Stability of octyl methoxycinnamate and identification of its photo-degradation product

A stability study of octyl methoxycinnamate (OMC) using C-18 HPLC indicated that OMC degraded into a new product when exposed to sunlight. When kept in the dark at 4, 20, 32 and 60 degrees C for one month, no degradation of OMC was detected. Online HPLC-APCI-MS revealed similar APCI mass spectra for OMC and its degradation product. Isolation of the photo-degradation product was done using semi-preparative HPLC. NMR spectra of OMC and the isolated photo-degradation product indicated the change from an E-octyl-p-methoxycinnamate into a Z-octyl-p-methoxycinnamate. NMR spectra of the unfractionated-light-exposed-OMC showed that the Z-OMC was the only product generated.