Influence of preharvest and postharvest practices in lettuce bioactive compounds, ... and more

Lettuce is one of the most commonly consumed leafy vegetables worldwide and is available throughout the entire year. Lettuce is also a significant source of natural phytochemicals. These compounds, including glycosylated flavonoids, phenolic acids, carotenoids, the vitamin B groups, ascorbic acid, tocopherols, and sesquiterpene lactones, are essential nutritional bioactive compounds. This review aims to provide a comprehensive understanding of the composition of health-promoting compounds in different types of lettuce, the potential health benefits of lettuce in reducing the risks of chronic diseases, and the effect of preharvest and postharvest practices on the biosynthesis and accumulation of health-promoting compounds in lettuce. The paper, by Xiao Yang, Mar?aI Gil, Qichang Yang & Francisco A Tom?s-Barber?n, reviews the available information about biactive compounds, and analyzes the impact of pre and postharvest practices. The paper is available for free. In relation to the main nutrients:- Increasing evidence indicates that lettuce genotypes may contain varied TPC and levels of specific phenolic compounds. - The primary carotenoids found in lettuce are ?-carotene, ?-cryptoxanthin, and lutein, although their concentrations vary across varieties (Table 5). Romaine lettuce had the highest content of lutein and ?-carotene, while crisphead lettuce contained the lowest contents; the amount of ?-cryptoxanthin varied from 2.57 mg/100 g FW in ?Lollo verde? to 10.46 mg/100 g FW in ?Red salanova? as indicated in Table 5. Additionally, neoxanthin, violaxanthin, zeaxanthin, and lactucaxanthin have been detected in lettuce. - Lettuce is the primary dietary source of sesquiterpene lactones due to its high level of consumption. Oxalate and sulfate conjugates of lactucin, deoxylactucin, and lactucopicrin are the main sesquiterpene lactones primarily found in the laticifer of lettuce leaves, stems, and flowering heads (Figure 2) and are mainly released in response to various stresses (Sessa et al., 2000). These compounds have been reported to exert potential antiobesity and antimalaria effects - The vitamin B complex is a group of eight water-soluble B vitamins that are required in cellular metabolism. Folate (vitamin B9) has been extensively documented in lettuce, which is a substantial source of folates in the diet. The three primary forms of folates found in butterhead, romaine, looseleaf, and crisphead lettuce were tetrahydrofolate, 5-methyl-tetrahydrofolate, and 5-formyl-tetrahydrofolate (Johansson et al., 2007). Folates serve as donors and acceptors in one-carbon metabolism and are involved in the biosynthesis of nucleotides, amino acids, formyl-methionyl tRNA, and pantothenate (Blancquaert et al., 2010). The total folate concentration varies between lettuce cultivars (Table 7). - The vitamin C content in lettuce, in particular, exhibits significant diversity in terms of leaf shape and color - About vitamin E, the ?-, and ?- tocopherols predominate in lettuce. The ?-tocopherol content of 17 cultivars ranged from 0.22 mg/100 g FW in the ?Legacy? cultivar (crisphead type) to 2.27 mg/100 g FW in the ?Salanca? cultivar (looseleaf type). Meanwhile, the ?-tocopherol content ranged from 0.09 and 0.51 mg/100 g FW. The total vitamin E content ranged from 0.33 to 1.10 mg/100 g FW. Vitamin K is a liposoluble vitamin that has been shown to decrease the risk of bone fracture, protect against CVD, and aid in blood coagulation. Phylloquinone is the primary dietary supply of vitamin K, and vegetables are the primary source of phylloquinone. In particular, lettuce is one of the most abundant vegetable sources of vitamin K in certain populations due to its high consumption levels Contents of the paper1 INTRODUCTION2 BIOACTIVE COMPOUNDS IN LETTUCE2.1 Normalization of the measurement of bioactive compounds in lettuce2.2 (Poly)phenols in lettuce2.2.1 Soluble (poly)phenols2.2.2 Bound (poly)phenols2.2.3 (Poly)phenols in different types of lettuce2.3 Terpenoids in lettuce2.3.1 Carotenoids2.3.2 Sesquiterpene lactones2.4 Vitamins in lettuce2.4.1 The vitamin B complex2.4.2 Vitamin C2.4.3 Vitamin E2.4.4 Vitamin K2.5 Bioactive compounds vary in lettuce types3 POTENTIAL BENEFITS FOR HUMAN HEALTH3.1 In vitro evidence3.1.1 Antioxidant bioactivity3.1.2 Anti-inflammatory effects3.1.3 Antidiabetic effects3.1.4 Anticancer effects3.1.5 Other effects3.2 In vivo evidence3.2.1 Preclinical studies3.2.2 Human intervention trials4 PREHARVEST APPROACHES THAT AFFECT BIOACTIVE COMPOUNDS4.1 Environmental factors4.1.1 Temperature4.1.2 Light4.2 Agricultural practices4.2.1 Cultivation systems4.2.2 Application of nitrogen fertilize4.2.3 Irrigation4.2.4 Pesticides4.2.5 Application of fungi4.2.6 Other factors4.3 Optimizing preharvest management to improve the accumulation of bioactive compounds5 POSTHARVEST APPROACHES THAT AFFECT BIOACTIVE COMPOUNDS5.1 Maturity5.2 Minimal processing5.3 Storage6 CONCLUSIONS AND FUTURE PERSPECTIVES6.1 To enable comparability, measurement units for bioactive chemicals in lettuce should be standardized6.2 The in vivo health effects of lettuce are mostly unknown and need additional investigation6.3 Innovative breeding technologies and PFALs(*) may help to improve the nutritional quality of lettuce6.4 Microbiological safety issues in lettuce (*) Plant factory with artificial light systems SourcesBioactive compounds in lettuce: Highlighting the benefits to human health and impacts of preharvest and postharvest practicesXiao Yang, Mar?aI Gil, Qichang Yang & Francisco A Tom?s-Barber?nCompr Rev Food Sci Food Saf. 2021 Dec 21. doi: 10.1111/1541-4337.12877https://pubmed.ncbi.nlm.nih.gov/34935264/ The picture is Fig. 1 of the original paper,?Illustration of the bioactive compounds in lettuce, their potential benefits for human health, as well as preharvest and postharvest practices that affect the constitution and concentrations of these health-promoting compounds