Protoberberine Alkaloids and Cancer Chemopreventive Properties of Compounds from Alangium salviifolium
New protoberberine alkaloids, namely alangiumkaloids A (1) and B (2), 27-O-trans-caffeoylcylicodiscic acid (3), and β-D-glucopyranos-1-yl N-methylpyrrole-2-carboxylate (5) together with myriceric acid B (4), isoalangiside (6), alangiside (7), 3-O-demethyl-2-O-methylalangiside (8), and demethylalangiside (9) have been isolated from Alangium salviifolium. The cancer chemopreventive properties and cytotoxic activities of the isolated compounds were evaluated. Compounds 3, 4, and 9 scavenged DPPH free radicals with IC50 values of 21.4, 21.8, and 24.0 μM, respectively. Alangisides 7 and 9 inhibited superoxide anion radical formation in the xanthine/xanthine oxidase (XXO) assay with IC50 values of 19.4 and 5.3 μM, respectively. Compounds 6–9 showed excellent antioxidant activity in the oxygen radical absorbance capacity (ORAC) assay with 12.8–24.9 ORAC units. Compounds 3 and 4 inhibited aromatase activity with IC50 values of 4.7 and 6.8 μM, respectively. Although the isolated compounds showed only weak cytotoxicity or were inactive, compounds 3 and 4 exhibited cytotoxic activity towards the MOLT-3 cell line with IC50 values of 5.6 and 3.9 μM, respectively, and compound 8 selectively inhibited the growth of the HepG2 cancer cell line with an IC50 value of 7.1 μM.