[Diterpenes and other components of Croton hirtus (Euphorbiaceae)]

The roots of Croton hirtus (Euphorbiaceae) collected in Paraiso, Cartago (Costa Rica) afforded, in addition to the few known metabolites, 20 new compounds: the bis-nor dolabradane 1, the dolabradanes 2 and 3, the kauranes 4-7, the cyclopropakauranes 8 and 9, the hirtusanes 10-15, the germacradiene esters 16-18 and the C-25 compound 21, presumably formed by a Diels-Alder reaction between compound 18 and a monoterpene. All structures were elucidated using high field 1D and 2D NMR techniques. MS fragmentation patterns are here reported. The absolute configurations of 4 and 9 were elucidated by using circular dichroism. The separation was performed with modern chromatographic technics.

Pure compound libraries; a new perspective for natural product based drug discovery

What often distinguishes the leaders in drug discovery and development from the rest is the quality of their compound libraries and the ease of access that they have to the information within those libraries. The screening of natural products can provide greater structural diversity than standard synthetic chemistry and offers significant opportunities for finding novel low molecular weight lead compounds. However, which strategy is the best for natural-product-based drug discovery? Two well established but relatively time consuming approaches are the screening of crude extracts and pre-fractionated extracts. This case study describes a third, pure-compound-screening approach, and discusses its benefits and pitfalls.

Diterpenes and other constituents from Croton draco (Euphorbiaceae)

Croton draco (Euphorbiaceae) from Guadalupe, San José, Costa Rica was collected in July 1992 and phytochemically studied (leaves, seeds, wood, bark, sap and flowers separately). Commonly known compounds such as 1-hydroxyjunenol, p-hydroxybenzaldehyde, p-methoxybenzoic acid, 3,4,5-trimethoxycinnamyl alcohol, the coumarin scopoletin, the nor-terpenoids 9-dehydrovomifoliol and 2,3-dihydrovomifoliol were obtained. Taspine, two aporphinic alkaloids, the diterpenes 9(11)-dehydrokaurenic acid, hardwikiic acid, the corresponding new 12-oxo derivative as well as five clerodanes and a phorbol ester were also isolated. Three clerodanes were not previously described and their NMR spectroscopical data and MS fragmentation patterns are reported.

In vitro antiplasmodial activity of 4-phenylcoumarins from Exostema mexicanum

The stem bark of Exostema mexicanum (Rubiaceae) is used in Latin American folk medicine as a quinine substitute for malaria treatment. Bioassay-guided fractionation of lipophilic and hydrophilic extracts from the stem bark and branches yielded two previously undescribed 4-phenylcoumarins: 4',8-dihydroxy-5,7-dimethoxy-4-phenylcoumarin (exomexin A) and 3',4'-dihydroxy-5,7,8-trimethoxy-4-phenylcoumarin (exomexin B). Together with five known derivatives the in vitro activities against a chloroquine-sensitive strain (poW) and a chloroquine-resistant strain (Dd2) of Plasmodium falciparum have been evaluated. The most lipophilic compound, 4',5,7,8-tetramethoxy-4-phenylcoumarin (O-methylexostemin) revealed the strongest antiplasmodial activity (IC50 values: 3.6 microg/ml [poW], 1.6 microg/ml [Dd2]).

Triterpenoid p-aminobenzoates from the seeds of zucchini

An investigation of the triterpenoid fraction of zucchini seeds afforded two novel multiflorane p-aminobenzoates, identified as 7-epi zucchini factor A and debenzoyl zucchini factor B. Multiflorane p-aminobenzoates could not be detected in zucchini sprouts, which contained bryonolic acid as the only multiflorane constituent. No compound of this type could be obtained from adult plant parts (roots, stems, leaves).

Sipandinolide: a butenolide including a novel type of carbon skeleton from Siparuna andina

From a lipophilic extract of leaves of Siparuna andina (Monimiaceae), which exhibited antiplasmodial activity in vitro, two new compounds have been isolated: sipandinolide (1), a compound with a novel type of carbon skeleton and (-)-cis-3-acetoxy-4',5,7-trihydroxyflavanone (2). Their structures were established by spectroscopic methods; 2 showed moderate antiplasmodial activity whereas 1 was inactive.

