A norsesquiterpene lactone and a benzoic acid derivative from the leaves of Cyclocarya paliurus and their glucosidase and glycogen phosphorylase inhibiting activities

Two novel compounds, 3-methoxypterolactone ( 1) and 2-amino-3,4-dihydroxy-5-methoxybenzoic acid ( 2), were isolated from leaves of Cyclocarya paliurus (Batal.) Iljinsk, together with nine known compounds: pterolactone ( 3), gallic acid ( 4), 4-hydroxy-3-methoxybenzoic acid ( 5), oleanolic acid ( 6), beta-boswellic acid ( 7), alpha-boswellic acid ( 8), beta-amyrin ( 9), beta-amyrone ( 10) and 3beta-O-trans-caffeoyl-morolic acid ( 11). The structure elucidation was based on spectroscopic methods, including two-dimensional NMR experiments ( (1)H- (1)H COSY, HMQC and HMBC). All isolated compounds were evaluated for their glycosidase and glycogen phosphorylase inhibitory activities. 2-Amino-3,4-dihydroxy-5-methoxybenzoic acid and gallic acid showed significant alpha-glucosidase and glycogen phosphorylase inhibitory activities.