Fred C. Seaman

Sesquiterpene lactones and species relationships among the shrubby Ambrosia taxa

Abstract The sesquiterpene lactone chemistry, chromosome numbers and morphology of selected Sonoran Desert Ambrosia taxa are reported. The sesquiterpene lactone distribution correlates with morphologically defined species groups.

The effects of tannic acid and other phenolics on the growth of the fungus cultivated by the leaf-cutting ant, Myrmicocrypta buenzlii

Abstract Using a liquid defined medium for the bioassays, the effects of tannic acid, naringin and 4-hydroxycoumarin on the growth of an ant-cultivated fungus were determined. The results with tannic acid indicated greater growth retardation than was obtained during bioassays on solid agar media. The reasons for this discrepancy are attributed to the undesirable properties of solid agar media for conducting tannin bioassays.

New cyanogenetic lipids from Ungnadia speciosa

Abstract A mixture of two new cyanogenetic lipids from the seeds of Ungnadia speciosa have been structurally characterized.

Sesquiterpene lactone patterns in diploid and polyploid Ambrosia dumosa

Abstract Diploid, tetraploid and hexaploid populations of Ambrosia dumosa yielded several different sesquiterpene lactone patterns. The distribution of chemical complements is useful in relating the different levels of this polyploid series.

Sesquiterpene lactones of diploid and tetraploid Ambrosia camphorata

Diploid and tetraploid specimens of Ambrosia camphorata have distinct sesquiterpene lactone patterns; however, no direct correlation between chemistry and morphological patterns is detectable.

Sesquiterpene lactones from Carphochaete bigelovii

Abstract Five sesquiterpene lactones with C 10 -diester side-chains have been identified as major constituents of a leaf surface extract of Carphochaete bigelovii . The structures were elucidated by spectroscopic methods and are reported for the first time. Chemosystematic implications are discussed briefly.

Isodehydroleucodin and another novel cis-lactonized guaianolide from montanoa imbricata

Abstract Montanoa imbricata yielded two guaianolides, isodehydroleucodin, which is the C-5,C-6-isomer of dehydroleucodin, and 9-oxo-isodehydroleucodin.

Biological Activity of Diterpenes

Various biological activities (Table 13 [pp. 489–490]) have been reported for plant diterpenes, principally from members of the Ericaceae, Euphorbiaceae, Lamiaceae, and Compositae. Each of the major diterpenoid classes from this last family will be discussed below in terms of its biological properties.

Compound Names, Structures, and Sources

The names (Table 1 [pp. 7–59]) and structures (Figure 1 [pp. 219–384]) of diterpenes reported from the Compositae are organized according to skeletal type following the sequence indicated in Figure 2 (p. 392). If a name was assigned to a structure at the time the compound was reported, that name was included in Table 1. Otherwise, the structure was given a name compatible with the names previously assigned to related compounds. If more than one name was applied in the literature to the same structure, usually the first-published name was included in Table 1, followed by additional names listed within brackets. The compound number listed with each name was used throughout this treatment when reference to the compound was made. Comments about a reported compound were also included in brackets on a line below the compound name. Usually these comments describe situations in which the name applied to the compound was incompatible with either the illustrated structure or the published spectroscopic data.

Diterpene Distribution: Compositae

Green plants possess (1) geranylgeraniol, the required precursor for both carotenoid and gibberellin biosynthesis, (2) the enzymatic machinery to cyclize geranylgeraniol (or its isomer) to ent-kaurene, and (3) the enzymes for the oxidation of ent-kaurene and other diterpene substrates (420). Normally, the steady-state concentration of the products of these pathways falls below the level of detectability of all but the most sensitive analytical instruments. By comparison, the compounds that are the focus of this review constitute an “abnormal” biosynthetic excess detectable in the form of resins. Often, general plant metabolism is isolated from these biologically active resins by the comparmentation of resin biosynthesis and storage within glandular trichomes.