Renato Capasso

Isolation, spectroscopy and selective phytotoxic effects of polyphenols from vegetable waste waters

Abstract Catechol, 4-methylcatechol, tyrosol and hydroxytyrosol were isolated and characterized as the main polyphenols from olive oil mill waste waters. In addition, the corresponding acetates were prepared. In phytotoxicity assays carried out on tomato (Lycopersicon esculentum) and vegetable marrow (Cucurbita pepo) plants, the compounds were selectively toxic, except for 4-methylcatechol and its acetate. The vegetation waters remained phytotoxic even after total extraction of the polyphenols, suggesting that other chemical products contribute to the overall phytotoxicity.

Fusaric and 9,10-dehydrofusaric acids and their methyl esters from Fusarium nygamai

Abstract Fusaric and 9,10-dehydrofusaric acids and their corresponding methyl esters were isolated from the culture filtrates of Fusarium nygamai . The methyl esters were characterized by chemical and spectroscopic methods and reported here for the first time as naturally occurring products. When assayed on tomato leaves and seedlings at 2.7 × 10 −3 and 2 × 10 −4 M, respectively, fusaric and 9,10-dehydrofusaric acids and their methyl esters showed wide chlorosis rapidly evolving into necrosis as well as a strong inhibition of root elongation, respectively. When assayed at 10 −4 M on brine shrimps ( Artemia salina ), fusaric and 9,10-dehydrofusaric acids did not prove to be toxic, while their methyl esters showed a toxicity level of 50%, expressed as mortality.

Cytochalasins: structure-activity relationships

Abstract Seven cytochalasins, 17- O -acetylcytochalasin A and two derivatives of cytochalasin B were assayed for Pseudomonas syringae , Bacillus megaterium , and for Geotrichum candidum . Their ability to inhibit the growth of tomato seedlings and their toxicity to brine shrimp (% larvae mortality were also investigated. Among the compounds assayed only cytochalasin A showed antibiotic and fungicidal activity. Toxicity to tomato seedlings was exhibited by both [14]- and [11]-macrocyclic cytochalasans, while the activity decreased in the derivatives acetylated on the 7-hydroxy group and markedly in cytochalasin E. In the brine shrimp bioassay, cytochalasin E was the most active mycotoxin, but generally, at low concentrations, the cytochalasins with the [11]-macrocyclic ring were more active than those with the [14]-macrocyclic ring; cytochalasin A appeared to be the most toxic.

Pinolidoxin, a phytotoxic nonenolide from Ascochyta pinodes

Abstract Ascochyta pinodes , the causal agent of pea anthracnose, cultured on sterilized wheat, produces toxic metabolites. The main phytotoxin, named pinolidoxin, was isolated and characterized using spectral and chemical methods as 2-(2,4-hexadienoyloxy)-7,8-dihydroxy-9-propyl-5-nonen-9-olide, a new phytotoxic 10-macrolide. When assayed on host (pea) and non-host (bean) plants, pinolidoxin was highly toxic; towards brine shrimps it was only weakly toxic.

Production of glucose and bioactive aglycone by chemical and enzymatic hydrolysis of purified oleuropein fromOlea Europea

Pure-grade oleuropein, a bitter, hypotensive, phenolic glucoside, was obtained from organic extracts of olive plant leaves by two Chromatographic steps. The purified compound was characterized by spectroscopic NMR and FAB-MS methods. The glucoside underwent chemical and enzymatic hydrolysis. Aglycone was characterized by spectroscopic methods (1H-NMR and FAB-MS). Glucose was measured by enzymatic methods. The enzymatic hydrolysis of oleuropein was carried out by a soluble β-glucosidase. The reaction was characterized in terms of kinetic parameters, optimal pH value, activation energy, inhibition constant by glucose, and thermal stability. Preliminary experiments were also performed in a continuousflow ultrafiltration membrane reactor. The cut-off of the membrane was lower than the molecular-weight of the enzyme, thus determining β-glucosidase confinement within the reactor. Under these conditions, β-glucosidase had a good long-term stability. This is an encouraging result in view of possible industrial applications.

