Toxic essential oils. Part III: Identification and biological activity of new allylmethoxyphenyl esters from a Chamomile species (Anthemis segetalis Ten.)

To determine the exact structure of previously tentatively identified minor essential-oil constituents of a Chamomile species (Antemis segetalis Ten. (Asteraceae)), we have synthesized a small combinatorial library of 54 regioisomeric allylmethoxyphenyl pentanoates and 2-pentenoates (49 completely new compounds). GC–MS in combination with 1D- and 2D-NMR analyses of the library compounds provided unambiguous data that led to a straightforward identification of the mentioned A. segetalis constituents as eugenyl angelate, 2-methylbutanoate and 3-methylbutanoate (0.21, 0.22, and 0.13 mg/100 g of fresh plant material, respectively). To assess the safety and potential beneficial pharmacological uses of these naturally occurring esters and several other library compounds (these were tested to provide relevant data for a SAR (structure–activity relationship) analysis), we have studied the effect of these compounds in several models of toxicity (acute toxicity against Artemia salina, cytotoxicity against two cell lines (fibroblast and melanoma)), as well as their acetylcholinesterase inhibitory and antibacterial activities. Anthemis segetalis constituents showed low to moderate activity in all tests. The obtained results suggest that the intake of these compounds in naturally available amounts, on their own, would probably not represent a risk to human health but the possible adverse interactions with the plant matrix should not be neglected.