Antioxidant properties of the leaves of different Juniperus L. (Cupressaceae) species.

1. Aim or purpose The use of traditional medicinal plants for primary health care have steadily increased worldwide in recent years. Different species of the genus Juniperus L. (Cupressaceae), particularly those under Juniperus section, are commonly employed in Turkish folk medicine to treat several diseases [1]. In continuation of our studies on Juniperus species under Juniperus section growing in Turkey, this work was designed to define and compare the antioxidant properties of methanol leaves extracts of five species: J. communis L. var. communis (Jcc), J. communis L. var. saxatilis Pall. (Jcs), J. drupacea Labill. (Jd), J. oxycedrus L. subsp. oxycedrus (Joo), J. oxycedrus L. subsp. macrocarpa (Sibth. & Sm.) Ball. (Jom). 2. Materials and methods The total phenolics, total flavonoids and condensed tannins were determined spectrophotometrically. In order to extensively characterise the antioxidant potential of the extracts different “in vitro” systems were utilized: the primary antioxidant activity was examined by DPPH and reducing power assays; the secondary antioxidant properties were determined by ferrous ions chelating activity assay. The ability of the extracts to inhibit lipid peroxidation was evaluated by thiobarbituric acid method in a bovine brain liposome system [1]. In order to investigate the antioxidant efficacy of the extracts in a biological setting, the ability to protect bacterial growth from the oxidative stress induced by hydrogen peroxide (H2O2) was evaluated on Escherichia coli [2]. The relationship between the phenolic content of the extracts and their antioxidant properties was analyzed. Finally, the toxicity was investigated using Artemia salina lethality bioassay [1]. 3. Results The total phenolic content of the extracts ranged from 71.77 ± 0.13 mg GAE/g extract (Jcc) to 133.28 ± 1.74 mg GAE/g extract (Joo); the flavonoid content ranged from 14.23 ± 0.51 mg QE/g extract (Jd) to 20.75 ± 0.12 mg QE/g extract (Jcs); the condensed tannins ranged from 19.95 ± 0.32 mg CE/g extract (Jcc) to 81.74 ± 1.21 mg CE/g extract (Joo). Juniperus spp. leaves extracts displayed good primary antioxidant properties, and Joo resulted the most active both in DPPH test (IC50 = 0.09 ± 0.01 mg/ml) and in reducing power assay (ASE/ml = 2.56 ± 0.06 mg/ml); furthermore, the extracts exhibited good anti-lipid peroxidation effects, and Jcs was the most active (IC50 = 4.39 ± 0.47 μg/ml). A total protection against H2O2-induced damage on E. coli was observed for Joo extract. The strong correlation between the antioxidant capacity and the total phenolic content indicate that phenolics largely contribute to the primary antioxidant properties of the extracts. Finally, all the extracts resulted non-toxic against A. salina (LC50 > 1000 μg/ml). 4. Conclusions Our findings improve the knowledge about these Turkish Juniperus L. species, also demonstrating the potential of their leaves as safe sources of natural antioxidants. References [1] Taviano MF, Marino A, Trovato A, et al. Antioxidant and antimicrobial activities of branches extracts of five Juniperus species from Turkey. Pharm Biol. 2011;49(1):1014-1022. [2] Smirnova GV, Samoylova ZY, Muzyka NG, et al. Influence of polyphenols on Escherichia coli resistance to oxidative stress. Free Rad Biol Med. 2009;46:759-768.