Abstract
Recent improvements in light-emitting diode (LED) technology afford an excellent opportunity to investigate the relationship between different light sources and plant metabolites. Accordingly, the goal of the present study was to determine the effect of different LED (white, blue, and red) treatments on the contents of glucosinolates (glucoiberin, gluconapin, sinigrin, gluconasturtiin, 4-methoxyglucobrassicin, 4-hydroxyglucobrassicin, glucobrassicin, and neoglucobrassicin) and phenolic compounds (4-hydroxybenzonate, catechin, chlorogenic acid, caffeate, gallate, sinapate, and quercetin) in Brassica juncea sprouts. The sprouts were grown in a growth chamber at 25 °C under irradiation with white, blue, or red LED with a flux rate of 90 μmol·m−2·s−1 and a long-day photoperiod (16 h light/8 h dark cycle). Marked differences in desulfoglucosinolate contents were observed in response to treatment with different LEDs and different treatment durations. In addition, the highest total desulfoglucosinolate content was observed in response to white LED light treatment, followed by treatment with red LED light, and then blue LED light. Among the individual desulfoglucosinolates identified in the sprouts, sinigrin exhibited the highest content, which was observed after three weeks of white LED light treatment. The highest total phenolic contents were recorded after one week of white and blue LED light treatment, whereas blue LED irradiation increased the production of most of the phenolic compounds identified, including 4-hydroxybenzonate, gallate, sinapate, caffeate, quercetin, and chlorogenic acid. The production of phenolics decreased gradually with increasing duration of LED light treatment, whereas anthocyanin accumulation showed a progressive increase during the treatment. These findings indicate that white LED light is appropriate for glucosinolate accumulation, whereas blue LED light is effective in increasing the production of phenolic compounds in B. juncea sprouts.
Highlights
Brassica juncea is an annually growing perennial herb, which belongs to the Brassicaceae family and is known as mustard green, Indian mustard, oriental mustard, leaf mustard, or Chinese mustard.This plant can grow to over 1 m in height, has erect, patent branches and is widely distributedHorticulturae 2020, 6, 77; doi:10.3390/horticulturae6040077 www.mdpi.com/journal/horticulturaeHorticulturae 2020, 6, 77 throughout Africa, Bangladesh, China, India, Japan, Korea, and Pakistan
These findings indicate that white light-emitting diode (LED) light is appropriate for glucosinolate accumulation, whereas blue LED light is effective in increasing the production of phenolic compounds in B. juncea sprouts
LED light-irradiated sprouts presented higher dry weight values than those of sprouts irradiated with blue LED light (Table 1)
Summary
Brassica juncea is an annually growing perennial herb, which belongs to the Brassicaceae family and is known as mustard green, Indian mustard, oriental mustard, leaf mustard, or Chinese mustard.This plant can grow to over 1 m in height, has erect, patent branches and is widely distributedHorticulturae 2020, 6, 77; doi:10.3390/horticulturae6040077 www.mdpi.com/journal/horticulturaeHorticulturae 2020, 6, 77 throughout Africa, Bangladesh, China, India, Japan, Korea, and Pakistan. Brassica juncea is an annually growing perennial herb, which belongs to the Brassicaceae family and is known as mustard green, Indian mustard, oriental mustard, leaf mustard, or Chinese mustard. This plant can grow to over 1 m in height, has erect, patent branches and is widely distributed. In Korea, it is used as food, both alone and as the main ingredient in kimchi, a traditional fermented vegetable product. Kimchi, containing leaves of B. juncea as an ingredient, has recently drawn attention as a functional food for health maintenance and disease control [2]. B. juncea contains various bioactive compounds, including glucosinolates [3], isothiocyanates [4], phenolic compounds [5,6], fatty acids [7], kaempferol glycosides [8], and various flavonoids [9]
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