RESUMEN

Essential oils (EOs) extracted from aromatic and medicinal plants have the potential to inhibit the growth of various pathogens and, thus, be useful in the control of dangerous diseases. The application of environmentally friendly approaches to protect agricultural and forestry ecosystems from invasive and hazardous species has become more significant in last decades. Therefore, the identification and characterization of essential oils with a strong inhibitory activity against aggressive and widespread pathogens are of key importance in plant protection research. The main purpose of our study is to evaluate the impact of essential oils originating from different genotypes of bee balm, mint, and marigold on Botrytis cinerea, Fusarium solani, and Phytophthora pseudocryptogea. Twelve essential oils, including five EOs originating from Monarda fistulosa, one oil each from Monarda russeliana, Mentha longifolia, Mentha piperita, Tagetes patula, and Tagetes erecta, and two EOs from Tagetes tenuifolia were derived by steam or water distillation. The chemical composition of the tested EOs was determined by GS-MS analyses and their corresponding chemotypes were identified. The most effective against all three pathogens were determined to be the EOs originating from M. fistulosa and M. russeliana. B. cinerea, and P. pseudocryptogea were also significantly affected by the M. piperita essential oil. The most efficient EOs involved in this investigation and their potential to control plant pathogens are discussed.

RESUMEN

INTRODUCTION: Centranthus kellereri is a Bulgarian endemic plant species, found only in two locations in the world: The Balkans Mountains (Stara Planina), above the town of Vratsa, and The Pirin Mountains, above the town of Bansko, Bulgaria. Being endemic and endangered species precluded any significant research on it. The hypothesis of this study was that the populations of C. kellereri may represent genetically, phytochemically, and morphologically distinct forms and these will differentiate from C. ruber. Furthermore, C. kellereri possibly imperfect embryology may preclude its more widespread distribution under natural conditions. RESULTS: This study revealed the phytochemical profile, antioxidant activity, embryology, surface microstructural morphological traits, and genetic differences between the C. kellereri plants from the only two natural populations and compares them to the ones of the related and better-known plant C. ruber. The essential oil (EO) content in aboveground plant parts and in roots was generally low and the EO composition varied significantly as a function of plant part, year of sampling, location, and species. Methylvaleric acid was a major EO constituent in the C. kellereri EO, ranging between 60.2% and 71.7% of the total EO. The EO included monoterpenes, sequiterpenes, long-chain alkanes and fatty acids. Phytochemical analyses of plant tissue revealed the occurrence of 32 compounds that were tentatively identified as 6 simple phenolics, 18 flavonoids, 1 quinone, 1 lipid, 1 alkaloid, 2 diterpenes, and 3 triterpenes. There were differences in detected compounds between the C. kellereri plants at the two locations and between the roots and shoots in both species. The total phenols and flavonoids varied between the two species but were also dissimilar between the plants from the two populations of C. kelleri. Free radical scavenging activity, measured with ABTS and DPPH in aqueous and methanol extracts, had similar values; however, overall, C. kellereri from Vratsa showed the highest antioxidant activity while C. ruber had the lowest activity. Genetic analyses showed a clear differentiation between C. kellereri and C. ruber, and between the two populations of C. kellereri. Embryological studies revealed the peculiarities of the male and female generative spheres of the two species that were defined as being sexually reproducing. The pollen had high viability; however, the low viability of seeds demonstrated possible high sensitivity of C. kellereri to the environmental conditions, perhaps the main factor modifying and restricting the population sizes. The SEM analyses exposed differences in surface microstructural traits between the species (C. kellereri and C. ruber) but also between the two populations of C. kellereri. The observed dissimilarities in genetic makeup, micromorphological characteristics, and phytochemical composition strongly indicate that the two populations can be classified as distinct subspecies or varieties of C. kellereri; var. pirinensis and var. balkanensis. Further research is needed to introduce C. kellereri into culture and develop it as a high-value specialty crop or ornamental in order to conserve C. kellereri natural populations. C. kellereri may be utilized as a source for phytochemicals of interest and as an ornamental plant like C. ruber; however, it may have a greater environmental plasticity and adaptation as evidenced by its current locations.

Asunto(s)

Antioxidantes , Aceites Volátiles , Antioxidantes/análisis , Extractos Vegetales/química , Fitoquímicos/química , Aceites Volátiles/química , Fenoles/análisis , Flavonoides/análisis

RESUMEN

The genus Nepeta, belonging to the family Lamiaceae, includes about 300 species, most of which are used in folk medicine due to their pronounced biological properties. The aim of the present study was to evaluate the agrobiological characteristics of Nepeta transcaucasica (N. transcaucasica) Grossh. and Nepeta cataria (N. cataria) L., cultivated in Bulgaria, and obtain their essential oils and determine their antimicrobial and antioxidant activities. The agrobiological characteristics of the two species growing in Kazanlak were analyzed; therefore, high variability in the population of N. transcaucasica and comparative homogeneity in N. cataria was shown. The species N. transcaucasica contained 0.28% essential oil with main components ß-citronellol (52.05%), eucalyptol (7.34%), ß-citronellal (6.06%), germacrene D (5.45%), (Z)-ß-ocimene (5.14%), and ß-caryophyllene (3.06%). The species N. cataria consisted of 0.19% essential oil with main components ß-citronellol (26.31%), geraniol (15.92%), neral (11.45%), nerol (9.56%), carvacrol (6.04%), and ß-citronellal (5.35%). The antibacterial activity against Gram-positive bacteria Listeria monocytogenes and Staphylococcus aureus and Gram-negative bacteria Escherichia coli (E. coli) and Salmonella enterica subsp. enterica serovar Abony was determined. The essential oils showed antimicrobial activity only against E. coli. The diameters of the inhibition zones were found to be 26 mm for the species N. transcaucasica and 10 mm for the species N. cataria. The antioxidant activity of the two essential oils was also determined by four different methods, DPPH, ABTS, FRAP, and CUPRAC, with the highest values for the ABTS radical, for the species N. transcaucasica (48.72 µM TE/mL), and the species N. cataria (310 µM TE/mL).