Abstract
The aim of the current work was to encapsulate olive leaves extract in biodegradable poly(lactic acid) nanoparticles, characterize the nanoparticles and define the experimental parameters that affect the encapsulation procedure. Moreover, the loaded nanoparticles were incorporated in a cosmetic formulation and the stability of the formulation was studied for a three-month period of study. Poly(lactic acid) nanoparticles were prepared by the nanoprecipitation method. Characterization of the nanoparticles was performed using a variety of techniques: size, polydispersity index and ζ-potential were measured by Dynamic Light Scattering; morphology was studied using Scanning Electron Microscopy; thermal properties were investigated using Differential Scanning Calorimetry; whereas FT-IR spectroscopy provided a better insight on the encapsulation of the extract. Encapsulation Efficiency was determined indirectly, using UV-Vis spectroscopy. The loaded nanoparticles exhibited anionic ζ-potential, a mean particle size of 246.3 ± 5.3 nm (Pdi: 0.21 ± 0.01) and equal to 49.2%, while olive leaves extract release from the nanoparticles was found to present a burst effect at the first 2 hours. Furthermore, the stability studies of the loaded nanoparticles’ cosmetic formulation showed increased stability compared to the pure extract, in respect to viscosity, pH, organoleptic characteristics, emulsions phases and grid.
Highlights
Oxidative stress is one of the main factors which cause skin aging [1,2,3,4,5,6,7,8,9]
Taking the multifactorial character of oxidative stress into account, we decided to evaluate the in vitro antioxidant activity of olive leaves extract (OLE), using two different antioxidant assays: (a) the radical scavenging ability of OLE was tested against the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical; and (b) the ability of OLE, OLE-NPs and poly(lactic acid) (PLA) to scavenge hydrogen peroxide (H2O2), a very important reactive oxygen species the production of which is increased during skin aging, was tested using the luminol chemiluminescence method
A potent antioxidant flavonoid which is used in many cosmetic formulations was used as the reference compound
Summary
Oxidative stress is one of the main factors which cause skin aging [1,2,3,4,5,6,7,8,9]. Skin is equipped with enzymes and endogenous antioxidants in order to control the reactive oxygen species (ROS) in balance and repair the damage caused by them. Over time this defensive mechanism of the skin weakens [2,7]. The main components of the leaves of the olive tree (Olea europea) are secoiridoids like oleuropein, ligostroside and dimethyloleuropein They contain flavonoids (such as luteolin-7-glucoside, apigenin, diosmetin, rutin) as well as phenolic compounds (such as tyrosol, caffeic acid, vanillin, vanillic acid, hydrotyrosol) [15,16,17]
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