Screening the Key Region of Sunlight Regulating the Flavonoid Profiles of Young Shoots in Tea Plants (Camellia sinensis L.) Based on a Field Experiment

Both UV and blue light have been reported to regulate the biosynthesis of flavonoids in tea plants; however, the respective contributions of the corresponding regions of sunlight are unclear. Additionally, different tea cultivars may respond differently to altered light conditions. We investigated the responses of different cultivars (‘Longjing 43’, ‘Zhongming 192’, ‘Wanghai 1’, ‘Jingning 1’ and ‘Zhonghuang 2’) to the shade treatments (black and colored nets) regarding the biosynthesis of flavonoids. For all cultivars, flavonol glycosides showed higher sensitivity to light conditions compared with catechins. The levels of total flavonol glycosides in the young shoots of different tea cultivars decreased with the shade percentages of polyethylene nets increasing from 70% to 95%. Myricetin glycosides and quercetin glycosides were more sensitive to light conditions than kaempferol glycosides. The principal component analysis (PCA) result indicated that shade treatment greatly impacted the profiles of flavonoids in different tea samples based on the cultivar characteristics. UV is the crucial region of sunlight enhancing flavonol glycoside biosynthesis in tea shoots, which is also slight impacted by light quality according to the results of the weighted correlation network analysis (WGCNA). This study clarified the contributions of different wavelength regions of sunlight in a field experiment, providing a potential direction for slightly bitter and astringent tea cultivar breeding and instructive guidance for practical field production of premium teas based on light regimes.

Phenolic Profile by HPLC-PDA-MS of Greek Chamomile Populations and Commercial Varieties and Their Antioxidant Activity

The phenolic profile of Greek chamomile populations was investigated by HPLC-PDA-MS. For comparison, three commercial varieties (Banatska, Lutea and Goral) cultivated under the same conditions were included in the study. All samples exhibited similar qualitative patterns but differed in their quantitative characteristics. Overall, 29 constituents were detected, belonging to phenolic acids, flavonol glycosides, flavone glycosides (mainly apigenin derivatives) and acylated polyamines. Quantitative results showed that both Greek populations had a high content in apigenin derivatives (0.39 and 0.31 %w/w) and caffeoylquinic acids (0.96 and 0.81 %w/w), whereas they had the highest amount of flavonol glycosides among the tested samples. Greek populations were comparable to the Banatska variety, while they were superior to the Lutea and Goral varieties cultivated under the same conditions. Results demonstrate that Greek chamomile populations studied here, are an excellent source of a wide range of phenolics which contribute to the medicinal and antioxidant properties of this herbal remedy. Antioxidant tests showed that chamomile extracts from the studied materials, especially from the Greek populations possess antioxidant activity, corresponding to their polyphenol content. This is the first report on the phenolic constituents of Matricaria recutita growing in Greece and well-established chamomile varieties.

Effects of Light Intensity and Spectral Composition on the Transcriptome Profiles of Leaves in Shade Grown Tea Plants (Camellia sinensis L.) and Regulatory Network of Flavonoid Biosynthesis

Black net shade treatment attenuates flavonoid biosynthesis in tea plants, while the effect of light quality is still unclear. We investigated the flavonoid and transcriptome profiles of tea leaves under different light conditions, using black nets with different shade percentages, blue, yellow and red nets to alter the light intensity and light spectral composition in the fields. Flavonol glycosides are more sensitive to light intensity than catechins, with a reduction percentage of total flavonol glycosides up to 79.6% compared with 38.7% of total catechins under shade treatment. A total of 29,292 unigenes were identified, and the KEGG result indicated that flavonoid biosynthesis was regulated by both light intensity and light spectral composition while phytohormone signal transduction was modulated under blue net shade treatment. PAL, CHS, and F3H were transcriptionally downregulated with light intensity. Co-expression analysis showed the expressions of key transcription factors MYB12, MYB86, C1, MYB4, KTN80.4, and light signal perception and signaling genes (UVR8, HY5) had correlations with the contents of certain flavonoids (p < 0.05). The level of abscisic acid in tea leaves was elevated under shade treatment, with a negative correlation with TFG content (p < 0.05). This work provides a potential route of changing light intensity and spectral composition in the field to alter the compositions of flavor substances in tea leaves and regulate plant growth, which is instructive to the production of summer/autumn tea and matcha.

Characterization and profiling of polyphenolics of Brassica microgreens by LC-HRMS/MS and the effect under LED light

An untargeted approach to profiling of polyphenolics of Brassicaceae microgreens was employed to characterize the phenolic composition in microgreens grown under 8 different treatments of combined amber (590 nm), blue (455 nm), and red (655 nm) LED, using full MS and HRMS/MS-ESI. Hydroxycinnamic acid (HCA) derivatives predominated the pool of phenolics in the microgreens, followed by free phenolic acids and flavonol glycosides/acylglycosides, with most of the HCA derivatives existing as malate esters. Most HCA malates in mustard (Barbarossa) and all HCA malates in mizuna (red kingdom)/ radish (red Rambo, organic) were significantly decreased under most treatments, whereas all malates were overall increased under combined lighting in radish (red Rambo), mustard (Garnet Giant), mizuna (organic), Pac choi (red Pac) and mustard (Scarlet Frills). The present study demonstrated that amber in combination with blue and red LED contributed to the altered phenolic profile and increase and/or decrease in quantity of certain phenolic compounds, particularly the HCA malates.