Thymus longedentatus essential oil and methanolic extract: Chemical composition and activity against filamentous plant pathogens

Milena Nikolova; Aneta Lyubenova; Ina Aneva

Milena Nikolova

, Aneta Lyubenova

, Ina Aneva

Abstract: Thymus longedentatus (Degen & Urum.) Ronniger is a Balkan endemic species with a lemon-like odor that has a limited distribution in Bulgaria. The species has been studied phytochemically, and was successfully cultivated in the ex situ collection of IBER, BAS in the last years. The reported strong herbicidal properties for the species' essential oil (EO) led us to examine it for other pesticidal actions. The present study aimed to determine the chemical composition of Thymus longedentatus EO and methanolic extract (ME) and to evaluate their growth inhibitory activity against filamentous fungal and oomycete plant pathogens. The chemical composition of EO and ME was studied, using gas-chromatography/mass spectrometry (GC/MS). The antifungal activity was evaluated by conducting in vitro bioassay towards economically important plant pathogens: Botrytis cinerea, Fusarium oxysporum var. fragariae, Fusarium oxysporum var. cyclaminis, Phytophthora cryptogea and Phytophtora nicotianae. Citral isomers - neral (26.8%) and geranial (43.1%) were identified as the main components of the EO profile. Rosmarinic acid, chlorogenic acid, feruloylquinic acid, oleanolic acid, ursolic acid, micromeric acid, arbutin, geranic acid and hydroquinone were the main secondary metabolites in the methanolic extract. A strong inhibiting effect against Botrytis cinerea, Phytophthora nicotianae and Phytophthora cryptogea was established for the essential oil. Oppositely, the methanol extract, in which the Citral isomers were not found, did not affect the mycelial growth of the tested plant pathogens. The potency of the essential oil rich in Citral isomers, against oomycete and fungal plant pathogens is revealed.

Keywords: bioassay; Botrytis cinerea; Citral isomers; Fusarium oxysporum; Phytophthora

Citation: Nikolova, M., Lyubenova, A. & Aneva, I. (2026). Thymus longedentatus essential oil and methanolic extract: Chemical composition and activity against filamentous plant pathogens. Bulg. J. Agric. Sci., 32(1), 130–136

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Date published: 2026-02-25

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