Biljana Dekić

DETERMINATION OF POLYPHENOL AND FLAVONOID CONTENT AND ANTIOXIDANT ACTIVITY OF ETHANOLIC, CHLOROFORM AND ETHYL ACETATE EXTRACT OF THE PLANT SPECIES Thymus serpyllum L.

This research aimed to examine the phytochemical composition, content of polyphenols and flavonoids, and antioxidant capacity of ethanolic, ethyl acetate, and chloroform extract of the plant species Thymus serpyllum L. The extracts were tested for the presence of alkaloids, tannins, saponins, phenolic compounds, flavonoids, steroids, terpenoids, cardiotonic glycosides, and coumarins. The total content of polyphenols was determined spectrophotometrically with the Folin-Ciocalteu reagent, according to Singleton's method, while the total content of flavonoids was determined using the method with aluminum chloride. The highest contents of polyphenols and flavonoids were determined in ethanolic extracts, where the measured values ranged from 111.00 ± 0.26 to 288.00 ± 0.23 mg GAE/g of dry extract for polyphenols, and 65.80 ± 0.19 to 198.22 ± 0.34 mg RE/g dry extract for flavonoids. The antioxidant activity was determined by the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. The tested extracts show a good effect on DPPH radical inhibition, with the IC50 values ranging from 35.15 ± 0.33 to 398.27 ± 0.24 μg/ml, and the greatest ability of ethanolic extract to neutralize the DPPH radical. Qualitative phytochemical analysis of the extracts showed a wide spectrum of phytochemicals, where ethanol, as the most polar solvent, extracts almost all tested phytochemicals.

SYNTHESIS, COMPLETE ASSIGNMENT OF 1H- AND 13C-NMR SPECTRA AND ANTIOXIDANT ACTIVITY OF NEW AZINE DERIVATIVE BEARING COUMARIN MOIETY

In this research, the synthesis of a new azine derivative with coumarin moiety was performed in three reaction steps, starting from 4-hydroxycoumarin. The first step in synthesis was the acetylation of 4-hydroxycoumarin to yield 3-acetyl-4-hydroxycoumarin and then the obtained 3-acetyl-4-hydroxycoumarin was reacted with hydrazine hydrate and give a corresponding hydrazone. Condensation of the hydrazone with 4-ethoxy-3-methoxybenzaldehyde afforded the target compound 1-[1-(4-hydroxy-2-oxo-2H-chromen-3-yl)-ethylidene]-2-(4-etoxy-3-methoxybenzylidene)-hydrazine in a good yield. The resulting azine derivative is fully spectrally characterized, including complete assignment of 1H- and 13C-NMR spectra, as well as 2D NMR (1H-1H COSY, NOESY, HSQC and HMBC) spectra. The antioxidant activity of corresponding hydrazone and target compound was evaluated by DPPH method where hydrazone derivative displayed a significant and target azine good antioxidant activity, with IC50 (μM) values 11.69 and 216.60, respectively.

SYNTHESIS AND COMPLETE NMR SPECTRAL ASSIGNMENTS OF NEW BENZYLAMINO COUMARIN DERIVATIVE

This research involves the reaction of 4-chloro-3-nitrocoumarin and (4-methoxyphenyl)methanamine, whereby a novel coumarin derivative 4-[(4-methoxybenzyl) amino]-3-nitro-2H-chromen-2-one was obtained in good yield. The reaction was carried out in ethyl acetate, in the presence of triethylamine. Also, a detailed spectral analysis of a new coumarin derivative is presented. Resonance assignment was achieved using one- (1H NMR and 13C NMR) and two-dimensional NMR techniques (1H-1H-COSY, NOESY, HSQC, and HMBC). The NOESY correlations of protons from arylamino substituent and coumarin core indicate their spatial orientation.

PHENOLIC AND FLAVONOID CONTENT AND ANTIOXIDANT EVALUATION OF HAWTHORN (Crataegus monogyna Jacq.) FRUITS AND LEAVES EXTRACTS

Considering the facts that phenolic compounds have many pharmacological effects, as well that antioxidant effect of phenolic compounds has been proven in various experimental systems, aim of this research was to determine the content of total phenols and flavonoids and evaluation of antioxidant activity in ethanol, ethyl acetate and chloroform extracts of fruits and leaves of the plant species Crataegus monogya Jacq., which is known as common hawthorn. The content of total phenolic compounds was determined by the spectrophotometric method using Folin-Ciocalteu reagent and the content of flavonoids was determined using aluminum chloride. In vitro evaluation of the antioxidant activity of tested extracts was performed using the DPPH method. The amount of total phenolics was varied in fruits and leaves extracts and ranged from 38.05 ± 0.18 to 365.11 ± 0.32 mg GAE/g dw. Ethyl acetate extract of hawthorn leaves showed the highest content of phenolic compounds (365.11 ± 0.32 mg GAE/g dw). The flavonoid content was different in the fruits and leaves of hawthorn and ranged from 21.11 ± 0.11 to 122.98 ± 0.21 mg RU/g dw, whereby the highest content of flavonoids was found in ethyl acetate extract of leaves (122.98 ± 0.21 mg RU/g dw). Antioxidant activity of the tested extracts was expressed as IC50 values and ranged from 5.53 ± 0.08 to 293.51 ± 0.28 μg/ml. Ethyl acetate extract of hawthorn leaves showed considerable antioxidant potential (IC50 = 5.53 ± 0.08 μg/ml). Based on the obtained results, a significant correlation was found between the antioxidant activity and the content of total phenolics and flavonoids compounds in hawthorn fruits and leaves extracts.

THE SYNTHESIS AND NMR SPECTRAL ASSIGNMENTS OF 3-NITRO-4-((6-NITROBENZOTHIAZOL-2-YL)AMINO)-2H-CHROMEN-2-ONE

Complete assignment of the 1H and 13C NMR chemical shifts of new coumarin derivate was described in this paper. A new coumarin derivate was synthesized in good yield by reaction of 4-chloro-3-nitrocoumarin and 6-nitrobenzothiazol-2-amine in ethyl acetate in the presence of triethylamine. The complete spectral assignment was achieved using of 1D (1H and 13C NMR) and 2D (1H-1H-COSY, NOESY, HSQC and HMBC) NMR experiments.

SYNTHESIS AND ANTIOXIDANT ACTIVITY OF A NEW 4-AMINOCOUMARIN DERIVATIVE