Monoterpenoids

Monoterpenoids are widely distributed in plant and animal kingdoms, both terrestrial and marine (379). Lists of their occurrence in higher plants have been compiled (19, 155, 175, 275, 395, 396). Thble 8.1.2 lists plant families that are, by far, the most prolific in accumulating monoterpenoids. a-Pinene, cineol and limonene are the most widely distributed monoterpenoids. 

Monoterpenoids apparently have a limited value in phylogeny and systematics (147) though some useful attempts in this direction have been made (87, 89 vol. 12, 155, 186). 

Several monoterpenoids are known to occur in higher plants in both optically active forms, and sometimes both antipodes (partially or fully racemic compounds) have been found to occur in the same plant (379). 

A comprehensive and critical review, covering the literature to April 1971, on the biosynthesis and metabolism of the monoterpenes has appeared.  

The isolation and properties of a monoterpene reductase from rose petals have been described. Geraniol and nerol were reduced by a solubilized enzyme preparation to give citronellol. The co-factor requirement was filled only by NADPH and the system had an optimum pH of 8. It was inhibited by p-chloromercuriophenylsulphonic acid, suggesting the presence of an S— group near the active site. 

Salvia officinalis has been shown to specifically incorporate [2- C]geraniol into (-)-camphor(12)and(-)-bomeol(13)(0.5 x 10 % and 3.3 x 10 %) such that the tracer is incorporated into C-2 of both monoterpenes. This work contains a salutary discussion of the dangers of relying solely on gJ.c. purification of terpenes for radioactive tracer studies. 

Changes in the monoterpene composition of Mentha aquatica have been produced by gene substitution. The oxidation of pulegone (11) to mentho-furan (16) is controlled by a single gene that is not completely dominant, whereas the reduction to menthone involves a different set. Changes in favour of low menthofuran composition have been produced in Mentha aquatica by gene substitution. 

The incorporation of into nepetalactone at different time intervals 

A number of reviews of raonoterpenoid biosynthesis have appeared, ]bi 

Ihe preferential participation of linaloyl pyrophosphate rather than 

Ihe oxidation of limonene to form carvone involves a shift of the endo-cyclio double bond in (5) to form (6), i,e, (+)-limonene and (-)-caiTVone are biogenetically related. It has been suggested that they are probably formed 

Time course studies with COo in Biyimis species suggest that -terpinene 

A full paper describing the conversion of 10-oxoderivatives of geraniol and 

---

J. E. Saxton, ed.. Indoles, Part Four, The Monoterpenoid Indole Alkaloids, Wdey-Interscience, New York, 1983. 

The iridoid monoterpenoid part of the strueture C-1-C-9-C-5-C-6-C-7 (B) is eonfirmed by the HH COSY plot ... 

Determination of enantiomeric distribution of monoterpenoids from geranium oil... 

Terpenoids are classified according to the number of five-carbon multiples they contain. Monoterpenoids contain 10 carbons and are derived from two isopentenyl diphosphates, sesquiterpenoids contain 15 carbons and are derived from three isopentenyl diphosphates, diterpenoids contain 20 carbons and are derived from four isopentenyl diphosphates, and so on, up to triterpenoids (C30) and tetraterpenoids (C40). Monoterpenoids and sesquiterpenoids are found primarily in plants, bacteria, and fungi, but the higher terpenoids occur in both plants and animals. The triterpenoid lanosterol, for example, is the precursor from which steroid hormones are made, and the tetraterpenoid /3-carotene is a dietary source of vitamin A (Figure 27.6). 

The terpenoid precursor isopentenyl diphosphate, formerly called isopentenyl pyrophosphate and abbreviated IPP, is biosynthesized by two different pathways depending on the organism and the structure of the final product. In animals and higher plants, sesquiterpenoids and triterpenoids arise primarily from the mevalonate pathway, whereas monoterpenoids, diterpenoids, and tetraterpenoids are biosynthesized by the 1-deoxyxylulose 5-phosphate (DXP) pathway. In bacteria,... 

Strategy ur-Terpined, a monoterpenoid, must be derived biologically from geranyl diphos-... 

Monoterpenoid (Chapter 6 Fonts On. Section 27.5) A ten-carbon lipid. 

In section 9.4 we described some of the transformations that are employed in the manufacture of valuable steroids. Sterols and steroids are, however, only a small fraction of the total range of terpenoids produced within the biosphere. Others include monoterpenoids based on the structures ... 

The third paper in this set Zavarin and Snajberk (1976) described their efforts to detect chemical races within big cone Douglas fir. Analysis of the cortical monoterpenoid fraction of 33 trees revealed that the major component was a-pinene, with P-pinene, 3-carene, and limonene present in lesser amounts. The monoterpene profiles of different populations varied somewhat from each other, but the overall profile of big cone Douglas fir was clearly different from that of Douglas fir. There was no evidence for gene flow between the southernmost population of Douglas fir at Lompoc and the closest population of big cone Douglas fir at Figueroa, sites separated by only 34 km. 

Gotsiou, P., Naxakis, G. and Skoula, M. 2002. Diversity in the composition of monoterpenoids... 

Snajberk, K. and Zavarin, E. 1986. Monoterpenoid differentiation in relation to morphology of Pinus remota. Biochem. Syst. Ecol. 14 155-163. 

The in vivo transformation of [6-14C]strictosidine (19) to gelsemine in Gelsemium sempervirens was claimed with an incorporation of 0.47% (33). This provides another experimental support to the proposal that strictosidine appears to be the original precursor in the biosynthesis of monoterpenoid indole alkaloids, although the detailed pathway of this biosynthetic process still remains obscure. 

The family Rubiaceae consists of about 450 genera and 6500 species of tropical and subtropical trees, shrubs, climbers, and herbs that are known to abound with iri-doid glycosides (monoterpenoid alkaloids, tannins, and anthraquinones). When looking for Rubiaceae in field collection, one is advised to look for plants with opposite simple leaves with an interpetiolar stipule, tubular flowers, which are often white, and capsules, berries, or drupes. 

Fassbinder C, Grodnitzky J and Coats J (2002), Monoterpenoids as possible control agents for Varroa destructor , J Agric Resources, 41, 83-88. 

---