Miriam Cojocaru

5-(12-heptadecenyl)-resorcinol, the major component of the antifungal activity in the peel of mango fruit

Abstract A mixture of5-(12- cis -heptadecenyl)- and 5-pentadecyl-resorcinol was isolated from the peel of mango fruit; it acts as a preformed agent against Alternaria alternata , a fungus responsible for the black spot disease of mango fruits in Israel. The chemical characterization was done by 1 HNMR, 13 CNMR and MS.

Accumulation of Secondary Carotenoids in Chlorella zofingiensis

Summary We have previously found that in Chlorella emersonii , grown under synergistic conditions of high irradiance and low nitrogen, chlorophyll and primary carotenoids were degraded, whereas secondary carotenoids were produced. In this study Chlorella zofingiensis was cultivated under similar conditions. Maximal growth was achieved in a culture growing under light irradiance of 150 μmol quanta m -2 s -1 and a nitrogen concentration of 0.5 mg/mL of KNO 3 . Higher nitrogen concentrations or higher irradiance inhibited cell division. The secondary carotenoids produced were identified as canthaxanthin (about 30 %) and astaxanthin (about 70 %) in the form of mono- and diesters. Maximal accumulation occurred in cells starved of nitrogen and grown at a light irradiance of 300 μLmol m -2 s -1 . Exposure of a thin layer of algal cells to sunlight resulted in de-esterification of the astaxanthin esters. It is suggested that secondary carotenoids have a photo-protective role, that is, under high light conditions they protect chlorophyll and other photosynthetic pigments against damage.

Sex Pheromone of the Vine Mealybug, Planococcus ficus in Israel: Occurrence of a Second Component in a Mass-Reared Population

Two pheromonal components were detected in airborne collections from the vine mealybug Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae) mass-reared on potato sprouts. The compounds were identified as (S)-lavandulyl senecioate (I) and (S)-lavandulyl isovalerate (II) by GC and GC-MS by comparison with synthetic standards. Chiral GC analysis on a cyclodextrin column established their chirality. Compound I was identified recently as the sex pheromone of P. ficus in California. The attraction of vine mealybug males to both components I and II was demonstrated in a Petri dish bioassay and in a flight assay in the rearing chamber. Indoors, both compounds displayed a similar level of attractiveness to the mass-reared males. However, trials in a vineyard indicated that feral males were attracted only to compound I. Reanalysis of the airborne pheromone indicated that laboratory first generation daughters of females that were collected in the vineyard produce only (S)-lavandulyl senecioate (I). The relative amount of (S)-lavandulyl isovalerate (II) increased gradually in each subsequent generation of P. ficus reared on potatoes. These findings indicate that feral P. ficus mealybugs produce and respond only to (S)-lavandulyl senecioate (I), whereas mealybugs that were reared in the laboratory on potato sprouts produce and respond to both (S)-lavandulyl senecioate (I) and (S)-lavandulyl isovalerate (II).

Inhibitory furanone produced by the biocontrol agent Trichoderma harzianum

Abstract An isolate of Trichoderma harzianum secretes substances into the growth medium which inhibit the growth of microorganisms. Three of these substances were isolated and one was identified as 3-(2-hydroxypropyl)-4-(2-hexadienyl)-2(5H)-furanone, a new natural product.

Withaminimin, a withanolide from Physalis minima

Abstract The structure of withaminimin, a new ergostane-type steroid from Physalis minima, was established by spectral analysis (1H and 13C NMR, MS) and chemical transformations, as (20S,22R)-15α-acetoxy-5α,6β,14α-trihydroxy-1-oxowitha-2,16,24-trienolide. An unusual MH2O+ quasi-molecular ion was observed in the chemical ionization mass spectrum of the natural product.

Antifungal terpenoids produced by cypress after infection by Diplodia pinea f. sp. cupressi

Abstract Two antifungal terpenoids, 6-isopropyltropolone β-glucoside and 5-(3-hydroxy-3-methyl- trans -1-butenyl)-6-isopropyl-tropolone β-glucoside, named by us cupressotropolone A and B, respectively, were isolated from the bark of Italian cypress, in response to infection by the fungus Diplodia pinea f. sp. cupressi . These tropolone glucosides inhibited in vitro germination of spores of Diplodia pinea f. sp. cupressi, Seiridium cardinale, Alternaria alternata and Verticillium dahliae .

