Polyphenol content or antioxidant activity? For antioxidant activity you could use Trolox. For polyphenol content it depends on the plant and what polyphenols are expected. Gallic acid is often used as standard for extracts with high content of hydroxybenzoic and hydroxycinnamic acids. But for an extract from Theobroma cacao, I would take catechin as standard.

Thank you Prof. Juadjur,

I want antioxidant that are used as standards like ascorbic acid. What are the other  standards for the test of antioxidant activity?

Best regards

You can use Ascorbic acid & BHT (synthetic antioxidants)

The best one in my experiments is Trolox then ascorbic acid

You can refer to this article were Trolox is used as standard

We are using tolox, gallic acid and quercetin.

Find attached file related with your query.

Neeraj your pdf research is very valuable I took it thanks alot

Dear Fatima

Thanks for appreciation.

Thank you very much.

Ascorbic acid or gallic acid

Thank you very much for your answer.

Thank you very much for your answer Prof. Lanez.

Trolox or ascorbic acid are the best

gallic acid

we use vitamin C , BHA, BHT and Trolox if there is

My opinion, the best antioxidant is the vitamin C.

is BHT better standard then trolox, for organic plant extracts

No simple answer really. Trolox deserves consideration as an antioxidant standard always because of the following 3 points:

1. The "TEAC" notion is widespread not only reserved for the ABTS assay. Many investigators have used Trolox equivalent antioxidant capacity measurements for all sorts of tests, e.g. FRAP, CUPRAC etd. So you will find it easier to compare your data with other literature values.

2. The Trolox response is pretty stable at solvent pH values below 10. This was important for my uses.

3. Auto-oxidation stability. You want to use a standard compound with good resistance to auto-oxidation. Vitamin C is notorious for low stability particularly if you have small metal ion impurities in the sample or solvent. But honestly, to say Trolox is more stable is probably conjecture (though i would be surprised if T was less stable than AsAc).

4. Here are some useful sources of evidence.

~Davies, Michael J., Luigi G. Forni, and Robin L. Willson. "Vitamin E analogue Trolox CEsr and pulse-radiolysis studies of free-radical reactions." Biochemical Journal 255.2 (1988): 513. (this article is available by open access shows Trolox stability with pH)

~Abramovič, H., Grobin, B., Poklar Ulrih, N., & Cigić, B. (2018). Relevance and standardization of in vitro antioxidant assays: ABTS, DPPH, and Folin–Ciocalteu. Journal of Chemistry, 2018. (this would be my number 1 reference)

Finally. This question has appeared in several places. Apologies if this post is repeated also.