The extract acts on the 5 alpha reductase enzyme that is known to control to a large extent the sebum secretion of the skin, explained the researchers in a paper published in the International Journal of Cosmetic Science.
According to the study, the extract at 2 percent outperformed 1 per cent zinc gluconate, an ingredient traditionally used to try to control sebum production, when tested on two groups of 25 subjects in France and two groups of 20 subjects in Thailand.
Explaining the choice of zinc gluconate at 1 per cent, study author Boris Vogelgesang told CosmeticsDesign.com USA: “Problems of solubility and stability in the formula can occur for concentrations higher than 1 per cent. Thus, 1 percent is probably a common and efficient concentration for zinc gluconate in cosmetic skin care formulations.”
Subjects applied formulations with either the extract or zinc gluconate twice daily on the whole face for a month, in a double blind study.
Instrumental measurements investigating the shine effect, as well as clinical and self evaluations, were performed in order to assess the relative efficacy of each ingredient.
Reduced shiny appearance
According to the scientists, the extract, which is marketed by BASF under the name Mat-XS Bright, reduced significantly the return of the shiny appearance after washing, as measured by an imaging system looking at the mirror like effect of the skin.
In addition, clinical evaluation showed a reduction in the shiny appearance of the skin and the visible pore size. Self evaluation also highlighted efficacy, with Caucasian volunteers stating improvements in complexion, evenness and radiance and Asian volunteers seeing improvements in skin shininess after 14 days.
According to the study, although those using zinc gluconate also experienced some improvements ‘for a large majority of the items evaluated, whether instrumentally or by clinical evaluation or by self assessment, results obtained with Orthosiphon stamineus leaf extract were directionally better’.
Regarding the results, the scientists were quick to point out that although 5 alpha reductase is known to play a large role in controlling sebum production, climatic factors such as temperature and humidity as well as food also have a strong effect on the oily appearance of the skin.
Source: International Journal of Cosmetic Science
On the effects of a plant extract of orthosiphon stamineus on sebum-related skin imperfections
B. Vogelgesang, N. Abdul-Malak, C. Reymermier, C. Altobelli and J. Saget