Petroleum ether (PE) and methanolic extracts of nine wild plant species were tested in vitro for their antimycotic activity against eight phytopathogenic fungi. The efficacy of PE extracts against all pathogens tested was higher than that of methanolic extracts. Wild marjoram (Origanum syriacum) PE extract showed the highest and widest range of activity. It resulted in complete inhibition of mycelial growth of six of eight fungi tested and also gave nearly complete inhibition of spore germination of the six fungi included in the assay, namely, Botrytis cinerea, Alternaria solani, Penicillium sp., Cladosporium sp., Fusarium oxysporum f. sp. melonis, and Verticillium dahlia. The other plant extracts showed differential activities in the spore germination test, but none was highly active against mycelial growth. Inula viscosa and Mentha longifolia were highly effective (>88%) in spore germination tests against five of six fungi tested, whereas Centaurea pallescens, Cichorium intybus, Eryngium creticum, Salvia fruticosa, and Melia azedarach showed >95% inhibition of spore germination in at least two fungi. Foeniculum vulgare showed the least antimycotic activity. Fractionation followed by autobiography on TLC plates using Cladosporium sp. as a test organism showed that O. syriacum PE extracts contained three inhibition zones, and those of Inula viscosa and Cichorium intybus, two, whereas the PE extracts of the remaining plants showed each one inhibition zone. Some of the major compounds present in these inhibition zones were identified by GC-MS. The possibility for using these extracts, or their mixtures, to control plant diseases is discussed.

Photoinduced intramolecular charge separation across proline-bridged donor-acceptor complexes of the type Pyr-(Pro)n-DMPD (where Pyr=pyrene-1-sulfonyl and DMPD=N,N-dimethyl-1,4-phenylenediamine) was studied. The steady-state emission spectrum for n=0, 1, 2, 3 showed an increase in emission intensity with the number of proline residues. Time-dependent emission measured by streak camera showed increasing emission signal amplitude with increasing n, along with a decrease in decay rate. In all these studies, Pyr-Pro was used as a control complex for the decay of the excited pyrene acceptor moiety without the donor DMPD. Detailed photon counting experiments carried out in DMF/water, DMF, and toluene showed single-exponential kinetics for n=0, 1 and multiexponential kinetics for n=2, 3. Rate constants observed in DMF are for n=0, k=approximately 5x10(10) s(-1); n=1, k=9.70x10(8) s(-1); n=2, k=35.9x10(8) s(-1) (70%) and 5.58x10(8) s(-1) (30%); and n=3, k=16.6x10(8) s(-1) (55%) and 3.87x10(8) s(-1) (45%). These results show that a significant percentage of the n=2 and n=3 molecules undergo faster electron transfer than for the n=1 case. Conformational analysis for Pyr-(Pro)n-DMPD molecules in water showed that whereas only one conformation is possible for n=1, eight are possible for n=2, and 32 are possible for n=3. Calculation of the free energy and electronic coupling for these conformers in water showed that only a few of these conformations have the appropriate energy and electronic coupling to be observed in the experimental time window from 20 ps to 20 ns. Assignment of the conformers undergoing electron transfer in Pyr-(Pro)n-DMPD for n=2 and 3 was based on the values for the n=1 case, for which the measured rate constant is approximately 10(9) s(-1) and the calculated electronic coupling matrix element Hda is 297 cm(-1). The similarity in ground state energy between the cis and trans conformers for n=2 and 3, their use in aqueous-organic and organic solvents, and the nature of the Pyr and DMPD acceptor and donor groups could be contributing causes for the multiexponential kinetics, which was not observed for the metal ion derivatives of proline peptides studied earlier in aqueous solution.

The binding between a ruthenium polypyridine guest RuG2, (where Ru = 4,4'-di-tert-butyl-bpy) 2 Ru (bpy = 2,2'-bipyridine) and G2 = 5-[4-(4'-methyl)-2,2'-bipyridyl]methyl-2,4,6-(1H,3H,5H)-pyrimidinetrione, and a series of host acyl derivatives of 3,5-bis[(6-aminopyrid-2-yl) amino]carbonylpyridine (R/H = n-Pr/H, phenyl/H, CF 3 /H, t-Bu/H, -(CH 2 ) 3 -CO 2 À H) and 3,5-bis[(6-amino-4-isopropoxypyrid-2-yl)amino]carbonylpyridine diacetyl derivative (R/X = CH 3 /i-OPr) was studied by fluorescence and NMR titrations. The RuG2 (which exists in the enolate form in the presence of the hosts) forms a number of H-bonds involving the amide groups of the hosts and the carbonyl groups of the G2 for all the hosts studied. Specific 1:1 association between RuG2 and all the complementary hosts was observed with binding constants, K a (l mol À1 ), for R/H in CH 2 Cl 2 of 3 Â 10 5 (t-Bu/H), 5 Â 10 6 (Ph/H), 3 Â 10 7 (n-Pr/H), 9 Â 10 7 (CF 3 /H) and b10 8 [-(CH 2 ) 3 CO 2 H) and for R/X of 4 Â 10 8 (Me/i-OPr). Similar, but weaker, binding was also observed in solvents of higher donor number such as d 6 -acetone, d 3 -acetonitrile and d 6 -DMSO with R/X = Me/i-OPr host showing the highest binding constant in CH 2 Cl 2 , d 6 -acetone and d 6 -DMSO. Differences in the binding constants of the ruthenium guest RuG2 to these hosts are analyzed in terms of the steric, electronic and solvational changes in the structure of the host amide substituents and the polarity of the solvents used.

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