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.