UV Irradiation and Salicylic Acid Immersion Enhance the Level of Mulberroside A in Isolated Mulberry Branches—A Huge Amount of Agro-Waste

Mulberroside A (MA) is an oxyresveratrol diglycoside that has many biological activities and pharmacological functions. To improve MA levels in the bark of isolated mulberry branches (Ramulus mori), a huge amount of agro-waste. We took isolated mulberry branches of a huge amount of agro-waste as experimental material and chose equivalent sections of branches for physiochemical treatments with three types of ultraviolet light (UVA, UVB and UVC) and salicylic acid. HPLC analysis showed that the most effective treatment on MA content was UVB irradiation in the wavelength range of 290–320 nm. The experimental results showed that the three types of UV irradiation stimulate the mulberry branch cortex to induce the biosynthesis and secretion of MA. When the isolated branches were soaked in different concentration of salicylic acid for different time, the MA concentration had increased significantly. The stimulatory effect of salicylic acid and UVA on MA synthesis in cortex cells of the isolated branches decreased with branch age; it was greatest in those harvested in June and lowest in those harvested in September. These results indicated that salicylic acid, like UV irradiation, can stimulate mulberry cortex cells and induce the biosynthesis and secretion of MA.