ESTUDO DO POTENCIAL ANTIOXIDANTE DO EXTRATO ETANÓLICO DA AMBURANA CEARENSIS COMO FATOR DETERMINANTE NA ESTABILIDADE OXIDATIVA DO BIODIESEL DE SOJA

Abstract

This master’s thesis aims to investigate the oxidative stability of biodiesel through the use of an ethanolic extract obtained from the exudate of Amburana cearensis as a natural antioxidant additive. The incorporation of antioxidants is a widely used strategy to mitigate the oxidative degradation of biodiesel; however, synthetic antioxidants are often associated with high cost, potential toxicity, and low biodegradability, making the discovery of new chemical substances an area of significant scientific advancement. Experimental results for the ethanol extract of Amburana cearensis demonstrated antioxidant efficacy as determined by the ABTS •⁺ radical scavenging assay, which showed high antioxidant activity even with mass loss over time. Thermogravimetric and differential thermal analysis (TG/DTA) revealed its thermal stability at high temperatures, with degradation beginning at 281°C. Chemical characterization by HPLC and DI-ESI-IT-MSn identified the compounds responsible for the antioxidant activity; the predominant metabolite was associated with coumarins, flavonoids, and phenolic acids. Fragments of five compounds were identified as butein, calicosin, cirsimaritin, 3,5,3-trihydroxy-7,4-dimethoxyflavone, and nevadensiv. The extract’s efficacy as an antioxidant in biodiesel was evaluated using the Rancimat method (EN 14112). The treated sample exhibited an induction time of 11.03 h with 3000 ppm of the ethanolic extract, coming very close to the limits established by the National Agency of Petroleum, Natural Gas, and Biofuels (ANP). Overall, the phytochemicals present in the exudate of Amburana cearensis demonstrate significant scientific, environmental, and socioeconomic potential, supporting its use as a green and regional alternative to synthetic antioxidants.