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

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.