Putaminoxin, a phytotoxic nonenolide from Phoma putaminum

Phoma putaminum, the causal agent of leaf necrosis of Erigeron annuus, a common weed of field and pasture, produced toxic metabolites when grown in liquid culture. The main phytotoxin, named putaminoxin, was isolated and characterized using spectroscopic and chemical methods as (5S)5-hydroxy-9-propyl-6-nonen-9-olide, a new 10-macrolide. When assayed on leaves of host and non-host plants, putaminoxin showed a wide range of toxicity, with leaves of E. annuus being most sensitive.

Ascaulitoxin, a phytotoxic bis-amino acid N-glucoside from ascochyta caulina

Abstract A new unusual phytotoxic bis-amino acid N-glucoside, named ascaulitoxin, was isolated from the culture filtrate of Ascochyta caulina, the causal agent of leaf and stem necrosis of Chenopodium album, a promising mycoherbicide for the biological control of this common noxious weed. Ascaulitoxin, characterized by extensive use of NMR techniques and chemical methods as N 2 - (2,4,7-triamino-5-hydroxy)-octanedioyl-β- d -glucopyranoside , showed phytotoxic activity against host and non-host plants.

Structure-activity relationship studies of putaminoxins and pinolidoxins: phytotoxic nonenolides produced by phytopathogenic Phoma and Ascochyta species

Putaminoxin and pinolidoxin, two structurally related nonenolides, isolated respectively from organic extracts of Phoma putaminum and Aschochyta pinodes cultures, together with some of their natural analogs and synthetic derivatives, were used in a structure-activity relationship study. Their phytotoxic, antifungal and zootoxic activities were assayed with the aim to find compounds with potential herbicidal properties. The strongest phytotoxic compounds proved to be putaminoxin and pinolidoxin, whose activity appeared to be correlated to the integrity of the nonenolide ring and to the presence of both the hydroxy groups and the unmodified propyl side chain. None of the assayed nonenolides showed antifungal activity, whereas pinolidoxin analogs and derivatives showed high to weak zootoxicity.

Structure-toxicity relationships of the eremophilane phomenone and PR-toxin

Abstract The structure-toxicity relationships of phomenone were studied on cuttings and seedlings of tomato, and on larvae of brine shrim. Four derivatives prepared by chemical modification of phomenone were tested in comparison with PR-toxin. The toxicity to tomato cuttings (wilting and necroses of leaflets) appeared to be dependent on the integrity of the phomenone molecule, as any structural modification markedly reduced or completely abolished its phytotoxicity. By contrast, the toxicity to tomato seedlings (growth inhibition of shoots and rootlets) and to brine shrimp (larvae mortality) suggested a role for the epoxy rings in eremophilane molecules, which was enhanced by acetylation, as demonstrated by the progressive loss of activity for the sequence PR-toxin, phomenone and 9-methoxy- 6,7-de-epoxyphomenone.

Ascochalasin, a New Cytochalasin from Ascochyta heteromorpha.

A previous analysis of the organic culture filtrate extracts of Ascochytu heteromorpha (Sch. et Sacc.) Curzi, a pathogenic fungus isolated from oleander (Nerium ofeundw L.) , led to the isolation of the known cytochalasins A 111 and B {2} (1). A further investigation of the extracts has revealed the presence of another two cytochalasins: deoxaphomin 131, isolated from Phoma sp. (strain S 298) ( 2 ) and identified as a biosynthetic precursor of cytochalasin B (3), and a new cytochalasin, which we have named ascochalasin 151. In the present note we report the isolation and the structure elucidation of ascochalasin. The chromatographic purification of culture filtrate organic extracts was performed using two SiO, columns in two successive steps. Cytochalasins A and B were obtained together with a mixture ofproducts with chromatographic behavior very close to that of 2. The mixture was purified by preparative tlc first on SiOz and then on reversed-phase plates, affording pure deoxaphomin and ascochalasin. Deoxaphomin 131 was identified by comparing our spectral data, ir, uv, nmr, and ms, with those reported by Binder and Tamm ( 2 ) . The acetyl derivative 4 of 3 gave a ‘H-nmr spectrum in which the appear-