Eryngial: An α,β‐Unsaturated Fatty Aldehyde as the Major Phytotoxin in Spiny Coriander (Eryngium foetidum L.) Essential Oil

Weed species many times possess allelochemicals as a part of their survival strategy. These metabolites can be potential targets in search of natural phytotoxins. This study aims to evaluate the phytotoxic ability of fatty aldehyde‐rich essential oil from spiny coriander (Eryngium foetidum) leaves, also known as fitweed or spiritweed and to further identify the active phytotoxins. This oil dose‐dependently inhibited the wheatgrass coleoptile and radicle growth in multiple bioassays with half maximal inhibitory concentration (IC50) 30.6‐56.7 μg/mL, while exhibiting a less pronounced effect on the germination (IC50 181.8 μg/mL). The phytotoxicity assessment of two oil constituents identified eryngial (trans‐2‐dodecenal), exclusively major fatty aldehydic constituent as the potent growth inhibitor with IC50 in the range 20.8‐36.2 μg/mL during an early phase of wheatgrass emergence. Eryngial‐inspired screening of eleven saturated fatty aldehydes and alcohols did not find a significantly higher phytotoxic potency. In an open vessel, eryngial as the supplementation in agar medium, dose‐dependently inhibited the growth of pre‐germinated seeds of one monocot (bermudagrass) and one dicot (green amaranth) weed species with IC50 in the range 23.8–65.4 μg/mL. The current study identified eryngial, an α,β‐unsaturated fatty aldehyde of coriander origin to be a promising phytotoxic candidate for weed control.