Characterization, Antioxidant and Anticholinesterase Activity of Compounds Isolated from Alkaloid Extracts of Citrus aurantifolia Root Bark

Xanthyletin (1), edulinin (2), 1-methyl-2-[(E)-(prop-1-enyl)]quinolin-4-one (3), 1,2-dimethylquinolin-4-one (4), lonchocarpol A (5), grandisinin (6), citracridone-I (7) and 5-hydroxynoracronycin (8) were isolated from alkaloid extracts of the root bark of Citrus aurantifolia. Their structures were characterized using spectral data (NMR, HRMS, and IR). Furthermore, compounds 2, 3, 4, and 6 known in the literature have been isolated for the first time in Citrus aurantifolia. However, compounds 1, 5, 7 and 8 are already known from the plant studied. The concentration required to reduce 50% of free radicals (RC50) was carried out. Compounds 3 (RC50= 185.836 µmol/L) and 4 (RC50= 218.277 µmol/L) compared with vitamin C (RC50= 17.033 µmol/L) showed antioxidant efficacy. The highest anticholinesterase activity was observed for compound 6 at 21.129 µM followed by compounds 3 and 4 at 251.130, 287.208 µM, respectively.