Polycyclic diterpenoids from Euphorbia characias

In addition to widespread flavonoids, a collection of Euphorbia characias from Sardinia afforded 13 oxygenated diterpenoids of the atisane, abietane, pimarane, and kaurane type. Four of these compounds (1, 3a, 7a,b) are new. The accumulation of substantial amounts of biologically active diterpenoids of limited availability, like ent-atisanes endowed with anti-HIV activity and ent-abietanolides active on the central nervous system, makes E. characias an interesting source of lead compounds for biomedical research.

Hyperforin analogues from St. John's wort (Hypericum perforatum)

Three oxygenated analogues of the prenylated phloroglucinol hyperforin (3-5) were isolated from the aerial parts of Hypericum perforatum and their structures elucidated by spectroscopic methods.

Bonaspectins and neobonaspectins, first sesquilignans and sesquineolignans from a convolvulaceous species

Four new tetrahydrofuran-type sesquilignans, named bonaspectin A, bonaspectin B, bonaspectin C 4''-beta-glucoside and bonaspectin D 4''-beta-glucoside, as well as two new 8.O.4'-type sesquineolignans, named neobonaspectin A and B, were isolated from the aerial vegetative parts of Bonamia spectabilis (Convolvulaceae), together with the known compound rel-(7S,8S,7'R,8'R)-3,3',4,4',5,5'-hexamethoxy-7.O.7',8.8'-lignan. Their structures were established on the basis of spectral data.

Diterpenoids from euphorbia pithyusa subsp. cupanii

The aerial parts of Euphorbia pithyusa subsp. cupanii collected in Sardinia afforded eleven novel diterpenoids belonging to the lathyrane (1a), premyrsinane (4a-g), and tigliane (5a-c) types. Compounds 4a-g and 5a are esters of two new parent alcohols, named premyrsinol and 4,12,20-trideoxyphorbol, respectively. Structures were elucidated by spectroscopic and chemical methods. Puzzling differences between the NMR data of lathyrol (1c) and its esters were rationalized in terms of flipping of the exomethylene around the mean plane of the macrocycle.

Furohyperforin, a prenylated phloroglucinol from st. John's wort (Hypericumperforatum)

Furohyperforin, an oxygenated analogue of the prenylated phloroglucinol hyperforin, was isolated from the aerial parts of Hypericum perforatum. Its structure was elucidated as 2 on the basis of extensive NMR investigations.

Isoterracinolides A and B, novel bishomoditerpene lactones from euphorbia terracina

An extract of Euphorbia terracina L. has yielded six acylated polyhydroxy terpenoid lactones (1-6), which all display the C22 17-ethyljatrophane carbon framework. Four of these (1-4) are delta lactones belonging to the previously described terracinolide type, and two of them (2, 3) are new. Two further new compounds have been named isoterracinolides A (5) and B (6) and exhibit an eight-membered lactone ring. Another isolated new compound is the jolkinolide-type, ent-abietane gamma lactone (7).

An expeditious procedure for the isolation of ingenol from the seeds of euphorbia lathyris

A short and practical process for the isolation of ingenol (1a) from an agricultural commodity (the seeds of Euphorbia lathyris) is described. Macrocyclic diterpene esters are obtained as byproducts, and the esterification pattern of the Euphorbia factors L2 (3), L3 (4a), and L8 (4b) was established by 2D NMR measurements. Full spectroscopic data for these compounds are reported.

Macrocyclic diterpenoids from Euphorbia semiperfoliata

In addition to known compounds, the aerial parts of E. semiperfoliata afforded an abietanolide (3), 13 jatrophane polyesters (4-9, 12, 14-19), two 4-deoxyphorbol diesters (23, 24), and a pair of epimeric diterpenes (21, 22) with a novel carbon skeleton, which was named euphoperfoliane. Structures were determined by spectroscopic analysis, and the main conformational features of jatropha-6(17),11-dienes are discussed in detail. The obtained isolation yield of several jatrophanes was unprecedented within the spurges (Euphorbia spp.), making E. semiperfoliata a unique source of macrocyclic diterpenoids.

