How to Measure Proanthocyanidins (PACs) in Cranberry Extract: DMAC vs EP5 Explained

Proanthocyanidins (PACs) are the key active compounds in cranberry extract, especially valued for their role in urinary tract health. However, accurately measuring PAC content is one of the most misunderstood and often misrepresented aspects of cranberry extract quality.

Buyers frequently encounter confusing situations such as:

• Different PAC percentages for the same product
• Large discrepancies between supplier claims
• Unclear testing methods on Certificates of Analysis (COAs)

This happens because PAC content depends heavily on the analytical method used, and not all methods measure the same thing.

This guide explains:

• What Proanthocyanidins are and why accurate measurement matters
• The main testing methods (DMAC vs EP5)
• Why results differ between methods
• How to verify supplier claims
• Best practices for ensuring reliable PAC testing

1. What Are PACs and Why Accurate Measurement Matters

PACs (proanthocyanidins) are a class of polyphenolic compounds found in cranberries. The most important type in cranberry is A-type PACs, which are associated with anti-adhesion activity against bacteria such as E. coli.

Why PAC measurement is critical:

• Determines product efficacy
• Supports label claims
• Affects pricing and cost
• Ensures regulatory compliance
• Prevents misleading specifications

However, not all PACs are equal, and not all methods measure them correctly.

2. The Two Main Methods for Measuring PACs

According to industry practice (including Coming Herb), two primary analytical methods are used:

2.1 DMAC Method (BL-DMAC)

What it is

The DMAC method (p-dimethylaminocinnamaldehyde assay) is widely considered the most accurate and specific method for cranberry PACs.

How it works

• DMAC reacts specifically with A-type PACs
• Produces a measurable colour change
• Quantified using spectrophotometry

Key advantages

• High specificity for cranberry PACs
• Strong correlation with biological activity
• Preferred method in clinical research
• Commonly used for high-quality supplements

Key limitation

• Results are typically lower numerically compared to other methods
• Requires careful standardisation

2.2 EP5 Method (European Pharmacopoeia 5th Edition, UV method)

What it is

The EP5 method is a UV spectrophotometric method used in some pharmacopoeial standards.

How it works

• Measures absorbance of a broader range of polyphenols
• Less specific to A-type PACs

Key characteristics

• Simpler and faster
• Less selective
• Includes other phenolic compounds in measurement

3. Why DMAC and EP5 Results Are Not Comparable

This is one of the most important points for buyers.

**DMAC and EP5 results are fundamentally different and cannot be converted directly.

Example:

15% PAC (DMAC) may equal approximately 50% PAC (EP5)

This difference occurs because:

Key takeaway:

A higher percentage does NOT necessarily mean higher quality.

This is why DMAC-grade products are often more expensive, even though the percentage appears lower.

4. Which Method Should You Use?

4.1 For supplements and clinical applications

Use:

• DMAC method

Reason:

• measures biologically relevant PACs
• aligns with clinical studies
• supports functional claims

4.2 For general food or non-specific applications

EP5 may be acceptable, but:

• it should be clearly labelled
• not confused with DMAC values

4.3 Industry best practice

Always specify: PAC content measured by DMAC method

This avoids misunderstanding and protects product positioning.

5. How to Verify Supplier PAC Test Results

Verifying PAC content is essential before purchasing.

5.1 Check the COA Carefully

A proper COA should include:

• PAC content (%)
• testing method (DMAC or EP5)
• reference standard used
• batch number
• test date

Warning signs:

• method not specified
• unusually high PAC values
• inconsistent reporting format

5.2 Use Third-Party Testing

Best practice:

• send sample to an independent laboratory
• request same method as supplier COA

For example:

If supplier claims "PAC 15% (DMAC)" → instruct lab to use DMAC method

This ensures a direct comparison.

5.3 Compare Multiple Suppliers Using the Same Method

Never compare: DMAC result from supplier A with EP5 result from supplier B

Always standardise the method first.

5.4 Understand Acceptable Tolerance

Analytical variation is normal.

Typical acceptable deviation: ±5–10% relative difference

Example:

• Supplier: 15% DMAC
• Lab: 14%–16% DMAC → acceptable

5.5 Review Method Details

Professional suppliers should be able to explain:

• method principle
• calibration standards
• validation data

Lack of clarity is a red flag.

6. Common Mistakes Buyers Make

Mistake 1: Choosing the highest percentage

A 50% EP5 product may be weaker than a 15% DMAC product.

Mistake 2: Ignoring test method

Without method specification, PAC value is meaningless.

Mistake 3: Assuming all PACs(proanthocyanidins) are equal

Only A-type PACs are strongly linked to cranberry benefits.

7. Practical Buying Strategy for Cranberry Extract

Step 1: Define requirement

Example:

• PAC ≥15% (DMAC)

Step 2: Request documentation

• COA
• specification sheet
• test method details

Step 3: Request samples

Test:

• solubility
• colour
• taste
• stability

Step 4: Send to independent lab

Confirm:

• PAC content (same method)
• heavy metals
• microbiology

Step 5: Place trial order

Evaluate:

• consistency
• logistics
• documentation

8. Why DMAC-Based Cranberry Extract Is More Expensive

Several factors explain the higher cost:

• more selective raw material sourcing
• stricter extraction control
• lower measured percentages
• higher functional relevance
• greater demand in supplements

You are paying for accuracy and efficacy, not just a number.

Accurate measurement of PACs in cranberry extract depends entirely on understanding and controlling the testing method used. The DMAC method is widely recognised as the most reliable approach for measuring biologically active PACs, while EP5 provides broader but less specific results.

For serious buyers, the key is not just knowing the PAC percentage, but ensuring that:

• the method is clearly defined
• the results are verified
• the supplier is transparent