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Sweet sagewort, also known as sweet wormwood (Artemisia annua L.), contains essential oil and other natural products. The objective of this study was to evaluate the effect of eight different distillation times (DTs; 1.25 minutes, 2.5 minutes, 5 minutes, 10 minutes, 20 minutes, 40 minutes, 80 minutes, and 160 minutes) on A. annua essential oil and its antioxidant capacity. Highest essential oil yield was achieved at 160-minute DT. The concentration of camphor (8.7% to 50% in the oil) was highest at the shorter DT and reached a minimum at 160-minute DT. The concentration of borneol showed a similar trend as the concentration of camphor. The concentrations of some constituents in the oil were highest at 2.5-minute DT (alpha-pinene and camphene), at 10 minutes (paracymene), at 20 minutes (beta-chamigrene and gamma-himachalene), at 80 minutes [transmuurola-4(15),5-diene and spathulenol], at 80to 160-minute DT (caryophylene oxide and cis-cadin-4-en-ol), or at 160-minute DT (betacaryophyllene, transbeta-farnesene, and germacrene-D). The yield of individual constituents reached maximum at 20to 160-minute DT (camphor) at 80to 160-minute DT [paracymene, borneol, transmuurola-4(15),5-diene, and spathulenol], or at 160-minute DT (for the rest of the oil constituents). DT can be used to attain A. annua essential oil with differential and possibly targeted specific chemical profile. The highest antioxidant capacity of the oil was obtained at 20-minute DT and the lowest from the oil in the 5-minute DT. This study suggests that literature reports on essential oil content and composition of A. annua could be compared only if the essential oil was extracted at similar DTs. Therefore, DT must be reported when reporting data on essential oil content and composition of A. annua. Artemisia annua is a multiuse medicinal plant that contains several natural products such as essential oil and antioxidant flavonoids (Ferreira et al., 2010) and is used currently as the only commercial source of artemisinin. Artemisinin is used as the raw material for production of artemisinin-based combination therapies (ACT) such as the first line of defense against multidrug-resistant Plasmodium falciparum malaria (Ferreira et al., 2010). For essential oil production, A. annua is cultivated in large areas of eastern Europe (Bulgaria, Hungary, and Romania), and the essential oil is extracted through steam distillation of the biomass (Nedkov and Attanassova, 2004). The essential oil of A. annua has applications in perfumery and cosmetics and in aromatherapy (Nedkov and Attanassova, 2004). The wide application of the A. annua essential oil is not only the result of its fine aroma, but also the result of the reported antifungal and antibacterial activities (Juteau et al., 2002), insecticidal activity (Tripathi et al., 2009), antioxidant activity (Cavar et al., 2012), and, partially, the result of the long history of this plant used as a medicinal plant in a number of traditional medicines in the Mediterranean region (Stojanov, 1973). Like with other aromatic plants, A. annua essential oil content and composition is modified by genotype and the environment (Tzenkova et al., 2010), by distillation method (Scheffer, 1993), and by other factors. A recent report (Ferreira et al., 2013) found that the DT affected essential oil content, artemisinin concentration, and antioxidant capacity of the plant residue from distillation of A. annua. Steam DT has been shown to significantly affect essential oil composition of other aromatic plants such as Japanese cornmint (Mentha canadensis L.) (Zheljazkov and Astatkie, 2012b), pine (Pinus ponderosa Dougl. ex Laws) (Zheljazkov et al., 2012a), oregano (Origanum vulgare L.) (Zheljazkov et al., 2012b), female and male Rocky Mountain juniper (Juniperus scopulorum Sarg.) (Zheljazkov et al., 2012c, 2013), peppermint (Mentha x piperita L.), lemongrass (Cymbopogon flexuosus Steud.), and palmarosa (Cymbopogon martinii Roxb.) (Cannon et al., 2013). However, the effect of DT on A. annua essential oil composition and on the yield of various oil constituents is unknown. We hypothesized that DT will have a significant effect on A. annua essential oil composition and yield of oil constituents and thus the antioxidant capacity. The objective of this study was to evaluate the effect of eight DTs on A. annua essential oil yield and composition, yield of oil constituents, and associated antioxidant capacity. Materials and Methods Plant material and essential oil distillation conditions. The plant material used in this study was obtained from field trials conducted in Mississippi (at the North Mississippi Research and Extension Center in Verona, MS, at lat. 34 43#22$ N and long. 88 43#22$ W). Certified seeds of A. annua were kindly provided by Mediplant, Switzerland. Seedlings were produced in a greenhouse and were transplanted out in the field and grown as described previously (Ferreira et al., 2013). The plants were transplanted in raised beds with plastic mulch in the spring