Phenylpropanoid amides from the roots of Solanum melongena L. (Solanaceae)

• Sixteen phenylpropanoid amides were isolated from the roots of Solanum melongena L.
• Two phenylpropanoid amides were firstly reported from natural source.
• Two phenylpropanoid amides were isolated from the genus Solanum for the first time.
• Four phenylpropanoid amides were firstly identified from S. melongena.
• The chemotaxonomic significance of the isolates was discussed.

Phytochemical investigation of the roots of Solanum melongena L. led to the isolation of 16 phenylpropanoid amides (1–16). Their structures were identified by analysis of spectroscopic data and comparison with those reported in the literature. This is the first report of the natural occurrence of N-trans-sinapoyloctopamine (9) and N-trans-caffeoyloctopamine (10). N-trans-feruloylnoradrenline (12) and N-cis-feruloylnoradrenline (16) were isolated from the genus Solanum for the first time. Four compounds including 3-(4-hydroxyphenyl)-N-[2-(4-hydroxyphenyl)-2-methoxyethyl] acrylamide (5), 3-(4-hydroxy-3-methoxyphenyl)-N-[2-(4-hydroxyphenyl)-2-methoxyethyl] acrylamide (6), N-trans-p-coumaroylnoradrenline (11), and N-cis-p-coumaroyloctopamine (15) were firstly reported from S. melongena. The chemotaxonomic significance of these compounds was summarized.