THE FIRST TEST-METHOD FOR THE EVALUATION OF
TOTAL ANTIOXIDANT POWER OF HERBAL PRODUCTS

Olga Zaporozhets, Olena Krushynska / Ольга Запорожець, Олена Крушинська


With most herbal medications, it isn`t necessary to identify a single active ingredient, as often it`s a combination of ingredients - including some at trace levels that remain unidentified - that shows greatest biological effect. Therefore, the tendency of total parameters evaluation is increasing. One of the most important of them is the total antioxidant activity, a quality criterion of natural products and phytomedicines, expressing their ability to scavenge reactive oxygen species.


For the last 10 years a real "antioxidant boom" has been observed
with the exponential growth of the related works and publications number.

In spite of all, no test method reported was found. So, we made an attempt to create
a simple and rapid test for the evaluation of antioxidant power using our modified sorbent.



A SOLID-PHASE REAGENT:
Cu(II) macrocyclic complex immobilized on silica gel


CuTAAB immobilized surpasses iron-phenanthroline-silica gel in sensitivity, the range of linear response, the productivity of the analysis. In addition, it may be regenerated easily. For all these reasons and due to its ability to interact with bioantioxidants, namely CuTAAB-SG was used to solve an interesting analytical problem of the test-evaluation of total antioxidant power.

more details about CuTAAB-SG and other solid-phase redox-reagents
on the base of Cu(II) and Fe(III) chelates immobilized

OBJECTS OF ANALYSIS:
Echinacea phytoceuticals, teas and wines


For the approvement of the proposed method some of the most popular herbal beverages and drugs have been chosen. Tea is the most consumed beverage worldwide and, so, is an important agriculturul product. It containes different components possessing P-vitamin and antioxidant activity, among which flavonoids, tannins and catechins are the most considerable. Echinacea is widely accepted for its immunostimulant medicinal usage. Extracts of the dried roots and the upper plants are known to show bacteriostatic, virusstatic and immunostimulating activity and to cause general beneficient therapeutical effect at infections and chronic inflammations. Consumption of red wines has been associated with the reduction of the risk of cardiovascular diseases (a well-known "French paradox"), cancer and other pathologies.

TEST PROCEDURE: "DROP-AND-MEASURE"

The proposed test procedure is extremely simple: a portion of the modified sorbent is treated with one drop of buffer solution and one drop of the analyzed extract and kept covered for 10 minutes; then the analytical signal is measured. Quercetin was chosen as a reference antioxidant compound due to its reducing properties and wide range of linear response (up to 240 ppm) in the reaction with the modified sorbent. The equation to calculate the product antioxidant activity in the units of quercetin concentration is presented in the slide.


ECHINACEA PHYTOCEUTICALS:
antioxidant power and its correlation with
total caffeic acid derivatives content

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.

Key publications:

Zaporozhets O.A., Krushynska O.A., Lipkovska N.A., Barvinchenko V.N. A new test method for the evaluation of total antioxidant activity of herbal products // J. Agric. Food Chem. – 2004. – V.52. – P.21–25 (full-text, pdf, 79 Kb).

Запорожець О.А., Крушинська О.А., Ліпковська Н.О., Барвінченко В.М. Застосування твердофазного редокс-реагенту для тест-оцінки загальної антиоксидантної активності рослинних об’єктів // Фармаком. - 2006. - №1/2. - С.51-58.

Запорожець О.А., Крушинська О.А. Комбіноване спектроскопічне і тест-визначення інтегральних показників якості препаратів з антиоксидантною активністю // Магістеріум "Природничі науки". Вип.16. - Київ: видавничий дім "Києво-Могилянська академія", 2005. – С.63–66.

Крушинська О.А., Запорожець О.А. Тест-оцінка антиоксидантної активності червоних вин // Вісник Київського національного університету імені Тараса Шевченка. Сер. "Хімія". – 2005. – Т.41. – С.21–23.

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)).

Крушинська О.А. Адсорбційно закріплені на кремнеземах хелати Купруму та Феруму – твердофазні редокс-реагенти для визначення органічних відновників. Дисертація на здобуття наукового ступеня кандидата хімічних наук за спеціальністю 02.00.02 – аналітична хімія. – Київський національний університет імені Тараса Шевченка, Київ, 2005.

на персональну сторінку Олени Крушинської/
to the personal page of Olena Krushynska