Antibacterial and phytotoxic activity of the Schiff’s bases of 5-phenyl-4-amino-3-mercapto-4H-1,2,4-triazole with the donor substituents in the 4th position on heterosystem

Background. Triazoles and Schiff’s bases have a high biological activity. For the practical use of the derivatives, their low toxicity is important. The purpose of this work was to investigate the antibacterial and phytotoxic properties of Schiff’s bases of 5-phenyl-4-amino-3-mercapto-4H-1,2,4-triazole with donor substituents in the 4th position of heterosystem. Materials and methods. In the study of antibacterial activity of the derivatives, corrosion-active 4-day association cultures of ammonifying and sulfate-reducing bacteria were used as a test culture of microorganisms. Sensitivity of bacteria to derivatives was determined by diffusion method in agar using sterile paper disks according to the standard method. In the investigation of phytotoxic activity of the derivatives, Lepidium sativum of the “Ajour” cultivar was used as a test plant. Seed germination and biometric indices (length, weight of the aboveground part and roots) of 5-day sprouts were determined, the phytotoxic effect of the derivatives was calculated. Experimental data were processed using methods of mathematical statistics. Results. The introduction of substituents does not provide for an increase in antibacterial properties of the studied compounds in relation to some corrosion active ammonifying and sulfate-reducing bacteria. Low activity was observed regarding the association culture of ammonifying bacteria to the compound without substituents in the phenyl fragment and the compound with fluor as a substituent in the phenyl fragment at a concentration of 2.0%. Derivatives with the methoxyl substituent in the phenyl fragment and with the hydroxyl substituent in the phenyl fragment did not show any antibacterial activity against the association culture of ammonifying bacteria isolated from ferrosphere in meat-peptone broth. Antibacterial action against the association of sulfate-reducing bacteria Desulfovibrio orizae with organic acid-producing bacteria Anaerotignum propionicum for derivatives were not detected. Phytotoxic properties were observed for the compound with the hydroxyl substituent that influenced the processes of growth in the test plant. Conclusion. The introduction of electron-donor substituents into the basic structure did not provide for an increase in antibacterial properties against corrosive bacteria. Phytotoxic properties were observed for the compound with the hydroxyl substituent in the phenyl fragment, which influenced the L. sativum growth processes by inhibiting growth of the above-ground part and roots. Other compounds either did not show any action, or demonstrated a weak stimulating effect on the growth and development of the test plant.

Study of Phytophthora infestans Mont. de Bary isolates in the planting of potatoes

Relevance. One of the most common diseases of potatoes and other nightshade family species is late blight caused by a pathogenic oomycete of the Phytophthora infestans (Mont.) de Bary. At least 100 species of phytophthora have been described in nature, affecting a wide range of plant species. The phytophthora population is heterogeneous and is represented by races, as well as different types of mating. This leads to a rapid adaptation of the pathogen and the emergence of new, more aggressive, and resistant races. Phytophthora is a parasite, the damage from which cannot be avoided within the organic farming framework. Therefore, it is particularly important to know the pathogenesis and racial composition of phytophthora in each individual region of Solanaceae cultivation.Research methodology. Differentiation and collection of material from the natural population were carried out using potato varieties with known R-genes in the genome. Isolation and introduction into the culture were carried out from leaves with the dampening chambers method, followed by cultivation on nutrient media. The pathogen was identified by microscopic analysis. Culture filtrates were obtained on the liquid nutritious medium, followed by liquid filtration and autoclaving. Phytotoxic activity was determined by the effect on the seedlings of the nightshade, grass, and pea families by the standard method. Molecular genetic analysis of the isolates was carried out by ISSR analysis; the primer, amplification mixture, and temperature profile of the reaction were selected according to the literature data; the calculation of genetic characteristics was carried out using POPGENE software packages.Results. Samples of seven Phytophthora infestans isolates were collected and introduced into culture. As a result of in vitro cultivation, morphological differences were revealed, expressed in the structure and color of the mycelium, the shape of the colonies, the nature of sporulation, the color of the reverse, and the medium under the colonies. The genetic differences of the natural phytophthora material introduced into the culture, collected from potato varieties with single resistance genes (R1, R3, R4), were revealed. Differences in the phytotoxic activity of the studied isolates' cultural filtrates were revealed. The isolated isolates demonstrate differentiation at the phenotypic, genetic and physiological levels, which allows us to speak about their belonging to races.

