Cytotoxic, α‑Glucosidase, and Antioxidant Activities of Flavonoid Glycosides Isolated from Flowers of Lotus lanuginosus Vent. (Fabaceae)

Objective: The objectives of this study were to isolate secondary metabolites from the flowers of L. lanuginosus Vent., elucidate their structures, and evaluate their biological activities. Materials and Methods: Chromatography methods of the n‑butanolic extract of fresh flowers of L. lanuginosus led five products (1–5). Their structures were characterized based on spectroscopic evidence (ultraviolet, infrared, high‑resolution mass spectrometry, and nuclear magnetic resonance) and compared to the spectral data signaled in the literature. Cytotoxic activities of the isolated compounds were evaluated against HCT‑116 and MCF‑7 cancer cell lines. α‑glucosidase and antioxidant activities were also performed. Results: Five compounds were isolated and characterized for the first time in L. lanuginosus Vent.: Lotaustralin (1), kaempferol-7-O-α-L-rhamnopyranoside (2), kaempferol-3-O-apiofuranosyl-7- O-rhamnopyranosyl (3), isorhamnetin-3-O-rutinoside (4), and kaempferol-3- O-(2’’-β-D-xylopyranosyl)-α-L-rhamnopyranoside-7-O-α-L-rhamnopyranoside (5). The results of cytotoxic activities against HCT‑116 and MCF‑7 cancer cell lines of the isolated compounds were presented. Among them, compounds 2 and 3 showed a moderate activity on HCT‑116 cancer cells with half maximal inhibitory concentration values ranging between 8 and 31.5 μM. Moreover, compounds (2–5) displayed significant antioxidant and moderate α‑glucosidase activities. Discussion and Conclusions: All the isolated products (1–5) are signaled for the first time in L. lanuginosus Vent. Among flavonoids glycosides, compound 2 showed the best cytotoxic activity. By the end of the present study, L. lanuginosus have been characterized as a highly cyanogenic plant and as an important source of polyphenols and flavonoids.