Decisive Climatic Factors for Production of Bioactive Saponarin-Rich Barley Sprouts: A Study of Seasonal Effect

Abstract

Saponarin content in barley sprouts may vary greatly with environmental conditions, such as climate, leading to difficulty in uniformly producing saponarin-rich barley sprouts in situ farmlands throughout the year. This research was an early attempt to identify the optimal conditions of various climatic factors, such as temperature, light, and humidity according to seasonal change, for maximizing the saponarin content of sprouted barley through the two-year field experiment. As a result, the growth index, as leaf length relative to growth period, of barley sprouts varied greatly with sowing time, and they tended to decrease with an increase in the ambient temperature, such as average daily temperature. In contrast, higher saponarin contents were observed in the sprouts collected in March, April, September, and October than those collected from May to August. We also found significantly positive correlations of saponarin content with daily temperature range and average light period, indicating that they could be decisive climatic factors for the production of barley sprouts with a higher saponarin content. Interestingly, the polynomial relationship between saponarin yield and leaf length showed the highest yield with 2.18 mg plant−1 at 15.9 cm in length, suggesting a best cutting time for the production of saponarin-rich barely sprouts based on the leaf length. Overall, the decisive climatic factors according to seasonal change for saponarin biosynthesis may be considered to be daily temperature differences and light hours.

Saponarin, a Di-glycosyl Flavone from Barley (Hordeum vulgare L.): An Effective Compound for Plant Defense and Therapeutic Application

“…Barley ( Hordeum vulgare L.) belongs to the family Poaceae (Graminaea), and is one of the leading global staple crops due to its wide range of nutrition and medicinal uses. , Although barley has been used as a food grain since the ancient times, until recently, the nutritional value of young barley leaves (YBL) was overlooked despite harboring significant metabolites, such as vitamins, minerals, chlorophyll, and flavone glycosides. , The green YBL also accumulates abundant saponarin (SA), which is a unique flavone with both C - and O -glycosides (apigenin-6- C -glucosyl-7- O -glucoside or isovitexin-7- O -glucoside) (Figure ). The genetic variation of SA in plants and its biological implications have led to industrial demand for its extraction from YBL in Korea, Japan, and other parts of world. , However, the level of a single SA compound in YBL can greatly vary with environmental conditions and growth stages. − Numerous previous studies have shown the significant capacity of SA to counter the effects of severe environmental stresses, such as drought, heat, and erratic temperature fluctuation. Additionally, exposure to ultraviolet (UV) and light-emitting diode (LED) radiations resulted in elevated SA production in YBL, which was accompanied by increased and steady transcript levels of the corresponding SA biosynthetic genes. − Moreover, the application of nonthermal plasma and mechanical stresses, as well as elevated carbon dioxide (eCO 2 ) have been reported to upregulate the SA level and enhance its antioxidant activity. − …”

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

“…This may be attributed to the insufficiency of the light intensity (i.e., 200 μmol m –2 s –1 ) experienced by these barley sprouts; this should be compared to the previously determined saturation point for barley plant photosynthesis of approximately 400 μmol m –2 s –1 PPFD . Similarly, several studies have reported that barley sprouts grown at low light intensity (i.e., 380 μmol m –2 s –1 ) using a chamber system contained low saponarin content (i.e., from 20 to 80 mg 100 g –1 ). ,, However, under higher light intensities (i.e., 570–1,700 μmol m –2 s –1 ) recorded in outdoor fields, saponarin content of barley sprouts ranged from 1000 to 1900 mg 100 g –1 . Moreover, the authors of previous study observed a positive correlation between saponarin yield and light duration ( r = 0.446, p = 0.006) but not light intensity ( r = 0.095, p = 0.584) .…”

“…Similarly, several studies have reported that barley sprouts grown at low light intensity (i.e., 380 μmol m –2 s –1 ) using a chamber system contained low saponarin content (i.e., from 20 to 80 mg 100 g –1 ). ,, However, under higher light intensities (i.e., 570–1,700 μmol m –2 s –1 ) recorded in outdoor fields, saponarin content of barley sprouts ranged from 1000 to 1900 mg 100 g –1 . Moreover, the authors of previous study observed a positive correlation between saponarin yield and light duration ( r = 0.446, p = 0.006) but not light intensity ( r = 0.095, p = 0.584) . Conversely, in this study, saponarin content in barley sprouts showed a significant polynomial relationship with Cum.…”

“…In South Korea, most commercial barley sprout production is performed in outdoor fields, but this production environment may not be economically feasible. For example, in a preliminary study, we found that the production of high-saponarin barley sprouts in upland fields during the summer season (i.e., from June to August) was inefficient . This was attributed to high levels of precipitation and cloudy weather, which contributed to low light intensity levels over the cultivation period.…”

“…Currently, growing barley sprouts is receiving great attention, especially in South Korea and other Asian countries, because it can be used as a raw material of health substances and dietary supplements . So far, many studies have been revealed the pharmacological effects of barely sprouts on diabetes, hypertension, and antioxidants by beneficial compounds, including flavonoids, policosanols, lutonarin, saponarin, etc. − Furthermore, with the recent increase in demand for health foods, the efficacy of barley sprouts is becoming more popular.…”