Non-polar secondary metabolites and essential oil of ex situ propagated and cultivated Sideritis syriaca L. subsp. syriaca (Lamiaceae) with consolidated identity (DNA Barcoding): towards a potential new industrial crop

Abstract Over the past decade, perennial plants of the genus Sideritis L. have attracted great scientific interest and they have become the subject of several studies, including the European Union’s herbal monograph. The present study aimed to explore the identity of a biotype of S. syriaca subsp. syriaca documented with DNA barcoding, investigated its macro- and micro- propagation and to study the chemical profile of the dichloromethane extract, as well as of the Essential Oil (EO) of the ex situ propagated and cultivated plant material. An improved in vitro propagation protocol, as well as pioneer effective propagation with cuttings (both at commercially acceptable rates) are provided for a DNA-barcoded biotype of Sideritis syriaca L. subsp. syriaca (malotira, Cretan mountain tea) which is a single-island endemic plant of Crete (Greece), with declining wild populations due to over collection. From the aerial parts of ex situ propagated and cultivated material (harvested in July) two phytosterols (β-sitosterol and stigmasterol), two ent-kaurene diterpenes; siderol and eubotriol, as well as one methylated flavone (xanthomicrol) have been isolated. This is the first time that eubotriol has been isolated from this taxon. The structures of the isolated compounds have been established by spectroscopic means and the complete Nuclear Magnetic Resonance (NMR) assignments for eubotriol are presented. Moreover, the essential oil was obtained by hydrodistillation of the plant material during the flowering stage and was analyzed by Gas Chromatography-Mass Spectrometry (GC–MS). Forty-four compounds were identified. The monoterpene hydrocarbons constituted the major fraction of the essential oil (34.2%), while β-phellandrene (18.5%) and kaur-15-ene (or ent-kaur-15-ene; 17.3%) were the main compounds. In conclusion, the above results document the first necessary steps taken for the ex situ conservation and sustainable exploitation of a new industrial crop with promising potential.