Tephrosia Vogelii oil use in biodiesel production and its conservation with Syzygium jambolanum DC (jambul) extract

Abstract

Tephrosia (Tephrosia Vogelii) is a legume that has about 8% oil plus rotenoids, which has been studied by several authors. This oil was analyzed in the seeds and used for transesterification of triglycerides providing glycerin and biodiesel as major products, which are a mixture of straight-chain alkyl esters. In transesterification, an  excess of alcohol is used in molar ratios of 6: 1 for methanol and 9: 1 to 12: 1 for ethanol, and subsequent removal of glycerin. Jambul (Syzygium jambolanum), a fruit from the myrtaceae family that is widely grown due its use in ornaments and for their edible fruits, was employed as an antioxidant extract. The biodiesel obtained was subjected to the Rancimat test, a standard method approved by the European standard EN 14214 (2003) and the Brazilian norm RANP 07/08, aiming at analyzing the oxidative stability of biodiesel, where the minimum allowed value of induction is 6 hours. Fatty acid composition was measured by gas chromatography, kindly provided by Maringa State University (UEM). Jambul extract showed antioxidant activity by scavenging DPPH free radicals and the value of 44.15%, relative to Trolox. Total concentration of phenols in solutions diluted up to ten times was found to be 4.45 mg ml^-1 of total phenolic contents. Rancimat test showed an induction period of 3.59 hours without the presence of antioxidant, indicating that the presence of this antioxidant was necessary. When Rancimat test was carried out in the presence of Jambul, an induction time  of 8.2 hours was observed , suggesting the efficiency of the applied antioxidant, and showing great similarity to the values obtained from a biodiesel synthesized from soybean oil. Biodiesel from soybean oil without butylated hydroxytoluene (BHT) showed an induction time of 4.2 hours, while in the presence of Jambul extract the induction time obtained was of 7.1 hours. New alternatives to soybean oil for biodiesel production are increasingly demanded, and the oil from seeds of Tephrosia (Tephrosia vogelii) can possibly be used for this purpose. The antioxidant proved to be of great feasibility and applicability for conservation, and does not require large amounts to obtain a satisfactory and consistent result as required by legislation, since its obtainment is derived from natural sources.