Abstract
Perilla frutescens (Lamiaceae) is a dietary staple in Asia. It is an abundant source of flavonoids that are bioactively beneficial to human health and fitness. The current popularity of plant-based consumption is being driven by the healthful benefits of bioactive nutrition, and the concentration of bioactive agents found in raw plant materials is an important factor in the assessment of food quality. To test the feasibility of promoting flavonoid productivity in perilla plants via environmental treatment, plant factory technology was applied to perilla plant cultivation. Apigenin (AG) and luteolin (LT) are two of the most potent anticarcinogenic flavonoids in perilla, and these are also found in many vegetables and fruits. Quantitative analysis of AG and LT was conducted on plants cultivated under nine environmental forms of treatment imposed by three levels of light intensity (100, 200, and 300 µmol·m−2·s−1) combined with three levels of nutrient-solution concentration (1.0, 2.0, and 3.0 dS·m−1) for hydroculture. The contents of AG in green and red perilla plant were increased by high nutrient-solution levels under the same light intensity. In green perilla, the highest concentration of AG (8.50 µg·g−1) was obtained under treatment of the highest level of nutrient-solution (3.0 dS·m−1) and 200 µmol·m−2·s−1 of light intensity, whereas in red perilla, the highest concentration of AG (6.38 µg·g−1) was achieved from the highest levels of both of these forms of treatment (300 µmol·m−2·s−1 and 3.0 dS·m−1). The increase in AG content per plant between the lowest and the highest levels was recorded by 6.4-fold and 8.6-fold in green and red perilla, respectively. The behavior of LT concentration differed between green and red forms of perilla. LT concentration in red perilla was enhanced under nutrient deficiency (1.0 dS·m−1) and affected by light intensity. Different responses were observed in the accumulations of AG and LT in red and green perilla during treatments, and this phenomenon was discussed in terms of biosynthetic pathways that involve the expressions of phenylpropanoids and anthocyanins. The total yield of flavonoids (AG and LT) was improved with the optimization of those forms of treatment, with the best total yields: 33.9 mg·plant−1 in green Perilla; 10.0 mg·plant−1 in red perilla, and a 4.9-fold and a 5.4-fold increase was recorded in green and red perilla, respectively. This study revealed that flavone biosynthesis and accumulation in perilla plants could be optimized via environmental control technologies, and this approach could be applicable to leafy vegetables with bioactive nutrition to produce a stable industrial supply of high flavonoid content.
Highlights
Secondary metabolites (SMs) in plants are an important part of food nutrition, and their content could be used to determine food quality
We found that rosmarinic acid (RA), a major phenylpropanoid compound in herbs of Lamiaceae family, is highly increased in P. frutescens grown under uptake stress created by a nutrient-limited condition combined with high light intensity (LI) in plant factories, while maintaining a constant concentration of perillaldehyde (PA), a main terpenoid found in perilla essential oils [16]
Concentrations of AG and LT in green perilla are shown in Figures 1(a) and 1(b), respectively, as the content per unit of leaf dry weight. e concentration of AG was decreased under an electrical conductivity (EC) of 1.0 dS·m−1 using the same LI, and it tended to increase with increases in the EC under LIs of 100 and 200 μmol·m−2·s−1 (Figure 1(a)). e concentration of AG was the lowest (2.95 μg·g−1) under an EC of 1.0 dS·m−1 and a LI of 200 μmol·m−2·s−1, but it was increased to the highest level (8.50 μg·g−1) of concentration (2.9-fold increase) under an EC of 3.0 dS·m−1 and LI of 200 μmol·m−2·s−1
Summary
Secondary metabolites (SMs) in plants are an important part of food nutrition, and their content could be used to determine food quality. Journal of Food Quality due to the lack of an effective method to control the SM content in plant cultivation. Both the production and accumulation of SMs are sensitive to environmental conditions [4, 5]. A few attempts have been made to evaluate the quality of plants grown under different environments by detailing the stable expressions of the secondary metabolisms and concentrations of bioactive SMs that are expected to be included in plant-based foods as an additional health promoting component [7]
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