Conifers are widespread through the northern hemisphere and many of their essential oils and oleoresins have acquired high commercial significance. After a short review of conifer taxonomy and some cytological aspects of oil secretion and accumulation, general characteristics of conifer oils and resins are discussed in more detail. Since considerable differences can be found in literature concerning the composition of commercially important conifer oils, we have analysed some of them originating from several species of the genera Abies, Larix, Pseudotsuga, Tsuga, Picea and Pinus. The results were compared with those of self‐distilled oils from authentic botanical origin and discussed in regard to the systematic grouping of the individual conifer. In addition to investigations of the chemistry of selected conifer oils, the paper outlines the influence of the raw material, especially the relation of needles to twigs and the effect that this variable has on the composition of an individual oil.

The essential root oils of the Pim pinella saxifraga subspecies eusaxifraga, alpestris and nigra were investigated by means of capillary GC and spectroscopic m ethods. A total of 48 com ponents was identified. Characteristic constituents of all oils are pseudoisoeugenol derivatives, sesquiterpenoids and trinor-sesquiterpene hydrocarbons, but the qualitative and quantitative patterns of the individual oils exhibit significant differences. The results obtained were discussed in regard to a chemotaxonomic reliable delimitation of the 3 described subspecies of Pimpinella saxifraga L.

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Economic loss caused by weeds and the cost of their control continues to increase annually. The herbicides currently in use have been shown to have undesirable effects, It has been suggested that understanding of the mechanism of actions of allelopathic chemicals may provide leads to the development of new herbicides. Hence, the allelopathic activity of the essential oils of three Nigerian medicinal plants; Eugenia uniflora L. leaves, Chromolaena odorata (L.) King and Robinson leaves, and Piper guineense Schum. and Thonn fruits have been examined.The essential oils were obtained by hydrodistillation according to British Pharmacopoeia method (1). The oils were assayed using the lettuce seedling root growth bioassay with prize head and black-seeded Simpson seeds. P. guineense oil showed mild inhibition from 25 ppm to 100 ppm. Above 100 ppm the inhibition was significantly higher, 50% at 400 ppm and 57 % at 800 ppm of oil. C. odorata showed mild stimulation at 25 ppm and little or no effect at higher concentration. E. uniflora oil caused a 15 % increase in seedling root length at 25 ppm which encreased to a maximum of 39 % at 200 ppm. Above 200 ppm the root length decreased. This pattern is characteristic of auxins.All aerial organs of higher plants are covered with a thin continuous wax layer. These epicuticular or surface waxes are a natural barrier of outer plant cells against environmental factors and consist of a very complex mixture of different components. The leaf waxes of the two Tilia species contain the following common wax lipids: alkanes, wax esters, aldehydes, acetates, primary alcohols, and fatty acids, all occuring in homologous series of very long chained and saturated components. Both Tilia species have the same lipid components with similar distribution patterns and identical distinct maxima in each homologous series. These substances from the lipid metabolism yield about 33-40% of the wax.In addition, triterpenoids are found in these Tiia waxes in high amounts of 44-56%. They originate from the isoprene metabolism. The triterpenol, 3-amyrin, was identified in both Tilia waxes, free as well as esterified. The two species contain the same triterpenoids (3-amyrin, 3-amyrin acetate, and 3-amyrin fatty acid esters but differ in their amounts. 3-Amyrin acetate was found to be the dominating major component of the epicuticular waxes in both Tilia species with about 34% of the wax.Cistus laurifolius L. secretes a sticky, flavonoid-containing resinous material onto the surface of leaves and stems. In addition to the well-known resin flavonoids of several Cistus species described in the last years (1-3), we were able to identify two new bright fluorescenting flavonols only found in young immature leaves of C. laurifolius but not detected on mature leaves. These two new compounds were identified as quercetin-5,3'dimethyl ether and its related 3,S,3'-trimethyl ether (4). It was very astonishing that these quite conspicious flavonols disappeared during the unfolding of the leaves.Recent results show that ultr...