Ultrasonic-assisted Emulsification of Passiflora Seed Oil Nanoemulsion

Abstract.

Passiflora edulis var. edulis is commercially valuable for its fruit. The seeds are a byproduct of the food industry and can be used as a source of oil for the cosmetic, pharmaceutical, and food industries. The aim of this study was to optimize the conditions for ultrasound-assisted emulsification of o/w nanoemulsions and evaluate their emollient activity. The Box-Behnken design (BBD) response surface methodology was used to determine the optimal emulsification conditions. The emollient activity of bamboo seed oil was evaluated in healthy volunteers using a skin moisture and viscoelasticity meter. The properties of the ultrasound-prepared nanoemulsion were significantly improved when the optimal ultrasound power was 85.34 W, irradiation time was 5.96, water content was 70.65%, and oil-surfactant ratio was 5:4. Finally, both bamboo seed oil and ultrasound-prepared nanoemulsions exhibited emollient activity.

1. Introduction

The widespread use of plant seed oils in cosmetic formulations is due to the composition of these oils, which are rich in fatty acids and triglycerides, which help to reduce transepidermal water loss by forming an occlusive film [1]. Some of the seed oils widely used in cosmetics are castor oil Ricinus communis for its skin softening and moisturizing properties, cocoa butter Theobroma cacao (Sterculiaceae), mango butter Mangifera indica (Anacardiaceae), coconut oil Cocos nucifera (Arecaceae), and sunflower oil Helianthus annuus (Compositae), which prevents epidermal water loss, an important factor in maintaining skin moisture [1].

Emulsions or nanoemulsions are commonly used to incorporate plant oils into cosmetics. Nanoemulsions are kinetically stable, isotropic, clear dispersions of two immiscible liquids in the range of 20–200 nm. They are translucent or transparent and have high kinetic stability. The small size of the dispersed droplets makes them inherently stable against destabilizing processes such as pyrolysis, sedimentation, flocculation, and coalescence, and allows for efficient transport of active ingredients from the formulation to the skin [2]. Given that nanoemulsions can be designed using different lipids, the effect of the physicochemical properties of the oil on the physical properties of the emulsified system needs to be considered [3].

Passiflora var. edulis is a plant of the family Passifloraceae. It is native to Brazil but grows in different subtropical regions between 1600 and 2700 m.a.s.l. and is a species that can still be found in the wild. Passiflora var. edulis was chosen as the subject of this study because it is widely cultivated in Colombia and there is great interest in exporting it to European countries [4]. In addition, the commercial interest in the seed oil of Passiflora var. edulis could contribute significantly to the value of the crop. Previous reports have identified the presence of saturated and polyunsaturated fatty acids and essential fatty acids in the oil extracted from the seeds of the plant species of the genus Moso, compounds that are commonly used as emollients in the cosmetic industry and have known antioxidant and antimicrobial activities. Nevertheless, there have been no reports to date on the application of Passiflora var. edulis seed oil in the cosmetic field, whereas Passiflora var. edulis seed oil (commonly known as Passiflora edulis) is a recognized cosmetic emollient ingredient.

Considering the potential application value of different oils extracted from plants of the Passifloraceae family in skin and hair care cosmetics, in this study, the chemical and physicochemical properties of bamboo seed oil were evaluated, the ultrasound-assisted emulsification conditions of bamboo seed oil nanoemulsion were optimized, and its emollient activity was evaluated.

2. Materials and methods

2.1. Plant materials

Mature fruits (10 kg) of P. edulis var. edulis were obtained from a local enterprise in the city of Bogotá (Colombia). The bamboo seeds were manually separated from the pulp and then washed with distilled water to remove all pulp residues.

2.2. Study on the extraction process of bamboo seed oil

The extraction was carried out according to a previously reported method [5]. Briefly, 1 kg of dried seeds were extracted with n-hexane (1:5 p/v) at room temperature for 96 h, and the solvent was changed every 24 h. The plant to liquid ratio was 1:5 w/v. Subsequently, the solvent was eliminated by decompression, and the obtained oil was stored in a desiccator until further analysis. The yield was 20.5%.

2.3. Chemical properties of passionflower seed oil

2.3.1. Preparation of fatty acid methyl esters

Cold esterification of fatty acids was performed according to the European Commission [6] using the method described by Hernandez et al. [5]. Briefly, PEO (100 mg), hexane (1 mL), and 0.5 mL of 2 N methanolic potassium hydroxide solution were mixed and shaken vigorously for 30 s in a 5 mL screw-top test tube to prepare the esterification reaction. After 45 min, the mixture turned clear; the upper organic phase was transferred to a clean autosampler vial and 1 μL was analyzed by GC-MS/EI.

2.3.2. GC-MS analysis

All GC-MS/EI analyses were performed on a Thermo Scientific™ TRACE™ 1300 gas chromatograph connected to an ISQ QD single quadrupole mass spectrophotometer and an AL1310 autosampler (Thermo Fischer, MA, USA) in liquid injection mode. Fatty acids were identified by comparison of retention times with standards and by comparison of mass spectra and fragmentation patterns with the NIST 267 library. Data analysis was performed using the Chromeleon® 7 Chromatography Data System Version 7.2.2.6394 software with the NIST 2007 target library. GC conditions were in accordance with ISO-5508 [7], as shown in Table 1.