# GC-MS Analysis of the Volatile Constituents in the Leaves of 14 Composite Plants
## 1 Introduction  
Emissions of volatile or aroma components from plant organs, including green tissues and flowers, play important roles in defending plants from pests, attracting pollinators, and increasing competitive advantages by inhibiting the growth of surrounding plants [1]. The green tissues of many Compositae members, which are characterized by unique aromas contain abundant volatile chemicals. An example is the genus _Artemisia_, the members of which release strong scents from their aerial parts [2]. Species in other genera, such as _Cirysanthemum indicanu_ var. _aromaticum_, a new variety of _Cirysanthemum indicanu_ endemic to Shennongjia, Hubei Province, China [3], are known for a special and tangay flavor throughout the whole plant [4]. _Opistbappus_ plants, including _Opistbappus taihangensis_ and _Opistbappus longlobus_ are also native to China, and are primarily restricted to the Taihang Mountains [5]. The volatile constituents contributing to the herbal scent were principally identified as terpenoid compounds. The terpenoids detected in the aerial parts of some _Artemisia_ plants include monoterpenes, such as \(\alpha\)-pinene, \(\alpha\)-terpinene and campene; sesquiterpenes, such as \(\beta\)-caryophyllene, germacrene D, \(\alpha\)-copaene and \(\alpha\)-cubebene; and oxygenated terpen, such as eucalypt, camphor, and thuijone [2, 6, 7]. Many of these compounds are regarded as aroma-active because of their special odors [8]. Due to their chemical components, many of these scented plants, have been used in folk medicines around the world. Numerous _Artemisia_ plants, including _Artemisia annua_, _Artemisia argyi_, _Artemisia sacrorum_, _Artemisia capillaris_, and _Artemisia japonica_, are used as traditional Chinese medicine and recorded in ancient Chinese pharmacopoeias [9]. Both _Artemisia afra_ and _Artemisia herba-alba_ are used to treat coughing, colds, and other diseases in Africa [10; 11]. In Turkey, _Artemisia absinthium_, _Artemisia spicigera_, and _Artemisia Santonicum_ are local folk medicines; among these, _A. absinthium_ has pharmacological functions such as antipyretic, antiseptic, antihelminic, tonic, and diuretic activities, and _A. santonicum_ acts as an anthelminic and diabetes drug [12]. Other species, such as _C. indicium_ var. _aromatic_ and _Opishopappus_ plants, also have pharmacological potential and are used to treat diseases in their origin areas [13; 14]. Another famous traditional Chinese medicine, _Crossostebirium chinense_, is commonly used to treat colds, rheumat, and arthralgia [15]. _Tanacorum vulgar_, an aromatic perennial plant that grows widely in Europe, Asia and North America, is regarded as a food additive and a resource for perfumery and herbal medicine with multifunctional properties [16; 17; 18]. The essential oils of _T. vulgar_ have been proven to possess the anti-inflammatory [19], antifungal [20] and antioxidant [21] activities. The volatile oils extracted from Compositae plants, especially the essential oils of many _Artemisia_ plants, have been demonstrated to possess insecticidal activities against grain storage pests [22; 23; 24; 25]. Since the secondary plant metabolites have low mammalian toxicity, undergo rapid degradation, and are more environmentally benign, they are considered as effective substitutes for traditional pesticides [26]. Not limited to insects, the growth of other surrounding plants can also be affected by the constituents from at least 39 genera of Compositae plants [27]. In addition, the phytotoxic effects of different constituents acting on plants are reportedly diverse, with the effects of four monoter genes on maize observed as camphor > eucalypt > \(\alpha\)-pinene > limonene [28; 29]. Thus, the allelochemicals from scented plants show great promise for applications in regulating plant growth and producing natural herbicides. Since many Compositae plants possess various volatile chemicals with high utilization value, compositional investigations and comparisons should be conducted in more species.