Phytochemical and biological investigations on two Nepeta species: Nepeta heliotropifolia and N. congesta subsp. cryptantha

Abstract

In the present study, the essential oil and aroma compositions of Nepeta heliotropifolia (NH) and N. congesta subsp. cryptantha (NC) were determined by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detector (GC/FID), and their phenolic compounds by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In addition, antioxidant, cytotoxic, anticholinesterase, urease, and tyrosinase activities of essential oils obtained from NH and NC aerial parts and ethanol extracts prepared from different parts of NH and NC were investigated. The major constituent of water-distilled essential oils was found to be germacrene D (36.7% and 38.5%, respectively), and their main aroma component was eucalyptol (48.0% and 24.7%, respectively). Among the studied parts of NH and NC, their flowers extracts were found to be the richest in phenolic compounds and in which the most abundant compound was rosmarinic acid (8,909.91 and 4,317.20 μg/g, respectively). NH and NC flower extracts exhibited also strong antioxidant activity in DPPH, ABTS, and CUPRAC assays. Among the tested samples, NH essential oil indicated the best cytotoxic effect against PDF, HT-29, and MCF-7 (IC₅₀ 52.34, 25.89, and 44.70 μg/ml, respectively), and the highest butyrylcholinesterase (77.21 ± 1.12% inhibition) and moderate acetylcholinesterase (41.36 ± 0.69% inhibition) inhibitory activities. PRACTICAL APPLICATIONS: This is the first report on the essential oil and aroma compositions, the phenolic compounds, the antioxidant with total phenolic and flavonoid contents, cytotoxic, anticholinesterase, urease, and tyrosinase activities of Nepeta heliotropifolia and N. congesta subsp. cryptantha, except for their essential oil compositions. The reported results suggested that Nepeta heliotropifolia and N. congesta subsp. cryptantha flowers being rich in rosmarinic acid and having strong antioxidant potential, and NH essential oil possessing significant cytotoxic and butyrylcholinesterase inhibitory effect could be source for nutraceutical, food, and drug industries.

Keywords: Nepeta; LC-MS/MS; aroma; biological activities; essential oil; phenolic compound.