Chemical composition of the essential oil and antioxidant activity of methanolic extracts from fruits and flowers of Hypericum lydium Boiss.

Abstract

This study was conducted to evaluate the essential oil composition and antioxidant activity of methanolic extracts from fruits and flowers of Hypericum lydium Boiss., a wild growing species of the Turkish flora. The antioxidant activities were determined through several biochemical assays. Both extracts showed an inhibitory effect against the formation of TBARS in a phosphatidylcholine liposome model system, moderate scavenging effect on DPPH and superoxide radicals, prominent reducing power and inhibitory effect on deoxyribose degradation in both the nonsite and site-specific assay, but a greater hydroxyl radical scavenging activity was observed in the non-site specific assay, suggesting that the extracts were better at scavenging hydroxyl radicals than at chelating iron. Correlation analysis indicated that there was a linear relationship between antioxidant potency, free-radical scavenging activity, reducing power and the content of flavonoids of fruits and flowers extracts. The essential oils obtained by hydrodistillation were analyzed by GC and GC–MS. In total forty-three compounds were identified. The most abundant components were monoterpenes hydrocarbons represented principally by α-pinene. The tested oil showed no antioxidant activity.

Introduction

Herbs used in the preparation of ethnomedical remedies provide attractive templates for the development of new products. There is an increasing interest in using medicinal and aromatic plants as natural sources in pharmaceutical, food, biotechnology, agricultural and cosmetic industries all over the world. Thus, efforts have been made to isolate and determinate a wide range of secondary metabolites produced by higher plants in order to discover novel compounds which could be potential bioactive agents (Harvey, 2008).

Essential oils obtained mainly from plant materials are a mixture of volatile molecules such as terpenoids, phenol-derived aromatics and aliphatic components. Different in vitro assays characterize most of the essential oils and phenolic compounds as antioxidants (Guimarães et al., 2010). Indeed several medicinal plants have been reported as sources of safe natural antioxidants (Santos et al., 2010, Piccaglia et al., 1993). In living systems antioxidants play a major role in the prevention of cancer, arteriosclerosis, malaria, rheumatoid arthritis, neurodegenerative diseases and aging processes by protecting the organism against oxidative damage (Moure et al., 2001). Mechanism of the activity can include suppressing reactive oxygen species formation, either by inhibition of enzymes or by chelating trace elements involved in free-radical production, scavenging reactive species, and upregulating or protecting antioxidant defences (Acker et al., 1998).

Reports concerning the antioxidant activities of numerous Hypericum species have appeared in the world literature (Conforti et al., 2002, Valentão et al., 2002, Rainha et al., 2011). Pharmacological studies concentrated most particularly on Hypericum perforatum revealing antidepressant, antiviral, antioxidant and antimicrobial properties of the extracts as well as the essential oil demonstrate the great importance of this genus for the pharmaceutical industry (Josey and Tackett, 1999, Schmitt et al., 2001, Radulović et al., 2007). These activities are mostly related to different groups of components present in the plant such as naphtodianthrones, phloroglucinols, flavonoids and phenolic acids being the major ones (Saddiqe et al., 2010). The genus Hypericum is represented by about 89 species in Turkey of which 43 are endemic (Davis, 1988). In Anatolian traditional medicines flowered aerial parts of principally H. perforatum, Hypericum scabrum and Hypericum lydium species find use to treat wounds, gastric ulcers, stomach ache, colitis, intestinal disorders and hemorrhoids (Sezik et al., 2001, Baytop, 1999).

Some Hypericum species growing wild in Turkey has already been investigated for their antioxidant activities and essential oil content. Ethanolic and water extracts obtained from Hypericum venustum were found to possess strong reducing power, free radicals and hydrogen peroxide scavenging activity (Spiteller et al., 2008). The antioxidant properties of ethanolic extracts obtained from H. scabrum, Hypericum lysimachioides var. lysimachioides and Hypericum retusum were evaluated using different tests and their antioxidative activities were found to be comparable with Vitamin E (Barış et al., 2011). Antioxidant properties of Hypericum origanifolium, Hypericum montbretii, H. perforatum and Hypericum hyssopifolium subsp. elongatum var. elongatum have also been reported (Öztürk et al., 2009, Çakır et al., 2003).

Essential oil composition of H. hyssopifolium var. microcalycinum, H. lysimachioides var. lysimachioides (Toker et al., 2006), H. scabrum, H. perforatum (Çakır et al., 1997), Hypericum scabroides (Bağcı and Bekçi, 2010), Hypericum apricum, Hypericum davisii (Bağcı and Yüce, 2010a), Hypericum pseudolaeve, Hypericum thymbrifolium (Bağcı and Yüce, 2010b), Hypericum capitatum (Bağcı and Yüce, 2011a), Hypericum salsolifolium and H. retusum (Bağcı and Yüce, 2011b) from Turkey have previously been investigated.

H. lydium is a perennial herb and can reach a height of up to 60 cm with yellow flowers and characteristic translucent glandular dots on the sepals margin (Davis, 1988). Previous works on this species have revealed the presence of hypericin, pseudohypericin, rutin, hyperoside, apigenin-7-o-glucoside, quercitrin and quercetin (Çırak et al., 2007).

Determination of the essential oil content and antioxidant activity of different extracts is important for the selection of Hypericum species with favorable active compounds profile and improved health benefit. To our knowledge there is no report on the antioxidant activity of extracts and the essential oil obtained from H. lydium. Based on report regarding the presence of polyphenols in aerial parts of the plant and on the assumption that their traditional uses might be partially attributed to an antioxidant activity, we evaluated the antioxidant effects of methanolic extracts obtained from fruits and flowers of this species through several biochemical assays, including inhibition of lipid peroxidation in soybean phosphatidylcholine liposomes induced with Fe³⁺/ascorbate, scavenging effect on DPPH and superoxide radicals, nonsite and site-specific hydroxyl radical mediated 2-deoxy-d-ribose degradation inhibition and reducing power. The antioxidant activities of the extracts were compared to that of quercetin as a typical example of a naturally occurring flavonol and α-tocopherol, as a typical example of lipid-soluble natural antioxidant. This is the first time that the antioxidant activity of the extracts obtained from fruits and flowers of H. lydium has been compared. The essential oil composition of the species has also been reported for the first time.