Antioxidant properties of Teaw (Cratoxylum formosum Dyer) extract in soybean oil and emulsions

The antioxidant activity of an extract from Teaw (Cratoxylum formosum Dyer) leaves was studied in soybean oil and soybean oil-in-water emulsions. Samples containing the extract or reference antioxidants including chlorogenic acid, which comprises 60% of the Teaw extract, were stored at 60 degrees C and analyzed periodically for peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) to allow both hydroperoxides and hydroperoxide degradation products to be monitored. Chlorogenic acid and the Teaw extract were more effective than a-tocopherol in inhibiting lipid oxidation in bulk oil but were less effective in an oil-in-water emulsion in accordance with the polar paradox. The PV/TBARS ratio for oil samples containing chlorogenic acid was higher than for alpha-tocopherol and BHT because chlorogenic acid inhibits both hydroperoxide formation by radical scavenging and hydroperoxide decomposition by metal chelation. The importance of the metal-chelating activity in retarding hydroperoxide decomposition was confirmed by studying the decomposition of oil samples containing added ferric ions. The PV/TBARS ratio was higher for citric acid than for (x-tocopherol in the presence of added ferric chloride, but the order was reversed in samples lacking ferric chloride. Samples containing added chlorogenic acid gave the highest PV/TBARS ratios both in the presence and absence of ferric ions. The PV/TBARS ratios for the samples containing antioxidants fell rapidly to lower values in a soybean oil-in-water emulsion than in the soybean oil. This was due to increased hydroperoxide decomposition in the emulsion at the same PV. The Teaw extract contained 12% oil-soluble components, which contributed to a slightly higher oil-water partition coefficient than that of chlorogenic acid. The antioxidant activity of the aqueous phase of the Teaw extract was reduced more than that of chlorogenic acid by partitioning of the oil-soluble components into oil, which showed that the less-polar components contributed to the antioxidant activity of the Teaw extract in aqueous media.

Inhibitory effects of olive oil phenolics on invasion in human colon adenocarcinoma cells in vitro

Studies in human, animal and cellular systems suggest that phenols from virgin olive oil are capable of inhibiting several stages in carcinogenesis, including metastasis. The invasion cascade comprises cell attachment to extracellular matrix components or basement membrane, degradation of basement membrane by proteolytic enzymes and migration of cells through the modified matrix. In the present study, we investigated the effect of phenolics extracted from virgin olive oil (OVP) and its main constituents: hydroxytyrosol (3,4-dihydroxyphenylethanol), tyrosol (p-hydroxyphenylethanol), pinoresinol and caffeic acid. The effects of these phenolics were tested on the invasion of HT115 human colon carcinoma cells in a Matrigel invasion assay. OVP and its compounds showed different dose-related anti-invasive effects. At 25 mu g/ml OVP and equivalent doses of individual compounds, significant anti-invasive effects were seen in the range of 45-55% of control. Importantly, OVP, but not the isolated phenolics, significantly reduced total cell number in the Matrigel invasion assay. There were no significant effects shown on cell viability, indicating the reduction of cell number in the Matrigel invasion assay was not due to cytotoxicity. There were also no significant effects on cell attachment to plastic substrate, indicating the importance of extracellular matrix in modulating the anti-invasive effects of OVP. In conclusion, the results from this study indicate that phenols from virgin olive oil have the ability to inhibit invasion of colon cancer cells and the effects may be mediated at different levels of the invasion cascade. (c) 2007 Wiley-Liss, Inc.