Free radicals, defined as atoms or molecules with odd number of electrons, exist in many chemicals and have been suggested to contribute in cell structure and tissue damage, which eventually cause human disease and aging mechanism (
11-
13). Antioxidants protect body against free radical-mediated and oxidative damage by scavenging free radicals (
14), so increasing antioxidant intake can be a preventive factor for lowering oxidation (
15,
16). Nowadays, there is a growing interest for identifying antioxidants from natural sources due to a new trend for substitution of synthetic antioxidants with natural ones, which exist in medicinal plants used in traditional medicine (
17,
18). Essential oils obtained from medicinal plants can be used as natural antioxidants (
5).
A.capillus- veneris is a fern widely used for various diseases in Iranian traditional medicine (
19). According to the literature, isolated phytochemicals of A. capillus- veneris were triterpenoidal compounds belonging to adiantane and filicane groups and identified as isoadiantone, isoadiantol-B, 3-methoxy-4-hydroxyfilicane and 3, 4-dihydroxyfilicane as well as three flavonoids of quercetin, quercetin-3-O-glucoside and quercetin-3-O-rutinoside (rutin). Modern pharmacological studies revealed antimicrobial, antifungal, anti-implantation, antioxidant, anti- inflammatory, anti-diabetic and anti-nociceptive effects of this plant (
20-
24). This paper discussed the above purposes since no research has been performed concerning chemical constituents and antioxidant activity of this species essential oil.
Table 1 demonstrates major constituents of the essential oil of
A.capillus- veneris. As shown in
Table 1, the main constituent of this volatile oil was carvone (31.58%). Other major constituents were carvacrol (13.72%), hexadecanoic acid (5.88%), thymol (4.05%), Hexahydrofarnesyl acetone (3.16) and n-nonanal (2.99%). In another study conducted to determine constituents of the essential oil of Adiantum flabellulatum, the major constituents identified from roots of this plant were n-decanoic acid (11.44%), 6,10,14-trimethyl-2-pentadecanone (11.23%), diethyl phthalate (8.63%), and nonanoic acid (6.15%). The major constituents identified from leaves of
A. flabellulatum were n-decanoic acid (11.77%), 2-isopropenyl-4a,8-dimethyl-1,2,3,4,4a,5,6,7- octahydronaphthalene (10.63%), [1R-(1α,7β,8α]-1,2,3,5,6,7,8,8a-octahydro-1,8a-dimethyl-7-(1-methylethenyl)-naphthalene (9.88%), α -panasinsen (8.11%), 4-tetradecyne (6.63%), β -pinene (5.16%) and nonanoic acid (4.01%) (1). Moreover, in another article about phytoconstituents of essential oil of
Adiantum edgeworthii, n-nonanal was the main constituent in leaves, while 2,6-di-tert-butyl p-cresol was the main active constituent in the roots of this plant (
25). These results indicate fundamental differences among essential oils of different species of
Adiantum genus.
Antioxidant activity of volatile oil of
A. capillus-veneris was assessed by DPPH assay, a simple and reliable experiment to screen antioxidant agents. Findings of this assay showed that the volatile oil of this plant has the potential of scavenging free radicals. Phytochemicals of this essential oil indicated that this effect could be somehow attributed to high contents of carvone (
26), carvacrol and thymol. Thymol and carvacrol as phenolic compounds are responsible for radical scavenging activity of many essential oils, which contain these two compounds (
27).
This study determined chemical composition and antioxidant activity of the essential oil of A. capillus- veneris. Phytochemicals responsible for its radical scavenging activity were discussed. In conclusion, the volatile oil of this plant could have the potential of other biological activities, so it is recommended to perform further experiments on this essential oil.