Young barley leaves can accumulate levels of the flavonoid saponarin comparable to open-field crops inside a plant factory, without the punishing light intensities that earlier work demanded, according to a new study published in Applied Biological Chemistry. By combining a carefully tuned hydroponic nutrient solution with the right barley cultivar, researchers raised saponarin concentration to 12.3 grams per kilogram of dry weight under modest white LED illumination of 210 micromoles per square meter per second of photosynthetic photon flux density, a level of light far gentler than the high-intensity treatments previously considered necessary.
Saponarin is a biologically active flavonoid glycoside found abundantly in young barley leaves, where it has been reported to show anti-inflammatory and hepatoprotective effects. In open-field cultivation, saponarin content has been reported at around 11 grams per kilogram of dry weight. Earlier plant factory attempts matched those levels only under blue light or ultraviolet treatment, but those conditions suppressed growth and biomass production. A 2021 study by some of the same team explored artificial light composition and color temperature, and a 2024 report showed that saponarin biosynthesis flux is controlled by light-induced reactive oxygen species, achieving open-field-comparable production only at light intensities of 500 PPFD or above.
The problem with that approach is economic. High-intensity lighting generates excessive heat and consumes large amounts of electricity, making it impractical for commercial plant factories.
The team grew barley seedlings hydroponically under white LED lights at 20 to 22 degrees Celsius, with a 12-hour daily light cycle, harvesting the primary leaf at 15 centimeters. Each cultivation condition was replicated with three separate trays, and saponarin and its related metabolites were quantified by HPLC. Statistical comparisons used two-way ANOVA with Duncan’s multiple range test at a significance level of p below 0.05.
In the first round of experiments, the researchers screened major nutrient supplies of nitrogen, phosphorus, potassium, calcium, and magnesium under both 6500 K and 3000 K white light at 210 PPFD. The 6500 K lamps, which are blue-rich, consistently outperformed the warmer 3000 K light for saponarin biosynthesis. A combined phosphorus and potassium treatment produced the highest saponarin concentration, 7.82 grams per kilogram of dry weight, and the highest total saponarin amount per plant, 79.0 micrograms, under 6500 K light. Biomass production, however, showed no significant effect from the nutrient treatments at this stage, pointing to light spectrum as the dominant factor in the biosynthetic response.
The team then tested plant hormones and biosynthetic precursors. Salicylic acid emerged as a potent enhancer of saponarin production, with a concentration of 10.0 milligrams per liter yielding 7.5 grams per kilogram of dry weight and a total saponarin amount of 74.3 micrograms per plant. Concentrations above 50 milligrams per liter lowered both saponarin levels and biomass. Abscisic acid showed a weaker effect, and growth was significantly suppressed above 0.1 milligrams per liter. Supplements of the saponarin precursors phenylalanine, cinnamic acid, and coumaric acid, tested up to 250 milligrams per liter, produced no effects on saponarin accumulation or biomass at all.
The decisive breakthrough came from combining the phosphorus and potassium source with salt. When the researchers supplied 600 milligrams per liter of K2HPO4 together with 0.1 percent sodium chloride under 6500 K light at 210 PPFD, saponarin concentration climbed to 12.3 grams per kilogram of dry weight and total saponarin per plant reached 150 micrograms, with biomass actually increasing to 12.2 milligrams of dry weight per plant. A lower dose of 200 milligrams per liter raised concentration to 11.5 grams per kilogram but did not boost biomass, while an excessive 1800 milligrams per liter slightly reduced both concentration and biomass, dropping total saponarin to 124 micrograms per plant. Adding salicylic acid on top of this nutrient combination backfired: at 1.0 milligram per liter, total saponarin fell significantly to 101 micrograms per plant compared with 150 micrograms without the hormone.
Cultivar choice proved equally important. Comparing six barley varieties, including Keunal-bori, Sakirang, Saknuri, Heimi, Heyang, and Hyenuri, under high and low light intensity, the team found that Keunal-bori delivered the highest total saponarin amount under 500 PPFD, reaching 212 micrograms per plant, driven by its large biomass and an 84 percent increase in total saponarin from nutrient supplementation. Hyenuri, by contrast, showed the highest saponarin concentration under high light at 14.98 grams per kilogram of dry weight, and under low light of 100 PPFD it led both categories, with 12.03 grams per kilogram and 114 micrograms of total saponarin per plant. Saponarin production fell across all cultivars at low light, but nutrient treatment still lifted total saponarin by 39 to 82 percent.
Energy accounting tipped the balance further toward Hyenuri for low-light operation. Electricity consumption for the 100, 210, and 500 PPFD settings was calculated at 1.8, 3.7, and 7.4 kilowatt-hours per square meter per day, totaling 16.2, 33.5, and 67.0 kilowatt-hours per square meter until harvest. Under 100 PPFD, Hyenuri achieved an energy efficiency for saponarin production of 201 milligrams per kilowatt-hour, exceeding Keunal-bori’s 144 milligrams per kilowatt-hour, likely because Hyenuri’s seedling density was 1.29 times higher. The authors conclude that Hyenuri is a suitable cultivar for energy-efficient saponarin production in plant factories.
Molecular analysis added a mechanistic layer. Quantitative RT-PCR of genes involved in saponarin biosynthesis showed that the K/P/Na nutrient treatment doubled OGT expression in both cultivars under high light, with a striking 14-fold increase in Hyenuri at 500 PPFD. Meanwhile, F3’M, a gene involved in the oxidative degradation of saponarin, was drastically suppressed in Hyenuri under the nutrient treatment, with F3’M1 expression falling up to 50-fold and F3’M2 falling 16-fold. This suppression plausibly explains Hyenuri’s lower accumulation of lutonarin, an oxidation product of saponarin, and suggests that controlling F3’M expression could be a key lever for maximizing saponarin retention. The authors caution that the effects of F3’M regulation on carbon metabolism, plant growth, and stress responses still require further investigation before the marker can guide breeding strategies for high-saponarin barley with stable agronomic traits in plant factories.
Subject of Research: Hydroponic nutrient composition and barley cultivar effects on saponarin production in young barley leaves under white LED lighting in plant factories
Article Title: Effect of hydroponic nutrient composition and the barley variety on saponarin production under white LED
Article References: Oh, K.-Y., Kang, S.-W., Seong, H.-J., Kim, K.-M., Jung, S.-I., Jang, Y.-S., & Kim, J.-H. (2026). Effect of hydroponic nutrient composition and the barley variety on saponarin production under white LED. Applied Biological Chemistry, 69(1), Article 65. https://doi.org/10.1186/s13765-026-01134-w
Image Credits: AI Generated
DOI: 10.1186/s13765-026-01134-w
Keywords: saponarin, young barley leaves, hydroponics, plant factory, white LED, K2HPO4, salicylic acid, barley cultivars, light intensity, energy efficiency, flavonoid, gene expression
News Source: Alan Morgan. (October 29, 2026). Nutrient Tweaks and Barley Variety Boost Saponarin Under Low LED Light. Scienmag.
