Sequential Solvent Extraction of Oil From Petroleum Nut (Pittosporum resiniferum Hemsl.) Using Ethanol and Hexane

Pittosporum resiniferum Hemsl. or petroleum nut oil can be potentially used as a biofuel or a source of high-value chemicals due to the presence of heptane, pinenes, myrcene, etc. which have therapeutic effects. This study investigated the sequential solvent extraction of petroleum nut oil using hexane and ethanol as solvents at varying solvent-to-fruit ratio (2 and 6 mL g-1), agitation time (30 and 120 minutes), and solvent sequence (whether hexane or ethanol is used as first solvent). Sequential solvent extraction was selected as the method to take advantage of the solvents’ different polarity to increase the oil yield. The sequential solvent approach is also commonly used to prepare extracts that are high in bioactive compounds for high-value products. Drying and milling the fruits prior to extraction resulted in higher oil yields with percent differences of 78.34% between dried and fresh fruit, and 56.38% between milled and un-milled fruits. The highest oil yield (15.75%) was obtained at high settings of solvent-to-fruit ratio and agitation time and using hexane-ethanol as the solvent sequence; while the lowest oil yield (7.86%) was obtained at low settings of solvent-to-fruit ratio and agitation time, also using hexane as first solvent. The highest oil recovery was 46.10%. All the individual and interactive effects of the factors were found to be significant on oil yield (p-value less than 0.05), with the individual effects of solvent-to-fruit ratio and agitation time having the largest positive effect on oil yield. Analysis of the interaction between solvent-to-fruit ratio and agitation time also indicates flexibility in the extraction process conditions which obtained the same results using either hexane or ethanol as the first solvent, and either using (1) a high solvent-to-fruit ratio setting coupled with low agitation time, or (2) a low solvent-to-fruit ratio setting coupled with high agitation time. The oil recovery of the sequential solvent extraction performed in this study was higher by 5.17% and 27.35% as compared to using ethanol and hexane as a single solvents, respectively. However, the cost was 19.61% and 7.41% higher as compared to ethanol and hexane as single solvents, respectively.