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Determination of active constituents of grape seed extract

Pulished on Sep. 02, 2019

Determination of active constituents of grape seed extract.

1. Beta - Smith method

This method is used to determine procyanidolic index in grape seed extract. Since there is no standard for procyanidins at present, the relative value of procyanidins in grape seed extract is determined by this method.

Principle:

Procyanidins are converted to red anthocyanins by heating under acidic conditions.

Operating procedures:

Weigh appropriate amount of grape seed extract (about 15~ 40mg) and dissolve it in methanol, and finally dissolve in 100ml. 1ml sample solution was added to 10ml colorimetric tube, and then 6ml hydrochloric acid-n-butanol solution (5/95, V/V) was added. The reaction was conducted at 97℃± 1 for 40min. After that, the solution was rapidly cooled and its absorbance was measured at 550nm.

Procyanidins index = A × 7.0 /W

A: absorbance; W: sample quality (g)

Since the procyanidins index of grape seed extract China measured by Bate- Smith method is generally between 80 and 100, sometimes it may be more than 100.

grape seed extract

Grape Seed Extract

2. Porter method

Due to the poor reproducibility of the Bate- Smith method and the incomplete reaction of procyanidins under these conditions. Therefore, Porter et al. improved the Bate- Smith method. The improvement of Porter method is mainly the addition of Fe3+ in the reagent to improve the degree of reaction and the stability of color. This method also measured the relative content of procyanidins, and the results were expressed by PVU(porter value unit). Porter method is based on the same principle as Bate- Smith method

Operating procedures:

Weigh appropriate amount of 95% OPC  Grape Seed Extract (about 10~ 30mg) and dissolve in methanol, and finally dissolve in 100ml. Then add 6ml hydrochloric acid -n-butanol (5/95, V/ V), 0. 2ml ammonium ferric sulfate solution (dissolved with 2mol. L-1 hydrochloric acid), react at 97℃± 1 for 40min, take it out and quickly cool it, and measure its absorbance at 550nm. [5]

PVU= A times 7.2 /W

A: absorbance; W: sample quality (g)

The American grape seed method evaluation committee considers the PVU of grape seed extract to be ideal between 250 and 350. If PVU is too low, it may indicate that the content of procyanidins in this product is low and PVU is too high, indicating that the content of procyanidins in this product is high. However, porter method cannot distinguish which proanthocyanidins are detected. Therefore, if PVU of a grape seed extract is 300, the product may have high content of oligomeric proanthocyanidins, or it may have high content of monomer and hyperpolymer proanthocyanidins.

The American grape seed method evaluation committee considered that these two methods could not be used for quantitative analysis of total polyphenols or procyanidins in grape seed extract.