It is known that caffeic acid and its derivatives make considerable contribution to the immunostimulating action of Echinacea. However, existing methods of the determination of caffeic acid derivatives total content in Echinacea tinctures have principle drawbacks, in particular, low selectivity. So, we have developed a simple and selective spectrophotometric method, allowing to control total caffeic acid derivatives in Echinacea medicines during their storage.

[Запорожец О.А., Крушинская Е.А., Барвинченко В.Н., Липковская Н.А., Погорелый В.К. Спектрофотометрическое определение гидроксикоричной кислоты и ее производных в препаратах эхинацеи // Хим. фарм. журн. – 2003. – Т.37, №12. – С.47–50 (= Zaporozhets O.A., Krushinsksya E.A., Barvinchenko V.N., Lipkovskaya N.A., Pogorelyi V.K. Spectrophotometric Determination of Hydroxycynnamic Acid and Related Compounds in Echinacea Preparations // Pharmaceutical Chemistry Journal. - 2003. – V.37, №12. - P.632-636 (full-text, pdf, 95 Kb)].

Total caffeic acid derivative concentration and total antioxidant activity of eight Echinacea purpurea water-alcohol medicines were determined. The results indicate that both values are widely different for various Echinacea medicines, even when produced by the same manufacturer. Thus, the problem of their quality control during manufacturing and storage is very important.

Strong correlation has been revealed between the antioxidant activity and total caffeic acid derivatives content of Echinacea, indicating the applicability of the developed test to the analysis of these phytoceuticals.

BLACK AND GREEN TEAS: antioxidant power and its correlation with
total flavonoids, total tannins and total polyphenols

Phenolic compounds are known to make significant contribution to the antioxidant properties of tea. In the table the values of antioxidant power, total flavonoids, total tannins and total phenolic content of different types of teas are compared.

The antioxidant power of green teas was found to be considerably higher than that of black teas. The ratio between the antioxidant activity of green and black tea produced by the same manufacturer makes about 2.2 (Maisky chai) - 2.4 (Hyleys). This fact is, probably, related to the processes of tea manufacturing. During green tea producing, tea leaves do not undergo any oxidation, and, therefore, contain large amounts of non-oxidized phenolic compounds. On the contrary, black tea looses a great part of its antioxidant properties during the fermentation.
The next figure represents the correlation between the antioxidant power, total flavonoids, total tannins and total polyphenols of green and black teas. It can be seen that for green, non-fermented teas, the antioxidant activity is really correlated with the content of phenolic compounds. For black, fermented teas the antioxidant power is rather low and has little difference for various trade marks.

RED WINES: antioxidant power and its correlation with total polyphenols

Antioxidant power and total polyphenol content (determined by a standard Folin-Ciocalteu method) of red wines were compared. It was interesting that both parameters were higher for Cahor wines.
And again a strong correlation exists between the antioxidant power evaluated by the test method and polyphenol content, in good agreement with the reported studies.

The obtained results show that CuTAAB-SG may be succesfully employed in quality screening of herbal products. Moreover, we expect that this modified sorbent could be applied to the analysis of biological samples, in particular, for the evaluation of blood serum antioxidant status.