Anthocyanins—More Than Nature's Colours

Research over the past decade has produced incontrovertible evidence for a vast array of health benefits arising from the consumption of fruits and vegetables. In an endeavor to identify the active health-promoting ingredients, many researchers have focused on the properties of the flavonoids, a large class of phenolic compounds that is abundant in such foods. Most prominent among the flavonoids are the anthocyanins—universal plant colorants responsible for the red, purple, and blue hues evident in many fruits, vegetables, cereal grains, and flowers. Represented by over 600 molecular structures as identified to date, anthocyanins are of particular interest to the food colorant industry due to their ability to impart vibrant colours to the product. Now it seems highly likely that they also enhance the health-promoting qualities of foods.

Anthocyanins were incorporated into the human diet many centuries ago. They were components of the traditional herbal medicines used by North American Indians, the Europeans, and the Chinese, and were habitually derived from dried leaves, fruits (berries), storage roots, or seeds. Anthocyanin-rich mixtures and extracts (though not purified compounds) have been used historically to treat conditions as diverse as hypertension, pyrexia, liver disorders, dysentery and diarrhoea, urinary problems including kidney stones and urinary tract infections, and the common cold. They have even been purported to yield improvements to vision and blood circulation.


Recent studies using purified anthocyanins or anthocyanin-rich extracts on in vitro experimental systems have confirmed the potential potency of these pigments. Demonstrable benefits include protection against liver injuries; significant reduction of blood pressure; improvement of eyesight; strong anti-inflammatory and antimicrobial activities; inhibition of mutations caused by mutagens from cooked food; and suppression of proliferation of human cancer cells. Along with other phenolic compounds, they are potent scavengers of free radicals, although they can also behave as pro-oxidants. Because of their diverse physiological activities, the consumption of anthocyanins may play a significant role in preventing lifestyle-related diseases such as cancer, diabetes, and cardiovascular and neurological diseases.
Many questions remain. We do not know, for example, whether these apparent health benefits stem from anthocyanins alone, or from their synergistic interactions with other phenolic compounds. Are the health-promoting qualities of anthocyanin-phenolic mixtures preserved across the various food systems? What is the fate of anthocyanin molecules after consumption? Reports on bioavailability of anthocyanins indicate that less than 1% of consumed anthocyanins is detectable in human plasma and urine. Are the health-protective qualities observed in in vitro studies also displayed in vivo? If so, what might be the mechanism of the biological activity of anthocyanins?
(Izabela Konczak & Wei Zhang, 2004. J.Biomed Biotechnol)
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What are Anthocyanins?

Anthocyanins are natural pigments widespread in the plant kingdom which provide many of the orange, red, blue, and black colors found in fruits, vegetables, flowers, leaves, roots and other storage organs. The anthocyanin molecule consists of two or three portions; the aglycone base on the flavilium nucleus, a group of sugars and often a group of acyl acids (Francis 1989).

The common aglycon forms or anthocyanidins found are cyanidin, delphinidin, peonidin, petunidin, malvidin and pelargonidin. In plants, anthocyanidins occur as glycosylated forms or anthocyanins. They may exist in a variety of protonated, deprotonated, hydrated and isomeric forms and the relative proportion of these different molecules is dependant on pH.
The red flavilium cation is dominant at very acidic pH (pH 1-3). In aqueous media (pH 4-5) hydration reactions generate the colorless carbinol pseudo-base, which can undergo ring opening to the light yellow chalcones (pH 2.5-5) at increased temperatures. The flavilium cation can be transformed to quinoidal base through proton transfer reactions (pH 6-7) and be further converted to the blue-purple quinoid anions (Kähkönen and Heinonen 2003).
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TOTAL MONOMERIC ANTHOCYANIN BY THE pH-DIFFERENTIAL METHOD

MATERIALS:

• potassium chloride buffer, pH 1.0
• sodium acetate buffer, pH 4.5
• Am I forgot something? Yes of course your extract should be ready ;D
  

