Chemical composition and antioxidant activity of volatiles from Patrinia Villosa Juss obtained by optimized supercritical fluid extraction
Introduction
The genus Patrinia, with about 20 species, which belongs to family Valerianaceae, is an herbaceous perennial plant natively grown in central to east of Asia and northeast of North America. Young leaves and flower buds of Patrinia species have been cooked and used as wild vegetables in some areas of China. The whole plant of Patrinia can be applied to medicine as anti-virus and anti-bacterial agent [1], [2], [3], especially two species, Patrinia Scabiosaefolia Fisch. and Patrinia Villosa Juss (P. Villosa Juss).
As for the chemical constituents of this genus, P. scabiosaefolia Fisch. [4], Patrinia scabra [5] and Patrinia gibbosa [6] have been more thoroughly investigated than P. Villosa Juss. Some iridoids, flavonoids and saponins in P. Villosa Juss have been studied [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19] most of them since 2005 [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19]. However, to the best of our knowledge, only two superficial studies of volatiles from P. Villosa Juss have been reported, which concerned the identification of five compounds in P. Villosa Juss [20], [21].
Supercritical CO2 fluid extraction (SFE-CO2), using CO2 instead of organic solvent and possessing unusual properties including high compressibility, liquid-like density, high diffusivity, low viscosity and low surface tension, can be considered one of the most potentially useful new methods of sample preparation in pharmaceutical and food processing industry [22], [23], [24]. This advanced extraction method has been successfully adopted to extract aurentiamide acetate from P. Villosa Juss in our previous study [10]. Many reports demonstrated that SFE-CO2 was superior to some conventional methods, e.g. hydrodistillation, steam distillation and solvent extraction for the isolation of volatile compounds from medicinal plants [25], [26], [27]. The integration of SFE with gas chromatography–mass spectrometry (GC/MS) permits the rapid analysis of volatiles, which has been adopted in the study of chemical composition of herb medicines [28].
Many diseases are associated with free radicals because oxidative damage to DNA, proteins and other macromolecules accumulates with age and has been postulated to constitute a major type of endogenous damage leading to aging [29]. Although almost all organisms are equipped with antioxidant defense and repair systems that have involved protecting them against oxidative damage, these systems are often inadequate to completely prevent the damage [30]. However, antioxidant supplements, or natural products containing antioxidants, may be used to help reduce oxidative damage to human body. Many papers have been reported to find safe and potent natural antioxidants from various plant sources. As harmless sources of antioxidants, wild herbs, spices, fruits, nuts and leafy vegetables have been investigated [31], [32], [33], [34]. Some volatiles or essential oils have been found to exhibit strong antioxidant activity [35], [36], [37], [38].
The aim of the present paper, therefore, was to choose the optimal SFE conditions using an orthogonal test design to obtain the extracts, which possessed strong antioxidant activity. Then, the chemical compositions of the extracts obtained by the optimal SFE conditions were determined by GC/MS. The results as guided by the antioxidant activity were compared with those obtained under the selected condition as guided by the yield of the volatile. Therefore, scavenging effects, yield of the extract and chemical composition were obviously different according to different evaluation standards in SFE. To our best knowledge, this is the first report of using SFE to extract the volatiles from P. Villosa Juss, and first time to systematically evaluate the antioxidant activity and chemical composition of the extract.
Section snippets
Chemicals and materials
The P. Villosa Juss was purchased from a local drug store and identified by Dr. Luping Qin (Department of Pharmacognosy, College of Pharmacy, the Second Military Medical University, Shanghai, China). To avoid degradation, the air-dried plant material was ground just before extraction.
Carbon dioxide (99.95%) was obtained from Beijing Analytical Instrument Factory. 1,1-Diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethyl-benzthiazoline-6-sulfonic acid) diammonium salt (ABTS), nonacosane, n
Results and discussion
Steam distillation has traditionally been applied for volatiles recovery from plant materials. In our initial study, the hydrodistillation method was used to extract the volatile compounds from P. Villosa Juss. However, because one of the disadvantages of the hydrodistillation methods is that volatiles undergo chemical alteration and the heat-sensitive compounds can easily be destroyed, the quality of the volatile extracts was poor after distilled for 8 h. Thus, SFE-CO2 method, having relatively
Acknowledgement
Financial support from Ministry of Science and Technology of the People's Republic of China (863 project) is gratefully acknowledged.
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