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

Abstract

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.

Keywords: Asteraceae; Pulicaria crispa; allelopathy; chemometric analysis; chemotype.

Figure 1

Classification of the chemical compounds of Pulicaria undulata EOs of Saudi and Egyptian ecospecies. (a) various classes and (b) oxygenated and non-oxygenated compounds.

Figure 2

Chemometric analysis of the essential oil of different Pulicaria undulata ecospecies: (a) agglomerative hierarchical clustering (AHC) and (b) principal components analysis (PCA). SA: Suadi, EG: Egyptian, IR: Iranian, AL: Algerian, SU: Sudanian, and YE: Yemeni. The blue color represents the present samples.

Figure 3

Phytotoxic effect of the EOs extracted from the aerial parts of both Saudi and Egyptian ecotypes of P. undulata on the (a) germination of seeds, (b) shoot growth, and (c) root growth of the weed Bidens pilosa. Different letters on each line mean significant differences (one-way randomized blocks ANOVA). Data are mean value (n = 3), and the bars represent the standard error. * p < 0.05, ** p < 0.01.

Figure 4

Phytotoxic effect of the EOs extracted from the aerial parts of both Saudi and Egyptian ecotypes of P. undulata on the (a) germination of seeds, (b) shoot growth, and (c) root growth of the weed Dactyloctenium aegyptium. Different letters on each line mean significant differences (one-way randomized blocks ANOVA). Data are mean value (n = 3) and the bars represent the standard error. * p < 0.05, ** p < 0.01.