Berry Pigments (Why Berries Have Pigments and Why All Berries Are Not Created Equal) Part 2 of 4 |
[follow the Wikipedia links] Let's begin with a brief review of Part 1 (click for complete file) A Plant's Only Purpose is to Regenerate and Propagate the Species How's that for a proposal? Given this as a premise, we can focus on how a plant uses its pigments to protect its seeds which store the genetic material for regeneration and propagation. Why is this of interest to consumers like us? Here are some simple relationships drawing all this together -- read them from top to bottom :
What are the principal pigment classes in berries? Most dark berries are rich in the pigment class of phenolic acids (also called just phenolics or polyphenols), numbering in the thousands in nature. Phenolics are particularly present in berries with dark colors, such as red, blue, violet and purple-black. Phenolics are sometimes richest in seeds, such as in Muscadine or Concord grapes, so extraction specifically from seeds yields dense concentrations of phenolics (particularly oligo-proanthocyanidins or OPCs) that are commonly used in manufacturing nutraceuticals.
Muscadine grapes, Vitis rotundifolia Another class of pigments – carotenoids -- are characteristic of red, orange, yellow and green plants but are not present in the skins of dark berries like the blueberry, cranberry or blackberry. Carotenoids are located in the seeds of these dark berries, however. Click here for a primer on carotenoids from the Berry Doctor's Journal! Perhaps because it is a plant relative of the tomato (family Solanaceae, rich carotenoid source), wolfberries ("goji") have exceptionally dense contents of three carotenoids – beta-carotene, beta-cryptoxanthin and zeaxanthin, and contain lycopene (yes!, in a berry) and lutein. Goji berries also have phenolics (preliminary evidence for high content of ellagic acid), vitamin C and polysaccharides, all of which possess antioxidant properties. From unconfirmed studies of ORAC on wolfberries, this synergy of antioxidants may make wolfberry one of the strongest antioxidant food sources known. Pigment interaction and antioxidant synergy One of the suspected interactions among antioxidant pigments is that they protect one another from oxidative stress. For example, carotenoids are thought to be the most powerful antioxidants due to their chemical structure (numerous carbon-carbon double bonds that sacrifice electrons to free radicals) and their preference to dissolve in lipids where they protect fat-soluble antioxidants like vitamins A and E. It's a beautiful design. The presence of carotenoids in lipid layers of sensitive cell structures means they are a last line of antioxidant defense against reactive oxygen species, ROS. If the phenolic protection against ROS has been inadequate, carotenoids provide additional antioxidant power close to sensitive cell functions. Another form of synergy is provided by the example of vitamin C (ascorbic acid), the universal water-soluble antioxidant. It replenishes other antioxidant qualities in phenolics and protects or restores vitamin E from oxidative stress. Other research has shown that numerous phenolic pigments in the same plant provide a synergy of antioxidant protection for each other. In other words, overall antioxidant strength in plants is 1) directly proportional to the concentration of phenolics and/or carotenoids in that plant, and 2) optimal in the design of Nature to provide several checks and counter-checks assuring maximal antioxidant protection
Açaí berries after harvest from the Brazilian rainforest Courtesy of Sambazon
Pigment Power: Why All Berries Are Not Created Equal Click here for a ranking of the top 10 berries having high ORAC and why this list is a reasonable guide to pigment power. The research comparing these 10 berries is not sufficient to be precise for how anthocyanin concentration may vary from one berry specie to another. Many factors of environment, genetics, soil and cultivation quality, etc. would affect pigment strength among berry species. The plain fact is that they are very different in pigment amounts and types, and there is a general proportionality of pigmentation to antioxidant strength. But, as a berry that grows high on palm tress in regions close to the equator, açaí -- at the top of the antioxidant rankings for all fruits -- is likely exposed to greater amounts of sun and ultraviolet stress than other berries, perhaps explaining its exceptional ORAC. This is the subject of Part 3 in this series: Under stress from its environment, would a berry manufacture more antioxidant chemicals to improve its defenses?
Açaí palms, Euterpe oleracea the berries grow near the top of the leaf canopy on panicles exposed constantly to the sun, possibly an explanation for the stress producing exceptional amounts of pigmentation to "protect" the seeds (see part 3 next week)
Next!
Reading
* Simon PW. Plant Pigments for Color and Nutrition, US Department of Agriculture and University of Wisconsin Archives (click!)
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