Comparative effects of thermal treatments and -irradiation on the volatile, non-volatile and antiradical activity of Egyptian anise essential oil

Abstract EN

The effect of various thermal treatments (electric oven, microwave) and g-irradiation at three doses (6, 8 and 10 KGy) on the composition of volatile and non-volatile of anise essential oil and also their antioxidant properties were considered.

The hydrodistilled oil (HD) of control and treated samples were subjected to gas chromatography–mass spectrometry (GC/MS) analysis.

The volatile profile of raw HD oil of anise consisted mainly of transe-anethole (79.68%) followed by hexahydrofarnesyl acetone (6.95%), para-anisaldehyde (5.49%); g-himachalene (2.53%) and estragole (0.76%).

Although the effect of roasting didn’t cause significant changes in the total yield of major compounds of HD anise oil which are phenylpropanoid derivative (transe anethole , para-anisaldehyde, cis-anethole and estragole (=methylchavicol), it is found that gamma irradiation revealed the same behavior at the 10 KGy irradiated sample but decrease the total yield of these compounds in 6.8 KGy irradiated sample compared to control one.

also the thermal and g- irradiation caused drastic increase in the total yield of sesquiterpenes whereas decreased oxygenated compounds in all samples under investigation compared to control one.

Such changes affected the antioxidant activity of the treated samples 1.1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging as well as β-carotene bleaching test against butylated hydroxy toluene (BHT).

The strongest effect of reduction of DPPH radical as well as the highest inhibiting effect of the oxidation of linoleic acid and the subsequent bleaching of β-carotene was by 8 KGy irradiated sample which comprised (84.57%±1.43); (85.21% ± 0.12) respectively, in comparison to BHT (98% ± 0.0) at the same concentration 30 µg/mL besides all samples under investigation revealed high antioxidant activities due to their high content of phenylpropanoid and oxygenated compounds.

These confirmed by total phenolic content.

High performance liquid chromatography (HPLC) method was used for the analysis of phenolic compounds in the selected sample.

Polyphenolic compounds were analysed on C18 Reversed Phase (RP) HPLC.

A total of 9 phenolic compounds were identified, the obtained results showed that the predominant compound was P-qumaric acid (43.36%) followed by ferulic acid (21.06%).