Determination of some biochemical parameters from leaves of Quercus ilex L.(Fagaceae), collected in Djabel Zagouan (Tunisia)

Abstract

Biochemical characterization, such as, fatty acids, essential oils composition, polyphenols content and antioxidant activities, were investigated from leaves, of Quercus ilex L.(Fagaceae), collected in DjabelZagouan (Tunisia). Only the fatty acid composition was determined by gas chromatography after transformation of the fatty acids into methyl ester derivatives compatible for injection in a Gas Chromatograph,and determined by gas chromatography (GC-FID). Essential oils were extracted by hydrodistillation and, analyzed by gas chromatography (GC-FID). Total phenolic content, concentration of flavonoids and,in vitro, antioxidant activities were determined, using spectrophotometric methods. The antioxidant activities was tested by the DPPH (2, 2-diphenyl-1-picrylhydrazyl), free radical scavenging assay.
Results showed that total fatty acid content varied from 1.78 to 4.86%, based on dry weight (dw) and the predominants fatty acids were oleic acid (63.43–59.76%), linoleic acid (14.93–16.05%) and palmitic acid (9.16–12.13%). The oils contain, an appreciable, amount of unsaturated fatty acids (73.86–85.59%).This study showed that Holm oak leaves, are rich in an unusual fatty acid, the oleic one. The essential oil yield varied, from 0.01 to 0.04%. So the major components, in leaves oils from Quercus ilex L., were trans-2-hexanal (14.89–16.93%), viridiflorol (12.94–15.24%) and sabinene (6.84–9.65%).The total phenolic, content of the samples, varied, from 2.93 to 3.40 mg/g of dry weight, expressed as gallic acid equivalents.
The total flavonoïd concentrations varied, from 1.83 to 2.72 mg/g, of dry weight quercetin equivalents. The extracts of the leaves were observed displaying strong DPPH free radical scavenging action, with IC 50value, ranged, from 102.66 to 134.83 µg/mL, comparing to the IC 50 value (48.31µg/mL), of reference standard. These results suggest that phenolics, in this species, provide substantial antioxidant activity and Quercus. Ilex L. may be a potential source of natural antioxidants.