## 3 Discussion  
With an average yield of 0.15 \(\pm\) 0.05% (_w/w_), the EO from _H. laricifolium_ aerial parts collected in Ecuador confirmed that _Hypericum_ is an EO-poor genus, with very low yields (\(<\)1%), although sometimes the literature reports higher EO yields, as with other genera, up to 3%, as for the EOs from flowers and leaves of _H. perforatum_[25]. The chemical profiles of _Hypericum_ EOs exhibit extensive qualitative and quantitative variability, including the distribution of the main constituents [5]. In general, the various parameters affecting the content, composition, and yields of _Hypericum_ EOs could be related to the effect of variables such as genetic factors, developmental stages, and seasonal variation phenological cycle, types of plant material and specific organs studied, methods of extraction, environmental conditions, and geographic distribution [5]. The main constituents of the EO from _H. laricifolium_ aerial parts collected in Ecuador were limonene (about 26.5%), (_E_)-\(\beta\)-ocimene (about 24.5%), (_E_)-\(\beta\)-ocimene (about 14.5%). In striking contrast, \(\alpha\)-pinene (20.2%), the cembranoid diterpene verticiol (13.4%), 3-methylnonane (12.3%), 2-methyl-octane (9.6%), and \(n\)-nonane (7.6%) occurred in major amounts in the EO from _H. laricifolium_ leaves collected in Venezuela [3]. Such differences in the EO composition between the two samples may thus be attributed to different geographic distribution, types of plant material and organs studied, and seasonal variation. Moreover, the two specimens were collected at different altitudes: at about 2500m a.s.l. in Ecuador and at 3900m in Venezuela. However, the EO differences may also indicate the existence of botanical varieties or subspecies. The most frequently reported major constituents of _Hypericum_ EOs are the monoterpene hydrocarbons \(\alpha\)- and \(\beta\)-pinenes, the sesquiterpene hydrocarbons (_E_)- \(\beta\)-caryophyllene \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Enantiomer** & **LRI a** &
\begin{tabular}{c} **Enantiomeric** \\ **Distribution (\%)** \\ \end{tabular} & _ee (\%)_ & **S.D.** & **(\%) EO b** \\ \hline (1S,5S)-(-)-\(\alpha\)-Pinee (**1**) & 935 & 8.16 & 83.68 & 1.21 & 0.20 \\ (1R,5R)-(+)-\(\alpha\)-Pinee (**2**) & 939 & 91.84 & 83.68 & 1.21 & 2.25 \\ (R)-(+)-Limonene (**3**) & 1056 & 5.85 & & 1.39 \\ (S)-(-)-Limonene (**4**) & 1062 & 94.15 & 88.30 & 2.01 & 22.34 \\ \hline \hline \end{tabular}  
* Calculated linear retention index; b calculated mean percent content in the EO based on the total content (%) of \(\alpha\)-pinene and limonene (Table 1); \(e\) (%) = percent enantiomeric excess; S.D. = mean standard deviation over three determinations.  
\end{table} 
Table 2: Enantioselective analysis of _H. laricifolium_ EO. Figure 4: Enantiomeric pairs detected by GC enantioselective analysis of the _H. laricifolium_ EO: (15,5S)-(-)-\(\alpha\)-pinene (**1**), (1\(R\),5R)-(+)-\(\alpha\)-pinene (**2**), (_R_)-(+)-limonene (**3**), (_S_)-(-)-limonene (**4**). and germacrene D, and the oxygenated sesquiterpenes spathulenol and caryophyllene oxide; however, in some cases, major constituents are \(n\)-alkanes, such as \(n\)-undecane and \(n\)-nonane [5]. The EO of Ecuadorian _H. laricifolium_ belongs to the \"terpenoid\" type; however, \(\alpha\)- and \(\beta\)-pinenes, and germacrene D are only minor components (<3%), while the high content (>12%) of \(\beta\)-ocimene stereoisomers and limonene, accounting for more than 65% of the oil, is unprecedented among _Hypericum_ EOs [5]. Such characteristic can thus be considered a reliable identification marker of the EO from Ecuadorian _H. laricifolium_ aerial parts. The results of the GC enantioselective analysis deserve a separate comment. In fact, the finding that a-pinene and limonene occurred in the EO as scalemic mixtures, although one enantiomer predominated in each couple (Table 2), indicated that the biochemical machinery of Ecuadorian _H.