Pyrolysis process and antioxidant activity of pyroligneous acid from Rosmarinus officinalis leaves

• Analyze the pyrolysis process and the pyrolysis products of Rosmarinus officinalis L.
• Compare the antioxidant effect of different organic extracts of pyroligneous acid.
• Analyze the compositions of extracts of pyroligneous acid by GC–MS.

We studied the pyrolysis process and products of Rosmarinus officinalis leaves. Three kinds of plant materials were used: fresh leaves, air-dried leaves, and air-dried leaves after essential oil distillation. The pyroligneous acids (PA) obtained by pyrolyzing the plant materials with different heating powers were extracted with organic solvents, including methanol, ethyl formate, dichloromethane, thiophene and tetrahydrofuran. The antioxidant activities, including free radical scavenging activity and ferric reducing power of the PA extracts were investigated. The synthetic antioxidants BHA and BHT were used as positive controls. The dichloromethane extract of PA showed superior antioxidant properties. The chemical compositions of the extracts were determined by GC–MS, and further proved that the dichloromethane extract had the best antioxidant characteristics.