A New Cyclic Terephthalate from the Methanolic Extract of Carissa opaca.

Carisphthalate, a new cyclic trimer of ethylene terephthalate (1) along with β-sitosterol (2), 6-hydroxy-7-methoxycoumarin (3), ursolic acid (4), epigenin (5), luteolin (6) and β-sitosterol 3- O-β-D-glucopyarnoside (7) have been isolated from the methanolic extract of the aerial parts of Carissa opaca. The structures of these isolates (1-7) were established by 1D (¹H, ¹³C), 2D NMR (COSY, HSQC, HMBC) spectroscopy and mass spectrometry (EIMS, HREIMS, FABMS, HRFABMS). The structure of compound 1 was also confirmed by single X-ray crystallographic analysis. All the compounds (1-7) were screened for DPPH free radical scavenging and enzyme inhibitory activities against the enzymes acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and lipoxygenase (LOX). [ABSTRACT FROM AUTHOR]