Leaves micromorphology, chemical profile, and bioactivity of in vitro-propagated Nepeta cyrenaica (Lamiaceae)

IntroductionThe endemic species Nepeta cyrenaica Quezel & Zaffran, native to northeastern Libya, is valued as an important honey-bearing plant. ObjectivesThis study was aimed to examine the micromorphology, phytochemistry, and bioactivity of in vitro-propagated N. cyrenaica for the first time. Materials and MethodsThe leaf indumentum was examined using light and scanning electron microscopy and further characterised for histochemistry. The chemical composition of essential oil (EO) was performed using GC-MS analysis, while dichloromethane (DCM), methanol (ME), ethanol (ET), and aqueous (AQ) extracts were analysed using qualitative and quantitative LC/MS analyses. The antioxidant activities of EO and extracts were assessed using three parallel assays, while enzyme-inhibiting effects were evaluated against four enzymes. ResultsThe leaves bear various types of glandular trichomes, with lipophilic secretion predominating. The main EO component of EO was 1,8-cineole. A considerable number of phenolics and iridoids were tentatively identified in the ME extract. Quantitative LC/MS analysis confirmed that ferulic acid, rosmarinic acid, and epigallocatechin gallate were present in the highest amount in the extracts, in which three iridoids were also quantified. Although the ME extract contained the highest amount of polyphenolics and iridoids, the DCM extract showed the best overall biological potential. Additionally, EO exerted the strongest acetylcholinesterase and tyrosinase inhibition. ConclusionThis study demonstrated that the endemic N. cyrenaica can be efficiently grown under in vitro conditions, where it develops various glandular trichomes that are thought to secrete and/or accumulate bioactive compounds with valuable medicinal potential.

Automated summary

This study examined the micromorphology, phytochemistry, and bioactivity of the endemic species Nepeta cyrenaica for the first time. The plant was found to have different types of glandular trichomes on its leaves, with lipophilic secretion being predominant. The main component of the essential oil was 1,8-cineole. Various phenolics and iridoids were tentatively identified in the leaf extracts. The study demonstrated the potential medicinal value of the bioactive compounds in Nepeta cyrenaica.