Sesquiterpene lactones (STLs) are a large group of terpenoids most commonly found in plants of the Asteraceae family, e.g., in chicory plants, displaying a wide range of interesting biological activities. However, further studies on the biological potential of chicory-derived STLs and analogues are challenging as only four of these molecules are commercially available (as analytical standards), and to date, there are no published or patented simple extraction–purification processes capable of large-scale STLs isolation. In this work, we describe a novel three-step large-scale extraction and purification method for the simultaneous purification of 11,13-dihydrolactucin (DHLc) and lactucin (Lc) starting from a chicory genotype rich in these STLs and the corresponding glucosyl and oxalyl conjugated forms. After a small-scale screening on 100 mg of freeze-dried chicory root powder, the best results were achieved with a 17 h water maceration at 30 °C. With these conditions, we managed to increase the content of DHLc and Lc, at the same time favoring the hydrolysis of their conjugated forms. On a larger scale, the extraction of 750 g of freeze-dried chicory root powder, followed by a liquid–liquid extraction step and a reversed-phase chromatography, allowed the recovery of 642.3 ± 76.3 mg of DHLc and 175.3 ± 32.9 mg of Lc. The two pure STLs were subsequently used in the context of semisynthesis to generate analogues for biological evaluation as antibacterial agents. In addition, other described chicory STLs that are not commercially available were also synthesized or extracted to serve as analytical standards for the study. In particular, lactucin-oxalate and 11,13-dihydrolactucin-oxalate were synthesized in two steps starting from Lc and DHLc, respectively. On the other hand, 11β,13-dihydrolactucin-glucoside was obtained after a MeOH/H₂O (70/30) extraction, followed by a liquid–liquid extraction step and a reversed-phase chromatography. Together, this work will help facilitate the evaluation of the biological potential of chicory-derived STLs and their semisynthetic analogues.

The main goal of our study was to find an optimal combination of tested factors to achieve lettuce rich in bioactive compounds sustaining its pleasant taste. We examined three red and three green cultivars in a greenhouse using two microbiological fertilisers (EM Aktiv and Vital Tricho), and their combination. Plants were grown in three consecutive growing seasons (autumn, winter, and spring). Lactones accumulated in autumn, whereas phenolics’ concentration rose during winter. Red cultivars showed higher phenolics and lactone content, where chicoric acid and luteolin-7-glucoside were the most abundant in the ‘Gaugin’ winter trial. Lactucopicrin was the predominant lactone among tested cultivars with the highest value in the red cultivar ‘Carmesi’. Solely applicated, the fertiliser EM Aktiv and Vital Tricho led to significantly higher phenolic acid and dihydrolactucopicrin content, while combined, there were notably increased levels of all detected lactones. Application of single fertilisers had no effect on flavonoid content, while the combination even reduced it. A sensory analysis showed a negative correlation between overall taste and total sesquiterpene lactones, lactucopicrin, caffeoylmalic, and chlorogenic acid, indicating a less bitter taste with decreasing content of these compounds. Our findings indicate that the cultivar, fertiliser, and growing season jointly affected all of the tested parameters, highlighting the differences in the application of EM Aktiv, Vital Tricho, and their combination.

Sesquiterpene lactones (STLs) are a large group of terpenoids most commonly found in plants of the Asteraceae family, e. g. in chicory plants, displaying a wide range of interesting biological activities. However, further studies on the biological potential of chicory derived STLs and analogues are challenging as only four of these molecules are commercially available (as analytical standards), and to date there are no published or patented simple extraction-purification processes capable of large scale STLs isolation. In this work we describe a novel three-step large scale extraction and purification method for the simultaneous purification of 11,13-dihydrolactucin (DHLc) and lactucin (Lc) starting from a chicory genotype rich in these STLs and in the corresponding glycosyl and oxalyl conjugated forms. After a small-scale screening on 100 mg of freeze-dried chicory root powder, the best results were achieved with a 17 h water maceration at 30°C. With these conditions we managed to increase the content of DHLc and Lc, at the same time favouring the hydrolysis of their conjugated forms. On a larger scale, the extraction of 750 g of freeze-dried chicory root powder, followed by a liquid-liquid extraction step and a reversed-phase chromatography, allowed the recovery of 642.3 ± 76.3 mg of DHLc and 175.3 ± 32.9 mg of Lc. The two pure STLs were subsequently used in the context of semi-synthesis to generate analogues for biological evaluation as antibacterial agents. In addition, other described chicory STLs that are not commercially available were also synthesized or extracted to serve as analytical standards for the study. In particular, lactucin-oxalate and 11,13-dihydrolactucin-oxalate were synthesized in two steps starting from Lc and DHLc, respectively. On the other hand, 11β,13-dihydrolactucin-glycoside was obtained after a MeOH/H2O (70/30) extraction, followed by a liquid-liquid extraction step and a reversed-phase chromatography. Together, this work will help facilitate the evaluation of the biological potential of chicory derived STLs and their semisynthetic analogues.

