15-oxo-zoapatlin,a diterpene lactone from Viguiera maculata

The isolation of a new diterpene lactone and two known diterpenoid acids from the aerial parts of Viguiera maculata is reported.     

Sesquiterpene lactone and diterpene constituents of helianthus annuus

One new furanoheliangolide derivative, 4,5-dihydroniveusin A, as well as the known compounds niveusin B and argophyllin A and B, were isolated from a Texas population of Helianthus annuus. Three previously characterized diterpene acids, grandifloric acid, ciliaric acid and 17-hydroxy-ent-isokaur-15(16)-en-19-oic acid were the principal constituents of this population.     

A diterpene from Laurencia obtusa

Laurencia obtusa collected at Kimmeridge Bay, Dorset contained 15-bromo-2,16-diacetoxy-7-hydroxy-9(11)-paraguarene as a major metabolise. Closely related compounds have recently been isolated from the sea hare Aplysia dactylomela collected at La Parguera, Puerto Rico.     

Absolute configuration of four cleistanthane diterpenes from velloziaceae

The absolute configurations of four cleistanthane diterpenes isolated from several species of Vellozia were determined by circular dichroism measurements.     

Inhibition and uncoupling of photosynthetic electron transport by diterpene lactone amide derivatives

Nine diterpene lactone amide derivatives 1-9 were synthesized from 6-oxovouacapan-7beta,17beta-lactone, which was obtained from 6alpha,7beta-dihydroxyvouacapan-17beta-oic acid isolated from Pterodon polygalaeflorus Benth., and tested for their activity on photosynthetic electron transport. Amide derivatives 3-5 behaved as electron transport chain inhibitors; they inhibited the photophosphorylation and uncoupled non-cyclic electron transport from water to methylviologen (MV). Furthermore, 4 and 5 enhanced the basal electron rate acting as uncouplers. Compound 6 behaved as an uncoupler; it enhanced the light-activated Mg2+-ATPase and basal electron flow, without affecting the uncoupled non-cyclic electron transport. Compounds 1-2 and 7-9 were less active or inactive. Compounds 3-5 did not affect photosystem I (PSI); they inhibited photosystem II (PSII) from water to 2,6-dichlorophenol indophenol (DCPIP). Compound 4 inhibited PSII from water to silicomolybdate (SiMo), but it had no effect on the reaction from diphenylcarbazide (DPC) to DCPIP indicating that its inhibition site was at the water splitting enzyme complex (OEC). Compounds 3 and 5 inhibited PSII from water to DCPIP without any effect from water to SiMo, therefore they inhibited the acceptor site of PSII. Chlorophyll a fluorescence kinetics confirmed the behaviour of 3-5.     

A cytotoxic diterpene from Alomia myriadenia

An extract of the aerial parts from Alomia myriadenia Schultz-Bip. ex Baker (Asteraceae) showed significant cytotoxicity against a panel of human cancer cell lines in a screening of extracts from Brazilian Atlantic Forest plant species. Employing a bioassay-linked HPLC-electrospray/MS method, followed by semi-preparative HPLC, the active component was isolated and characterized as a mixture of epimers of the labdane diterpene 12S,16-dihydroxy-ent-labda-7,13-dien-15,16-olide.     

A minor diterpene from Amaracus akhdarensis

A new isopimarane diterpenoid, isoakhdartriol, was isolated in very small amount from the aerial part of Amaracus akhdarensis. Its structure, isopimar-15-en-3β,8β,19-triol, was established by spectroscopic means.     

Two cleistanthane type diterpenes from Croton sonderianus

Sonderianol (12-hydroxy-3-oxo-cleistanth-8, 11, 13, 15-tetraene) and 3, 4-seco-sonderianol (methyl 12-hydroxy-3, 4-seco-cleistanth-8, 11, 13, 15, 18(4)-penten-3-oate), two new diterpenes with cleistanthane skeletons, were isolated from heartwood of Croton sonderianus.     

Vellozone,a tetracyclic triterpene from Vellozia stipitata

The isolation of (20R)-20-hydroxy-24-methylenedammar-3-one from Vellozia stipitata is described.     

A diterpene from Euphorbia maddeni

From the anticancer-active CHCl₃, extract of the plant Euphorbia maddeni, a polyacylated diterpene of jatrophone type, euphornin, has been isolated and its structure elucidated by physico-chemical methods.     

A new lactone from water-stressed chickpea

The isolation of a new lactone, 2-methyl-2,3,4-trihydroxybutanoic acid-1,4-lactone, from leaves of water-stressed chickpea is described. Elucidation of the structure was by chemical and spectroscopic methods. The lactone could not be detected in the leaves of well-watered plants. Its occurrence in other species is confirmed.     

A linear diterpene diol from Lemna minor

Four known isoprenoids were isolated from Lemna minor besides a novel diterpene which was attributed the structure (4R)-4-hydroxyisophytol by spectroscopic studies and chemical correlation.     

Diasin,A diterpene from Croton diasii

The trunkwood of Croton diasii Pires (Euphorbiaceae) contains diasin, a novel rearranged labdanic diterpene which includes furan, carbomethoxy, γ     

A diterpene acid from baccharis tucumanensis

The new clerodane diterpene 1 was isolated from the aerial parts of Baccharis tucumanensis (Compositae). Its structure has been determined from spectral data combined with chemical transformations.     

A diterpene related to erythroxydiol from Helichrysum refluxum

From Helichrysum refluxum, in addition to known compounds, a diterpene acid related to erythroxydiol Z was isolated. The structure was elucidated by NMR techniques.