Spectrokinetic studies of the photostability and the photodegradation of Diethylstilbestrol

A spectrokinetic study has been carried out for research purposes on the photodegradation and photostability of the photoactive Diethylstilbestrol compound (DES) a synthetic oestrogen sometimes used in the treatment of specific cancers. Both photochemical and photostability studies were carried out in order to contribute new knowledge to the research on DES. Due to the drug’s use in treatment of diseases it is important to find a way of inhibiting or reducing problems of photosensitivity in the compound. In order to do this a set of sugars capable of forming inclusion complexes with other molecules, known as cyclodextrins were studied in order to determine their ability in changing the photostability of DES. Studies were carried out incorporating both the CD monomers and the CD polymers with the DES compound in order to determine their effect on DES photostability and whether the monomers or the polymers would result in a better photostabilisation. A number of methods were employed in the studies including spectrophotometry, fluorescence spectroscopy, ATR-FTIR spectroscopy and SEM. The initial investigations confirmed that DES is photoactive and that the reaction is solely photochemical. It was determined that no thermal activity was involved in the reactions taking place. Other studies carried out on the effect of wavelength provided an insight into the wavelengths at which DES is most sensitive and fluorescence studies allowed a proposal of the reaction mechanism of DES. On analysing the findings of the cyclodextrin studies it can be determined that all of the cyclodextrins had an effect on the behaviour of DES however the β-P-CD had a substantial effect on reducing the photodegradation of DES compared with the other CDs studied so was more favourable for a complex. The formation of an inclusion complex with DES was successfully obtained using both the β polymer (β-P-CD) and the β monomer (HP-β-CD). The complex also enabled the preparation of a safe formulation of the CD/drug complex by fully dissolving the complex in water resulting in the solubilisation of water insoluble DES. This was followed by analysis of the complex using ATR-FTIR and SEM methods. The results indicated a strong possibility of the formation of a complex. Two novel formulations were made using the optimised complexes. These were tested in order to determine their photostability in comparison to DES alone. Both formulations were successful in significantly reducing the photodegradation of DES