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Antioxidant Activities of Lutonarin Isolated from Young Barley Leaves

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Abstract

Lutonarin was isolated from young barley (Hordeum vulgare L. var. nudum Hook) leaves. It has been suggested that lutonarin found in plants, especially in leaves, plays a role in removing reactive oxygen species 6). In this study, we examined the antioxidative effects of lutonarin and related flavones against the free radical DPPH and Fenton's reaction in vitro. The DPPH radical-scavenging activity was higher in the flavones with a catechol struc-ture in the B-ring of the flavone compared to those in which the B-ring contained only a single hydroxyl mole-cule. Furthermore, the higher DPPH radical scavenging activity of saponarin compared to apigenin suggests that the 6-C-and/or 7-O-glucosyl moiety in saponarin stimu-lates its radical scavenging activity. In a comparison of lutonarin with luteolin, the inhibitory action against the oxidation of ethyl linoleate by Fenton's reaction appeared to be weakened by the 6-C-and/or 7-O-glucosyl moiety.

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... Barley contains phenolic compounds as antioxidants as well as rich vitamins, and it can be cultivated in less than one month. Examining the antioxidant activity of extracts is a major research theme for young green barley leaves, and the research has revealed that the main components of potent antioxidant activities are flavonoids such as saponarin and lutonarin [1][2][3][4]. ...
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We clarified that photo-irradiation of young green barley from three different light sources, natural light, 100% red light-emitting diodes (R-LEDs), and a mixture of 90% red-LEDs + 10% blue-LEDs (RB-LEDs), had significantly different results in growth degree (weight and height) and in components of young green barley. Barley that has sprouted for 15 days after germination did not show any apparent difference in height in response to irradiation by the three tested light sources, but by the 20th day of sprouting the height showed a positive effect by R-LEDs irradiation. By 15 days of sprouting the barley had achieved the heaviest weight by natural light irradiation, while the barley irradiated by R-LEDs had made remarkable progress at 20 days of sprouting. On the other hand, the irradiation by RB-LEDs showed a suppressive tendency after 15 days or more. The amino acid content, as indicated by dry weight conversion, was greatest in the barley irradiated by RB-LEDs, followed by R-LEDs, and natural light, which showed that LEDs irradiation is effective. In addition, four cyanogenic glucosides were isolated, identified, and quantified, as they are components frequently assessed in barley research. With regard to vitamin E, R-LEDs irradiation increased γ-tocopherol. Our results indicate that irradiation by LEDs would be effective for the enhancement of the functionality of young green barley.
... In recent years, young green barley has been increasingly used as a functional food ingredient. The majority of studies on young green barley plants have focused on the antioxidant activity of secondary metabolites, such as phenolic compounds, whose primary components are flavonoids including saponarin and lutonarin [1]- [4]. Meanwhile, studies have shown that cultivated young green barley has different levels of amino acids, vitamin C, and polyphenol content depending on the harvest time [5]. ...
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In recent years, young green barley has been increasingly used as a functional food ingredient. Studies have shown that cultivated young green barley has different levels of amino acids, vitamin C, and polyphenol content depending on the harvest time. Furthermore, some studies have investigated the effect of the growing conditions on cultivated barley in particular the use of light-emitting diodes (LED). Young green barley was exposed to three light sources of different wavelengths (sun light [ASL], light-emitting diode[LED] - Red 9 + Blue 1 [LED-R9:B1], LED - Red 4 + Green 1+ Blue 1 [LED-R4: G1:B1]). Under light with photon densities of 200 μmolmL-2·s-1, the dry weight of young green barley was not affected, while the differences were observed in the morphology of the underground portion of the plant (roots) depending on the light source. The roots of the plant grown in ASL weighed twice as much as those that were grown under LED irradiation. Furthermore, LED irradiation caused an increase in the amino acid content in plants; the amino acid content of plants grown under LED-R9:B1 was twice as much as that grown under ASL irradiation. Four kinds of cyanogenicglucosides (CGs) were isolated, identified, and their levels were measured. The plant grown under LED-RGB irradiation, including LED-G, produced approximately 20% more CGs as compared to the plants grown under the other two light sources. Thus, it was inferred that young green barley exhibited a stress response under LED-G light and accumulated CGs in the stems and leaves with prepare for any damage that may occur on the leaf surface. The nitrogen (N) content in the root was the lowest, while the CG content was the highest in the plant grown under LED-RGB irradiation. It is inferred that the N content decreased because N was eliminated from the roots to allow for accumulation of CGs response to stress. In general, the growth experiments to use an irradiation condition in which the distance between the light source and plant floor is fixed. It is not clear whether the photon density level received by the top leaves is fixed according to plant growth, by changing the height of plant growing shelf. Therefore, against this background, when the photon density was increased from 200 to 300 μmolmL-2·s-1 under ASL irradiation, only a minimal change was observed in the root weight, while the weight of the part of the plant above the ground surface (stems and leaves) increased by approximately 30%, with a 10% increase in the amino acid content.
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