Abstract
Epidemiological studies associate fruit and vegetable consumption with a reduced risk of degenerative diseases. Bioactive components of these foods may be responsible for their health-promoting effects. Blueberries are a rich source of candidate bioactive components such as vitamins, phenolic acids and anthocyanins. Anthocyanins are pigments that contribute to the intense colours of blueberries; they have numerous bioactive properties, such as anti-inflammatory, antioxidant and anticancer effects. Gut microflora metabolises anthocyanins to phenolic acids and aldehydes. These metabolites have higher chemical and microbial stability, and they may contribute to beneficial health effects.
This study investigated the properties of a commercial blueberry extract, malvidin-3-galacotside, as one of the most abundant anthocyanins in blueberries and metabolites (malvidin in its aglycone form and 2,4,6-trihyodroxybenzaldehyde) that can be derived from malvidin-3-galacotside during gastrointestinal transit.
Analysis of the blueberry extract confirmed it is rich in phenolic and flavonoids and exhibited antioxidant properties in vitro, including radical scavenging and metal chelating activities. High-performance liquid chromatography demonstrated that malvidin-3-galactoside was the most abundant form of malvidin-glycoside in the extract.
The effects of the blueberry-derived agent on the Caco-2 colorectal cell line were then investigated. All these agents exhibited concentration-dependent cytotoxicity and stimulated apoptosis of Caco-2 cells. At non-cytotoxic concentrations, none of the test agents provided significant antioxidant protection against oxidative stress-induced Caco-2 cells using tert-butyl hydroperoxide. Instead, when used at higher concentrations, the blueberry-derived agents stimulated the production of intracellular ROS, with the blueberry extract and the 2,4,6-trihydroxybenzaldehyde producing the most marked effects.
Finally, the effects of the blueberry-derived agents were tested when used in combination with the chemotherapeutic agent 5-fluorouracil. In all cases, the cytotoxic effects of the combination treatments were at least equivalent to the additive effects of the individual agents. However, the blueberry extract, and more marginally, the 2,4,6-trihydroxybenzaldehyde elicited synergistic effects with 5-fluorouracil.