PHENOLIC ACIDS AND FREE RADICAL SCAVENGING ACTIVITY OF ALCHEMILLA JUMRUKCZALICA PAWL

PHENOLIC ACIDS AND FREE RADICAL SCAVENGING ACTIVITY OF ALCHEMILLA JUMRUKCZALICA PAWL.

M. Nikolova*¹,I. Dincheva ², A. Vitkova ¹ and I. Badjakov ²

Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences ¹, 23, Acad. G. Bonchev Str. 1113 Sofia, Bulgaria

AgroBioInstitute ², 8 Dragan Tsankov Str., 1164 Sofia, Bulgaria

ABSTRACT: Comparative study of free radical scavenging activity and phenolic acid content of Bulgarian endemic Alchemilla jumrukczalica and the commercial herbal - Alchemilla vulgaris complex was carried.The methanol extracts of studied samples showed significant antiradical activity. The concentration of the extracts needed for 50% inhibition of DPPH was found to be 12,09 µg/ml and 19,62 µg/ml for A. jumrukczalica and A. vulgaris complex, respectively.Ten free and seventeen bonded phenolic acids were identified and quantified by performed of gas chromatography mass-spectrometry (GC-MS). Gentisic, protocatechuic, salicylicand trans-cinnamic acids were represented in the greatest quantityamong the identified phenolic acids. This is the first detailed analysis on qualitative and quantitative composition of phenolic acids inAlchemilla species

INTRODUCTION:In the course of phytochemical studies of the high mountain medicinal plants from Bulgaria in particularAlchemilla species ¹, the Bulgarian endemicAlchemillajumrukczalica(Rosaceae) was investigated. No phytochemical studies on Alchemillajumrukczalica have been reported.Alchemilla vulgaris complex is the commercial herbal - mixture of Alchemila species, herb with well documented medicinal application ².

The extract of A. vulgaris complex was used as positive control.Species of genus Alchemilla have been studied mainly for the content of flavonoids,triterpenes, tannins and total phenols ^3-6.With regard to phenolic acids, we only had data for the content of ellagic and gallic acids in Alchemillaspecies ^{7, 8}. Phenoliccompounds are considered free-radical scavengers^{9, 10}. That is why the objectives of present study were to;

1)      Compare the antioxidantactivity of the extracts of the studied species, and

2)      Identify and quantify phenolic acids in these extracts that may contribute to antioxidant activity.

Plant Material: The plant material of Alchemillajumrukczalica was collected in Central Balkan. A voucher specimen of A. jumrukczalica (SOM 165680) has been deposited at the Herbarium of Institute of Biodiversity and Ecosystem Research.

Preparation of Extracts: Air dried leaves of A.jumrukczalica and A. vulgaris complex was extracted with 80% methanol threefold. After evaporation of the solvent the received extracts were used for evaluation of antiradical activity and content of phenolic acids.

Antiradical Assay: The antioxidant activity of the methanol extracts was evaluated by the scavenging effect on 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH^.) radicals ^{11, 12}.

The extracts showed significant antiradical activity with IC₅₀ values of 12, 09 µg/ml and 19, 62 µg/ml respectively for A.jumrukczalica and A. vulgaris complex. Obtainedvalues are comparable with those of commercial antioxidant butylated hydroxytoluene (BHT) - 12.65 µg/ml and syringic acid - 4.40 µg/ml.

Phenolic Acid Analysis: Free and bonded phenolic acids were extracted with ethyl acetate from acidulated methanol-water extract of plant materials before and after thermal hydrolysis. Ten free and seventeen bonded phenolic acids were identified and quantified by performed of gas chromatography mass-spectrometry (GC-MS). The extracts of the both samples contain free phenolic acids in comparable quantities while the amount of bonded phenolic acids was higher in the extract ofA. Jumrukczalica.Among the identified free phenolic acids gentisic, protocatechuic, salicylicand caffeicacids are represented in the greatest quantity. Salicylic, protocatechuic, caffeic, trans-cinnamic, gentisic and vanilic acidswere the major bonded phenolic acids in the studiedextracts (Table 1). The presence of such a variety of phenolic acids largely explain the high free radical scavenging of the extracts, taking into account that this type of compounds carry a high antioxidant properties ^{9, 10}.

TABLE 1: FREE AND BONDED PHENOLIC ACID OF A. JUMRUKCZALICA PAWL. AND A. VULGARIS COMPLEX EXTRACTS

In conclusion, the present study is the first detailed report of qualitative and quantitative composition of phenolic acids inAlchemilla species. The methanol extracts of A.jumrukczalica and A. vulgaris complex showed significant antiradical activity. No significant difference was found in the content of phenolic acids and antiradical activity of studied samples. These resultsrevealed the extract of A. jumrukczalica as potential source of antioxidant activity.

ACKNOWLEDGEMENTS: The authors are grateful for the financial support provided by the Bulgarian National Science Fund, Ministry of Education, Youth and Science (Project DTK-02/38)

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