Modulation of CYP1A1 activity by a Ginkgo biloba extract in the human intestinal Caco-2 cells.

Ginkgo biloba is a widely consumed dietary supplement. Some dietary active compounds modulate the activity of biotransformation enzymes inside the enterocytes and more interestingly of cytochrome P-450 1A1 (CYP1A1). This enzyme is of a particular interest because of its implication in the metabolism of some exogenous pro-carcinogens or endogenous molecules. In the present work, we have used Caco-2 cells to study the effect of a standard reference material of a Ginkgo biloba extract (GBE) (10-400 µg/ml), as well as of its major individual active compounds (kaempferol, quercetin, isorhamnetin, ginkgolides and bilobalide), alone or in mixtures, at realistic intestinal concentrations, on the induction of CYP1A1 activity, in the presence or absence of benzo[a]pyrene (B[a]P) (0.1 µg/ml), a well-known CYP1A1 inducer. 3-O-rutinosides of kaempferol, quercetin and isorhamnetin were also tested. We have demonstrated a strong induction (p < 0.005) of CYP1A1 activity and a slight, but significant (p < 0.005), decrease of this activity in the presence of B[a]P by the GBE at the realistic exposure level of 100 µg/ml. The inductive effect was explained, in part, by quercetin and kaempferol after 24h exposure while unknown compounds seem to be responsible for the strong CYP1A1 induction observed after 6h exposure. The inhibitory potency of flavonols on CYP1A1 activity in presence of B[a]P was much stronger for the aglycones than for the 3-O-rutinosides, explaining the slight effect observed with the GBE, mainly composed of glycosylated flavonoids. These results indicate that GBEs may disturb intestinal CYP1A1 activity and, in turn, affect the metabolism of other compounds. The present paper thus highlights the necessity to take these side effects into account when administrating Ginkgo biloba herbal supplements.

Dietary cadmium intake by the Belgian adult population.

The aim of this study was to estimate the dietary cadmium (Cd) intake of the Belgian adult population, to compare this dietary Cd exposure to the tolerable weekly intake (TWI) recently established by the European Food Safety Authority (EFSA) and to determine the major food groups that contribute to dietary Cd exposure in Belgium. Food consumption data were derived from the 2004 Belgian food consumption survey (two 24 h recalls, 3083 participants). Cadmium concentrations in food items (n = 4000) were gathered from the control program of the Belgian Federal Agency for the Safety of the Food Chain for the period 2006-2008. Dietary intake per individual was calculated from consumption data and median Cd concentrations. The population mean, median and 95th percentile of the dietary intake values were 0.98, 0.85 and 2.02 µg kg⁻¹ body weight per week respectively. Two percent of the Belgian adult population has a dietary Cd intake above the recent TWI of 2.5 µg kg⁻¹ body weight established by EFSA in 2009. Cereal products and potatoes contribute for more than 60% to Cd intake.

Monitoring the persistence of genes deriving from genetically modified plants in the soil environment.

To study the gene persistence in the soil environment, soil samples were collected from sugar beet (Beta vulgaris) and chicory (Cichorium intybus) experimental fields just before harvest. They were homogenized, mixed and stored at constant humidity in a non-heated room. Sub-samples of soils were subsequently collected at regular intervals, dried and sieved through a 1.8-mm mesh before DNA was extracted. Specific primers were then used for the detection of plant DNA by hot start PCR. Results reveal that, under laboratory conditions, transgenic and non-transgenic sugar beet DNA was still detected after 25 days incubation in the soil taken from a sugar beet experimental plot while detection of chicory DNA was still possible after 50 days incubation in soil taken from the chicory experimental plot. This might be in correlation with the stronger resistance of chicory radicles to decomposition as compared to radicles from sugar beets.