Evaluation of octyl p-methoxycinnamate included in liposomes and cyclodextrins in anti-solar preparations: preparations, characterizations and in vitro penetration studies

Figures & data

Table 1 Composition of formulations 1–4

Ingredient
Trade names	INCI names	Free OMC gel cream	β-CD/OMC gel cream	Lipo/OMC gel cream	β-CD/OMC + lipo/OMC gel cream
Phase A
Structure^® XL	Hydroxypropyl starch phosphate	5% w/w	5% w/w	5% w/w	5% w/w
Distilled water	Water	qb100.0	qb100.0	qb100.0	qb100.0
Phase B
Eumulgin^®	Polyglyceryl-2	3% w/w	3% w/w	3% w/w	3% w/w
VL 75	Dipoly-hydroxystearate, lauryl glucoside
Phenova	Phenoxyethanol and parabens	0.5% w/w	0.5% w/w	0.5% w/w	0.5% w/w
BHT	Butylated hydroxytoluene	0.05% w/w	0.05% w/w	0.05% w/w	0.05% w/w
OMC	Octyl methoxycinnamate	8% w/w	4.75% w/w	4.38% w/w	4% w/w
Lipo/OMC			3.25% of OMC = 50 mL of lipo/OMC	1.62% of OMC = 25 mL of lipo/OMC
β-CD/OMC				2% of OMC = 6.63 g of β-CD/OMC	4% of OMC = 13.26 g of β-CD/OMC

Abbreviations: β-CD, β-cyclodextrins; INCI, International Nomenclature of Cosmetic Ingredients.

Table 2 Weight employed to determine sun protection factor by spectrophotometry

λ (nm)	EE (λ) × I (λ)
290	0.0150
295	0.0817
300	0.2874
305	0.3278
310	0.1864
315	0.0839
320	0.0180
	1.0000

Abbreviations: EE, erythemogenic effect of radiation of wavelength (λ); I, intensity of solar light with wavelength (λ).

Figure 1 Removal of the epidermis using a scalpel.

Figure 2 Electron micrograph of liposomes formed after the hydration of the dry phospholipids film containing OMC.

Note: Scale bar = 500 nm.

Abbreviation: OMC, octyl p-methoxycinnamate.

Table 3 ¹H-nuclear magnetic resonance chemical shift changes (Δδ, ppm) for OMC in cyclodextrins

Protons	OMC	β-CD/OMC complex	Δδ* β-CD/OMC
H3H5	6.8 ppm	6.5 ppm	−0.30 ppm
H2H6	7.6 ppm	7.2 ppm	−0.40 ppm
H1′	6.4 ppm	6.0 ppm	−0.40 ppm
H2′	7.6 ppm	7.1 ppm	−0.50 ppm

Note: Δδ* = δ with cyclodextrins – pure δ OMC.

Abbreviations: OMC, octyl p-methoxycinnamate; β-CD, β-cyclodextrins.

Figure 3 ¹H-NMR spectrum of the OMC (A), ¹H-NMR spectrum of the β-CD/OMC (B), molecular structure of the sunscreen (C) and complexation reaction (D).

Abbreviations: OMC, octyl p-methoxycinnamate; β-CD, β-cyclodextrins.

Figure 4 Powder X-ray diffraction patterns of β-CD/OMC (2:1) physical formulation (black) and β-CD/OMC (2:1) complex (red).

Abbreviations: OMC, octyl p-methoxycinnamate; β-CD, β-cyclodextrins.

Figure 5 In vivo values after immersion and in vitro SPF of cream with free OMC (A), cream with lipo/OMC complex (B), cream with β-CD/OMC complex (C), and cream with both complexes (D) (mean ± standard deviation).

Abbreviations: β-CD, β-cyclodextrins; OMC, octyl p-methoxycinnamate; SPF; sun protection factor.

Figure 6 Light micrograph of the pig ear skin. The method totally removed the epidermis (E), remaining the dermis.

Notes: Staining with hematoxylin and eosin. Scale bar = 20 μm.

Table 4 Octyl p-methoxycinnamate solubility in the receptor medium

Receptor medium	Solubility (μg/mL)
Phosphate buffer pH 7.4	37.2
Phosphate buffer pH 7.4 containing 2% (w/w) de polysorbate 80	111.8
Phosphate buffer pH 7.4 containing 4% (w/w) de polysorbate 80	215.1
Phosphate buffer pH 7.4 containing 5% (w/w) de polysorbate 80	271.1

Figure 7 In vitro skin distribution of OMC in the epidermis and the dermis, 6 hours after application of cream with free OMC, cream with lipo/OMC complex, cream with β-CD/OMC complex and cream with both complexes (mean ± standard deviation, n = 4).

Abbreviations: OMC, octyl p-methoxycinnamate; β-CD, β-cyclodextrins.