# Forest Volatile Organic Compounds and Their Effects on Human Health: A State-of-the-Art Review
## 3 Results
### Pintenes  
Pinene is a bicyclic monoterpene hydrocarbon with two structural isoforms, \(\alpha\)- and \(\beta\)-pinenes. Both L- and/or D-forms, as well as racemic forms, may occur. These two isoforms are important constituents of conifer oleoresins and are widely distributed in plants, although \(\alpha\)-pinene is generally more abundant. \(\alpha\)-pinene (2,6,6-trimethylbicyclo[3.1.1]hept-2-ene) is a bicyclo[3.1.1]hept-2-ene substituted by methyl groups at positions 2, 6, and 6, respectively. Both optical forms are present in conifer essential oils [138]. Table 6 reports the most common tree species whose total essential oil contains a quantity of \(\alpha\)-pinene at a percentage of more than 20% [70]. \(\beta\)-pinene (6,6-dimethyl-2-methylidenebicyclo[3.1.1]heptane) is a bicyclo[3.1.1]heptane substituted by methyl groups at positions 6 and 6, respectively, and an exocyclic double bond [139]. It usually accompanies \(\alpha\)-pinene in turpentine and other essential oils and is present with both optical forms. It is \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Plant Source** & **Botanical Family** &
\begin{tabular}{c} **Part of the Plant** \\ **Used** \\ \end{tabular} & **Content (\%) \({}^{*}\)** \\ \hline _Bosvetilia freerana_ & & & \\ Birdwood & & & \\ \hline _Bosvetilia sacra_ [PERSON] & & & \\ \hline _Cupressus semiperoviens_ L. & & & \\ \hline _Juniperus communis_ L. & & & \\ \hline _Juniperus phonicca_ L. & & & \\ \hline _Dryrobalanops aromatica_ & & & \\ [PERSON] & & & \\ \hline _Abies alba_ Mill. & & & \\ _Larix laricina_ [PERSON] & & & \\ \hline _Pica abies_ (Mill.) [PERSON] & & & \\ \hline _Pinus divaricata_ Aiton & & & \\ \hline _Pinus mugo_ [PERSON] & & & \\ \hline _Pinus nigra_ [PERSON] & & & \\ \hline _Pinus resinosa_ Ait. & & & \\ \hline _Pinus strobus_ L & & & \\ \hline _Pinus slvnetris_ L & & & \\ \hline \hline \end{tabular} \({}^{*}\) Content (%) = the relative quantity, expressed as a range of percentages, of \(\alpha\)-pinene included in tree-derived essential oils.  
\end{table} 
Table 6: Tree species whose total essential oil contains more than 20% of \(\alpha\)-pinene [106]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Functional Response** & **Model** & \
\begin{tabular}{c} **Molecules/Mechanisms** \\ **Involved in Targeted Pathways** \\ \end{tabular} & **Ref.** \\ \hline \multirow{4}{*}{**Analgesic**} & Swiss mice & Induced nociception & [136] \\ \cline{2-3}  & ICR mice & Writhing test & [90] \\ \cline{2-3}  & Rats & Mechanical hyperalgesia & [133] \\ \cline{2-3}  & Swiss mice & Writhing test & [127] \\ \cline{2-3}  & Swiss mice &
\begin{tabular}{c} Mechanical hyperalgesia, IL-1\(\beta\), \\ TNF-\(\alpha\) \\ \end{tabular} & [137] \\ \hline Abbreviations: CASP, caspase; COX-2, cyclooxygenase-2; ERK, extracellular signal-regulated kinase; ICR, imprinted control region; IL, interleukin; iNOS, inducible NO synthase; JNK, \(\alpha\)-synuclein N-terminal kinase; LC3, microtubule-associated protein light chain 3; MAPK, mitogen-activated protein kinase; MBT, marble burying test; MCF, monocyte chemoattractant protein; NF-kB, nuclear factor-B; NO, nitric oxide; p38, protein 38; PGE, prostaglandin E; ROS, reactive oxygen species; TGF, tumor growth factor; TNF, tumor necrosis factor.  
\end{table} 
Table 5: _Cont._the main compound of essential oil derived from _Piper expense_[53]. Table 7 reports the most common tree species whose total essential oil contains a quantity of \(\beta\)-pinene at a percentage of more than 20% [70]. In a recent review of the scientific literature, it has been reported that, although many in vitro studies exist about the pharmacological activities of pinene and pinene-containing essential oils, few in vivo studies and even less clinical trials on the topic have been conducted so far [23]. In fact, none of the reviewed clinical studies tested isolated pinene, but mixtures of different molecules or whole essential oils have been often tested.