Monoterpene-flavonoid conjugates from Sarcandra glabra and their autophagy modulating activities

Abstract

Fourteen new monoterpene-flavonoid conjugates including four monoterpene-conjugated chalcones (glabratins A–D, 1–4), seven monoterpene-conjugated dihydrochalcones (glabratins E–K, 5–11), and three monoterpene-conjugated flavanones (glabratins L–N, 12–14), together with four known analogues (15–18) were isolated from the aerial parts of Sarcandra glabra. The structures and the absolute configurations of these compounds were elucidated by the spectroscopic data, single-crystal X-ray diffraction, and electronic circular dichroism (ECD) calculations. Compounds 1, 4–6, 9–14, and 18 showed obvious cell autophagy-inducing activities at 25 μM in HEK293 cells. Furthermore, the bioassay results also showed that 18 induced cell autophagy in a dose dependent manner. Our findings revealed a rare class of monoterpene-flavonoid conjugates in nature and firstly reported their autophagy-inducing activities.