88 ANTI-AGEING
CRBP-1 RA
TABLE 1: VITAMIN A ANALOGUES INCLUDED IN CHINA’S CATALOGUE OF USED COSMETIC RAW MATERIALS (EDITION 2021)
06162 06163 06164
COL 1, AP-1 GAG, TYR
Figure 4: Mechanism of epidermal action of retinoic acid
chaperone for RA and retinaldehyde and promotes their metabolism via oxidizing enzymes.8-9 Retinol derivatives, on the other hand, have
to be converted to retinol and then to RA via a long pathway in order to be effective, and both RA, retinol, and retinol derivatives activate the receptor TRPV1 (capsaicin receptor), which inevitably results in irritation. Even liposomes in preparation form still
release retinol, which is converted to RA, with varying degrees of irritation (Figure 5). Also, second-generation Vitamin A actives, which are subject to varying degrees of phototoxicity, are generally recommended for nighttime use. In view of the respective disadvantages of
the first and second generation of Vitamin A, such as poor stability, poor safety (irritation, phototoxicity), long conversion pathway, and weak onset of action, there is an urgent need for better Vitamin A to be developed.
HPR: third-generation vitamin A derivative Through years of research on vitamin A, we developed a third generation vitamin A: HPR (INCI: Hydroxy pinacolone retinoate) (Figure 6) in 2019. It is synthesized from retinoic acid and
small-molecule pinacol, and is characterized by retaining both the efficacy group of retinoic acid without conversion to retinoic acid, and directly binding to the receptor to act, while significantly reducing irritation and improving stability. A series of tests on its stability, safety
Retinol ester O O R = -CH3 , -(CH3 )14 CH3
■ Long pathway converted to retinoic acid onset of action, slow onset of action
■ Commonly used in cosmetics
■ Period of application required for effectiveness
■ Highly irritating ■ Unstable ■ Commonly used in cosmetics
Figure 5: Information on the second generation of dimension A PERSONAL CARE November 2024
www.personalcaremagazine.com
■ Retinoic acid precursor substance ■ Highly irritating ■ Unstable ■ Faster onset of action ■ Cosmetic use
■ Highly efficacious ■ Highly irritating ■ High side effects ■ Fast acting ■ Medicinal use
R OH
06165 06166 06167 06168 06169 05269
O O O Figure 6: Molecular structure of HPR
and efficacy have demonstrated its great advantages over other vitamin A analogues in cosmetic applications.
Stability studies Considering the formulation emulsification application and transportation process conditions, we examined the thermal stability, comparing the changes in AC-HPR-S10(ANECO prepared a third-generation vitamin A derivative-HPR with DMI) and retinol at 80°C, two hours (h), and 50°C, nine days (d), as shown in Figure 7. The results showed that the retinol residue
after 2h at 80°C was only about 17%, while the content of HPR remained almost unchanged. In the test at 50°C for 9d, it was found that the content of HPR was also almost unchanged, while retinol was not detected after five hours. This shows that HPR has better thermal
stability than retinol. We also examined the stability of HPR and retinol in the formulation. HPR and retinol were prepared as
separate emulsions at the same addition level (formulation samples were routinely placed
Retinol Retinal O H
in the laboratory) and their stability in the formulations was investigated. As can be seen in Figure 8, after 16 weeks,
the amount of HPR remained essentially unchanged, whereas the retinol residue was only about 60% after four weeks, with about 10% remaining after 16 weeks. This reveals the superior stability of HPR in the formulation.
Safety studies We tested HPR for phototoxicity, and patch test, respectively.
Phototoxicity test According to the OECD TG432 In Vitro 3T3 NRU Phototoxicity Test (2019) method and determination criteria, the sample ‘HPR hydroxy pinacolone retinoate’ was tested by Intertek, its MPE value was -0.0380, and PIF value was 1.000 (Table 2). The MPE value was -0.0380 and the PIF
value was 1.000, and it was judged that it was not phototoxic (Table 3). Therefore, it can be used in the morning and evening.
Retinoic acid(RA) O
OH Retinol
Retinol/saccharomyces polypeptide
Retinyl propionate Retinyl retinoate Retinyl linoleate Retinyl acetate Retinyl palmitate Retinal
Hydroxypinacolone retinoate
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