Application of Raman spectroscopy in comparative study of antiobesity influence of oxytocin and freeze‐dried extracts of Uvariodendron anisatum Verdeck (Annonaceae) in Sprague Dawley rats

Abstract

Obesity is a condition affecting a substantial number of people in the world. Obese people have increased risks of developing chronic metabolic diseases such as type II diabetes, hypertension, and cancer, among others. Predicting potential development together with rapid diagnosis of the condition followed by early interventions is therefore necessary. This work investigated, first, utility of Raman spectroscopy in performing comparative antiobesity influence studies of oxytocin and a freeze‐dried extract of a local herbal plant exhibiting oxytocin‐like properties called Uvariodendron anisatum Verdeck (Annonaceae) (UAV) on diet induced obesity in Sprague Dawley rat models. Second, we looked for obesity biomarker Raman spectral bands. The blood extracted from the rats were applied onto conductive silver paste smeared glass slides and excited using a 785‐nm laser. Raman spectra of blood from oxytocin‐ and UAV‐treated rats displayed similar profiles with low doses of UAV (100 mg/kg of body weight) being more similar to oxytocin than high doses (200 mg/kg of body weight) as revealed by cosine similarity value of 0.997. Their profiles were also different from blood of obese and nonobese (normal controls) animals. A prominent peak in spectra of treated rats centred at 401 cm−1 can be oxytocin's biomarker band in blood. Comparison of average intensity trend of fructose bands at around 638 and 812 cm−1 between prepared fructose solution and blood of treated rats revealed elevated levels of fructose in blood of rats intraperitoneally injected oxytocin and UAV extracts. The result implied upregulation of fructose in oxytocin‐ and UAV‐treated animals. Principal component analysis confirmed that Raman spectral profiles from blood of obese rats were different from those of nonobese rats with bands ascribed to fructose (638, 812, and 1,217 cm−1) and branched chain amino acids (BCAAs; 478, 1,318, and 1,443 cm−1), being utilized in the segregation of the spectral data sets. It also showed that spectra from oxytocin‐treated and UAV‐treated rat's blood were similar implying identical influence of the drugs on the animals. The study showed potential of Raman spectroscopy as tool for quick obesity (or metabolic syndrome) screening with intensity of Raman bands associated with fructose and BCAAs as biomarkers. Besides, the same bands may be used in comparative efficacy studies of antiobesity drugs. The results reported here are rare in literature.

Revealing the Relationship between Electric Fields and the Conformation of Oxytocin Using Quasi-Static Amide-I Two-Dimensional Infrared Spectra

“…The ability of an IR probe to quantitatively report on the local electric field is crucial for successful application to study the local structure in proteins, and numerous IR spectroscopic studies have been reported for the OT molecule. − Thus, for the sake of direct comparison, the IR spectra of the OT molecule are studied experimentally and theoretically (Figure ). The theoretical anharmonic IR peak of the disulfide bond lies on 552 cm –1 , which is slightly larger than our experimental value of 547 cm –1 and other experimental values of 542 cm –1 , and the strength of the IR peak of the disulfide bond is much smaller than that of amide-I.…”

“…De Barros et al investigated the Fourier transform infrared information of OT and sustained release using natural rubber latex membranes and identified absorption IR peaks for functional groups of OT . Birech et al studied the antiobesity influence of OT using Raman spectroscopy and confirmed that OT played an important role in obese rats . Joly et al studied optical and structural properties of copper–oxytocin dictations in the gas phase, and the experimental and theoretical results showed a global enhancement of the photofragmentation yield as compared to the one recorded for the doubly protonated OT .…”

Developmental Trends of Peptide Drugs and Their Quality Assessment using Secondary Structure Analysis

“…Oxytocin receptor CD, [30] NMR, [31] FTIR, [32] Raman [33] Cyclosporin 1202.61 (11 aa) aL*L*V* (Bmt) * (Abu)G*LVLA (Cyclization at D-Ala1-Ala11) Cyclic peptide calcineurin inhibitor CD, [34] X-ray, [35] PXRD, [34] NMR, [36] FT-IR [37] Leuprolide 1209.42 (9 aa) Pyr-HWSYlLRP-NHEt (Pyr = L-pyroglutamyl).…”