*3.1. Solubility*

The highest solubility of 89.41 mg/mL for EFV was observed for flaxseed oil and the solubility data are summarized in Table 3. Flaxseed oil was therefore used as the oil phase for constructing pseudo-ternary phase diagrams for the self-emulsifying nanoemulsions. In addition to the physicochemical properties of the EFV the molecular volume, polarity of the oil, chain length and saturation or unsaturation of triglyceride chains of the vegetable oils also influence solubility (MCT) have due to their higher fluidity, better solubility properties [40]. Medium chain triglycerides (MCT) containing oils are best for LBDDS as they are resistant to oxidation and possess high solvent capacity when compared to long-chain triglycerides (LCT) oils because of the high effective concentration of ester functional groups in the oil [41]. However, most of the vegetable oils selected for this study (Table 3) are predominantly and commonly composed of LCT and C<sup>18</sup> chains. It was observed that as the proportion of the unsaturated component C18:3 component of the vegetable oils increases the solubility of EFV increased. Flaxseed oil has approximately 50% C18:3, soybean oil approximately 9.5% C18:3, grapeseed, sunflower and olive oil contain C18:3 of <2% [42–44].


**Table 3.** Saturation solubility of efavirenz (EFV) in vegetable oils.