METHODS:

1. Turn on the spectrophotometer. Allow the instrument to warm up at least 30 min before taking measurements (Ignaz : It depend on the type of your spectrophotometry)
2. Determine the appropriate dilution factor for the sample by diluting with potassium chloride buffer, pH 1.0, until the absorbance of the sample at the l_vis-max is within the linear range of the spectrophotometer (i.e., for most spectrophotometers the absorbance should be less than 1.2). Divide the final volume of the sample by the initial volume to obtain the dilution factor. (Ignaz: If you use Shimadzu, 0.4-0.7 are the better absorbance range, the important thing is that you MUST determine your own l_vis-max)
   
   
3. Zero the spectrophotometer with distilled water at all wavelengths that will be used (l_vis-max and 700 nm).
4. Prepare two dilutions of the sample, one with potassium chloride buffer, pH 1.0, and the other with sodium acetate buffer, pH 4.5, diluting each by the previously determined dilution factor (step 2). Let these dilutions equilibrate for 15 min.
5. Measure the absorbance of each dilution at the l_vis-max and at 700 nm (to correct for haze), against a blank cell filled with distilled water.
6. Calculate the absorbance of the diluted sample (A) as follows:

   A = (A_{l vis-max}– A₇₀₀)_{pH 1.0} – (A_{l vis-max}– A₇₀₀)_{pH 4.5}

7. Calculate the monomeric anthocyanin pigment concentration in the original sample using the following formula:

   Monomeric anthocyanin pigment (mg/liter) = (A x MW x DF x 1000)/(ex1)

• where MW is the molecular weight, DF is the dilution factor (for example, if a 0.2 ml sample is diluted to 3 ml, DF = 15), and e is the molar absorptivity.

(Monica Giusti & Ronald E Wrolstad, 2001) Read More......

Anthocyanin articles

1. LC/PDA/ESI-MS Profiling and Radical Scavenging Activity of Anthocyanins in Various Berries. Here
2. The Change of Total Anthocyanins in Blueberries and Their Antioxidant Effect After Drying and Freezing. Here
3. Sour Cherry (Prunus cerasus L) Anthocyanins as Ingredients for Functional Foods. Here
4. Effect of Light on Anthocyanin Levels in Submerged, Harvested Cranberry Fruit. Here
5. To Stretch the Boundary of Secondary Metabolite Production in Plant Cell-Based Bioprocessing: Anthocyanin as a Case Study. Here
6. Effect of Grape Seed Extract and Quercetin on Cardiovascular and Endothelial Parameters in High-Risk Subjects. Here
7. Characterization of Acylated Anthocyanins in Callus Induced From Storage Root of Purple-Fleshed Sweet Potato, Ipomoea batatas L. Here
8. Caffeoylquinic Acids Generated In Vitro in a High-Anthocyanin-Accumulating Sweet Potato Cell Line. Here
9. New Family of Bluish Pyranoanthocyanins. Here
10. Anthocyanins and Human Health: An In Vitro Investigative Approach. Here
11. Nature's Swiss Army Knife: The Diverse Protective Roles of Anthocyanins in Leaves. Here
12. Molecular Mechanisms Behind the Chemopreventive Effects of Anthocyanidins. Here
    
13. Bioavailability and Biokinetics of Anthocyanins From Red Grape Juice and Red Wine. Here
14. Quantification and Purification of Mulberry Anthocyanins With Macroporous Resins. Here
15. The Effect of Two Methods of Pomegranate (Punica granatum L) Juice Extraction on Quality During Storage at 4^°C. Here
16. Anthocyanin Concentration of “Assaria” Pomegranate Fruits During Different Cold Storage Conditions. Here
17. Urinary Excretion of Cyanidin Glucosides and Glucuronides in Healthy Humans After Elderberry Juice Ingestion. Here
    

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