Variation of Saponarin Content in Barley Sprouts (Hordeum vulgare L.) by Natural Light Shielding: Implication of the Importance of Light Intensity

Abstract

Saponarin is a functional metabolite produced by barley sprouts, and the mass production of saponarin by this crop is attractive for dietary supplement manufacturing. Light is the most important environmental factor determining plant growth, survival, and the production of secondary metabolites including flavonoids. This study was conducted to investigate the importance of light intensity for saponarin production in barley sprouts using a hydroponic growth system. Light intensity was manipulated by using shielding treatments to 100, 80, 70, and 50% natural sunlight (NS), and crop cultivation was performed on a monthly cycle. We found that the growth rate and biomass of barley sprouts did not differ in response to the shield treatments, whereas the saponarin content did. The highest saponarin content (i.e., from 1329 to 1673 mg 100 g −1 ) was observed in the 100% NS treatment, and it gradually decreased as light intensity also decreased. Statistical analysis revealed a significant polynomial relationship of saponarin content with cumulative PPFD (R 2 = 76%), implying that the absolute total amount of light exposure over the growth period has a large effect on saponarin productivity in a hydroponic facility. Taken together, our results showed that shielding conditions, which are often unintentionally created by the design of cultivation facilities, can adversely affect saponarin production in barley sprouts. In addition, it was confirmed through our findings that light conditions with at least 70% NS in the cultivation facility enable the production of an amount corresponding to the saponarin content of the sprouts (>1000 mg 100 g −1 ) produced in the open field. Further studies are needed to investigate the underlying physiological and molecular mechanisms responsible for the relationship of saponarin content with light quantity and quality in barley sprouts.

Transcriptome and metabolome analysis reveals mechanism of light intensity modulating iridoids biosynthesis in Gentiana macrophylla Pall.

“…Among the ecological factors, light is considered to be essential. LED light sources of different intensities have been found to have distinct effects on the plant growth (Proietti, et al 2023;Shang, et al 2023), the protective enzyme system (Gong, et al 2023), the photosynthesis (Yoon, et al 2023), and the accumulation of secondary metabolites (Barh, et al 2022;Yoon, et al 2023). Photosynthesis plays a vital role in oxidation respiratory chain, as the primary driving force to initiate alteration during the growth and development of plants.…”

“…Treated with different light intensities (natural light, shade rate 50%, shade rate 70%, and shade rate 90%), the contents of chlorophyll a (Chl a), Chl b, Chl a + b, and Chl a/b in Angelica dahurica enhanced, while the ratio of Chl a/b reduced with increasing shade ). Moreover, the content of saponarin in Barley Sprouts was decreased along with reducing light intensity (Yoon, et al 2023). The content of total sesquiterpenoid was highest in the rhizome of Atractylodes lancea under 80% mild shading compared with 100% strong light and 7% low light (Guo, et al 2022a).…”

Transcriptome and metabolome analysis reveals mechanism of light intensity modulating iridoid biosynthesis in Gentiana macrophylla Pall.

“…Among the ecological factors, light is considered to be essential. LED light sources of different intensities have been found to have distinct effects on the plant growth [ 36 , 37 ], the protective enzyme system [ 38 ], the photosynthesis [ 19 ], and the accumulation of secondary metabolites [ 19 , 39 , 40 ]. Photosynthesis plays a vital role in the oxidative respiratory chain as the primary driving force to initiate changes during plant growth and development.…”

“…For the glycolysis/gluconeogenesis pathway is a metabolic process, involving in the conversion of 6-carbon glucose to 2-carbon molecules, then bonding with the tricarboxylic acid cycle [ 48 ]. It suggests that glycolysis/gluconeogenesis deferred by impaired photosynthetic carbon assimilation, would affect the secondary metabolites pathway in plants [ 19 ]. So far, the biosynthesis pathway of iridoids was partially revealed as initiating from MVA or MEP pathway to generate IPP and DMAPP, then, under the geranyl diphosphate synthase GES , geraniol 8-hydroxylase G10H , 8-hydroxygeraniol dehydrogenase 8-HGO , (S)-8-oxocitronellyl enol synthase IS , 7-deoxyloganetic acid glucosyltransferase 7-DLGT , and 7-deoxyloganate 7-hydroxylase 7-DLH to successively generate geraniol, 8-hydroxygeraniol, 8-oxogeranial, 7-deoxyloganetic acid, 7-deoxyloganic acid and loganic acid, and finally under secologanin synthase SLS to generate secologanate [ 49 ].…”

“…For example, exposure to different light qualities, the content of artemisinin in Artemisia annua shoots was enhanced by 2.3, 2.5 and 1.9 folds under white, blue and red light, respectively [ 16 ]; the accumulation of coumaeoylquinic acid in Hypericum perforatum leaves was increased by 89%, 65%, 84% and 74% under white, blue, red and green light, respectively [ 16 ]. Treated with different light intensities, the content of total sesquiterpenoids was highest in the rhizome of Atractylodes lancea under 80% mild shading compared to 100% strong and 7% low light [ 17 ]; the contents of total phenols and flavonoids in Polygonum minus were significantly increased under 50% and 70% shade, respectively [ 18 ]; the content of saponarin in Barley Sprouts was decreased along with the reduction of light intensity [ 19 ]; the synthesis of monoterpene in Lilium ‘Siberia’ was increased under light intensities of 200 and 600 µmol/m 2 /s [ 20 ]; 23 terpenoid derivatives were identified in the leaves of Pinus massoniana , while, most of which were decreased under low light treatment [ 21 ].…”