This study assessed the impact of biofertilisers on primary and secondary (specialised) metabolites in six lettuce cultivars (‘Kiribati’, ‘Murai’, ‘Aquino’, ‘Gaugin’, ‘Aleppo’, and ‘Carmesi’) grown in anthropogenic soil during an autumn greenhouse experiment. Four treatments were tested: control (no fertilisation), effective microorganisms (EM), Trichoderma, and their combination. Red cultivars showed higher total antioxidant capacity (TAC) and total phenolic content (TPC), with red Lollo ‘Carmesi’ having the highest TAC, TPC, carotenoids, total soluble solids, sweetness index, and sugars. Red Oak ‘Murai’ exhibited the highest chlorophyll b and total chlorophyll, while green cultivars ‘Kiribati’ and ‘Aquino’ excelled in chlorophyll a and overall taste, respectively. Biofertilisers did not affect TAC or most chlorophyll types but increased TPC (EM by 18.6% and combined treatment by 19.6%) and chlorophyll a (EM by 28.6% and Trichoderma by 23.8%). Combined fertilisers improved taste with reduced glucose and fructose content and sweetness index, though sucrose remained unchanged compared to the control. Major organic acids (malic, citric, and tartaric) were most abundant in ‘Murai’ and ‘Kiribati’, unaffected by treatments. Phenolics content peaked in ‘Murai’ and ‘Carmesi’, characterised by chicoric and chlorogenic acid, caffeoylquinic acid glucoside, and flavonoids (quercetin derivatives, kaempferol); biofertilisers mainly influenced gallic acid, while kaempferol was affected by all biofertilisers and increased in the range of 12.5–25%. The key sesquiterpene lactones identified were lactucin, lactucopicrin-15-oxalate, and 11β,13-dihydrolactucin. The content of sesquiterpene lactones analysed in this study increased significantly, especially with EM treatment (14.7–185.7%) and combined fertilisers (12.5–128.6%), highlighting the lactone-rich cultivars ‘Carmesi’ and ‘Gaugin’. Red cultivars ‘Carmesi’ and ‘Murai’ exhibited the most favourable phytochemical profiles, suitable for cultivation and processing of quality-based products. In contrast, the green cultivar ‘Aquino’ received the highest sensory scores, delivering the most appealing overall taste despite its lower metabolite content. EM treatment and combined fertilisers are recommended for increasing chlorophyll a, myo-inositol, TSS, propionic acid, TPC, kaempferol, and major lactones under greenhouse autumn conditions.

In this study, we explore the use of the immobilized lipase Novozym 435 in the selective acylation of chicory sesquiterpene lactones (STLs) - lactucin (Lc), 11β,13-dihydrolactucin (DHLc), lactucopicrin (Lp), and 11β,13-dihydrolactucopicrin (DHLp) - using aliphatic vinyl esters as acyl donors. Despite the scarcity of these STLs due to their challenging extraction process and high cost, our results demonstrate the broad applicability and very high efficiency of this method. Furthermore, this methodology enables the selective acylation of the primary alcohol without transesterifying the existing ester in the substrates (Lp and DHLp). We also describe the enzyme-substrate binding modes in the acylation reactions with STLs, as well as the nature of their interactions with crucial amino acid residues at the active site, providing further insight into the potential of this approach. This study forms a foundation for the tailored functionalization of STLs, offering possibilities for the synthesis of STL derivatives with significant potential applications as pharmaceuticals or biocontrol agents.