Long Chain Alkyl Esters of Hydroxycinnamic Acids

1 Long Chain Alkyl Esters of Hydroxycinnamic Acids 

Long chain alkyl esters of ferulic acid are common constituents in the family. From the seeds of Hyoscyamus niger even a diester, 1,24-tetracosanediol diferulate could be isolated (Ma et al. 2002). Solanum tuberosum started to accumulate long chain alkyl (mono)esters three to seven days after wound treatment. The alcohol components ranged from hexadecyl (Cj Hjj) to octacosyl (C gHj,) all even numbers plus two esters of odd chain length alkanols [nonadecyl (Cj Hj ), heneicosyl (C jH j)]. The major metabolites were represented by hexadecyl and octadecyl ferulates. The authors suppose that the formation of all these ferulates is temporally and spatially correlated with suberin formation since they were restricted to the wound periderm (Bernards and Lewis 1992). For a coherent account of suberin chemistry interested readers are directed to a review on the macromolecular aromatic domain in suberized tissues (Bernards and Lewis 1998). 

Straight-chain eicosanyl congeners could be characterized, though in much lower concentration than their C, and C,g homologues (Jenett-Sians 1996). Octadecyl caflfeate was isolated from the roots of Metremia tuberosa and a branched isomer, 6-methyl-heptadecyl caffeate, from the roots of M. dissecta (Garcm-Aig ez et al. 1999). 

Cuscutin, a metabolite of the holoparasitic Cuscuta lehmanniana Bge. growing on elms (Ulmus L., Ulmaceae), turned out be an ester with an unusual substitution pattern in its acyl residue, namely hexadecyl 3,5-dihydroxycinnamate (Fig. 6.3). This metabolite could not be detected in the host (Kamilov and Nikonov 1977). Snch a rare 3,5-dihydroxycinnamoyl moiety is also present in an anthocyanin of Ipomoea asarifolia (Table 6.1). 

For acylation of monosaccharide (glucose) units in the carbohydrate chain of anthocyanins with HCA as well as glycosidic linkages to phenolic hydroxy groups of HCA see Sect. 6.7.3. 

---