Iridoids from Pentas lanceolata.

From the aerial parts of Pentas lanceolata, belonging to the family Rubiaceae, a series of iridoid glucosides was isolated by preparative HPLC. Seven iridoid glucosides were identified. Besides asperuloside and asperulosidic acid, characteristic iridoids for Rubiaceae, five new iridoids were isolated, namely, tudoside (1), 13R-epi-gaertneroside (2), 13R-epi-epoxygaertneroside (3), and a mixture of E-uenfoside (4) and Z-uenfoside (5). Further, it was shown that the compound reported as citrifolinin B (6) is in fact the same as tudoside and should be revised. Also, the configuration of the previously reported iridoids gaertneroside and epoxygaertneroside has been elucidated.