134 JOURNAL OF COSMETIC SCIENCE
Figure 2. DTA curves of AVB and its binary mixtures 1:1 (m/m) with lipid-based excipients: (A) solid
lipids, (B) liquid lipids, and (C) surfactants. Samples were analyzed under nitrogen atmosphere (50 mL/min−1),
heating rate of 10°C/min−1, and temperature range of 25–500°C.

135 ImprovedPROVED AVB PhotostabilityOTOSTABILITY UsingING NLCs
melting temperature, between 14.93°C–7.9°C, were observed in the binary mixtures with
Tween 80, oleic acid, mineral oil, isopropyl myristate, Tween 20, and Span 80. The smallest
variations in the AVB melting temperature (3.74°C–1.63°C) were observed in the binary
mixtures with carnauba wax, caprylic and capric acid triglyceride, sesame oil, and Span 85.
These changes observed in the endothermic event, in the presence of excipients, may be
related to the dissolution of AVB in molten lipids/oils or its solubilization by surfactants.
The mass loss curves of AVB and its binary mixtures with lipid-based excipients are shown
in Figure 3. The DTG T
peak of the AVB was 323.84°C. The smallest anticipations of the
weight loss temperature of AVB (3.26°C at 12.26°C) were observed in the binary mixture
with caprylic and capric acid triglyceride, carnauba wax, beeswax, oleic acid, and sesame
oil. A greater loss of thermal stability of AVB was observed in the binary mixtures with
Poloxamer 188 (anticipation of 24.27°C) and Span 80 (anticipation of 34.25°C). DTG
curves of the mixtures with glyceryl monostearate, isopropyl myristate, mineral oil, Tween
80, Tween 20, and Span 85 showed AVB-DTG T
peak anticipation between 14.6°C–19.37°C.
FOURIER TRANSFORM INFRARED SPECTROSCOPY
Figure 4 shows the FTIR spectra of AVB, the binary mixture of AVB with solid lipids
(Figure 4A), liquid lipids (Figure 4B), and surfactants (Figure 4C). The FTIR spectrum of
the isolated AVB showed groups at 2,963 cm−1 (C-H bond of aliphatic groups), 1,666 cm−1
(aryl ketone), 1560–1500 cm−1 (C-C-C =O and OH bending), and 1,256 cm−1 (aryl alkyl
ether). These groups have been correlated to the photoprotective activity of AVB.26,27The
characteristic FTIR peaks of AVB were present in the binary mixtures with solid lipids
(Figure 4A) and liquid lipids (Figure 4B). In the spectra of mixtures of AVB with all tested
surfactants (Figure 4C), the band in 2,963 cm−1 was not observed. In the mixtures of AVB
with Tween 80 and Tween 20, no changes were observed in 1,666 cm−1 and 1,256 cm−1,
while in the AVB-Poloxamer 188 mixture, a decrease in the intensity of these bands was
observed. Binary mixtures of AVB with Span 80 and Span 85 showed similar FTIR spectra
to the ones observed for the isolated excipients, with bands overlapping in 1,666 cm−1 and
1,256 cm−1. No changes were observed in the absorption of the enol bands in this region
for all excipients.
The interpretations of results given by the analysis methods are extremely complex.
Generally, interactions are observed, but by themselves they do not allow us to reach a
conclusion of whether components were incompatible. Therefore, it is necessary to carry out
analyses using different methods and interpret them together. The interactions observed in
DTA may indicate dissolution and/or solubilization of the active ingredient in the lipid and
surfactant excipients, not necessarily incompatibilities between them. In the development
of delivery systems, these phenomena of physical interaction between active and matrix-
forming components are often required to improve parameters such as: solubility, EE,
active loading, and stability.19,20
In DTG, anticipations of mass loss may also be related to these physical interactions.
Also, at these high temperatures (which are much higher than the production and storage
temperatures of these formulations), there may be oxidation of the lipid material (or other
degradation phenomena), and these degradation products interfere with the mass loss
temperature of the product. However, it does not necessarily indicate an interaction of the
incompatibility type between the active ingredient and the excipients evaluated. In these