Structures of the two saponins isolated from commercially available root extract of Primula sp

The two main saponins of commercially available extract of Primula sp. were isolated by HPLC. Their structures were elucidated by spectroscopic methods as already known primulasaponin (1) and the new 3-O-¿[alpha-rhamnopyranosyl-(1-->2)-beta- galactopyranosyl-(1-->3)-[beta-xylopyranosyl-(1-->4)-beta-glucopyranosyl - (1-->2)]-beta-glucuronopyranosyl]¿-protoprimulagenin A (2).

Sesquiterpene glycosides from Calendula arvensis

The extract of the aerial parts of Calendula arvensis afforded four new sesquiterpene glycosides 1-4 in addition to three known compounds. The structures of the new compounds were established by high field 1H-nmr spectroscopy.

Rare Flavonoid Aglycones from Anaphalis margaritacea and Two Gnaphalium Species

Anaphalis margaritacea, Gnaphalium chilense and G. microecephalum have been analyzed for flavonoid aglycones deposited externally on aerial parts. Anaphalis was found to produce, among others, several rare flavonoids, all of which are O-substituted in position 6 and mostly also in position 8. Both Gnaphalium species exhibit 3,5-dihydroxy-6,7,8-trim ethoxyflavone as the major exudate flavonoid.

Acetylenes and Other Constituents from Artemisia dracunculus

The aerial parts of ARTEMISIA DRACUNCULUS afforded several known compounds as well as three new acetylenes, two phenylpropane derivatives, two monoterpenes, hex-3 Z-en-1-ol and vomifoliol A glucosides. The structures were elucidated by spectroscopic methods and a few chemical transformations.

Aromatic Constituents from Vladimiria souliei

The polar parts of the title plant gave several lignans including six new ones named vladinol A-F. The structures were elucidated by high field (1)H-NMR spectroscopy and a few chemical reactions. The stereochemistry was determined by the observed NOE's and by comparison of the (1)H-NMR data with those of related lignans.

Eudesmanolides from Artemisia santonicum

The reinvestigation of the aerial parts of ARTEMISIA SANTONICUM afforded, in addition to three known eudesmanolides, six new ones, all closely related to taurin. The structures were elucidated by high-field NMR spectroscopy.

Sesquiterpene Glycosides from Calendula persica

The polar fractions of the extract of the aerial parts of CALENDULA PERSICA afforded eight sesquiterpene glycosides, five derived from viridiflorol, two of beta-eudesmol, and one of 4alpha-hydroxygermacra-1(10) E,5E-diene. In addition to fucopyranosides, also chinovopyranosides were present. The structures were elucidated by high field NMR techniques.

Constituents of Evolvolus arbuscula ssp. canus

From the aerial parts of EVOLVOLUS ARBUSCULA ssp. CANUS (Convolvulaceae) the nor-sesquiterpenoids, 15-norpanasinsan-5beta-ol-8-one, 15-nor-panasinsan-5,8-dione, and caryophyllenoxide, have been isolated together with some aliphatic compounds and sterols.

New Pseudoguaianolides from Ambrosia maritima

The investigation of the aerial parts of two collections of AMBROSIA MARITIMA afforded in addition to known pseudoguaianolides nine new ones including two nor-sesquiterpene lactones and two dimeric lactones. The structures were elucidated by highfield (1)H-NMR spectroscopy.

Amplectol: A Novel Acetylenic Thiophene Derivative from Blumea amplectens var. arenaria

The aerial parts of BLUMEA AMPLECTENS var. ARENARIA afforded taraxasteryl acetate, dihydrosterculic acid, the sesquiterpene ferutinin, and the acetylenic thiophene diol, 3,4-dihydroxy-8-[5'-methylthiophen-2'-yl]-1, 5-octadien-7-yne, named as amplectol. Thestructures were elucidated by spectroscopic methods. A biogenetic pathway for the formation of amplectol in the plant is also suggested.

