## 3 Analytical Platforms for Terpenoids
### Metabolic Profiling of Plant Terpenoids  
In classic plant biotechnology, the metabolomic approach is generally used for metabolic profiling of a target set of metabolites, such as fatty acids, alkaloids, terpenes, phenolics, etc., in plant physiology and genetic research, along with other tools including genomics, transcriptomics, and proteomics [62]. Different analytical approaches were employed to determine the metabolomic compounds, and were utilized to estimate targeted metabolites such as NMR, GC-MS, LC-MS, and CE-MS. In plant extracts, there are no specific chemical technologies for the identification of monoterpenoids and sesquiterpenoids, unlike for other secondary metabolites such as triterpen, carotenoids, phytosterols, flavonoids, and other primary metabolites [63]. Volatile compounds can be classified as endogenous or emitted. Solvents such as hexane, pentane, diethyl ether, dichloromethane, chloroform, ethyl acetate, and solvent mixtures can be used to extract endogenous volatiles. The use of an organic solvent has the advantage of reducing the activation of enzymes, which may alter the original composition of volatile compounds. A solid-phase extraction (SPE) column has been used in some cases to remove nonvolatile compounds from the organic solvent extracts. On the other hand, static headspace sampling techniques such as solid phase microextraction, monotrap, and a dynamic headspace sampling system have been used for emitted volatiles [64]. Earlier studies of terpenoid metabolite profiling from different plant species are as follows: twenty-three terpen were recently analyzed using different accelerated solvent extraction (ASE) methods [65]. In a comprehensive analysis of terpenes and terpenoids in medicinal cannabis biomass, a total of 49 distinct individual compounds were detected [52]. Using 12 cannabis samples, 30 terpene compounds were detected in another study [66]. [PERSON] et al. used a robust testing method to quantify 30 selected terpenoids in dry plant materials, with 30 monoterpenoids and sesquiterpenoids quantified [53]. Using a solid-phase microextraction method, 28 terpen were identified and quantified in Muscat grape cultivars [67]. In another study of _Citrus medica_ (finger citron), a total of 62 volatiles were detected, among which monoterpenoid limonene and \(\gamma\)-terpinene were most abundant [68]. The different developmental stages of eight Artemisia plants were analyzed by GC-MS profiles, which consisted of 40-90% of monoterpene and sesquiterpene derivatives [54]. Another study comparing the terpene profiles of four important fruits (gooseberry, crab apple, cherry silver berry, and scarlet haw-thorn) identified 79 terpenoid compounds [69]. Three different extraction methods were used, and a total of 81 volatile compounds were identified in _Exocarpium citri_ Grandis, around 58% of which were terpenes [70]. Similarly, different methods were tested on _Ocimum basilicum_ leaves and 18 terpenoid compounds were identified [71]. [PERSON] et al. performed metabolite profiling on three different ginger (_Zingiber officinal_) lines containing 102 compounds, among which 29 monoterpenoids and 47 sesquiterpenoids were identified [72]. Table 2 shows the metabolite profiling and identified terpenoid compounds in the different plant species.