Chemical constituents from leaves of Uncaria rhynchophylla / 中草药

ABSTRACT

Objective: To study the chemical constituents from the leaves of Uncaria rhynchophylla and their antioxidant activities. Methods: The compounds were isolated by various column chromatography. Their structures were identified by spectroscopic methods including 1H-NMR, 13C-NMR, MS, HR-MS, etc. The antioxidant activities were evaluated by DPPH radical scavenging assay. Results: Seventeen compounds were isolated from the leaves of U. rhynchophylla, and identified as 18, 19-hydroxy- vincosamide (1), α-tocopherol (2), α-tocospiro A (3), dihydroactinidiolide (4), ursolic acid lactone (5), 3, 4-dehydrotheaspirone (6), chakyunglupulin A (7), ursolic acid (8), protocatechuic acid (9), quercetin (10), epicatechin (11), chlorogenic acid ethyl ester (12), quercetin-3-O-robinobioside (13), rutin (14), methyl caffeate (15), strictosamide (16), and vincosamide (17). The anti-oxidative IC50 values of compounds 10, 11, and 13-15 were 7.52, 8.21, 8.14, 2.13, and 5.35 μmol/L, respectively, which were better than the positive control Vit E (IC50 value was 9.53 μmol/L). Conclusion: Compound 1 is a new compound named as vincosamide A, and compounds 2-7, 9, 12, 13, and 15 are isolated from genus Uncaria Schreber nom. cons. for the first time. Moreover, compounds 10, 11, and 13-15 have the certain prospects in the development of natural anti-oxidative agents.