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Comparison of chemical composition and antioxidant capacity of glycosidically bound and free volatiles from clove (Syzygium aromaticum L. Merill et Perry)

In this study the comparison of chemical composition and antioxidant capacity of glycosidically bound and free volatiles from clove (Syzygium aromaticum L. Merill et Perry) were examined. The volatile aglycones were extracted from their nonvolatile glycosidically bound compounds by enzymatic hydrolysis with β -glycosidasae enzyme, while free volatiles (essential oil) were extracted using Clevenger-type apparatus. The chemical composition analyses of volatiles were run on coupled system gas chromatography-mass spectrometry (GC-MS) with two different polarity column. Totally of 15 compounds were identified in volatile aglycone fraction, including aromatic compounds, aliphatic alcohols, acids and esters. The major aglycone was phenylpropanoide eugenol (80.5 %). Other quantitatively important aglycones were vanillin (7.2 %), chavicol (2.3 %) and benzyl alcohol (1.1 %). In comparison, free essential oil has only five identified compounds with eugenol as major (91.2 %). A comparison between the chemical composition of glycosidically bound and free volatile compounds showed only eugenol as identical. Phenylpropanoide eugenyl acetate (7.1 %), and sesquiterpene hydrocarbons trans-caryophyllene,  -humulene and δ -cadinene were present in smaller percentages. 2, 2´- diphenyl-1-picrylhydrazyl radical scavenging method (DPPH method) was used to evaluate the antioxidant capacity of clove volatile compounds. The results were compared with commercial antioxidants BHT and  -tocopherol. The results show that antioxidant capacity decreased in the order  -tocopherol ≥ essential oil > BHT > volatile aglycones. The better essential oil antioxidant capacity than volatile aglycones capacity could be explained with higher eugenol content and with eugenyl acetate present in them. In spite of lower free volatiles antioxidant capacity that contributes to overall clove capacity and confirm clove’ s significant role among spice plants. This is a guideline to replacing commercial antioxidants with natural ones.

Syzygium aromaticum L. Merill et Perry

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