Abstract
The present investigation was focused on the study of the chemical composition variability and biological activities of the essential oils from Clinopodium nepeta subsp. nepeta and subsp. glandulosum. Essential oils extraction was performed using hydrodistillation and the separation of the constituents was carried out by gas chromatography coupled with mass spectrometry (GC-MS). Antifungal activities were tested against Aspergillus flavus, Aspergillus terreus, Microsporum canis, Microsporum gypseum, Trichophyton mentagrophytes, and Candida albicans. Toxicity and repellency were evaluated against the stored product pests Tribolium confusum and Sitophilus zeamais. Both essential oils were characterized by a high content of oxygenated monoterpenes. Piperitone ranks first in the subspecies nepeta and piperitenone oxide is the dominant constituent in the subspecies glandulosum. All tested samples displayed noteworthy antifungal properties, with the highest activity observed for the essential oil of C. nepeta subsp. glandulosum, collected in Béni-M’tir, against T. mentagrophytes (MIC = 40 µg/mL). The essential oil samples of C. nepeta subsp. glandulosum were strongly repellent to the insect species (PR > 80%, after 2h) and highly toxic to S. zeamais reaching 97.5%–100% mortality after 24 h of exposure. In conclusion, this study showed considerable intra-specific changes in the quality of C. nepeta essential oils, which is reflected in different rates of antifungal and insecticidal activity.
Highlights
All across the globe, environmental problems such as soil and water pollution and food contamination are continuously increasing, inducing many disasters and human tragedies.Molecules 2020, 25, 2137; doi:10.3390/molecules25092137 www.mdpi.com/journal/moleculesThe excessive and indiscriminate use of available pesticides to control the losses of stored crops and to reduce insect-borne diseases as malaria, filaria and trypanosomiasis induced disturbances in ecosystem functioning [1,2]
The aim of this paper was to compare the phytochemical profile and to test the biological efficiency of the essential oils extracted from C. nepeta subsp. nepeta and C. nepeta subsp. glandulosum growing in different localities in North and North-western Tunisia (Table 1)
The main purpose of this study was to investigate for the first time the phytochemical variability in Tunisian C. nepeta essential oils taking into consideration the subspecies nepeta and glandulosum and their environmental origin (Béni-M’tir and Bizerta), and its effect on the biological properties
Summary
Environmental problems such as soil and water pollution and food contamination are continuously increasing, inducing many disasters and human tragedies.Molecules 2020, 25, 2137; doi:10.3390/molecules25092137 www.mdpi.com/journal/moleculesThe excessive and indiscriminate use of available pesticides to control the losses of stored crops and to reduce insect-borne diseases as malaria, filaria and trypanosomiasis induced disturbances in ecosystem functioning [1,2]. According to the harvesting time and the environment in which they are found, the same plant species or subspecies may present different chemical compositions of essential oils [10]. The nature of the produced secondary metabolites and essential oils influences the mechanisms of actions and determines the medicinal and economic utility of various plants. In this context, differences in essential oils productivity, including an increase or decrease in the yields, and variation of the chemical composition depending on harvesting phase (vegetative, pre-flowering, flowering and fruiting), as well as the plant geographical origin have been previously investigated [11,12]
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