What Are Flavonoids?

Flavonoids are a large and diverse group of naturally occurring compounds found throughout the plant kingdom. The name comes from the Greek word flava, meaning yellow, reflecting the characteristic colour of many flavonoid compounds. The collective name “flavonoids” was proposed by Geissman in 1952.

Flavonoids are structurally related compounds that are often classified as polyphenols. Many have a basic skeleton containing 15 carbon atoms, generally consisting of a phenolic component and a cinnamic acid-derived building block.

The flavonoid family includes several structurally different groups, including flavones, flavonols, chalcones, catechins and anthocyanidins. Their chemical diversity contributes to their wide range of functions and applications in cosmetic formulations.

Antioxidant Properties of Flavonoids

One of the most important properties of flavonoids in cosmetic applications is their antioxidant activity.

Certain flavonoids can help scavenge free radicals and provide antioxidant protection. This property is particularly relevant to skincare because oxidative stress can contribute to changes in the appearance and condition of skin cells.

Flavonoids in Red Wine

Flavonoids found in red wine derived from Vitis vinifera, including quercetin, kaempferol and anthocyanidins, are associated with free radical-scavenging activity.

Flavonoids in Green Tea

Green tea (Camellia sinensis, also known as Thea viridis) contains flavonoid compounds including catechins and catechin gallate esters. These compounds have demonstrated antioxidant activity against free radicals.

The antioxidant properties of these plant-derived compounds have been recognised through dietary use for generations, while similar antioxidant activity has also been observed when certain flavonoid-containing materials are applied topically in cosmetic formulations.

Flavonoids and Skin Protection

The antioxidant properties of flavonoids make them relevant to cosmetic formulations designed to support skin exposed to environmental stress.

By incorporating flavonoid-rich botanical extracts into skincare products, formulators can take advantage of naturally occurring antioxidant compounds while also benefiting from the additional properties of the botanical source.

Flavonoids are therefore commonly considered when developing formulations focused on antioxidant skincare and maintaining the appearance of healthy, protected skin.

Flavonoids as Natural Colourants

In addition to their antioxidant properties, flavonoids can contribute natural colour to cosmetic ingredients and botanical extracts.

Different groups of flavonoids can produce a range of colours:

Chalcones and Flavonols

Chalcones and flavonols can contribute yellow colours and are therefore of interest as potential sources of natural colour in cosmetics and toiletries.

Anthocyanidins

Anthocyanidins are responsible for red, blue and violet colours found in many plants. Their natural pigmentation makes anthocyanidin-containing botanical materials particularly interesting for applications where naturally derived colour is desired.

Flavones

Flavones are generally colourless, but they can strongly absorb ultraviolet radiation. In plants, this property contributes to their role in interactions with pollinating insects.

The use of flavonoid-containing materials as natural colour sources in cosmetics and toiletries continues to develop, although their relatively poor light stability can present a formulation challenge.

Flavonoid Glycosides and Aglycones

Flavonoids may occur naturally in plants as glycosides or as aglycones.

Flavonoid Glycosides

Glycosides are flavonoid molecules in which one or more hydroxyl groups are substituted with a sugar component. These sugars can include galactose, glucose, mannose and rhamnose.

Aglycones

Aglycones are flavonoid molecules that do not contain a sugar moiety.

This distinction is important when working with botanical extracts because the chemical form of a flavonoid can influence its properties and behaviour within a cosmetic formulation.

Cosmetic Applications of Flavonoids

Flavonoids can be incorporated into cosmetic formulations through purified ingredients or, more commonly, through botanical extracts naturally containing flavonoid compounds.

Antioxidant Skincare

Flavonoid-rich botanical extracts can be used in facial creams, serums, lotions and other skincare products designed around antioxidant properties.

Green Tea-Based Formulations

Green tea extracts containing catechins and other polyphenolic compounds are widely relevant to cosmetic formulations where antioxidant properties are desired.

Botanical Skincare

Flavonoid-containing plant extracts can be incorporated into formulations that combine antioxidant properties with the broader sensory and skin-conditioning characteristics of botanical ingredients.

Natural Colour Cosmetics

Selected flavonoid-containing materials can also be explored as naturally derived colour sources for cosmetics and toiletries, although light stability must be considered during formulation development.

Formulation Considerations for Flavonoids

When incorporating flavonoid-rich ingredients into cosmetic formulations, their chemical structure, source and stability should be considered carefully.

Light stability can be particularly important when flavonoid-containing materials are being used for their colour. The stability of the specific extract or isolated compound should therefore be evaluated under the intended formulation and packaging conditions.

The final performance of a flavonoid-containing ingredient will also depend on the botanical source, extraction process, concentration and overall formulation environment.

Why Use Flavonoids in Cosmetic Formulations?

Flavonoids are valuable cosmetic ingredients because they combine several interesting properties within a diverse family of naturally occurring compounds.

Their main areas of interest include:

• Antioxidant activity
• Free radical-scavenging properties
• Support for skin exposed to environmental stress
• Natural colour potential
• Compatibility with botanical and plant-derived cosmetic concepts

Their diversity also allows formulators to select different flavonoid-containing botanical sources according to the desired positioning and performance characteristics of the finished product.

Flavonoids in Cosmetic Product Development

For cosmetic product development, flavonoids can be particularly useful when developing products based on botanical, antioxidant or naturally derived ingredient concepts.

The choice of flavonoid source should take into account the intended cosmetic benefit, extract composition, stability, colour, formulation compatibility and packaging requirements.

References

Source: Dermatologic, Cosmeceutic and Cosmetic development – Kenneth A. Walters, Michael S. Roberts.