Content of antioxidants in plant extracts obtained by supercritical extraction

Abstract

The content of natural antioxidants in extracts of medicinal plants, fruits, and seeds obtained by supercritical fluid extraction was determined by a microcalorimetric technique using the model reaction of induced cumene oxidation. All tested extracts can be divided into two groups according to their antioxidant activity. The first group includes extracts containing strong antioxidants with high inhibition rate constants; the second group includes preparations containing week antioxidants capable of reducing the oxidation rate. Among the preparations studied, the maximum concentrations of antioxidants were found in the extracts of sage (10.0 × 10−2 mole/kg), rosemary (5.3 × 10−2 mole/kg), cranberry (1.4 × 10−2 mole/kg), and carrot (1.2 × 10−2 mole/kg). The rate constants of reactions between antioxidants and peroxide radicals were calculated (k 7 = (0.4 − 9.0) × 104 liter/(mole sec)). With respect to this value, several types of natural antioxidants can be distinguished in each extract. The most active antioxidants are those contained in the rosemary extract, their reaction rate constants being about 2.3 × 105 liter/(mole sec). It is suggested that the most active components are tocopherols, polyphenols, and quinones.