Compositae, polyacetylenes

In practice, it is found that every species of plant can protect itself from all but a very few species of fungi, most of which are highly specific for particular varieties of plant. Many higher plants protect themselves against fungal invasion by producing phytoalexins, substances absent from healthy plants. Thus Leguminosae synthesize isoflavonoid protectants the Solanaceae diterpenes and the Compositae polyacetylenes (Cruickshank,... 

Naturally Occurring Acetylene Compounds. XX. A Preliminary Communication on Some Polyacetylenic Pigments from Compositae Plants. Acta Chem. Scand. 8, 1769 (1954). 

The acetylene compounds - Panaxynol and falcarindiol, isolated from the roots of Saposhnikovia divaricata (Turcz.) Schischk. (Umbelliferae), selectively inhibited 5-LOX (ICso = 2 pM), leukocyte-type 12-LOX (IC50 = 1 pM), platelet-type 12-LOX (IC50 = 67 pM), and 15-LOX (IC50 = 4 pM). The same compounds had only marginal effects on COX activities with IC50 > 100 pM [126]. Bidens campylotheca Schultz Bip. ssp. campylotheca (Compositae) is a Hawaiian folk medicine for throat, stomach and asthmatic disorders. The polyacetylenes isolated from the aerial parts of the plants, such... 

A. millefolium contains sesquiterpene lactones, polyacetylenes, coumarins, and flavonoids. Extracts have often been used in cosmetics in concentrations of 0.5-10%. A. millefolium was weakly genotoxic in Drosophila mela-nogaster. In provocative testing, patients reacted to a mix of Compositae that contained yarrow, as well as to yarrow itself. In clinical use, a formulation containing a 0.1% extract was not a sensitizer and alcoholic extracts of the dried leaves and stalks of the flower were not phototoxic (6). However, positive patch tests to A. millefolium have been reported (7). 

New Polyacetylenic Compounds from Terrestrial Plants.- The majority of new compounds have been isolated from members of the large Compositae family, and many are reported as a result of Bohlmann s continuing study of this family. Most are closely related to known structural types and their structures therefore follow easily from spectral data. The growing use of high resolution n.m.r. for this purpose is apparent. Unless otherwise indicated the species mentioned belong to the Compositae. 

Known Polyacetylenic Compounds from Terrestrial Plants.- A large number of new sources of known polyacetylenic compounds have been reported, mainly by Bohlmann and co-workers, often as an offshoot of their studies on the Compositae terpenes. These new sources are recorded in Table 1, along with the major compound types isolated from them. Known compounds which were isolated along with the compounds described in the previous section are not included in the table. 

In 1952 Anchel reported that a number of antibiotics produced by Basi-diomycetes were polyacetylenes . Compounds of this class had been known since 1935 to be produced by plants and those of the Compositae had been investigated systematically by Sorensen. The general chemistry of polyacetylenes was studied by Jones and his colleagues and by Bohlmann - . Many of these energy-rich compounds are extremely unstable and pol5nnerise rapidly in the solid state. However, they show characteristic ultraviolet absorption spectra which are useful in structural determinations. 

The synthesis of enynes is of interest in the chemistry of certain natural products. Terminal enynes occur in several natural products such as histrionicotoxin and laurencin, and the internal enyne unit is found along with polyacetylenes and allenes in natural products from Compositae and Umbelliferae. Both internal Z-and. E-enynes are also useful as precursors to stereochemically define d dienes on their partial reduction. A group from Phillips-Duphar has described an efficient synthesis of the functionalized enyne (95), which serves as the C5 synthon for the convergent synthesis of vitamin A. The l,3-dichloro-2-ether (94) is dechlorinated, substituted, and isomerized in one step on reaction with two molar equivalents of sodium acetylide in liquid ammonia, giving (95) with an E Z ratio... 

Carbon-14 work has shown that the pulvinic acid pigments found in lichens are derived via the shikimic acid pathway, and that the unsaturated ylidenebutenolides found with polyacetylenic compounds in the Compositae are derived from oleic acid. No biosynthetic studies have been reported for the terpenoid ylidenebutenolides freelingyne, peridinin and the several sesterterpenes from marine sponges. 

New and Known Polyacetylenes from Nature.— In investigations of numerous members of the tribe Inuleae (Compositae), the pentaynene (1) has been found to be particularly widespread. Osmites hirsuta, however, was found to contain the isovaleric esters (2a) and (2b). The pentaynene (1) has also been... 

Bentley, R.K., Jones, E.R.H. andThaHer, V. (1969b) Natural acetylenes. Part XXX. Polyacetylenes from Lactuca (lettuce) species of the Liguliflorae sub family of the Compositae. /. Chem. Soc. (C), 1096-1099. 

Figure 10.18 Dihydromatricaria acid is found in cantharid beetles feeding on Compositae which contain polyacetylenic acids. Lucibufagins are similar to cardenolides, sequestered by fireflies. Romallenone is present in the defensive foam of a grasshopper...

This was really the first of a series of papers on polyacetylenes from Compositae by Sorensen s group. The work was interrupted by war, and other papers in the series did not appear until 1950. 

Sorensen, N. A. Structural patterns of polyacetylenic compounds isolated from the plant family Compositae, p. 569- In I. U. P. A. C. Symposium on the Chemistry of Natural Products, Australia i960. London Butterworth Co. 1961. 

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