Zinc Ricinoleate

Dumas, Elizabeth R., et al. Journal of cosmetic dermatology, 2009, 8(3), 197-204.

Although zinc ricinoleate does not have antimicrobial activity, it exhibits anti-odour activity. This activity is thought to be based on the inhibition of two hydrolytic enzymes produced by bacteria in the human axillary region. This work first demonstrated the in vitro antimicrobial activity of hops extract against Corynebacterium siccatus and Staphylococcus epidermidis. The hops extract was then combined with zinc ricinoleate in an appropriate matrix to reduce body odor.
Evaluation Methods and Results
· To demonstrate the efficacy of a deodorant formulation containing hops/zinc ricinoleate, a clinical study was conducted to evaluate its inhibitory effect on axillary malodor formation by a sensory panel. The results of this study showed a reduction in malodor ratings from 6.28 to 1.80 after 8 hours of deodorant application.
· An important issue with hops acids is their susceptibility to oxidation. The addition of ascorbic acid was found to improve the stability of hops acids in a dose-dependent manner between 0.05% and 0.2%. In addition, the presence of zinc ricinoleate has a protective effect on hops acid and can slow down its oxidative degradation.

Kuhn, H., et al. Journal of Surfactants and Detergents, 2000, 3, 335-343.

Zinc ricinoleate [Zn(Ri)2] is a highly effective deodorant commonly used in cosmetic formulations. This work explored the interaction mechanism between Zn(Ri)2 and active odor substances through molecular dynamics computer simulation. The dynamic characteristics of the Zn(Ri)2 molecular structure in vacuum, oil phase and aqueous solution were simulated based on simple molecular mechanics approximation.
The actual molecular conformation was determined and the adduct of ammonia and Zn(Ri)2 was simulated. Upon detailed examination of the structures in both vacuum and oil phases, it became evident that the Zn2+ ion is predominantly shielded by the oxygen ligands. The calculated structural changes resulting from the interaction between Zn(Ri)2 and water molecules led to a reduction in the effectiveness of this electrostatic shielding.
In an aqueous solution, nucleophilic attacks by odor-active compounds on the relatively exposed Zn2+ atom occur more readily. Furthermore, the simulation of the addition product of Zn(Ri)2 with ammonia indicated a fundamental structural transformation, which contributed to an enhancement in both the solubility and adsorption activity of Zn(Ri)2.