Investigation of Cinnamaldehyde Derivatives as Potential Organic UV Filters

Abstract

Long-term exposure to ultraviolet (UV) rays has been attributed to irreversible health defects at the cellular level. Most importantly, damage to DNA by UVA and UVB rays can result in uncontrolled cellular growth, leading to skin cancer. As a result, topical treatments have been developed over time to protect the skin from UVA and UVB rays. The active ingredients in sunscreens or sun creams are sometimes unsaturated, aromatic organic compounds capable of absorbing harmful UV photons at a great range of wavelengths. Absorption capabilities of these species depend on their degree of conjugation and their molar absorptivity. With this knowledge, two cinnamaldehyde derivatives were synthesized into five potential organic UV filters by the aldol condensation reaction. The products were identified using nuclear magnetic resonance (NMR) and attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopies, and ultraviolet-visible (UV-vis) spectroscopy was used to determine the UV absorption range and intensity of absorption for each compound. Since the compounds would hypothetically be utilized in topical ointments to aide in skin protection, these compounds were assessed in the presence of Pseudomonas aeruginosa, a representative bacterium of the skin’s natural flora. A time-course assay was conducted to detect growth effects of P. aeruginosa in the presence of the organic compounds. According to the spectroscopic and bacterial analyses of these UV-blocking compounds, three compounds were determined to be potential UV filters that cover UVA region while demonstrating no apparent harm to the natural skin bacteria P. aeruginosa, while the other two likely diminished bacterial growth by simple niche inhibition.