Study of the role of antimicrobial glucosinolate-derived isothiocyanates in resistance of Arabidopsis to microbial pathogens.

Crude aqueous extracts from Arabidopsis leaves were subjected to chromatographic separations, after which the different fractions were monitored for antimicrobial activity using the fungus Neurospora crassa as a test organism. Two major fractions were obtained that appeared to have the same abundance in leaves from untreated plants versus leaves from plants challenge inoculated with the fungus Alternaria brassicicola. One of both major antimicrobial fractions was purified to homogeneity and identified by 1H nuclear magnetic resonance, gas chromatography/electron impact mass spectrometry, and gas chromatography/chemical ionization mass spectrometry as 4-methylsulphinylbutyl isothiocyanate (ITC). This compound has previously been described as a product of myrosinase-mediated breakdown of glucoraphanin, the predominant glucosinolate in Arabidopsis leaves. 4-Methylsulphinylbutyl ITC was found to be inhibitory to a wide range of fungi and bacteria, producing 50% growth inhibition in vitro at concentrations of 28 microM for the most sensitive organism tested (Pseudomonas syringae). A previously identified glucosinolate biosynthesis mutant, gsm1-1, was found to be largely deficient in either of the two major antimicrobial compounds, including 4-methylsulphinylbutyl ITC. The resistance of gsm1-1 was compared with that of wild-type plants after challenge with the fungi A. brassicicola, Plectosphaerella cucumerina, Botrytis cinerea, Fusarium oxysporum, or Peronospora parasitica, or the bacteria Erwinia carotovora or P. syringae. Of the tested pathogens, only F. oxysporum was found to be significantly more aggressive on gsm1-1 than on wild-type plants. Taken together, our data suggest that glucosinolate-derived antimicrobial ITCs can play a role in the protection of Arabidopsis against particular pathogens.

Chalconoids from Fissistigma bracteolatum.

Phytochemical studies on the leaves of Fissistigma bracteolatum yielded besides the two known compounds 2-hydroxy-3,4,6-trimethoxychalcone (1) and 5,7,8-trimethoxyflav-3-ene (2), five new chalconoids 2-hydroxy-3,4,6-trimethoxychalcene (3), 2-hydroxy-3,4,6-trimethoxydihydrochalcone (4), 2'-hydroxy-3',4',6'-trimethoxydihydrochalcone (5), 2'-hydroxy-3',4',6'-trimethoxy-beta'-methoxychalcane (6) and 2'-hydroxy-3',4',6'-trimethoxy-beta'-ethoxychalcane (7). The structures of these compounds were determined by mass and NMR spectroscopic methods.

A chlorinated amide and piperidine alkaloids from Aloe sabaea.

Phytochemical investigations of Aloe sabaea afforded a new chlorinated amide, N-4'-chlorobutylbutyramide, and the toxic piperidine alkaloids coniine, gamma-coniceine and the quarternary N,N-dimethylconiine. This is the first report of the occurrence of a chlorinated compound in the Aloeaceae family.

Two new beta-carboline alkaloids from Hedyotis capitellata var. mollis.

Two new beta-carboline alkaloids, hedyocapitelline and hedyocapitine, were isolated from Hedyotis capitellata var. mollis (Rubiaceae). Their structures were elucidated by spectroscopic data (1)H- and (13)C-NMR, MS, IR, UV).

21'-Di-dehydro-deacetyllanatoside C, a biotransformation product of deacetyllanatoside C from senescent shoot cultures of Digitalis lanata.

Feeding deacetyllanatoside C to senescent shoot cultures of Digitalis lanata resulted in the formation of a new product, which was isolated by semi-preparative HPLC. The molecular structure was elucidated by means of HPLC-mass spectrometry and NMR as 21'-di-dehydro-deacetyllanatoside C.

Resorcinol derivatives from two Ardisia species.

Besides a series of known sterols and triterpenoids, 2-methyl-5-(Z-nonadec-14-enyl)resorcinol and 5-(Z-nonadec-14-enyl)resorcinol have been isolated from leaves of Ardisia silvestris. The last mentioned diphenol has also been obtained from roots of Ardisia gigantifolia. The structures of these resorcinol derivatives were elucidated.

Isolation of bis-indole alkaloids with antileishmanial and antibacterial activities from Peschiera van heurkii (syn. Tabernaemontana van heurkii).

Extracts from leaves and stem bark of Peschiera van heurkii (Muell. Arg.) L. Allorge (syn. Tabernaemontana van heurkii Muell. Arg., Apocynaceae) have been assayed for antileishmanial and antibacterial activities. The activities were concentrated in the alkaloid fractions which yielded 20 indole and bisindole alkaloids. The strongest leishmanicidal and antibacterial activities were observed with the dimeric alkaloids conodurine (1), N-demethylconodurine (= gabunine) (2), and conoduramine (3). Weak toxicity towards macrophage host cells and strong activity against the intracellular amastigote form of Leishmania were observed for compounds 1 and 2. In vivo, 1 was less active than glucantime (= N-methylglucamine antimonate), the drug of reference, while 2 was devoid of activity at 100 mg/kg.

Triterpenoids and their glycosides from the bark of Schefflera octophylla.

A new triterpene and its glycosides were isolated from the bark of Schefflera octophylla together with asiatic acid and asiaticoside. Based on spectroscopic data, especially 2DNMR, and chemical transformations the structures of the new compounds were determined as 3 alpha-hydroxy-urs-12-ene-23,28-dioic acid and 3 alpha-hydroxy-urs-12-ene-23,28-dioic acid 28-O-[alpha-L-rhamnopyranosyl (1----4)-O-beta-D-glucopyranosyl (1----6)]-beta-D-glucopyranoside. For the first time asiaticoside was isolated from a plant other than Centella asiatica.

Iridoids from Verbascum pulverulentum.

From the roots of VERBASCUM PULVERULENTUM Vill. two iridoids of the 6- O-alpha- L-rhamnopyranosylcatalpol-type have been isolated and structural elucidated.