Background: In the flora of China and Vietnam, Luculia piceana Hook of the family Rubiaceae is described as a medicinal plant. Earlier chemical studies of L. piceana in China isolated iridois, glycosides of cincholic acid, and kaempferol glycosides from the stem, however, no chemical studies have been conducted with L. piceana in Vietnam.
Methods: The stem of L. piceana was extracted with a mixture of 90%EtOH–H2O at room temperature and the extract was further fractionated by using liquid-liquid extraction and repeated column-chromatographic techniques. Spectroscopic data (IR, MS, 1H NMR, and 13C NMR) were used to determine structures of isolated compounds.
Results: Thirteen compounds were isolated and structurally determined. Oleanolic acid (2), scopoletin (3), cleomiscosin A (4), (E)-mappianine E (5a), (Z)-mappianine E (5b), vanillic acid (6), 2-hydroxyacetophenone-4-O-β-D-glucopyranoside (7), sweroside (10), and 2-methoxyacetophenone-4-O-β-D-glucopyranoside (11) were isolated for the first time from L. piceana. Compounds 6, 10, 11, loganin (8), 7-ketologanin (9) were not active (IC50 > 300 μg/ml), 7 showed a weak activity (IC50 268.35 μg/ml) in the DPPH-scavenging assay. IC50 value of 100.57 μg/ml. A mixture of 5a/5b was cytotoxic against the human cancer cell line HepG2 (IC50 100.57 μg/ml) in the MTT assay.
Conclusion: L. piceana in Vietnam was investigated for the first time. We isolated compounds of varied biological origins including monoterpene indole, iridoid, coumarin, coumaro-lignoid, phytosterol, oleanane triterpenoid, phenolic acid, and acetophenone. Nine of thirteen compounds are newly isolated from L. piceana. The study determined weak scavenging activity of an acetophenone and weak cytotoxicity of a mixture of two monoterpene indoles against HepG2 cell.