The effects of different night-time temperatures and cultivation durations on the polyphenolic contents of lettuce: Application of principal component analysis

Abstract

The present study was conducted to characterize the polyphenolic contents of lettuce leaves grown under different night-time temperatures (4, 12, and 20 °C) and cultivation durations (5, 15, and 20 days) using high performance liquid chromatography-tandem mass spectrometry (LC/MS/MS). The assay method was validated based on specificity, linearity, accuracy, precision, and the performance limit. The total polyphenolic contents were highest (2462.6 mg/kg) after transplantation at a night temperature of 20 °C on day 20 and lowest (1132.7 mg/kg) at the same temperature on day 5. Quantification and principal component analysis showed that the relative contents of quercetin and kaempferol were markedly higher during the early stage of cultivation (day 5) than those of day 15 and 20, and that night-time temperatures of 12 and 20 °C on day 20 were favorable for producing polyphenol-rich lettuce containing caffeic acid. In conclusion, a synergistic effect between high night-time temperatures (12 and 20 °C) and cultivation duration (20 days) produced lettuce rich in polyphenols compared to that at low temperature (4 °C).

Characterization of phenolic compounds in green and red oak‐leaf lettuce cultivars by UHPLC‐DAD‐ESI‐QToF/MS using MSE scan mode

“…A caffeoyltartaric acid (peak 10 : Rt = 9.06 min, λmax = 301, 323 nm) was detected in the extracted MS chromatogram set at m/z 311 in the negative ion mode, presenting the corresponding fragmentation pattern: The dehydrated protonated molecule at m/z 293 was the base peak in low energy function; and intense fragments of the deprotonated tartaric ( m/z 149) and caffeic ( m/z 179) acids and the losses of water ( m/z 293) and CO 2 ( m/z 135; base peak) were observed in the high energy function. Two isomers of caffeoyltartaric acid have been already reported in lettuce in literature, also in green and red oak‐leaf cultivars …”

“…Taking into account all the above considerations, the chromatographic peaks were tentatively identified as follows: 1 , trans ‐3‐CQA; 2 , trans ‐1‐CQA; 3 , trans ‐5‐CQA; 4 , cis ‐3‐CQA; 5 , trans ‐4‐CQA; 6 , cis ‐5‐CQA; and 7 , cis ‐4‐CQA. Only 3 CQA isomers had been reported previously in green lettuce, ie, 5‐CQA, 3‐CQA, and an unidentified CQA isomer, and only 5‐CQA in the red oak‐leaf cultivar trans ‐5‐CQA ( 3 ) was the major phenolic compound in both oak‐leaf cultivars, as occurs in other lettuce varieties . The following major CQAs were cis ‐5‐CQA and trans ‐3‐CQA (40% and 5% of the total intensity of trans ‐5‐CQA, respectively in the green cultivar, and about 5% for each CQA isomer in the red cultivar).…”

“…Lettuce ( Lactuca sativa L.) is one of the most popular leafy vegetables in the world, commonly consumed fresh in salad dishes. Lettuce contains several kinds of phenolic compounds: hydroxycinnamic acids being the most abundant class followed by flavonols, flavones, hydroxybenzoic acids, and anthocyanins . The contents of polyphenols in lettuce tissues are susceptible to high variations among cultivars and growing conditions; indeed anthocyanins have been only detected in red colored cultivars and isoflavones, in iceberg lettuce .…”

“…Regarding the analytical techniques used to characterized polyphenols in lettuce, high‐ or ultrahigh‐performance liquid chromatography (HPLC or UHPLC) coupled with diode array detection (DAD) and mass spectrometry (MS and MS/MS) are the most commonly used . Ultrahigh‐performance liquid chromatography achieves rapid analysis and can obtain better peak separation than HPLC and, coupled to time‐of‐flight (ToF) or quadrupole ToF (QToF) instruments, provides a highly attractive analytical technique with very high resolution and accurate mass measurements of the precursor and fragment ions .…”

Editorial: Advances and Trends in Development of Plant Factories

“…Dong et al studied soluble flavonoids and found that “Xiangfen 1” banana can be a rich source of natural antioxidants in human diets. Jeong et al (2015) characterized the polyphenolic contents of lettuce leaves grown under different night-time temperatures and cultivation. Plant-derived phenylpropanoids (PPPs) compose the largest group of secondary metabolites produced by higher plants (Korkina et al, 2011).…”