Peonidin

The generic garden peony.

Introduction

Peonidin is a naturally occurring O-methylated anthocyanidin primarily known for its role as a plant pigment. It exhibits an appealing range of colors, notably purplish-red hues in flowers such as peonies and roses, from which it derives its name. It also imparts color to some blue flowers like the morning glory (Ipomoea tricolor Cav cv). Beyond its aesthetic contributions, peonidin has gathered interest for its potential health benefits and uses in food coloring due to its color stability across different pH levels.

Chemical Structure and Color Alteration

Peonidin, like other anthocyanidins, has a highly conjugated chemical structure, which refers to alternating single and double bonds within the molecule. This structure is what enables peonidin to absorb and reflect specific wavelengths of light, thereby exhibiting color. The extent of conjugation changes with alterations in pH, which in turn, changes the color of peonidin:

• At pH 2.0, peonidin exhibits a cherry red color.
• At pH 3.0, it transitions to a strong yellowish pink.
• At pH 5.0, it turns grape red-purple.
• At pH 8.0, peonidin becomes deep blue.

Unlike many anthocyanidins, peonidin retains its color stability even at higher pH levels, a trait that has been capitalized upon in isolating it as a blue colorant from the "Heavenly Blue" morning glory.

Commercial Use

Due to its unusual color stability, a cafeoyl-acylated buffered formulation of peonidin has been patented for utilization as a food coloring agent. This aspect of peonidin provides a natural alternative to synthetic food colorants, aligning with an increasing consumer demand for natural food additives.

Health Implications

Research has revealed that peonidin, along with other anthocyanidins, possesses potential inhibitory and apoptotic effects on cancer cells in vitro, notably against metastatic human breast cancer cells. However, a significant concern regarding the use of anthocyanidins for therapeutic purposes is their bioavailability. Despite showing promise in vitro, anthocyanidins are rapidly eliminated from the human body, which casts doubt on their efficacy in vivo.

Dietary Sources

The principal dietary source of peonidin is raw cranberries, providing 42 mg per 100 g of fruit. Other significant sources include:

• Blueberries, plums, grapes, and cherries, ranging from 5 to 12 mg/100 g.
• Purple-fleshed sweet potatoes, with certain cultivars containing up to 40 mg/100 g (cooked).
• Raw black rice and black bananas.

Fresh fruits have been found to contain higher levels of peonidin compared to their frozen counterparts; for instance, frozen blueberries almost lack peonidin. This disparity underscores the general guideline that fresh fruits tend to be more nutritious and health-beneficial due to their higher content of phenolic compounds.

Conclusion

Peonidin's unique chemical structure not only imparts vibrant colors to various flora but also holds potential health benefits and commercial value as a natural food colorant. While its in vitro anti-cancer effects are promising, further research is needed to fully understand its bioavailability and efficacy in vivo. Nonetheless, the consumption of peonidin-rich fresh fruits aligns well with the broader nutritional advice favoring fresh over processed foods for better health outcomes.

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External links

Nutrition lookup (USDA)

Portions of content adapted from Wikipedia's article on Peonidin which is released under the CC BY-SA 3.0.