Eucalyptus spathulenol from

There are a number of allelochemicals among the mono-, sesqui-, and diterpenoids. In particular, plants in arid and semiarid regions produce diverse volatile terpenoids with allelopathic activity.5 Among the volatile monoterpenes, 1,8-cineole (4) and camphor (5) exhibit strong growth inhibitory effects on plants and are considered to be involved in plant competition. 1,4-Cineole (6), a minor isomer of 1,8-cineole, is a potent inhibitor of asparagine synthetase.6 -Menthane-3,8-diols (fir 7 and frw .r8), -menth-2-en-l-ols (cis 9 and trans 10), thymol (11), carvacrol (12), 1,8-cineole, cr-pinene (13), and /3-pinene (14) were isolated as allelopathic monoterpenes from Eucalyptus species.7 Eucalyptus trees also produce allelopathic sesquiterpenes including spathulenol (15), and a-, (3-, and 7-eudesmols (16-18).7... 

The only other class of sesquiterpenes isolated from Eremophila is the aromadendrane type which is represented by a single compound, (-r)-spathulenol (94), found in E.cuneifolia (67), E. paisley, E. racemosa and E. drummondii var brevis (14). First isolated from Eucalyptus spathulata (84), this compound has since been found to occur in a broad spectrum of plant genera (85). 

Among the oxygenated sesquiterpenes (Fig. 96.12), the oxidation product from p-caryophyllene, caryophyllene oxide, is widespread in plants. Also spathulenol is a widespread sesquiterpene alcohol. For example, it occurs in German chamomile and together with y-eudesmol as major oil component in Eucalyptus oleosa [36]. Daucol and carotol are aroma components found in the fruit oils from carrots (Daucus carotd) [27]. 

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