Procyanidin B2 in Apples: A 275μg/g Powerhouse for Heart Health?

In today's pursuit of health and natural products, the plant extract industry is thriving. As a daily fruit, apples have a nutritional value far beyond our imagination, especially the active ingredient procyanidin B2 contained in them. Apple polyphenols are mainly composed of phenolic acid components, including anthocyanins, anthocyanins, flavonoids, and chlorogenic acid._[1] Among them, anthocyanins account for 71% to 90% of the polyphenol content in apples, which are the most active ingredients._[2] Proanthocyanins are dimers formed by catechins or epicatechins, as well as trimers, tetramers, and even decamers. According to the degree of polymerization, two to four oligomers are referred to as oligomeric proanthocyanidins, and those with pentamers or more are referred to as polymeric proanthocyanidins.

1.1 Uneven distribution
The distribution of procyanidin B2 in apples shows significant unevenness. Research has shown that there are some differences in the content of procyanidin B2 in different parts of apples. The determination results of various apple varieties using the HPLC method showed that the content of procyanidin B2 in apple peel ranged from 275.24 to 548.42 μ g/g. In comparison, the content in fruit flesh ranged from 90.19 to 247.06 μ g/g. This difference is primarily due to the distinct physiological functions and metabolic activities of various apple parts._[4] 

1.2 Differences between Varieties
There are significant differences in the content of procyanidin B2 among different apple varieties. A study on five different varieties of apple resources found that the order of procyanidin B2 content in the peel from high to low is American No. 8 (548.42 μ g/g), Gala (526.71 μ g/g), Yellow Banana (497.16 μ g/g), Red Fuji (393.23 μ g/g), and Green Apple (275.24 μ g/g)._[4] The scattered distribution of polyphenol content in wild apple resources in China indicates that their polyphenol content varies and their diversity is rich._[5] In six small apple varieties in Northeast China, researchers detected 12 types of flavonoid components, including procyanidin B1, B2, and B4. The epicatechin content of these varieties ranged from 10.20 to 73.77 mg/kg, with flavanols playing a major role in the flavonoid components._[6]

1.3 Impact of Regional Factors
The procyanidin B2 content in apples also depends on the growing region. Research has found that the content of flavonols and anthocyanins in wild apple resources in North America is relatively low, while the content of hydroxycinnamic acid, anthocyanins, and dihydrochalcone is moderate. The content of five types of polyphenolic substances in wild apple resources from Russia is at a moderate level, and China's wild apple resources exhibit rich diversity.

2.1 High-performance liquid chromatography method
Currently, high-performance liquid chromatography (HPLC) is a commonly used method for determining the content of procyanidin B2 in apples. Typical detection conditions include: a Phenomenex Luna C18 column (250mm × 4.6mm, 5 μ m) as the chromatographic column; Mobile phase A is a 0.5% phosphoric acid solution, and phase B is water acetonitrile (50:50, V/V); Flow rate of 1.0mL/min; Column temperature 30 ℃; The detection wavelength is 280nm6. This method demonstrates excellent linearity(R²=0.9998), with a recovery rate of 97.72% and high accuracy._[4]

2.2 Ultra-high performance liquid chromatography combined with mass spectrometry technology
Ultra-high performance liquid chromatography coupled with mass spectrometry (UPLC-MS) has also been applied in the study of apple polyphenols. A study used this method to determine the polyphenol composition and content of 20 wild and closely related apple resources from China, Russia, and North America, successfully detecting 5 categories and 22 polyphenolic substances._[5]

3.1 Powerful antioxidant properties
Procyanidin B2 has excellent antioxidant capacity. Research has shown that in non-concentrated reduced (NFC) apple juice, anthocyanins are the main contributors to in vitro antioxidant capacity. Procyanidin B2,  epicatechin, and epicatechin gallate, three monomeric phenols, exhibit strong DPPH radical scavenging ability, while ABTS radical scavenging ability is more dependent on total phenolic content._[7]

3.2 Anti-inflammatory and anti-allergenic properties
Procyanidin B2 also exhibits significant anti-inflammatory and anti-allergenic properties. The scientific researchers of the South China Botanical Garden of the Chinese Academy of Sciences developed a compound natural whitening and wrinkle-resistant composition containing proanthocyanidin B2 and red sandalwood stilbene as active ingredients, and obtained the national invention patent authorization. This composition has stable properties and is suitable for use in skincare products as it is non-irritating, anti-allergenic, whitening and spot lightening, and anti-aging.