Agave Steroidal Saponins as Potential Bioherbicides

Agave saponins are a valuable resource for the prospective development of new forms of agrochemicals. The extraction method was optimized and applied to 17 Agave species. Thirteen saponin fractions (SFs) were assayed on wheat etiolated coleoptiles, and analysed using UPLC-QTOF-MSE, NMR spectroscopy and the HMBC method for aglycone identification (HMAI). Six SFs were assayed on standard target species (STS) and weeds. The new extraction method reduces costs to obtain SFs with the same activity. The tested SFs assayed on etiolated wheat coleoptiles that belong to the subgenus Agave were among those with the highest activity levels. The combination of HMAI together with UPLC-MS allowed the identification of 20 aglycones in the SFs, and no isolation or hydrolysis of the saponins was required. A Principal Component Analysis (PCA) showed that for the active SFs the structural key would be the length of their sugar chain. The presence of a carbonyl group at C-12 implied an enhancement in phytotoxic activity. Six SFs were assayed on seeds, and no activity on Solanum lycopersicum (tomato) was observed; however, good activity profiles were obtained on weed E. crus-galli (IC50 < 80 ppm), better than the commercial herbicide Logran®. These findings represent a possible lead for the development of natural herbicides through the use of saponins of subgenus Agave species.

Metabolic Profile and Mycoherbicidal Activity of Three Alternaria alternata Isolates for the Control of Convolvulus arvensis, Sonchus oleraceus, and Xanthium strumarium

Alternaria alternata isolates C1, S1, and X3 were isolated respectively from the weeds Convolvulus arvensis, Sonchus oleraceus, and Xanthium strumarium in Algiers during 2016 and identified by morphological and molecular analyses. The aim of this investigation was to chemically characterize the exometabolome of these fungi and to evaluate the myco-herbicidal potential of their culture filtrates, crude extracts, or fractions towards target weeds. Results revealed a great heterogeneity in the biochemical profiles of the exometabolome with the remarkable presence of two compounds: tenuazonic acid (TeA) and triprenyl phenol-7 (SMTP-7). To the best of our knowledge, SMTP-7—found in all the isolates—as well as 12-methoxycitromycin detected in the culture filtrate of isolate C1, have never been reported to be produced by A. alternata. Some fractions of isolates C1 and S1 showed symptoms (necrosis and chlorosis) on the detached leaves of C. arvensis and S. oleraceus, respectively with up to 100% phytotoxic effect at low concentration. In conclusion, biochemical characterization revealed great difference of C1, S1, and X3 exometabolomethat is likely to explain the difference in their phytotoxic activity. Some fractions (d1, e1, h1, i1, a2, and f2) of isolates C1 and S1 of A. alternata caused severe necrosis and chlorosis on the injured detached leaves of C. arvensis and S. oleraceus, respectively.

Comparative Chemical Profiles and Phytotoxic Activity of Essential Oils of Two Ecospecies of Pulicaria undulata (L.) C.A.Mey

The Asteraceae (Compositae) family is one of the largest angiosperm families that has a large number of aromatic species. Pulicaria undulata is a well-known medicinal plant that is used in the treatment of various diseases due to its essential oil (EO). The EO of both Saudi and Egyptian ecospecies were extracted via hydrodistillation, and the chemical compounds were identified by GC–MS analysis. The composition of the EOs of Saudi and Egyptian ecospecies, as well as other reported ecospecies, were chemometrically analyzed. Additionally, the phytotoxic activity of the extracted EOs was tested against the weeds Dactyloctenium aegyptium and Bidens pilosa. In total, 80 compounds were identified from both ecospecies, of which 61 were Saudi ecospecies, with a preponderance of β-pinene, isoshyobunone, 6-epi-shyobunol, α-pinene, and α-terpinolene. However, the Egyptian ecospecies attained a lower number (34 compounds), with spathulenol, hexahydrofarnesyl acetone, α-bisabolol, and τ--cadinol as the main compounds. The chemometric analysis revealed that the studied ecospecies and other reported species were different in their composition. This variation could be attributed to the difference in the environmental and climatic conditions. The EO of the Egyptian ecospecies showed more phytotoxic activity against D. aegyptium and B. pilosa than the Saudi ecospecies. This variation might be ascribed to the difference in their major constituents. Therefore, further study is recommended for the characterization of authentic materials of these compounds as allelochemicals against various weeds, either singular or in combination.