylacetic acid; 2,5- and 3,4-dihydroxybenzoic acids; and 2,3-, 2,5- and 3,4-dihydroxybenzaldehydes. Caffeic acid was the major compound, probably arising from the degradation of the chlorogenic acid of leaf. Aliphatic acids having two or more carboxyl groups were also isolated and included the following: malonic, succinic, fumaric, malic, and citric acids. A dihydroxycinnamaldehyde and a dihydroxynaphthoic acid are reported in tobacco leaf for the first time.