## 1 Introduction  
Essential oils (EOs) are natural, oily, colorless, and volatile liquids soluble in alcohol, ether, and vegetable oils, but insoluble in water. These are found in oil glands present at different depths in the flowers, buds, herbs, fruits, seeds, leaves, twigs, bark, and roots. These oils are commonly used in perfumery, toiletties, and personal hygiene products. EOs extraction is usually conducted by steam or hydro-distillation, cold pressing, organic solvent, and supercritical CO\({}_{2}\) extraction from specific plant organs [1]. The extraction method along with the soil type, provenance, genotype, climate, age, organ, and plant vegetative stage affects the quality and quantity of their components [2]. EOs are composed by complex mixtures of lipophilic compounds at different concentrations in which two or three major components prevail at high concentrations as compared to trace amounts of others compounds. Usually, those main compounds are responsible for the attributed biological properties [3]. Most of the commercial EOs are mainly chemotyped by gas chromatography (GC) and mass spectrometry (MS) analyses. These instrumental analytical techniques allow for a precise characterization of the volatile fraction. Other techniques, such as liquid chromatography, Raman, and Fourier-Transformed Infrared Spectroscopy(FT-IR) are extensively used for the assessment of authenticity, impurities, geographical origin, and possible adulteration [4; 5]. EOs are an important ingredient in packaging, food, and pharmaceutical industries, since they exhibit biological activities, such as antimicrobial, analgesic, sedative, and anti-inflammatory properties. They can also penetrate the skin and unfold local effects, such as skin hydration and skin elasticity, possibly due to accumulation in the fatty tissue after dermal application [6]. Citrus oils are of especial interest, since they represent one of the largest EOs production worldwide. The most commercialized citrus species are sweet oranges, tangerines, lemons, limes, and grapre fruits in decreasing order. The oil content of citrus peels range between 0.5 and 5.0% (w/v) and it is composed by a mixture of monoterpene and sesquiterpene hydrocarbons and their oxygenated derivatives. The main component of citrus oils is limonene ranging from 68 to 98% in sweet orange, from 45 to 76% in lemon and from 32 to 45% in bergamot [7]. Citrus oils possess antioxidant and hydrating activities that could prevent the damaging effect of air pollutants, and UV radiation, such as phototoxicity, skin aging, inflammation, and melanoma [8]. Therefore, they could also replace synthetic antioxidants, such as benzoates, nitrites, butylhydroxyanisole, and butylhydroxytoluene, which have shown harmful effects on human health [9]. Particularly, the _Citrus limon_ (L.) essential oil (LEO) has been used in topical preparations to nourish, exfoliate, reduce itching, and treat pimples and wrinkles. These biological activities are attributed to the composition of non-polar isoprenoids, such as limonene (54.6%), \(\gamma-\)terpinene (19.1%), \(\beta-\)pinene (14.5%), \(\alpha\)-pyrene (3.9%), gerani (2.3%), and myrceene (1.5%) [10]. The exact composition depends on the climate, cultivation conditions, variety and cultivar, extraction, and separation techniques. This oil is also considered as safe due to their non-toxic nature and hypoallergenicity. However, the compounds of this oil are highly volatile, water insoluble, and instable to heat, oxygen, and light, resulting in being challenging for the development of topical preparations [11]. Therefore, several strategies involving microparticulate systems have been developed to formulate oily bioactive substances (OBS) utilizing polymeric and lipidic materials. The former involves techniques, such as solvent evaporation, emulsion polymerization, and inclusion polymers utilizing toxic solvents that yield impurities in the resulting product [12].