Comparative Metabolite Profile, Biological Activity and Overall Quality of Three Lettuce (Lactuca sativa L., Asteraceae) Cultivars in Response to Sulfur Nutrition

Abstract

The main objective of the present study was to assess the effects of sulfur (S) nutrition on plant growth, overall quality, secondary metabolites, and antibacterial and radical scavenging activities of hydroponically grown lettuce cultivars. Three lettuce cultivars, namely, Pazmanea RZ (green butterhead, V1), Hawking RZ (green multi-leaf lettuce, V2), and Barlach RZ (red multi-leaf, V3) were subjected to two S-treatments in the form of magnesium sulfate (+S) or magnesium chloride (−S). Significant differences were observed under −S treatments, especially among V1 and V2 lettuce cultivars. These responses were reflected in the yield, levels of macro- and micro-nutrients, water-soluble sugars, and free inorganic anions. In comparison with the green cultivars (V1 and V2), the red-V3 cultivar revealed a greater acclimation to S starvation, as evidenced by relative higher plant growth. In contrast, the green cultivars showed higher capabilities in production and superior quality attributes under +S condition. As for secondary metabolites, sixteen compounds (e.g., sesquiterpene lactones, caffeoyl derivatives, caffeic acid hexose, 5-caffeoylquinic acid (5-OCQA), quercetin and luteolin glucoside derivatives) were annotated in all three cultivars with the aid of HPLC-DAD-MS-based untargeted metabolomics. Sesquiterpene lactone lactucin and anthocyanin cyanidin 3-O-galactoside were only detected in V1 and V3 cultivars, respectively. Based on the analyses, the V3 cultivar was the most potent radical scavenger, while V1 and V2 cultivars exhibited antibacterial activity against Staphylococcus aureus in response to S provision. Our study emphasizes the critical role of S nutrition in plant growth, acclimation, and nutritional quality. The judicious-S application can be adopted as a promising antimicrobial prototype for medical applications.

Selenium Enrichment of Green and Red Lettuce and the Induction of Radical Scavenging Potential

“…The foliar application at a concentration of 0.119 mg plant −1 (Se2) accumulated 4.1-4.9 μg Se g −1 DM in the green lettuce (V1), and 3.3-4.7 μg Se g −1 DM in the red lettuce (V2). This is consistent with our recently published findings [21], where the green multi-leaf lettuce (V1) demonstrated superior crop productivity compared to the red multi-leaf (V2).…”

“…The lowest recorded yield, DM, and number of leaves were observed in the red lettuce (V2) grown under Se3 level in comparison to green lettuce (V1) grown under Se3 treatment (Figure 2A-C). This is consistent with our recently published findings [21], where the green multileaf lettuce (V1) demonstrated superior crop productivity compared to the red multi-leaf (V2).…”

“…The concentrations of Se in addition to macronutrients (magnesium, Mg; phosphorus, P; potassium, K, and calcium, Ca) as well as micronutrients (iron, Fe; manganese, Mn; Copper, Cu; zinc, Zn) were performed by inductively coupled plasma mass spectrometry (ICP-MS; Agilent Technologies 7700 Series, Böblingen, Germany) in accordance with DIN EN ISO17294-2 (Deutsches Institut für Normung, Berlin, Germany, 2005) as described by Abdalla et al [21]. Sulfur (S) and nitrogen (N) concentrations of lettuce plants were determined by using elemental analyzer (Flash EA1112, Thermo Fisher Scientific, Milano, Italy), as described by Abdalla et al [21].…”

“…It is considered to be one of the most popular leafy vegetables, offering numerous health benefits owing to its low caloric value as well as low fat and sodium content. Additionally, it is a good source of vitamin C, fiber, iron, and folate [21].…”

In vitro propagation, lactucin quantification, and antibacterial activity of Indian lettuce (Lactuca indica L.)

“…The leaf extract, which contained a low lactucin concentration, showed weaker or no antibacterial activity. Thus, the antibacterial activity of the tissue extracts could be attributed to the presence of lactucin; however, as reported by previous studies, diverse sesquiterpenoids, phenolic, flavonoids, and minerals are also present in the crude extract and could potentially have an antibacterial effect (Nishimura et al 1986;Kim et al 2008;Michalska et al 2009;Kim and Yoon 2014;Padilla-Gonzalez et al 2016;Ha et al 2017;Abdalla et al 2021). A previous study by Pavlović et al (2011) showed that the extracts of Lactuca sativa grown in greenhouses showed high antibacterial activity against various bacterial strains, particularly against Staphylococcus aureus and Proteus mirabilis.…”