Development of nanoemulsion formulation of mustard oil, its chemical characterization and evaluation against post harvest anthracnose pathogens

Abstract

Oil-in-water nanoemulsion (NE) formulations of mustard oil known for prominent antimicrobial activities have been prepared, characterized and tested against anthracnose pathogens Colletotrichum musae and Colletotrichum capsici. Physico-chemical properties viz., appearance, stability, pH, centrifugation, storage-stability, thermodynamic stress, persistent foam, droplets size and zeta potential were tested for the NE formulations. The NE formulations were prepared using low energy emulsification process with the optimized composition (w/w) of mustard oil (5%), Tween 20 and sodium dodecyl benzene sulfonate emulsifiers blend (20–30%), co-surfactants (4%), and de-ionized water. The required hydrophile-lipophile balance value for emulsifier blends was determined as 11.39–11.74. Only 3 (viz., NF2, NF3 and NF6) out of 15 NE formulations with transparent faint yellow color (pH 6.3) passed all the physico-chemical parameters tested. Among these, NF2 (foam height < 1 mL) was selected for further study. The average diameter (23 nm), polydispersity index (0.38) and zeta potential (− 12 mV) of mustard oil droplets in NF2 indicated the formation of a stable and homogeneous NE formulation. Application of NF2 exhibited low level of sensitivity to C. capsici and C. musae with maximum growth inhibition (6.2–7.3%) at 1.0% dose. Out of 18 phytochemicals detected in mustard oil by gas chromatography-mass spectrometry, 11 have been reported with antifungal properties including trans-13-octadecenoic acid with the highest relative abundance. The observed antifungal activity may be attributed to the presence of at least some or all the identified phtytochemicals in mustard oil. Further bio-assay on sensitive plant pathogenic fungi is underway to explore the application of the developed NE formulation.