3.3 Prevention of diabetes and abnormal liver function
Proanthocyanidins (including procyanidin B2) in apples can effectively prevent diabetes and liver dysfunction. As a natural antioxidant, anthocyanins have various biological activities such as anti-inflammatory, antiviral, and anti-tumor effects. Animal experiments found that the experimental mice fed with procyanidins showed significant improvement in diabetes and liver dysfunction.

4.1 Functional Foods and Health Products
Procyanidin B2 has broad application prospects in the fields of functional foods and health products. With the increasing demand for natural health products among consumers, apple extract rich in procyanidin B2 can be added as a natural antioxidant to various foods and health products. Consuming two apples per day can have beneficial effects on heart health markers, providing a scientific basis for the development of apple-based functional foods.

4.2 Cosmetics and Personal Care Products
In the fields of cosmetics and personal care products, procyanidin B2 also shows great potential. The compound natural whitening and anti-wrinkle composition containing procyanidin B2 has been granted patent authorization. This combination has multiple effects, such as non-irritating, anti-allergenic, whitening, spot-lightening, anti-aging, etc., which meet the current demand for natural, safe, and effective ingredients in the cosmetics market.

4.3 Medical Auxiliary Applications
In addition, its potential in preventing diabetes and liver dysfunction is also worth further research and development.

Although procyanidin B2 in apples has various health benefits and application prospects, its development and utilization still face some challenges:

• Extraction process optimization: It is necessary to develop more efficient and environmentally friendly extraction processes to improve the extraction rate and purity of procyanidin B2.
• Stability issue: Procyanidin B2 is prone to degradation during processing and storage, and effective protection techniques need to be studied.
• Bioaccumulation: How to improve the bioavailability of procyanidin B2 is a key issue that needs to be addressed.
• Standardization and Quality Control: It is necessary to establish a standardized quality evaluation system to ensure the stability and reliability of products.

Future research should focus on gaining a deeper understanding of the mechanism of action of procyanidin B2, developing high-value-added products, and exploring its potential applications in different fields.

Procyanidin B2, as an important bioactive component in apples, exhibits uneven distribution and is influenced by factors such as variety, region, and location. Its various health benefits, such as antioxidant, cardiovascular protection, anti-inflammatory, and anti-allergenic, make it have broad application prospects in the fields of functional foods, cosmetics, and medicine. With the continuous advancement of plant extract technology and the increasing demand for natural products from consumers, the development and utilization of procyanidin B2 in apples will usher in new opportunities. For more details, please contact Serrisha. (Email: cwj@appchem.cn)

Reference:

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[3]Yang Jingyu, Li Yan,Wang Fang, et al. Hepatoprotective effects of apple polyphenols on CCl4-induced acute liver damage in mice[J]. Agric Food Chem, 2010, 58(10):6525-6531.

[4]Wang Jiao, Song Xinbo, Liu Chenghang, Liu Dailin. HPLC Determination of Proanthocyanidin B2 in Different Varieties of Apples[J]. Food Science, 2012, 33(24):293-295.

[5]Wang Dajiang, Wang Kun, Li Jing. Study on Polyphenol Content Characteristics in Fruits of 20 Wild Malus Resources[J]. Chinese fruit trees, 2017, (04): 74-78. DOI:10.16626/j.cnki.issn1000-8047.2017.04.025.
[6]Liu Chang, Zhao Jirong, Wang Kun. Analysis of Flavonoid Components and Contents of Different Apple Fruits in Northeast China[J]. Forest By-Product and Speciality in China, 2020, (05): 25-28. DOI:10.13268/j.cnki.fbsic.2020.05.007.

[7]Wang Yangi, Guo Yurong, Wang Yongtao. Analyses of Phenolic Composition and Antioxidant Activities of NFC Apple Juices from Different Cultivars[J]. Journal of Chinese Institute of Food Science and Technology, 2020, 20(05): 74-83. DOI:10.16429/j.1009-7848.2020.05.010.