Glucosinolates Distribution during Growth and Development in Radish Plants

Glucosinolates (GSLs) are a group of plant secondary metabolites in Brassica species.  Isothiocyanates (ITCs) including sulforaphane (SFA) and sulforaphene (SFE) are two hydrolysis products from GSLs and are known to induce detoxification enzymes relating to cancer cell death. The diversity and content of GSLs are closely related with plant development and different plant organs. In this study, distribution of GSLs in radish plants (Raphanus sativus L.)  were quantified in different plant parts during development using high performance liquid chromatography and ultra performance liquid chromatography equipped with ultraviolet and mass detector, respectively. Quantitative analysis conditions of desulfo-GSL extraction method were optimized. The total GSL contents are dramatically varied in different organs and development stages of radish plants. The concentration of total GSLs by different organs in mature stages (12 weeks-old) were varied—mostly 20-fold—ranging from 305.5 to 8282.9 nmol/g D.W. The amount of GSL in mature seeds was notably high compared with those in other organs. The highest content of total GSLs at the mature growth stages (12 weeks-old) were determined at mature seeds followed by flower stalk, flower, root (bottom), root (upper), inner leaves, outer leaves, root (middle) and silique. The total GSLs concentration in mature seeds (3394.0 nmol/g D.W.) was notably high compared with those in other parts. Glucoraphenin (GRE) was abundant. Of 10 GSLs in radish, the major GSL types were detected aliphatic GSLs containing GRE, glucoraphasatin (GRH) and glucoerucin (GER) in spring. However, different GSLs including glucoputrajivin (GPT), GRH, and GER were detected in radish plants in fall. The influence of planting season on GSLs content and composition in radish was clear. Total GSLs content harvested at spring season (2729.9 nmol/g D.W.) was 4.5 times higher than the content in fall. Individual GSLs harvested at spring was more diverse than the GSLs in fall. Radish in spring was occurred reproductive organs while the radish in fall was not. Thus, reproductive organs might be up-regulated GSL biosynthesis, which is related with defense mechanism and propagation in radish plants.