They have chemistry in more ways than one

Married couple Johannes and Amor Marx proved they truly have chemistry between them when the pair walked across the stage at the Nelson Mandela University Summer Graduation to receive their doctorates in chemistry.

With the guidance of their promoter, Dr Nicole Vorster, the couple’s research showed that a novel bioplasticiser, synthesised from compounds found in the leaves of the eucalyptus tree, could be used as a natural-based, non-toxic plasticiser substitute in the cosmetic and pharmaceutical industries.

Plasticisers are small molecules added to coatings to make them more flexible.

Recent trends towards replacing toxic plasticisers used in cosmetic and pharmaceutical products with safer, more environment-friendly alternatives prompted this research.

The method to synthesise the bioplasticiser, called PMD-citronellal acetal (technically para-menthane-3,8-diol) from citronellal and PMD was previously developed at the InnoVenton Institute for Chemical Technology at the university.

Amor investigated the properties and stability of this novel bioplasticiser in selected cosmetic products which she formulated for this project, while Johannes investigated the same bioplasticiser as an additive to ethylcellulose tablet coatings in the pharmaceutical industry.

Amor’s research focused particularly on the leaching of plasticiser out of products such as lip gloss and nail polish, which can be problematic as the plasticisers can be absorbed by the skin.

She compared the properties and stability of the bioplasticiser with a controversial phthalate plasticiser which until recently has been commonly used in such cosmetic products.

The results showed that the novel bioplasticiser exhibited good plasticising properties, did not leach from the cosmetic products, and was found to be very stable within the cosmetic products tested.

Johannes wanted to determine whether the novel bioplasticiser would perform in a similar way to other commonly used plasticisers in pharmaceutical coatings, in relation to ethylcellulose.

Ethylcellulose is an enteric coating for gelatin capsules designed to resist disintegration in the gastric environment to protect and deliver the pharmaceutically active ingredient to the target site intact.

His research showed that the citronellal PMD-acetal outperformed a commonly used bioplasticiser in pharmaceutical coatings, triethyl citrate, by providing a more flexible, more disintegration-resistant ethylcellulose film.