Monoterpenes metabolism pinene

Plants especially from the Lamiaceae family can inhibit the growth of several weeds by releasing phytotoxic monoterpenes (a-pinene, P pinene, camphene, limonene, a-phellandrene, p-cymene, 1,8-cineole, borneol, pulegone, and camphor) (Angelini et al., 2003). The herbicide effect of 1,4-cineole and 1,8-cineole is also described by Dayan et al. (2012). Plants that are exposed to essential oils often metabolize them, and when citral was added geraniol, nerol and their acids appeared. When citronellal metabolization was tested, citronellol and citronellic acid were formed, and with pulegone (iso)-menthone, isopulegol and menthofuran were found (Dudai et al., 2000). 

Pine EOs prevented bone loss in an osteoporosis model (ovariectomized rats). The monoterpenes borneol, thymol and camphor directly inhibited osteoclast resorption [388]. It was observed that inactive monoterpenes can be metabolized to their active forms in vivo thus, ds-verbenol, a metabolite of a-pinene, inhibited osteoclastic resorption activity, in contrast to the parent compound a-pinene. 

To date over 30 plant terpenoid synthases have been cloned as cDNAs, and many of these were found to encode enzymes of secondary metabolism (43). Isolation and analysis of six genomic clones encoding monoterpene ((—)-pinene and (—)-limonene), sesquiterpene ((E)-a-bisabolene and S-selinene) and diterpene (abietadiene) synthases from Abies grandis, and a diterpene (taxadiene) synthase from Taxus brevifolia have been reported (44). Overexpression of a cotton farnesyl diphosphate synthase (EPPS) in transgenic Artemesia annua has resulted in 3- to 4-fold increase in the yield of the sesquiterpenoid anti-malarial drug, artemisinin, in hairy roots (45). 

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