Effects of UV-B Radiation on the Content of Bioactive Components and the Antioxidant Activity of Prunella vulgaris L. Spica during Development.

Yuhang Chen,Wenming Wang,Miao Zhao,Qiaosheng Guo,Chen Li,Li Liu,Liping Cao,Qin Qin,Xuerong Zhang

doi:10.3390/molecules23050989

Abstract

The effects of UV-B radiation on the content of bioactive components and the antioxidant activity of Prunella vulgaris L. spica during development were studied. The experimental design involved two levels of UV-B radiation intensity (0 and 120 μW cm−2 nm−1). The results showed that the contents of total flavonoids, rosmarinic acid, caffeic acid and hyperoside, as well as the antioxidant capacities (DPPH● and ABTS•+ scavenging activities), in the spicas significantly decreased during spica development. The content of salviaflaside in the spicas significantly increased during development. The highest contents of total flavonoids, rosmarinic acid, and caffeic acid and the highest antioxidant activities were found in spicas in the full-flowering stage, while the highest content of hyperoside was found in spicas in the bud stage. In addition, the highest content of salviaflaside was found in spicas in the mature-fruiting stage. UV-B radiation significantly promoted the synthesis of secondary metabolites, increased the contents of the main bioactive components in the three developmental stages of isolated dried spicas, and significantly increased the DPPH● and ABTS•+ scavenging activities of P. vulgaris spicas in the mature-fruiting stage. Moreover, the total flavonoids content was positively correlated with the DPPH● and ABTS•+ scavenging activities, and the correlation with the DPPH● scavenging activity was very strong. This result shows that the highest contents of the main bioactive components in the spicas were not all found in the same developmental stages of P. vulgaris. Our research revealed that the best stage for harvesting P. vulgaris spica was between the bud stage and the full-flowering stage since harvesting at this point provides a higher content of bioactive components and a higher antioxidant capacity, which is relevant for medicinal applications.

Highlights

The depletion of the stratospheric ozone layer has become a serious global environmental problem that has led to an increase in the amount of ultraviolet-B radiation (UV-B, 280–320 nm) reaching the Molecules 2018, 23, 989; doi:10.3390/molecules23050989 www.mdpi.com/journal/moleculesEarth’s surface, and the amount of UV-B radiation on the Earth’s surface will continue to increase in the coming decades [1,2]
This study focuses on the effects of UV-B radiation on the contents of bioactive components and the antioxidant activity of the ethanol extract during the three developmental stages of P. vulgaris to determine which stage is most sensitive to UV-B radiation and identify the optimum stage for harvesting based on the contents of bioactive components and the antioxidant activity of the ethanol extract of the spicas
The contents of total flavonoids, rosmarinic acid and caffeic acid were significantly different in the spicas from the three developmental stages, and spicas in the full-flowering stage had the highest contents (Figure 1)

Summary

Introduction

The depletion of the stratospheric ozone layer has become a serious global environmental problem that has led to an increase in the amount of ultraviolet-B radiation (UV-B, 280–320 nm) reaching the Molecules 2018, 23, 989; doi:10.3390/molecules23050989 www.mdpi.com/journal/moleculesEarth’s surface, and the amount of UV-B radiation on the Earth’s surface will continue to increase in the coming decades [1,2]. It is necessary to determine whether increasing exposure to UV-B radiation can be used as a simple and environmentally friendly method for increasing the contents of bioactive components in medicinal plants. Previous studies have shown that UV-B radiation can induce secondary metabolism processes while increasing the contents of bioactive components in medicinal plants [6,7]. These experiments evaluated UV-B radiation during each plant’s growth period, which was operationally difficult (especially in places without a stable supply of electricity) and required a large economic investment in production. Further studies to explore the optimal method of UV-B radiation for improving the content of bioactive compounds in medicinal plants are necessary

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Discussion

Conclusion