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. 2020 Apr 30;25(9):2105.
doi: 10.3390/molecules25092105.

Development of Water-in-Oil Emulsions as Delivery Vehicles and Testing with a Natural Antimicrobial Extract

Giovana Colucci  1   2 , Arantzazu Santamaria-Echart  1 , Samara C Silva  1   3 , Isabel P M Fernandes  1 , Caroline C Sipoli  2 , Maria F Barreiro  1
Affiliations

Development of Water-in-Oil Emulsions as Delivery Vehicles and Testing with a Natural Antimicrobial Extract

Giovana Colucci et al. Molecules. .

Abstract

Water-in-oil (W/O) emulsions have high potential for several industrial areas as delivery systems of hydrophilic compounds. In general, they are less studied than oil-in-water (O/W) systems, namely in what concerns the so-called fluid systems, partly due to problems of instability. In this context, this work aimed to produce stable W/O emulsions from a natural oil, sweet almond oil, to be further tested as vehicles of natural hydrophilic extracts, here exemplified with an aqueous cinnamon extract. Firstly, a base W/O emulsion using a high-water content (40/60, v/v) was developed by testing different mixtures of emulsifiers, namely Tween 80 combined with Span 80 or Span 85 at different contents. Among the tested systems, the one using a 54/46 (v/v) Span 80/Tween 80 mixture, and subjected to 12 high-pressure homogenizer (HPH) cycles, revealed to be stable up to 6 months, being chosen for the subsequent functionalization tests with cinnamon extract (1.25-5%; w/v; water-basis). The presence of cinnamon extract leaded to changes in the microstructure as well as in the stability. The antimicrobial and antioxidant analysis were evidenced, and a sustained behavior compatible with an extract distribution within the two phases, oil and water, in particular for the higher extract concentration, was observed.

Keywords: cinnamon extract; emulsions; hydrophilic extracts; natural compounds; sweet almond oil; water-in-oil.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Optical microscopy of the produced 40/60 water-in-oil (W/O) emulsions. Primary emulsions: (a) S80/T80 54/46; (b) S80/T80 80/20; (c) S85/T80 80/20. After 12 high-pressure homogenizer HPH cycles: (d) S80/T80 54/46; (e) S80/T80 80/20; (f) S85/T80 80/20. Bar = 10 μm, 200× magnification.
Figure 2
Figure 2
Stability over time of the base emulsions prepared using different number of HPH cycles.
Figure 3
Figure 3
Images of system S80/T80 54/46 with 12 cycles HPH: (a) Fresh. (b) After 6 months of storage at room temperature.
Figure 4
Figure 4
Images of W/O (a) base emulsion and emulsions containing (b) 1.25%, (c) 2.5%, (d) 3.75%, and (e) 5% of cinnamon extract.
Figure 5
Figure 5
Confocal laser scanning microscopy (CLSM) images (2048 × 2048 pixels) of W/O emulsions at 40/60 ratio: (a) Base emulsion and emulsions containing the cinnamon extract at concentrations of: (b) 1.25%, (c) 2.5%, (d) 3.75%, and (e) 5% (w/v). Bar = 10 μm.
Figure 6
Figure 6
Percentage of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging: (a) Emulsions containing cinnamon extract and the extract methanol/water solutions, for a 50× dilution. (b) Emulsions containing cinnamon extract at different dilutions.
Figure 7
Figure 7
Appearance of emulsions after centrifugation at 3000 rpm for (a) 4 cycles and (b) 1 cycle.
Figure 8
Figure 8
Appearance of emulsions after the thermal treatment at 80 °C.
See this image and copyright information in PMC

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