Inclusion complexes of GA₃ and the plant growth regulation activities

Gibberellic acid (GA₃) is an important phytohormone that is applied in agriculture, nurseries, tissue culture, tea gardens, etc. However, it has some drawbacks such as potential hazardous effects on mammals and labile in the condition of a weak base or acid. In this study, the enhanced stability and bioavailability of GA₃ were achieved by forming the inclusion complexes of GA₃ with cyclodextrins (β- or γ-CD) and its derivative (HP-β-CD). In the preliminary plant growth regulation assay, GA₃/CDs displays superior bioactivity compared to pure GA₃ to help with the early seedling growth of cucumber and mung bean and the root growth of cucumber and mung bean, respectively. The results showed that there was a certain relationship between the inclusion ability, stability and bioactivity. The inclusion stability constants of gibberellin clathrate are consistent with the order of stabilities of the inclusion complex. Among these complexes, GA₃/HP-β-CD possess highest inclusion constant, and the binding ability of the HP-β-CD not only enhances the stability of gibberellic acid in the stability test but also plays a slow release role in the bioactivity assay. Therefore, the complex of GA₃ may be used as a promising plant growth regulator.