Evaluation of plant-derived saponins for crude oil dispersion and prospects in environmental remediation

Petroleum contamination continues to threaten soil and water systems in tropical regions, prompting interest in plant-derived saponins as sustainable alternatives to synthetic surfactants for crude oil dispersion. This study evaluated saponins extracted from Butyrospermum paradoxum (BP), Piliostigma reticulatum (PR), Waltheria indica (WI), Trigonella foenum-graecum (TFG), and Jatropha curcas (JC) to determine their suitability for environmental remediation. Notably, the saponin-rich extracts from these plants have not been previously studied for crude oil dispersion, highlighting the novelty of this work. Saponins were obtained using ultrasound-assisted extraction and purified through a fermentation-based process, yielding extract recoveries ranging from 11.65% (JC) to 32.53% (BP) and total saponin contents between 252.39 mg/g (TFG) and 606.32 mg/g (WI). Purity increased following fermentation, with PR reaching the highest level (70.48%). Interfacial analyses revealed strong variation among species: BP showed the greatest reduction in surface tension (45.41 to 30.43 mN/m), while BP and PR exhibited the lowest critical micelle concentrations (CMC) (60 mg/L). Emulsification stability surpassed the 50% effectiveness threshold in BP (74.67%), WI (64.81%), and PR (57.16%). Droplet size measurements further identified BP (41.43 nm, PDI 0.220) and PR (54.81 nm, PDI 0.226) as capable of forming stable nanoscale emulsions, whereas TFG and JC generated larger, polydisperse droplets with lower stability. Overall, BP and PR emerged as the most efficient natural surfactants, demonstrating strong potential for crude oil dispersion and offering promising prospects for sustainable environmental remediation.