Dietary flavonoid intake and colorectal cancer risk: evidence from human population studies.

Flavonoids are biologically active polyphenolic compounds widely distributed in plants. More than 5000 individual flavonoids have been identified, which are classified into at least 10 subgroups according to their chemical structure. Flavonoids of 6 principal subgroups- flavonols, flavones, anthocyanidins, catechins, flavanones, and isoflavones- are relatively common in human diets. Flavonoids are a large and diverse group of phytochemicals and research into their anti-carcinogenic potential with animal and cellular model systems supports a protective role. Whether dietary intake of flavonoids is protective against colorectal cancer in humans cannot be easily extrapolated from cell line and animal findings. Epidemiological assessment of the relationship between dietary flavonoid intake and colorectal cancer is limited, with different case-control and cohort study design investigating different combinations of flavonoids. Epidemiologic studies on flavonoid intake and colorectal cancer risk that were conducted yielded inconsistent results, with positive, inverse, and null associations. Because only a very limited number of epidemiological studies have been conducted to examine the associations of dietary intake of flavonoids with colorectal cancer risk, it is premature to make public health recommendations at this time. However, the data to date are promising and emphasize the need for further investigation of these important bioactive plant compounds. This review summarises the epidemiological evidence from case-control and cohort studies on the associations of dietary flavonoid intake with the risk for colorectal cancer. The difficulties in investigating this topic and possibilities for further research are then discussed.

Hypotensive, vasorelaxant and cardiodepressant activities of the ethanol extract of Sideritis raeseri spp. raeseri Boiss & Heldr.

Sideritis raeseri spp. raeseri Boiss & Heldr is a native plant from the Mediterranean region that is used due to its medicinal and culinary properties. The aim of this study was to evaluate the effects of ethanol extract of S. raeseri on the blood pressure, vascular and cardiac contractions. Arterial blood pressure was registered directly from the carotid artery in the anaesthetized rabbits. Aortic rings and the spontaneously beating atria were mounted in tissue bath. An intravenous injection of extract of S. raeseri (0.025-7.5 mg/kg) caused a dose dependent decrease of the arterial pressure and heart rate, with EC(50) value of 24.31±3.87 mg/kg and 88.14±7.51 mg/kg, respectively. In aortic preparations precontracted with KCl (80 mM), the extract of S. raeseri (0.005-1.5 mg/ml) elicited a vasodilatator action (EC(50) 0.11±0.008 mg/ml). In spontaneously beating rat atria, the extract of S. raeseri (0.005-1.5 mg/ml) produced decrease of chronotropic and inotropic activity (with EC(50) value of 0.63±0.03 mg/ml and 0.40±0.08 mg/ml). Administration of verapamil induced inhibition of force and rate of the atrial contraction. These results demonstrate that the ethanol extract of Sideritis raeseri spp. raeseri Boiss & Heldr can produce hypotension, vasodilatation, negative chronotropic and inotropic effects.