Synthesis of 19-noraldosterone, a potent mineralocorticoid

19-Noraldosterone has been prepared for biological re-evaluation through an extension of a recent synthesis of 19-hydroxyaldosterone: 21-hydroxy-6 beta,19-epoxy-4-pregnene-3,20-dion-20-ethylene ketal-18,11 beta-lactone (1a) was acetylated and then reduced with zinc-acetic acid-isopropanol to the 19-ol 2b. Treatment with sodium acetate transposed the double bond into conjugation, and 2a thus obtained was oxidized with pyridinium chlorochromate to the 19-oxo compound 3. Decarbonylation to the 19-nor lactone 4 was effected by heating with alkali. Protection of the C-3 carbonyl was achieved by ketalization and the resulting mixture of the 5-ene and 5(10)-ene ketals 5 was reduced with DIBAH to the corresponding mixture of the hemiacetals 6. Acid hydrolysis of the latter afforded 19-noraldosterone (7), accompanied by the 18,21-anhydro ketal 8. 19-Noraldosterone in the solid state exists in the cyclic form 7b, which appears to be also the predominant isomer present under conditions of mass spectrometry. [1H]NMR indicates that in chloroform 19-noraldosterone exists mostly as an equilibrium mixture of structures 7a and 7b. Sodium periodate oxidation furnished the gamma-etiolactone 9, confirming the 17 beta configuration in 7.

Farnesyl-homogentisic acid derivatives from Otoba parvifolia

Abstract The seeds of Otoba parvifolia contain six novel compounds, apparently derived from homogentisic acid, including 3-farnesyl-2,5-dihydroxybenzaldehyde, 2-(1′-farnesyl-2′-hydroxy-5′-oxocyclohex-3′-en-1′-yl)-acetic acid lactone, 3-(1′-farnesyl-2′-hydroxy-4′-oxocyclopentan-1′-yl)-3-methoxy (and ethoxy) propanoic acid lactones and methyl esters. New spectral evidence obtained for the known furofuran lignans xanthoxylol and phillygenol, isolated from the same source, was used as a basis for comments on the structure of horsfieldin.

Synthesis of 18,19-dihydroxycorticosterone

A four-step synthesis of 18,19-dihydroxycorticosterone 5c, starting with 19,21-dihydroxy-3,20-dioxopregn-5-ene-18,11 beta-lactone-di-(ethylene ketal) 2, is presented. Reduction of 2 with sodium aluminum bis-(methoxyethoxy)hydride gave 11 beta,18,19,21-tetrahydroxy-pregn-5-ene-3,20-dione-di-(ethylene ketal) 3a. Acetylation furnished the corresponding 18,19,21-triacetate 3b, which on treatment with a mixture of perchloric and acetic acids gave 18,19-dihydroxycorticosterone 18,19,21-triacetate 4b. Mild saponification yielded the title compound which, on the basis of ir and nmr spectra, exists as one C-20 isomer of the hemiacetal structure 5c. Periodate oxidation of 5c gave the expected 11 beta, 19-dihydroxy-3-oxoandrost-4-ene-17 beta, 18-carbolactone 6b.

18,21-Anhydroaldosterone and derivatives

18,21-Anhydroaldosterone 8, 18,21-anhydro-19-noraldosterone 9, and 3 alpha, 5 beta-tetrahydro-18,21-anhydro-19-noraldosterone 13, which may be present in acid-processed urine, were prepared by cleaving their 20-ketal derivatives 2, 3, and 12 with hot mineral acid. Compounds 8 and 9 were also made by direct dehydration of aldosterone 5 and 19-noraldosterone 10 in good yield. The reverse ring opening of 8 to 5 could be carried out in moderate yield with an acetic acid-acetic anhydride-perchloric acid mixture, while an analogous ring opening of 9 gave only a poor yield of 10.