Elsholtzia rugulosa: Phytochemical Profile and Antioxidant, Anti-Alzheimer's Disease, Antidiabetic, Antibacterial, Cytotoxic and Hepatoprotective Activities

Elsholtzia rugulosa Hemsl., a species of the Labiatae family, has a long history of use as a honey plant, herbal tea, and folk medicine in China. However, little is known about its composition and biological activities. The present study aimed to investigate the total phenol and flavonoid contents, phytochemical composition, and multiple biological activities of this plant. The total flavonoid content of the ethyl acetate fraction (EAF) was higher than those of the petroleum ether fraction (PEF), n-butanol fraction (NBF), and water fraction (WF). The EAF also had much stronger antioxidant, cytotoxic, hepatoprotective, and acetylcholinesterase (AChE) and alpha-glucosidase inhibitory activities than the PEF, NBF, and WF. More importantly, the IC50 values of the EAF and NBF against alpha-glucosidase were much lower than that of the positive control acarbose, indicating their potent alpha-glucosidase inhibitory activities. The isolation of the EAF led to the acquisition of 9 compounds, four of which (beta-daucosterol, methyl rosmarinate, betulinic acid, and oleanolic acid) possessed significant alpha-glucosidase inhibitory activities. Maltol 6'-O-(5-O-p-coumaroyl)-beta-D-apiofuranosyl-beta-D-glucopyranoside and rosmarinic acid were the major phenolic compounds in the EAF according to the HPLC-DAD analysis. All these findings indicate that the EAF, NBF, and some isolated compounds have the potential to be developed as antidiabetic drugs. Moreover, the dual inhibition of AChE and butyrylcholinesterase (BChE) of certain fractions indicates their potential in the development of anti-Alzheimer's disease drugs. The present study provides a new understanding of the phytochemistry and bioactivity of E. rugulosa.