Antioxidant and pro-oxidant in vitro evaluation of water-soluble food-related botanical extracts

The total phenol content, antioxidant and pro-oxidant activities of deodourised, water-soluble aniseed, basil, caraway, cardamon, fennel, ginger, juniper, laurel and parsley extracts were estimated using a number of in vitro assays. The laurel and basil extracts contained the highest phenol content of 107.3 ± 1.3 GAE [mg gallic acid equivalents/g (dry wt.) extract] and 98.5 ± 1.4 GAE, respectively, whilst the ginger extract contained the lowest content at 14.9 ± 0.9 GAE. Juniper, laurel and basil extracts were consistently better than the other extracts in terms of iron(III) reducing activity, inhibition of β-carotene-linoleate thermal co-oxidation and N,N-dimethyl-p-phenylenediamine and hydroxyl radical scavenging assays. Potential pro-oxidant activities of the extracts were assessed using both DNA and bovine serum albumin (BSA) as substrates. None of the extracts were capable of stimulating hydroxyl-mediated DNA fragmentation; however, the extracts could be categorised in the protein oxidation assay as extracts with (i) no significant (p > 0.05) effect, (ii) a significant (p < 0.05) protective effect or (iii) a significant (p < 0.05) pro-oxidant effect. The extracts from juniper, laurel and basil had a pro-oxidative effect upon BSA at a dose of 2 mg/ml, as estimated from the degree of carbonylation measured.