## 1 Introduction  
_Ocimum basilicum_ L. (sweet basil) belonging to the family Lamiaceae, the genus includes about 35 species of aromatic annual and perennial herbs and shrubs [1]. _O. basilicum_ is a multipurpose herb characterized by its rich and aromatic essential oil content [2, 3]. The aromatic leaves, flowers, and seeds are added to foods and beverages for flavor; extracted as active ingredient for use in perfumes, soaps, cosmetics, and dental products; they are included in traditional herbal medicines to treat fevers, headaches, kidney problems, gum ulcers, childbirths, rheumatoid arthritis, and menstrual irregularities [4, 5, 6]. Beside these traditional medical uses, recent scientific studies have demonstrated potent antioxidant [7], antiviral [8], and anti-proliferative activities [9] of some compounds occurring in _O. basilicum_ leaf essential oil and extract [10]. Basil oil presents remarkable differences in composition, and some chemotypes from different geographical origins have been reported [1, 2]. _O. basilicum_ is rich in essential oils and have been the subject of numerous chemical studies [11, 12]. Four major essential oil chemotypes in _O. basilicum_ were recognized, each with a number of small variants: (1) methyl chavicol-rich; (2) linalool-rich; (3) methyl eugenol-rich; and (4) methyl cinnamate-rich [13]. In basil, as in the other species of the Lamiaceae family, essential oil is stored in glandular trichomes [14]. Although the essential oil composition of a great number of Lamiaceae species is well known, little information is available on the secretion products of the various types of trichomes. Most of previous works concerned the morphology and structure of the glands and involved microscopical observations [15, 16, 17, 18, 19]. Only in a few cases the morphological study was accompanied and supported by chemical analyses of secreted oils: in _Mentha piperita_[20, 21], _Salvia officinalis_[22, 23, 24], _Thymus vulgaris_[25], _Rosmarinus officinalis_[26, 27], and _Ocimum basilicum_[28]. O. basilicum_ bears capitate and peltate glandular trichomes, distributed on both sides of the leaf. The subcuticular space of peltate trichomes appeared intensely colored with lipophilic stain, thus indicating the presence of VOC [28]. On the contrary, capitate trichomes did not present any staining with lipophilic stain, indicating the presence of polysaccharides [28; 29; 30; 31; 32]. Volatile plant constituents have different ecological functions. They play an important role in the process of plant growth, such as plant-plant competition and cooperative co-evolution, in the attraction of pollinators, in defense against insects and against the attraction of herbivores [33; 34; 35]. In recent years, micro-extraction methods for determining the composition of VOCs from plant material have developed considerably. These techniques have high sensitivity, and can be applied to matrices of gas, liquid, and solid samples. In summary, microextraction techniques include solid phase microextraction (SPME), stir-bar sorptive extraction (SBSE), single drop microextraction (SDME), hollow fiber liquid phase microextraction (HF-LPME), dispersive liquid liquid microextraction (DLLME), and the gas purge microsyringe extraction (GP-MSE). These techniques, however, requires appropriate calibration with the use of standard substances. Furthermore, the absorption of the fibers depends on the chemical class of the products present in the matrix [36; 37; 38]. Another approach is to isolate the secreting structures and to study their contents [36; 37; 38; 39; 40]. The method used by us refers to microneedles shuttle analysis [41]. The aim of this work is to compare the VOCs content directly sampled in capitate and peltate trichomes with the composition of the VOCs determined by hydrodistillation (essential oil) of the leaves of _O. basilicum_.