By Ahmed El-Ghorab, Takayuki Shibamoto and Mostafa Ozcan
Abstract: Abstract: Essential oils of caper (Capparis ovata Desf. var. canescens) buds and leaves obtained by steam distillation followed by solvent extraction were analyzed by GC and GC/MS. Eighty-six compounds were identified from the caper bud extract and 100 from the caper leaf oil. The major volatile compounds found in caper bud oil were benzyl alcohol (20.4%), furfural (7.4%), ethanal methyl pentyl acetal (5.9%), 4-vinyl guaiacol (5.3%), thymol (5.1%), octanoic acid (4.8%) and methyl isothiocyanate (4.5%). The major volatile compounds found in caper leaves were methyl isothiocyanate (20.0%), thymol (15.5%), 4-vinyl guaiacol (4.3%), hexyl acetate (3.6%) and trans-theaspirane (2.6%). These oils inhibited hexanal oxidation by 80% over 40 days at the level of 200 μg/mL. Also, they inhibited oxidation of 1,1-diphenyl-2-picrylhydrazyl hydrate by over 70% at the 500 μg/mL level. The dichloromethane and methanol extracts from caper buds and leaves exhibited higher antioxidant activities than those of their essential oils in both testing systems. Key Word Index: Capparis ovata Desf. var. canescens, Cappasidaceae, capers, essential oil composition, methyl isothiocyanate, benzyl alcohol, thymol, antioxidant activity.
Introduction
Capparis ovata Desf. var. canescens is one of the most commonly used seasoning ingredients in Mediterranean kitchens. Certain species and varieties of capers have been cultivated in special regions of the Mediterranean. These plants show strong resistance to harsh environmental conditions and have become an important economic resource in Southern Europe in recent decades (1–3). The main producers and exporters of capers are Spain, Morocco and Italy. Recently, packed brined caper products have been exported from Turky to European countries (4,5).
Capers are used for flavoring foods such as anchovies, pasta, pizza and commerical frozen foods. Various parts of the caper plant, especially the buds and leaves, have been used in drugs, cosmetics and foods (4). The flavor intensity is directly related to bud maturity, and capers as large as 1 cm are commonly used. Caper leaves steeped in vinegar have been used to treat ulcers (6).
Chemical studies on Capparis spinosa L. have reported the presence of glycosides, such as quercetin and kaempferol (7) and an anti-inflammatory principle (8). A few other substances such as alkaloids, glucosinolate, lipids flavonoids and miscellaneous isothiocyanate glucosides have also been identified in different species of genus Capparis (9–13).
Recently, the presence of antioxidants in natural plants, including herbs and spices, has received much attention as a disease preventive substance (14). Natural antioxidants of plant origin are generally classified as vitamins, phenolic compounds, or flavonoids. In addition to the use of the plant per se, volatile or flavor chemicals isolated from various plants have been shown to have certain antioxidative activities.
The volatile compounds and antioxidative activity of caper buds and leaves have not been reported prior to this study. Therefore, in the present study, the chemical compositions and antioxidant activities of the essential oils obtained from both caper (Capparis ovata Desf. var. canescens) buds and leaves were investigated.
