HLB determination for nanoemulsions of four essential oils from Northern Peru

Abstract

Essential oils, recognised for their diverse biological activities, are of considerable interest for the development of medicinal, cosmetic, and repellent formulations. However, their limited aqueous solubility restricts practical applications. This limitation can be addressed through nanotechnology, particularly by employing nanoemulsions, which not only enhance aqueous dispersion but also improve the bioavailability and stability of active constituents. To obtain stable formulations, it is crucial to determine the hydrophilic–lipophilic balance (HLB), which depends on the proportion and type of surfactants used in the emulsions. The objective of this study was to establish the HLB of nanoemulsions formulated with essential oils from four plant species native to northern Peru: Minthostachys mollis, Bursera graveolens, Myrcianthes oreophila, and Artemisia absinthium. For this purpose, 11 nanoemulsions were prepared with each essential oil using the low-energy input method, and their droplet size and polydispersity index were determined. The chemical composition of the oils was analysed by gas chromatography–mass spectrometry (GC–MS). The results indicated that optimal HLB values were 13.08 (F4) for M. mollis, 11.16 (F7) for B. graveolens, 12.44 (F5) for M. oreophila, and 13.72 (F3) for A. absinthium. The oil of M. mollis showed a high concentration of pulegone (75.35%), whereas B. graveolens oil was dominated by limonene (71.16%). In its turn, M. oreophila oil contained α-pinene, 1,8-cineole, linalool, and β-pinene as major constituents, while cis-chrysanthenol was the principal component of A. absinthium oil. These findings highlight the development of stable nanoemulsions of four active essential oils from Northern Peru with practical application in health and agriculture areas.