Pterostilbene is a stilbenoid chemically related to resveratrol and is found in blueberries and grapes. It belongs to the group ofphytoalexins, agents produced by plants to fight infections. Based on animal studies it is thought to exhibit anti-cancer, anti-hypercholesterolemia, anti-hypertriglyceridemia properties, as well as the ability to fight off and reverse cognitive decline. It is believed that the compound also has anti-diabetic properties, but so far very little has been studied on this issue.
Pterostilbene is a double-methylated version of resveratrol exhibiting a higher bioavailability as it is more easily transported into the cell and more resistant to degradation and elimination. In rats, pterostilbene's oral availability is 67%-94%, and its half-life has been published to be between 78 minutes and 104 minutes.
Pterostilbene has anti-inflammatory, antineoplastic, and antioxidant actions via modulations of gene expression and enzyme activity. In plants the substance displays antifungal and antiviral activities.
In general, studies have focused on the trans isomer of pterostilbene.
Animal studies[edit source | edit]
Lowering blood lipids and cholesterol[edit source | edit]
Studies that used animals fed on blueberry based diets found significant reduction in blood lipid count and cholesterol count. While lipids and cholesterol stored in the cells do not pose much harm, elevated lipid and cholesterol levels in the blood have been linked to heart disease and stroke. In the mentioned study blueberries were found to be more effective than ciprofibrate, a cholesterol-lowering drug predominantly used outside the United States. According to the study pterostilbene binds to PPARs, breaking down the cholesterol.
Diabetes[edit source | edit]
Similar to what has been discovered with the drug metformin, pterostilbene has been shown to lower blood glucose levels in rats by as much as 56 percent, while simultaneously raising insulin and hemoglobin levels to near normal levels. Pterocarpus marsupium, a tree that contains high levels of pterostilbene in its heartwood, has also showed an anti-diabetic effect in humans, with 67% of participants in a clinical study obtaining control of their blood sugar levels after 12 weeks and an average drop of 32 mg/dl in fasting blood glucose levels.
Cognitive decline[edit source | edit]
In a study of 40 19-month-old rats fed either a normal diet or a diet containing blueberry, strawberry, or spinach extracts, the rats that were fed blueberry extracts had a significant reversal in motor-skill decline due to aging as well as other cognitive impairments. All of the diets above, except the normal one, resulted in some reversal or reduction of cognitive decline but none greater than the blueberry group. A similar study with blueberries in a group of adults exhibiting age-related memory decline demonstrated a significant improvement in memory tests after just 12 weeks of drinking blueberry juice. A study out of Tufts University on pterostilbene supplementation in elderly rats showed that pterostilbene conferred significant memory improvement as well. The authors theorized that the memory improvement may be due to pterostilbene's unique ability as an anti-oxidant to cross the blood-brain barrier and co-localize in the hippocampus (the brain's memory center) where it may offer protection against free radical damage.
Possible anti-cancer effects[edit source | edit]
In 2002, Rimando and University of Illinois at Chicago collaborators found in experiments using rat mammary glands that pterostilbene possessed potent anti-oxidant characteristics and possible cancer-fighting properties at concentrations similar to resveratrol.
Additional work by Rimando and collaborators revealed a possible mechanism for pterostilbene's purported anti-cancer properties. Using mice cells, they demonstrated that pterostilbene, as well as other analogs of resveratrol, potently inhibits an enzyme called cytochrome P450. (Cytochromes are found within the cells of animals, plants, bacteria, and other microorganisms that transport electrons. They’re also a factor in people’s varying response to drugs and toxins entering their bodies. Cytochrome P450 enzymes activate a variety of compounds known as "procarcinogens," which can turn substances such as cigarette smoke and pesticides into carcinogens.)
According to Rimando, Pterostilbene showed strong inhibitory activity, much more than resveratrol, against a particular form of cytochrome P450 in a mouse mammary gland culture assay.
Human studies[edit source | edit]
The first human clinical trial on the effect of pterostilbene on cholesterol and blood pressure was completed at the University of Mississippi in April 2012. The safety data from the double-blind, randomized, placebo-controlled clinical study demonstrated that pterostilbene is safe in doses up to 250 mg/day. Efficacy data from the clinical study was published on Sept. 12, 2012. This study showed that pterostilbene at high doses was associated with reduced blood pressure and minor weight loss. (http://www.prnewswire.com/news-releases/clinical-study-showed-a-blueberry-antioxidant-pteropure-pterostilbene-significantly-reduced-blood-pressure-in-adults-170538836.html).
In wine[edit source | edit]
While resveratrol has been touted for its heart healthy benefits, pterostilbene is not found in wine despite darker grapes having the highest concentrations among the fruit. The reason believed is that it is unstable in light and air.
Toxicity[edit source | edit]
Pterostilbene is not known to be toxic to humans. There is some anecdotal evidence that doses of 200-250mg or more at once may induce temporary hypoglycemia in normal individuals.