Rapid microwave-assisted Porter method for determination of proanthocyanidins

Proanthocyanidins have been widely developed and utilised in food, medicine, health care products and cosmetics. Porter-high-performance liquid chromatography (HPLC) is a quantitative method often utilised in many fields. This method uses a water bath to reflux the proanthocyanidins, but the process is cumbersome, the reagent consumption is large, and multiple batches of simultaneous treatments cannot be evaluated.

To establish a more convenient, rapid and high-batch processing method for determining the content of proanthocyanidins in functional food by HPLC.

N-Butanol-hydrochloric acid and iron salt are used as the reaction medium in the Porter method. After investigating the optimal conditions, the hydrolysis of proanthocyanidins can be performed in a microwave reactor at a power of 640 W for 75 s in the Porter reaction system. The content of proanthocyanidins was determined by HPLC with external standards.

After the rapid pretreatment of samples, proanthocyanidins were determined by HPLC with a diode array detector at a detection wavelength of 525 nm with 0.53 μg/mL and 1.61 μg/mL limits of detection and quantification, respectively, for proanthocyanidin ions, and the linearity was 0.9999. Intra- and inter-day relative standard deviation values were between 1.5% and 3.1%, and the recovery was between 91.40% and 107.43% for the determination of different products, such as capsules, tablets and tea, which were similar to the values obtained with the conventional Porter method.

This method is a time-saving and low cost approach for quantitative analysis of various proanthocyanidin health products that offers the advantages of high-batch processing and environmental friendliness.