Anticholinesterase, antioxidant, and beta-amyloid aggregation inhibitory constituents from Cremastra appendiculata

The tubers of Cremastra appendiculata (D. Don) Makino (Orchidaceae) are used in traditional Chinese medicine for the treatment of cancer and bacterial infections. Its 95% ethanol extract was found to display potent inhibitory activities on butyrylcholinesterase (BChE) (IC50 = 23.66 µg/mL) and β-amyloid peptide aggregation (74.09% at 100 μg/mL). Active ethyl acetate extract afforded one bibenzyl (1), four phenanthrenes (2–5), and one rotenoid (6) by a bioassay-guided isolation. Compounds 2, 3, and 5 exhibited potent BChE inhibitory effects with IC50 values of 19.66, 32.80, and 37.79 µM, respectively. Kinetic studies indicated that both 2 and 3 were mixed-type BChE inhibitors. Their strong binding affinities to BChE were further confirmed by fluorescence quenching analysis. Meanwhile, 2 and 3 showed the effective DPPH and ABTS radical scavenging activities (EC50 < 11 μM) and inhibition effect on β-amyloid peptide aggregation (64.49 and 29.50% at 20 μM, respectively), suggesting they could serve as multifunctional potential agents for AD drugs development. This paper revealed the potential medicinal and economic values of C. appendiculata and its chemical constituents in AD prevention/treatment.