Insights into the infrared and Raman spectra of fresh and lyophilized royal jelly and protein degradation IR spectroscopy study during heating

Abstract

<jats:p><p> In terms of chemical composition, a honeybee secretion known as royal jelly (RJ) is very complex product containing water, proteins, carbohydrates, lipids, mineral salts and small amounts of polyphenols, vitamins and enzymes. Despite its chemical diversity, the bands originating from vibrational modes of the present proteins were successfully assigned in 1800–1200 cm^–1 (Raman and IR) region where the interference of bands from other vibrational species is not substantial. The protein bands were attributed to amide I, amide II and amide III modes and their intensities, additionally, enabled to determine the protein secondary structures. The remaining bands up to 4000 cm^–1 were attributed to other group vibrations whereas the region below 1200 cm^–1comprises bands from complex interacting modes within the major RJ components that can not be unequivocally attributed to distinct modes. The work also represents a pioneering effort to collect and interpret the Raman spectrum of fresh and lyophilized RJ samples and to correlate and describe the observed similarities/differences between IR and Raman spectra.</p></jats:p>