Phenolic content as Antioxidant and Antimicrobial Activities of Pistacia Atlantica Desf. (Anacardiaceae) extract from Libya

Abstract

The aim of the work is to search for new, potentially biologically active extract .The chemical and biological investigations of different extracts of P. atlantica, resulted that the ethyl acetate extract of P. atlantica leaves contains a complicated mixture of phenolics, which includes mainly gallotannins as previously detected by 2D paper chromatographic screening. The isolation and identification of six polyphenoles (1-6) , were elucidated for the first time from this plant , including three polyphenolic acid ; gallic acid (1); ellagic acid (2) ; 3,3'-dimethoxyellagic acid (3) and three gallotannines, 2,3-di-O-galloyl-(α/β)-4C1-glucopyranose, nilocitin (4) ; 1,3-di-O-galloyl-β-D-4C1-glucopyranos (5); 1,2,3,4,6- penta-O-galloyl-b-D-4C1-glucopyranose(6).The structures of all isolated compounds were elucidated by conventional methods, spectroscopic analysis, including 1D and 2DNMR,ESIMS and HRESI mass as well. The search for new, potentially biologically active extract becomes much more efficient after identification of all compounds in that mixture. The in vitro antioxidant activity using the stable free radical DPPH (2,2-diphenyl-1-pycrylhydrazyl) method of the P. atlantica extracts proved that ethyl acetate extract possesses a distinct radical scavenging effect at the different concentrations and the extract completely inhibited DPPH absorbance at a concentration 77 μl , the percentage of inhibition obtained 96.4% can be considered as a full absorbance inhibition of DPPH . Also, the IC50 (the concentration that inhibits 50% of the absorbance of DPPH) of ethyl acetate extract of P. atlantica showed an IC50 value of 8.41±0.24 μg/ml compared with IC50 value of ascorbic acid 1.82±0.33 μg/ml. It could be concluded from the obtained results that the P. atlantica ethyl acetate extract shows a very high antioxidant capacity which is very close to the value of the reference standard used, which may be attributed to its high polyphenolic content. P. atlantica extracts demonstrated inhibitory effects against pathogenic microorganisms: Staphylococcus aureus, NCTC 7447; Bacillus subtilis, NCTC 10400; Escherichia coli, NCTC 10416; Pseudomonas aerogenasa NCIB 9016); Candida albicans, IMRU 3669.The active ethyl acetate extract shown a sensitizing effect against Staphylococcus aureus ,20mm inhibition zone while the methanolic extract effect against Bacillus Subtilis was 19.5mm inhibition zone.The present study has revealed that Pistacia Atlantica Desf. (Anacardiaceae) growing in Libya is capable of synthesizing and accumulating different types of phenolics, including mainly ellagitannins, gallotannins which were elucidated for the first time from this plant .It could be concluded from the obtained results that the P. atlantica is a promising source for bioactive compounds which have potential applications as bioactive antioxidant agents for the treatment of diseases