Further Sesquiterpene Lactones from Eupatorium altissimum

A reinvestigation of the aerial parts of EUPATORIUM ALTISSIMUM afforded, in addition to several, previously isolated sesquiterpene lactones, five new ones. The structures of these were elucidated by highfield (1)H-NMR spectroscopy.

Germacra-1,10Z,4E-dien-12,8alpha-olides from Mikania micrantha

The aerial parts of MIKANIA MICRANTHA from a collection in Paraguay gave, in addition to mikanolide, deoxymikanolide, and miscandenin, five new germacranolides all derived from 14,15-dihydroxygermacra-1(10) E,4 Z-dien-12,8alpha-olide.

Further eudesmane derivatives from verbesina species

The aerial parts of VERBESINA PERSICIFOLIA DC afforded a new eudesmane derivative in addition to known compounds. The roots of V. SUBCORDATA gave also new eudesmane cinnamates in addition to several known ones as well as a 5alpha-hydroxybicyclogermacra-1 (10) E, 4 (15)-diene. A reinvestigation of V. VIRGINICA L. gave two new ( Z)-configurated coumarates. Furthermore the structures of some sesquiterpenes are revised. The structures were elucidated by highfield NMR spectroscopy and a few chemical reactions.

[Further Compounds from Centaurea stoebe.]

From CENTAUREA STOEBE the following compounds have been isolated: cnicin, salonitenolide, salonitenolid-8- O-(4'-acetoxy-5'-hydroxyangelate), stoebenolide, 3-hydroxy-2-methylbutyrolactone, and 3-(3, 4-dihydroxy-5-methoxyphenyl)-prop-1-yl 3-hydroxy-11-methyloctadecanoate.

Further beta-Cyperone Derivatives from Haplopappus freemontii

The roots of HAPLOPAPPUS FREEMONTII afforded in addition to the known 8-oxo-beta-cyperone two further derivatives. The structures were elucidated by highfield (1)H-NMR spectroscopy.

Bisabolone derivatives and sesquiterpene lactones from centaurea species

The investigation of three CENTAUREA species collected in Argentina afforded, in addition to several known sesquiterpene lactones, a new guaianolide, a germacranolide, and two bisabolone derivatives. The structures were elucidated by highfield (1)H-NMR spectroscopy.

New Guaianolides and Farnesol Derivatives from Arctotis arctotoides1

The aerial parts of ARCTOTIS ARCTOTOIDES afforded eight known sesquiterpene lactones and three new ones, the 11beta,13-dihydroguaianolides 9 and 10 as well as the chlorohydrine 8. Furthermore two 2Z-farnesol derivatives 12 and 13 were isolated. The structures were elucidated by highfield (1)H-NMR. The stereochemistry of several compounds has been revised.

New pseudoguaianolides from Gaillardia megapotamica var. scabiosoides

The aerial parts of Gaillardia megapotamica var. scabiosoides afforded known pseudoguaianolides and three new ones. Furthermore, a new guaianolide and an acetylenic sulfoxide were isolated.

Alicyclic diterpenes from solidago species

The aerial parts of SOLIDAGO DRUMMONDII afforded in addition to known compounds like germacrene D and beta-caryophyllene, eight alicyclic diterpenes all derived from geranylgeraniol. The main constituent was also isolated from S. RACEMOSA and S. FLEXICAULIS. The structures were elucidated by highfield (1)H-NMR spectroscopy.

New Vernolepin Derivatives from Vernonia glabra and Glaucolides from Vernonia scorpioides

The aerial parts of VERNONIA GLABRA afforded in addition to vernolepin, vernodalin and vernomenin, four further sesquiterpene lactones derived from vernolepin ( 1), two germacranolides and together with vernodalol the corresponding lactone 9. From VERNONIA SCORPIOIDES two further glaucolides ( 14) and ( 15) were isolated. The structure of the tiglate ( 16) is revised. The structure were elucidated by spectroscopic methods.

New Clerodane Derivatives from Teucrium scordium

A reinvestigation of the aerial parts of TEUCRIUM SCORDIUM afforded in addition to several known diterpenes five new clerodane derivatives, all closely related to teucrin. The structures and the stereochemistry were elucidated by high resolution (1)H-NMR spectroscopy.