Raman Spectroscopic Study of the Influence of Oxytocin and Uvariodendron anisatum Verdeck (Annonaceae) Freeze-dried Extracts on Diet Induced Obesity in Sprague Dawley Rats

Obesity is a condition affecting many people in the world. Obese people have increased risks of developing chronic metabolic diseases such as type II diabetes, hypertension, cancer among others. Early and rapid diagnosis of the condition together with effective treatment is therefore necessary. This work investigated, first, Raman spectroscopic similarities between oxytocin and a freeze-dried extract of a local herbal plant exhibiting oxytocin-like properties called Uvariodendron anisatum Verdeck (Annonaceae) (UAV). Secondly, whether Raman spectroscopy could be used for comparative studies of the influence of oxytocin and UAV on diet induced obesity in Sprague Dawley (SD) rat models. We also sought for obesity or metabolic syndrome biomarker Raman spectral bands. Both oxytocin and extract samples together with blood extracted from the rats were excited using a 785 nm laser with conductive silver paste smeared glass slides as Raman sample substrates. It was found that Raman spectral profiles of oxytocin solution and UAV freeze dried extracts powder were identical with a cosine similarity value of 0.95 implying presence of similar Raman active molecules. The prominent peaks were those assigned to disulphide S-S stretching mode at 508 cm-1 and to tyrosine at 645 cm-1, 846 cm-1 and 1617 cm-1. Raman spectra of blood from oxytocin- and UAV-treated rats displayed similar profiles which were different from those of obese and non-obese (normal controls) animals. A prominent peak in spectra of treated rats centred at 401 cm-1 could be used as oxytocin biomarker band in blood. Comparison of average intensity trend of fructose bands at around 638 cm-1 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 (PCA) showed that the Raman spectral profiles from blood of obese rats were different from those of non-obese rats. It also showed that spectra from oxytocin treated and UAV treated rats blood were similar indicating identical influence. The study shows the potential of Raman spectroscopy as tool for quick obesity (metabolic syndrome) screening with intensity of Raman bands associated with fructose acting as biomarkers. The same bands can also be used in comparative efficacy studies of anti-obesity drugs. Further studies are needed to validate these Raman spectroscopic results since, to the best of our knowledge, this was the first such investigation regarding comparison of UAV and conventional oxytocin together with their influence on obese SD rats. Weather human subjects exhibits similar results are also not known.