The antiradical activities of various antioxidants were determined using the free radical, 2,2-Diphenyl-1-picrylhydrazyl (DPPH*). In its radical form. DPPH* has an absorption band at 515 nm which dissappears upon reduction by an antiradical compound. Twenty compounds were reacted with the DPPH* and shown to follow one of three possible reaction kinetic types. Ascorbic acid, isoascorbic acid and isoeugenol reacted quickly with the DPPH* reaching a steady state immediately. Rosmarinic acid and δ-tocopherol reacted a little slower and reached a steady state within 30 min. The remaining compounds reacted more progressively with the DPPH* reaching a steady state from 1 to 6 h. Caffeic acid, gentisic acid and gallic acid showed the highest antiradical activities with a stoichiometry of 4 to 6 reduced DPPH* molecules per molecule of antioxidant. Vanillin, phenol, γ-resorcylic acid and vanillic acid were found to be poor antiradical compounds. The stoichiometry for the other 13 phenolic compounds varied from one to three reduced DPPH* molecules per molecule of antioxidant. Possible mechanisms are proposed to explain the experimental results.

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Use of a Free Radical Method to Evaluate Antioxidant Activity

The biochemistry and medical significance of the flavonoids.

The reaction mechanisms of three antioxidants are proposed in order to explain experimental results obtained from a kinetic study using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH . ) method, previously adapted in our laboratory. In its radical form, DPPH . shows an absorbance maximum at 515 nm which disappears upon reduction by an antiradical compound. BHT, a synthetic antioxidant, slowly reacts with DPPH . reaching a steady state within 5 h. This 2.8-stoichiometric complete reaction follows a 1.5-order with respect to DPPH . and 0.5 to BHT. The kinetic rate constant, k, is estimated to be 5.0 L/(mol·s) at 20 °C and the energy of activation, Ea , is equal to 35 kJ/mol in methanol. Eugenol reacts with DPPH . reaching a steady state within 2 h. This 1.9-stoichiometric reaction follows a 2-order with respect to both DPPH . and eugenol, k and Ea are estimated to be 5.4 × 10 10 L 3 /(mol 3 ·s) at 20 °C and 30 kJ/mol, respectively. The eugenol mechanism may involve a dimerization between two phenoxyl radicals. The reaction with isoeugenol is rapid and reversible, with a stoichiometry of 1.1. It is first order with respect to isoeugenol with k (direct reaction) equal to 8.9 × 10 −2 s −1 at 10 °C. This reaction is consistent with a pseudo-monomolecular mechanism.

Kinetics and Mechanisms of Antioxidant Activity using the DPPH.Free Radical Method

Phenolic compounds and antioxidant activities of buckwheat (Fagopyrum esculentum Moench) hulls and flour

The impetus for developing analytical methods for phenolic compounds in natural products has proved to be multifaceted. Hundreds of publications on the analysis of this category of compounds have appeared over the past two decades. Traditional and more advanced techniques have come to prominence for sample preparation, separation, detection, and identification. This review provides an updated and extensive overview of methods and their applications in natural product matrices and samples of biological origin. In addition, it critically appraises recent developments and trends, and provides selected representative bibliographic examples.

Extraction, separation, and detection methods for phenolic acids and flavonoids

バラ科サンザシ属Crataegus monogynaおよびCrataegus laevigataの花部および葉部の主フラボノイド含量

A number of medicinal species of the Apiaceae, Borraginaceae and Lamiaceae families present high rosmarinic acid and total hydroxycinnamic derivative contents. Species of genera Sanicula (Apiaceae), Lycopus, Melissa, Mentha, Origanum and Salvia (Lamiaceae) contain rosmarinic acid in large amount, more than 3%, based on dry weight. The antioxidant activity of hydroalcoholic extracts, on DPPH, is partly in relation with the hydroxycinnamic derivative content.

[Rosmarinic acid, total hydroxycinnamic derivatives and antioxidant activity of Apiaceae, Borraginaceae and Lamiceae medicinals].

From 42 Rosaceae species, only the Rosoideae species exhibit high tannin content and elastase inhibiting activity such as Filipendula ulmaria, Geum montanum, G. rivale, Alchemilla xanthochlora and Sanguisorba minor. Other studied species from Spiraeoideae, Maloideae and Prunoideae subfamilies are less rich in tannin and also less active.

Teneur en tanins et activite inhibitrice de l'elastase chez les rosaceae

The qualitative and quantitative composition of the main aromatic and polyphenolic constituents of Mitcham type peppermint (Mentha x piperita L.) tisane, were examined and compared with those of leaves before and after infusion. The original peppermint leaves contained 2.4% essential oil of which menthol was 0.99%, total polyphenolic compounds 19% and total flavonoid compounds 12% comprising eriocitrin 7%, luteolin-7-rutinoside 1.5%, hesperidoside 0.6% and total hydroxycinnamic compounds 7% (rosmarinic acid 1.4%). The tisane contained 21% of the original essential oil corresponding to 25 mg/l, with increased alcohol and ketone contents and lower contents of hydrophobic terpenecarbons, oxides and esters. It contained also a high proportion of the polyphenolic compounds (about 750 mg/l) corresponding to an extraction yield of 75%. In consequence the monograph "Peppermint leaf" of the Pharmacopoeia should be amended.

[Aromatic and polyphenolic composition of infused peppermint, Mentha x piperita L].

Les parties aeriennes sechees d'Alchemilla xanthochlora Rothm. (16 lots), d'A. glabra Neygenf. (1 lot), A. coriacea Buser (2 lots) et A. filicaulis Buser (3 lots) presentent une composition similaire en flavonoides et en tanins. Dans le cas d'A. xanthochlora, les teneurs moyennes des principaux constituants sont les suivantes: flavonoides totaux 2,22 %, glucuronyl-3 quercetol 1,18 %, tanins totaux 16,0 %, acide ellagique 0,36 %. Les teneurs en flavonoides sont plus elevees avant floraison, les teneurs en tanins plus elevees apres floraison. L'etude comparee de 4 lots d'origine commerciale a permis de proposer des normes pour une revision de la monographie « Alchemillae herba de la Pharmacopee.

Carnat Ap

Papers

バラ科サンザシ属Crataegus monogynaおよびCrataegus laevigataの花部および葉部の主フラボノイド含量

[Rosmarinic acid, total hydroxycinnamic derivatives and antioxidant activity of Apiaceae, Borraginaceae and Lamiceae medicinals].

Teneur en tanins et activite inhibitrice de l'elastase chez les rosaceae

[Aromatic and polyphenolic composition of infused peppermint, Mentha x piperita L].

Standardization of the aerial parts of Alchemilla