Nanoemulsion design of Cynara cardunculus leaves extract rich in sesquiterpene lactones

Background A Cynara cardunculus leaf extract enriched in sesquiterpene lactones (CcLERSLs) exhibited strong phytotoxic activity, notably inhibiting weed root growth. However, the poor water solubility limits practical application. This study aimed to develop and optimize an oil‐in‐water nanoemulsion containing CcLERSLs, using grape seed oil as carrier, and pectin and Tween®80 as emulsifiers. Ultrasound‐assisted emulsification and response surface methodology were applied to optimize droplet size, stability and bioavailability. Phytotoxicity and storage stability were evaluated. Results Models for droplet size and zeta‐potential identified ultrasound amplitude and Tween®80 content as significant variables, respectively. Model validation confirmed high predictive accuracy, particularly for droplet size, and this guided the formulation of the CcLERSLs nanoemulsion (5% w/w GSO, 4% Tween® 80, 1% pectin, 80% ultrasound amplitude). Phytotoxicity against Portulaca oleracea , Plantago lanceolata and Phalaris arundinacea showed a ≥3‐fold increase in activity compared with the crude extract, particularly for root inhibition. P. oleracea was the most sensitive and the nanoemulsion outperformed the commercial herbicide at 400–800 ppm. The nanoemulsion remained physically stable at 4 and 25 °C for 90 days but degraded significantly at 45° C. Conclusions Nanoemulsion formulation enhances bioavailability of the CcLERSLs and significantly improves its phytotoxic activity, supporting its potential as a promising natural herbicide.