Optimizing phenolic content and antioxidant activity in cardoon extracts through biostimulant application

Cynara cardunculus var . altilis DC., a Mediterranean plant of the Asteraceae family, is traditionally consumed as a vegetable and valued for its fiber content. Beyond its agronomic role, cardoon is rich in bioactive compounds, particularly phenolics, which contribute to the hepatoprotective, antidiabetic, antioxidant, anti-inflammatory, antimicrobial, and antifungal properties [ 1 ] [ 2 ]. This study investigates the effect of two biostimulant formulations, protein hydrolysate (PH) and algae-based solution (SW), on phenolic content and antioxidant activity of cultivated cardoon extracts. The genotype cv ”Bianco Avorio” (La Semiorto Sementi, Sarno, Italy) was selected for its high productivity and adaptability to floating systems [ 3 ], a technique that eliminates issues related to soil presence and allows for more precise control of nutrients. Plants were cultivated in floating raft culture in the greenhouses of “Nello Lupori” Experimental Farm, Tuscia University. Physiological parameters such as chlorophyll, anthocyanins, and flavonols were monitored throughout the cultivation period and five sampling events conducted. Extracts were obtained via maceration and by microwave-assisted extraction with an ethanol/water solution. Total phenolic content (TPC) was determined using the Folin-Ciocalteu method, while antioxidant activity was evaluated via the DPPH assay. Experimental results showed that PH-treated plants showed an increase in TPC compared to both SW-treated plants and untreated. Similarly, DPPH assay confirmed higher antioxidant activity in PH-treated extracts. These findings suggest that the application of the biostimulant PH can permit the production of extracts with distinctive features compared to others, an added value that can enhance their potential use in medicine and nutraceutical sector, but also for agricultural application. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany