Antioxidant activity and chemical composition of Juniperus excelsa ssp. polycarpos wood extracts

Abstract Extracts from the wood of Juniperus excelsa ssp. polycarpos were analysed for their antioxidant activity using the DPPH method and compared with ascorbic acid and butylated hydroxytoluene. The most active extracts were analysed for their chemical composition using gas chromatography–mass spectrometry. Acetone extract was found to be moderately active as an antioxidant agent at 58.38%, which was lower than the value of vitamin C (98.56%) at the concentration of 14.20 mg/mL. The major components identified in the acetone extract as trimethylsilyl (TMS) derivatives were pimaric acid TMS (24.56%), followed by α-d-glucopyranoside,1,3,4,6-tetrakis-O-(TMS)-β-d-fructofuranosyl 2,3,4,6-tetrakis-O-(TMS) (21.39%), triflouromethyl-bis-(TMS)methyl ketone (9.32%), and cedrol (0.72%). The dissolved water:methanol (1:1 v/v) partitioned from acetone extract afforded 12 fractions; among them, the F9 fraction was found to have good antioxidant activity (88.49%) at the concentration of 14.20 mg/mL. The major compounds identified in F9 fraction were α-d-glucopyranoside, 1,3,4,6-tetrakis-O-(TMS) (20.22%) and trifluoromethyl-bis-(TMS)methyl ketone (5.10%).


Introduction
Persian juniper (Juniperus excelsa ssp. Polycarpos) is a dioecious tree up to 6-7 m tall or a low shrub with dense head (Emami et al. 2011), also widely distributed in other areas such as south-east Arabia, Iran, Caucasus, Baluchistan, Afghanistan, north-west Himalaya (Townsend & Guest 1966) Armenia, India, Uzbekistan, and Pakistan (Franco 1964).
The extracted compounds of different types of Juniperus and their antibiotic activities have been expressed (Angioni et al. 2003;Filipowicz et al. 2003). The potential uses of the extracted compounds are in clued, aromatherapy, fragrance, soup, candle, lotions, and cosmetics materials (Yesenofski 1996).
Recent studies also indicated that the inhibitory effects of the extracted compounds were registered in various types of pathogenic fungi and similar micro-organisms (Soković et al. 2004). The largest compound in the fruit cones of Juniperus communis were terpenes (32.1%) which is used to treat indigestion, and also as disinfectant in dyspepsia as well as some other antibiotic effects (Lamparsky & Klime 1985).
Cedrol was found in the essential oil of Conifers, especially in the genera Cupressus and Juniperus (Connolly & Hill 1991). Its main uses are in the chemistry of aroma compounds (Breitmaier 2006). Result of Lindh et al. (2015) studies suggested that cedrol strongly attracts pregnant female mosquitoes after to create cedrol-baited traps. Sabinene was the most abundant compound in Juniperus thurifera L. var. Africana oils from the dried leaves and the oil had good antibacterial activities (Bahri et al. 2013). α-pinene, germacrene d, myrcene, abietadiene, and cis-calamenene were the main chemical composition of essential oil from Juniperus oxycedrus ssp. macrocarpa (S. & m.) Ball. and Juniperus oxycedrus L. ssp. rufescens (L. K.) berries and showed good antioxidant capacity (Hanène et al. 2012). Fatty acids and their methyl ester such as hexadecannoic and octadecanoic acids are relatively common essential oils in higher plants (Shabi et al. 2010). Juniperus has high resistance against wood eating pests; humidity has no effect on it. The scent extracted from the tree also repels snakes and scorpions and other blood sucking insects (Zargari 1983).
In the present study, for the first time, the aim was firstly, to assess in vitro antioxidant activity of wood extracts from J. excelsa ssp. polycarpos with voucher specimen number 1893, and secondly to analyse the chemical composition of the extracts by GC/MS.

Antioxidant activity
Statistically, there were significant differences among the treatments (F1 to F12, water:methanol, n-hexane, acetone, butylated hydroxytoluene (BHT), vitamin C and their concentrations ( Table S1). The lowest antioxidant activity (22.25%) was observed at the concentration of 0.44 mg/mL, which was lower than the antioxidant activity value of vitamin C (60.66%) at the same concentration. The moderate activity came from acetone extract (53.98%) at 14.20 mg/mL, which was lower than the antioxidant activity value of vitamin C (98.56%) at the same concentration (Table S2). The same trend was observed with the reference (BHT). Emami et al. (2011) reported that the essential oils from various parts of both J. excelsa subsp. polycarpos and Juniperus excelsa subsp. excels species had relatively low antioxidant activity, but these activities suggested the possible uses of these essential oils in very low concentrations for preserving food materials.

Wood extract
Acetone extract of the fresh wood of J. excelsa ssp. polycarpos afforded 12% (v/w) in yield. Seventeen compounds of trimethylsilyl (TMS) derivatives were identified (Table S3).

Conclusion
The chemical composition and antioxidant activity of extracts from the wood of J. excelsa ssp. polycarpos were reported for the first time.