Dr. Pran Kishore Deb Dr. Balakumar Chandrasekaran Assistant Professor Pharmaceutical Medicinal Chemistry Faculty of Pharmacy, Philadelphia

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1 Dr. Pran Kishore Deb Dr. Balakumar Chandrasekaran Assistant Professor Pharmaceutical Medicinal Chemistry Faculty of Pharmacy, Philadelphia University-Jordan 1

2 Learning Outcomes At the end of this lecture students will be able to Define anthocyanins Outline the significance of anthocyanins Outline examples of various anthocyanins Outline natural distribution of anthocyanins Explain the chemistry of anthocyanins 2

3 ANTHOCYANINS Anthocyanins are the largest and most important group of water soluble pigments in nature Responsible for the blue, purple, red colors of fruits and vegetables The word anthocyanin derived from two Greek words: Anthos means flowers Kyanos, means dark blue Anthocyanins are glycosides of anthocyanidins Anthocyanins = Glycosides Anthocyanidins = Aglycons 3

4 Significance of Anthocyanins Ecological importance in nature Aid to plant pollination and seed dispersal - as colour attractants to insects and birds Regarded as potential natural colorants in the food industry Dietary significance - antioxidant and anti-inflammatory properties Lowers the risk of cardiovascular disease, diabetes, arthritis and cancer Incorporating anthocyanins as food colorants Improve overall appearance Beneficial to our health Estimated daily intake of anthocyanins mg/d in the United States Major sources of anthocyanins Blueberries, cherries, raspberries, strawberries, black currants, purple grapes and red wine 4

Significance of Anthocyanins Plants defense system Protection against predators like parasites, pathogenic microorganisms But less effective than flavonols Not found to be toxic to higher animal

5 Significance of Anthocyanins Plants defense system Protection against predators like parasites, pathogenic microorganisms But less effective than flavonols Not found to be toxic to higher animal species Anthocyanins protects plants against herbivory and microorganisms in several ways: Serve in plant camouflage Aposematism (concept of warning coloration) Bright colors of this granular poison frog signal a warning to predators of its toxicity 5

6 Chemistry of Anthocyanidins and Anthocyanins They have 15-carbon atoms in their basic skeleton Arranged in the form C6-C3-C6 Belongs to the family of compounds known as flavonoids Distinguished from other flavonoids presence of Flavylium ion Consists of two aromatic rings (A & B) linked by heterocyclic ring C About 23 anthocyanidins (aglycons) are found in nature Only 6 of them are most common Name R 1 R 2 Pelargonidin H H Cyanidin OH H Delphinidin OH OH Peonidin OCH 3 H Petunidin OCH 3 OH 6 Malvidin OCH 3 OCH 3

7 Chemistry of Anthocyanidins and Anthocyanins More than 500 different anthocyanins are reported Generally anthocyanins are 3-monoglycosides and 3,5-diglycosides Although very rare, glycosylation at the 3, 4, or 5 positions of the B-ring is also possible Glycosides of 3 non-methylated anthocyanidins are most widespread Cyanidin, delphinidin, pelargonidin Name R 1 R 2 Pelargonidin-3-glucoside H H Cyanidin-3-glucoside OH H Delphinidin-3-glucoside OH OH Peonidin-3-glucoside OCH 3 H Petunidin-3-glucoside OCH 3 OH 7 Malvidin-3-glucoside OCH 3 OCH 3

8 Chemistry of Anthocyanidins and Anthocyanins Type and intensity of colors of anthocyanins largely depends on Substitution pattern of the anthocyanidin (particularly of the B-ring) If hydroxyl groups predominate = color goes toward bluish shade If methoxyl groups predominate = color goes towards redness ph and pattern of glucosylation ph<2 = intensely red or orange ph 2-4 = Blue species prevailed ph 5-6 = Colorless (e.g. Chalcone, carbinol pseudobase) ph >7 = Anthocyanins are degraded based on their substituents Color stability decreases towards neutrality ph 8-9 = Some anthocyanins showed stable color E.g. 3-glucosides of pelargonidin, peonidin, malvidin (Blue) 8

9 Chemistry of Anthocyanidins and Anthocyanins Stability of Anthocyanidin It is influenced by the ring-b substituents Additional OH or OCH 3 groups decreases the stability in neutral media Pelargonidin is the most stable anthocyanidin Color degradation Presence of oxygen, light, ascorbic acid, metal ions and enzymes Particularly an important factor when incorporating them into foods Determining the shelf-life of the product Name R 1 R 2 Pelargonidin H H 9

10 Chemistry of Anthocyanidins and Anthocyanins Stability of Anthocyanins - Highly reactive compounds Readily degrade or react with other constituents in mixtures Form colorless or brown compounds Stability should be increased - to retain their color and functionality Glucosylation primarily at the C-3 increases stability and solubility 5-glucosylated structures degrade more easily than 3-glycosides Acylation of sugar residues improves the anthocyanin stability Acylation with cinnamic acids (p-coumaric, caffeic, ferulic) or Acylation with aliphatic acids (acetic, malonic, succinic) 10

11 REFERENCES 1. Jaclyn Shipp and El-Sayed M. Abdel-Aal. Food Applications and Physiological Effects of Anthocyanins as Functional Food Ingredients. The Open Food Science Journal, 2010, 4, Castaneda-Ovando, Araceli, et al. Chemical Studies of Anthocyanins: A Review. Food Chemistry 2009, 113, Miguel M. G. Anthocyanins: Antioxidant and/or Antiinflammatory Activities. Journal of Applied Pharmaceutical Science 2011, 1(6), Nel A.P. Tannins and Anthocyanins: From Their Origin to Wine Analysis A Review. S. Afr. J. Enol. Vitic., 2018, 39(1), 1-20.

The PLANT PHENOLIC COMPOUNDS Introduction & The Flavonoids

The PLANT PHENOLIC COMPOUNDS Introduction & The Flavonoids The plant phenolic compounds - 8,000 Phenolic structures known - Account for 40% of organic carbon circulating in the biosphere - Evolution of