Study on the Polar Extracts of Dendrobium nobile, D. officinale, D. loddigesii, and Flickingeria fimbriata: Metabolite Identification, Content Evaluation, and Bioactivity Assay

The polar extract of theDendrobiumspecies orF. fimbriata(a substitute ofDendrobium), between the fat-soluble extract and polysaccharide has barely been researched. This report worked on the qualitative and quantitative studies of polar extracts fromD. nobile,D. officinale,D. loddigesii, andF. fimbriata. Eight water-soluble metabolites containing a new diglucoside, flifimdioside A (1), and a rare imidazolium-type alkaloid, anosmine (4), were identified using chromatography as well as spectroscopic techniques. Their contents in the four herbs were high, approximately 0.9–3.7 mg/g based on the analysis of quantitative nuclear magnetic resonance (qNMR) spectroscopy. Biological activity evaluation showed that the polar extract ofF. fimbriataor its pure component had good antioxidant and neuroprotective activity; compounds1‒4and shihunine (8) showed weak α-glucosidase inhibitory activity;4and8had weak anti-inflammatory activity. Under trial conditions, all samples had no cytotoxic activity.Keywords:Dendrobium;Flickingeria fimbriata;qNMR;α-glucosidase inhibition;antioxygenation;neuroprotection