Chemoprofiling of Himantoglossum robertianum (Loisel.) P. Delforge leaves reveals predominance of gastrodigenin and structurally related compounds

Purpose: The purpose of this study was to phytochemically profile Himantoglossum robertianum leaves. In fact, despite its wide distribution and its use in traditional medicine, this orchid is still understudied and little is known about its phytochemicals. Methods: The analyses were performed by 1H NMR fingerprinting, elucidated by further 2D NMR and UHPLC-MS experiments. Both primary and secondary metabolites were qualified and quantified. The study was carried out comparing six natural populations by metabolomics approach, allowing further considerations on the influence of the environment on the concentration of metabolites. Results: This work brings to light a surprising phytochemical parallel between H. robertianum and the medicinal orchid Gastrodia elata. In fact, the most abundant specialized metabolites resulted: gastrodigenin, gastrodin, bis(4-hydroxybenzyl)ether, parishin A, parishin C, and parishin E. Interestingly, these metabolites are all known for their potential in the treatment of neurological disorders and are, indeed, the active principles of Gastrodia elata, an important orchid used in Traditional Chinese Medicine. The active metabolites were present in all the natural populations, where only slight variations in their concentration were revealed. Conclusion: Mapping the metabolome of H. robertianum leaves has provided new insights into the study of orchids, including diagnostic signals for rapid identification of gastrodigenin-like compounds directly from the 1H NMR profile of a crude extract. From a bioprospecting perspective, finding active metabolites in leaves makes the plant source more valuable than the perennial hypogeal organs that are usually the herbal drug of orchids (i.e. G. elata).