of 2008. The plantation in 2009 and in 2010 was established by self-seeding of plants from the previous year. Samples for this study were generated in the fall of 2010 by harvesting whole plants. The essential oil was extracted from fresh biomass in 2-L steam distillation units (Hearthmagic, Rancho Santa Fe, CA), as described previously (Ferreira et al., 2013; Gawde et al., 2009; Zheljazkov et al., 2010). The size of all samples was 500 g; samples included leaves and branches not thicker than 2 mm. The DTs Received for publication 3 June 2013. Accepted for publication 10 Aug. 2013. This research was funded by ARS Specific Cooperative Agreement 58-6402-4-026 with CRIS MIS-172050 (research grant ‘‘Medicinal Herbs Research in Mississippi’’ awarded to Dr. Jeliazkov [Zheljazkov]). To whom reprint requests should be addressed; e-mail vjeliazk@uwyo.edu, Valtcho.pubs@gmail.com. 1288 HORTSCIENCE VOL. 48(10) OCTOBER 2013 were 1.25, 2.5, 5, 10, 20, 40, 80, and 160 min, all conducted in three replicates. These DTs were selected based on literature reports and a previous study by Ferreira et al. (2013). The length of each DT was measured from the moment that the first drop of essential oil was deposited in the separator. At the end of each DT, the separator part was removed from the apparatus, and the collected essential oil plus some water was decanted into a glass vial. The essential oil was separated from water by placing the samples in a freezer and decanting the oil after the water was frozen. The oil yield (content) was calculated as the weight (g) of oil per weight (g) of fresh A. annua biomass. Gas chromatography analysis of essential oil. The essential oil samples of A. annua (all in three replicates) were analyzed on a Hewlett Packard (Hewlett-Packard, Palo Alto, CA) gas chromatograph (GC) model 6890 fitted with an autosampler. The carrier gas was helium, 40 cm·sec, 11.7 psi (60 C), 2.5 mL·min constant flow rate; the injection split 60:1, 0.5 mL, the injector temperature was 220 C; and the oven temperature program as follows: 60 C for 1 min, 10 C/min to 250 C. The GC column was HP-INNOWAX (Hewlett-Packard; crosslinked polyethylene glycol; 30 m · 0.32 mm · 0.5 mm), and the flame ionization detector temperature was 275 C. The identification of individual peaks was done using internal standards by retention time and by mass spectroscopy. Oxygen radical capacity. The antioxidant capacity of the oil extracts was determined by the oxygen radical absorbance capacity Table 1. Mean essential oil (EO) content (%, as the weight of oil per weight of fresh A. annua biomass) and the concentrations (% of total oil) of alpha-pinene, camphene, paracymene, eucalyptol, camphor, borneol, and beta-caryophyllene obtained from the eight distillation times (DTs). DT (min) EO content Alpha-pinene Camphene Paracymene Eucalyptol Camphor Borneol Beta-caryophyllene 1.25 0.005 f 1.2 abc 1.8 bc 1.2 e 3.5 b 50.4 a 1.6 a 5.2 de 2.50 0.04 e 2.1 a 3.5 a 2.9 bc 5.9 a 49.9 a 2.0 a 4.1 e 5 0.05 de 1.9 ab 3.3 ab 3.1 bc 5.1 a 47.5 a 1.9 a 4.8 de 10 0.05 de 1.9 ab 3.0 ab 4.7 a 5.8 a 36.8 b 1.0 b 6.3 d 20 0.07 d 1.7 ab 2.8 ab 3.7 ab 3.6 b 33.3 bc 1.0 b 8.3 c 40 0.11 c 1.2 bc 2.0 bc 2.6 bcd 2.4 bc 27.0 c 0.9 b 9.1 c 80 0.18 b 0.84 c 1.4 c 2.0 cde 1.7 c 16.8 d 0.8 b 11.8 b 160 0.23 a 0.51 c 0.9 c 1.6 de 1.1 c 8.7 e 0.3 c 14.3 a Within each column, means sharing the same letter are not significantly different at the 5% level. Fig. 1. Plots of essential oil (EO) content and the concentrations of eight constituents vs. distillation times along with the fitted power, exponential, and MichaelisMenton (M-M) nonlinear regression models. Equations of the fitted models are shown within each plot. HORTSCIENCE VOL. 48(10) OCTOBER 2013 1289 method (Huang et al., 2002a, 2002b) and as described in more detail previously (Zheljazkov et al., 2012b, 2013). Statistical analysis. The effect of DT on essential oil content as well as the concentration and yield of alpha-pinene, camphene, paracymene, eucalyptol, camphor, borneol, beta-caryophyllene, transbeta-farnesene, beta-chamigrene, germacrene-D, gammahimachalene, transmuurola-4(15),5-diene, spathulenol, caryophyllene oxide, and ciscadin-4-en-ol was determined using a oneway analysis of variance. For each response variable, the validity of normal distribution and constant variance assumptions on the error terms was verified by examining the residuals as described in Montgomery (2013). The effect of DT was significant (P < 0.05) on all responses. Consequently, multiple means comparison was completed using Duncan’s multiple range test method at the 5% level of significance to generate letter grouping. The analysis was completed using the GLM Procedure of SAS (SAS Institute Inc., 2010). The relationship between DT and most of the concentration and yield response variables was adequately modeled (Bates and Watts, 2007) by either the Michaelis-Menten (eq. [1]) or the power (eq. [2]) or

Distillation Time Effect on Essential Oil Yield, Composition, and Antioxidant Capacity of Sweet Sagewort (Artemisia annua L.) Oil