Pigmented edible bean coats as natural sources of polyphenols with antioxidant and antibacterial effects

• Pigmented edible bean coats represent a good source of antioxidant phenolics.
• Flavonoids and proanthocyanidins were the main polyphenols in the bean coats studied.
• Bean coat extracts mainly inhibited the growth of gram-positive bacteria.
• Bean coats rich in polyphenols can be good candidates for use as food preservatives.

Food preservatives are important for the storage of foods, and natural polyphenols with antioxidant and antibacterial effects are often effective as food preservatives. In this study, we systemically investigated the phenolic composition, antioxidant and antibacterial effects of 28 pigmented edible bean coat extracts. Most of these bean coat extracts had a relatively high level of total phenolic content, mainly flavonoids and proanthocyanidins, and they also exhibited much higher antioxidant effect than most common fruits, vegetables and cereal grains. In addition, most of them showed antibacterial effects, mainly against gram-positive bacteria, higher than the effect of phenol. Correlation analysis and principal component analysis indicated that flavonoids and proanthocyanidins were mostly responsible for the antioxidant and antibacterial effects of these bean coat extracts. Therefore, the pigmented bean coats rich in polyphenols with antioxidant and antibacterial effects are potential candidates as food preservatives.