By Renata Rutckeviski and Socrates Egito
In the last decade, many branches of industry, including food, cosmetics, and pharmaceuticals, have shown a growing interest in obtaining natural oils from unconventional sources. However, therapeutic studies of animal oils have been neglected.
The bullfrog (Rana catesbeiana Shaw) is an amphibian that has been widely used in the meat and leather market. Its fatty dermal tissue, normally discarded during its food processing, can be reused by biotechnological process for production of natural oil with potential therapeutic properties.
Due to positive popular reports regarding the use of bullfrog oil in the treatment of allergic and inflammatory processes, our research group, at the Federal University of Rio Grande do Norte, Brazil, has conducted studies to evaluate this oil under the guidance of Professor Socrates Egito and his research team: Renata Rutckeviski, M.Sc., Francisco Xavier-Junior, Ph.D., Andreza Morais, M.Sc., Everton Alencar, M.Sc., and Lucas Machado, M.Sc.
Bullfrog oil has several advantages for therapeutic applications, including greater biocompatibility and biodegradability, besides a more sustainable process of production than that of synthetic oils. It is also a rich source of polyunsaturated fatty acids, such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These compounds may act by reducing the synthesis of pro-inflammatory mediators, reinforcing the oil’s use as an adjunct in the treatment of immune and inflammatory diseases.
Moreover, the oil’s high concentration of unsaturated fatty acids can be a problem due to a higher susceptibility to lipid oxidation, which is the major cause of quality deterioration in many natural products. This process and other factors modify the physicochemical properties of the oil associated with rancidity, taste and color changes, viscosity, and nutritional quality which reduce its pharmaceutical quality and shelf life. Therefore, the lack of quality control and characterization studies of this oil can compromise the authenticity and effectiveness of products containing bullfrog oil.
This study assessed the oxidative stability of bullfrog oil by conjugated dienes and trienes UV–Vis spectrophotometer analyses. Additionally, the oxidation induction time was determined by the Rancimat method. Peroxide, acidity, iodine, and saponification value were also evaluated. This study further demonstrated that the antioxidant BHT has proven to be more effective than BHA in increasing the oxidative stability of the bullfrog oil.
In addition to this study, our group is developing new formulations based on bullfrog oil for oral and topical use. The oil itself and its lipidic systems did not show cytotoxicity effect in normal fibroblasts cells (3T3). However, the cellular viability study of the oil and the developed formulations showed an inhibitory activity over melanoma cell lines (B16F10).
Therefore, bullfrog oil and the formulations based on it presented desirable chemical characteristics required to be used for the development of pharmaceutical products. As future prospects, our group intends to study the kinetic stability of bullfrog oil and evaluate its anti-allergic, anti-inflammatory, and anti-tumor activity against lung cells.
The authors would like to thank their fellow collaborators: Andreza Morais, M.S.; Éverton Alencar, M.S.; Francisco Xavier-Junior, Ph.D.; and Lucas Machado, M.S.