Effect of solar radiation on the functional components of mulberry (Morus alba L.) leaves.

Background: The functional components of mulberry leaves have attracted the attention of the health food industry, and increasing their concentrations is an industry goal. This study investigated the effects of solar radiation, which may influence the production of flavonol and 1-deoxynojirimycin (DNJ) functional components in mulberry leaves, by comparing a greenhouse (poor solar radiation) and outdoor (rich solar radiation) setting.

Results: The level of flavonol in leaves cultivated in the greenhouse was markedly decreased when compared with those cultivated outdoors. In contrast, the DNJ content in greenhouse-cultivated plants was increased only slightly when compared with those cultivated outdoors. Interestingly, the flavonol content was markedly increased in the upper leaves of mulberry trees that were transferred from a greenhouse to the outdoors compared with those cultivated only in the outdoors.

Conclusion: Solar radiation conditions influence the synthesis of flavonol and DNJ, the functional components of mulberry leaves. Under high solar radiation, the flavonol level becomes very high but the DNJ level becomes slightly lower, suggesting that the impact of solar radiation is great on flavonol but small on DNJ synthesis. © 2016 Society of Chemical Industry.