Flavonoids are natural compounds with color enhancement properties, a plant protection arsenal and health benefits to humans. A large class of phenols, flavonoids are vital to ecosystems and sensory experiences in life.
It's a jungle out there. Flavonoids are a group of polyphenolic compounds or phenols found predominantly in plants. They create the vibrant colors of many fruits, vegetables, and flowers and are integral to plant survival.
Flavonoids are abundant in plants, fruits, and seeds. They contribute color, fragrance, and taste characteristics. They make food more appealing and flavors more tempting. They can also create bitterness or toxic effects.
Several subclasses of flavonoids exist, including flavanols, flavones, isoflavones, flavanones, and anthocyanins. Each subclass has its distinct features.
Creation of Flavonoids in Nature
Plants synthesize flavonoids in a series of biochemical processes. They're formed primarily in response to environmental stressors such as UV light, pathogen attacks, herbivore overgrazing or temperature changes.
They're created in the phenylpropanoid pathway, a primary metabolic route of plants. The amino acid phenylalanine converts into flavonoids through enzyme-driven processes.
Phenylpropanoid Pathway: This initial phase involves the conversion of phenylalanine into cinnamic acid through the action of phenylalanine ammonia-lyase (PAL). Further enzymatic reactions lead to the production of different flavonoid structures.
Diversity of Structures: There are more than 6,000 types of flavonoids, but they can be broadly categorized into several classes, including flavonols, flavones, flavanones, catechins, isoflavones, and anthocyanins. Each subclass has its own unique physiological roles and health benefits.
Color Contribution: One of the most notable features of flavonoids is their contribution to the pigmentation of plants, especially in fruits and flowers. Anthocyanins, for example, impart red, purple, and blue hues, helping attract pollinators and seed dispersers.
Anthocyanins give berries their red or blue colors. The hue shifts based on acidity of the soil. An acidic environment (pH < 7) causes red colors, and alkaline conditions produce blue shades.
Functions of Flavonoids in Nature
Protection Against Consumers: Many flavonoids act as deterrents to herbivores due to bitter taste or potential toxicity. These properties are also found in phenols. Flavonoids can have antibacterial and antifungal properties to protect plants from pathogens.
UV Protection: Flavonoids absorb UV light, acting as natural sunscreen for plants. They prevent DNA damage and help plants survive in sun-strong environments.
Pollinator Attraction: Colors and aromas produced by flavonoids and phenol compounds attract different pollinators.
Facts About Flavonoids
Culinary Benefits: Flavonoids contribute to the flavor, aroma, and color of foods.
Cultural Significance: Some traditional medicines historically use flavonoid-rich plants.
Natural Colorants: Flavonoids extracted from fruits and flowers are used in food manufacturing as colorants.
Bioavailability: Flavonoids vary in bioavailability, meaning not all are absorbed equally by the body. Cooking or processing can influence their effectiveness, enhancing or diminishing their properties.
Human Health: Flavonoids often have antioxidant or anti-inflammatory properties, and may help improve heart and brain function.
Flavonoids are abundant in food. Some sources include:
Berries (strawberries, blueberries, blackberries) - rich in anthocyanins.
Citrus Fruits (oranges, lemons) - high in flavanones.
Tea (green and black) - abundant in flavonols.
Dark Chocolate - significant amounts of flavonoid compounds, particularly catechins and flavanols.
Onions and Apples - good sources of quercetin and other flavonoids.
Red Wine - is attributed various cardiovascular benefits due to to its high flavonoid content.
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