Newly synthesized dopamine ester derivatives and assessment of their antioxidant, antimicrobial and hemolytic activities

• A series of dopamine esters with increasing lipophilicity was synthesized.
• Candida antarctica Lipase (Novozyme 435) was used as a biocatalyst.
• Esterification had little effect on radical-scavenging capacity.
• Middle chain length derivatives of dopamine displayed a high hemolytic activity.
• Middle chain length derivatives of dopamine exhibited a high antimicrobial activity.

Preparation of dopamine derivatives was carried out as a response to the increasing demand for new lipophilized antioxidants in food, cosmetic and pharmaceutical industries. A large series of dopamine esters (DA-C3 to DA-C18:1) with increasing lipophilicity was synthesized using lipase from Candida antarctica (Novozyme 435) as a biocatalyst. The highest conversion yield (52.75%) was reached when caprylic acid (DA-C8) was used as acyl donor. Synthesized compounds were purified and evaluated for their antioxidant activity using the DPPH and the ABTS tests. Results showed that esterification had little effect on radical-scavenging capacity. However, long chain fatty acid esters displayed higher protective effect of oil against oxidation at 70 °C as compared to the parent dopamine or to the BHT. The hemolytic activity of dopamine esters was studied. Middle chain length derivatives (DA-C8 and DA-C12) of dopamine and oleic acid derivative (DA-C18:1) showed the highest hemolytic activity against human erythrocyte. The antimicrobial activities of dopamine esters were also evaluated using well diffusion and minimal inhibition concentration methods. Among all the tested compounds, DA-C8 and DA-C12 exhibited the highest antibacterial activities. These results open up potential applications by using dopamine derivatives as antioxidants and antimicrobial compounds in cosmetic, food and pharmaceutical industries.