Exogenous applications of caffeic acid affect the essential oils of marigold cultivars planted on sandy soil

Marigold essential oil (EO) has various applications in food and pharmaceutical industries. Expanding the production of marigold cultivars (CULTs) led to several variations in EOs, and thus a diversity of their activities. Egyptian sandy soils are subjected to abiotic stresses that impede the cultivation of aromatic plants. Caffeic acid (CA) reduces the negative effects of environmental stresses. Consequently, this research was done to determine how CA affected marigold CULT flowers [Fiesta Gitana (FIG) and Crown Orange (CRO)] and their EOs on sandy soil to find out the extent of the opportunities for expanding their cultivation in sandy soils. CA was applied to both CULTs at 0, 20, 40, 60, and 80 mg L −1 . Obtained results showed that CA treatments produced variations in the flower yields and EOs of both CULTs. The major constituents of CRO EO were α-cadinol, γ-cadinol and Δ-cadinene; whereas, FIG EO’s main components were similar to those of CRO EO, besides t -cadinol which is distinguished as a fourth main compound. Sesquiterpenes (hydrocarbons, SCH and oxygenated, SCHO) were the major classes of FIG and CRO EOs. The maximum flower and EO yields, as well as the highest levels of Δ-cadinene and t -cadinol were produced by plants treated with 80 mg L −1 CA. The highest concentration of α-cadinol was found in EO isolated from plant flowers that had been subjected to 40 mg L −1 CA. It may be concluded that CA can be added to marigold CULTs so as to lessen the negative consequences of stress-related variables on sandy soil; in addition, it can increase the sources of EOs.