The use of astringents in the cosmetic industry is widespread as tonic lotions, cleansers,
deodorants and antiperspirants. Aluminium chlorohydrate, among others aluminium salts,
is highly used as an astringent. Recently, the use of aluminum in cosmetics raised
the concern about its safety to humans. Although the regulatory agencies worldwide
assure the safety of this raw material, this issue has led the search for substitutes
of aluminium salts to serve consumer needs. In the deveolpment of new raw materials
it is wise to evaluate a priori the in vitro efficacy to address the extremely complex functional systems of living organisms.
Colorimetric titration methods for evaluating tannins based on precipitation of hide
powder (1) are very laborious and not specific to tannins (2). The objective of this
study was to apply the isothermal titration calorimetry (ITC) method, as described
elsewhere by others (3,4,5), to evaluate the interaction of bovine gelatin with 8
commercially available natural and semi-synthetic tannin containing extracts. The
bovine gelatin is an especially good source of proline binding sites found in human
skin. The tannins belong to the hydrolysable and condensed types present in 5 different
plant species. ITC is a reliable and fast technique to evaluate important parameters
like enthalpy, entropy, stoichiometry and association binding constant in an unique
experiment for further decision support. All raw materials had the efficacy compared
to aluminium chlorohydrate. The developed methodology has provided an useful tool
for astringency evaluation of tannins and will illuminate the road toward better cosmetics.
References: 1. Folin O, Ciocalteau V J (1927) Biol Chem 73: 627.
2. Verza S G, Kreinecker MT, Reis V, Henriques A T, Ortega GG (2007) Quimica Nova
30(4): 815–820.
3. Frazier R A, Papadopoulou A, Mueller-Harvey I, Kissoon D (2003), J Agric Food Chem
51(18): 5189–5195.
4. Frazier R A, Papadopoulou A, Green RJ (2006) Pharm Biomed Anal 41(5): 1602–1605
5. Frazier R A, Deaville ER, Green RJ (2010) Pharm Biomed Anal 51(2): 490–495,.
