α-Glucosidase Inhibitory Prenylated Anthranols from Harungana madagascariensis.

Four new prenylated anthranols, harunganols C-F (1-4), along with kenganthranol A (5), harunganin (6), and ferruginin A (7), were identified from the leaves of Harungana madagascariensis. The structures of compounds 2, 5, and 7 were confirmed by single-crystal X-ray diffraction analysis. Compound 1 is a unique symmetrical anthranol dimer connected via a CH2 group. Compound 4 possesses a unique C-10 hemiketal group. All anthranols were evaluated for their α-glucosidase inhibitory activities. They displayed a higher potency compared to acarbose except for 3 and 4. In particular, harunganol C (1) showed an IC50 value of 1.2 µM.

Structurally diverse (9ß-H)-pimarane derivatives with six frameworks from the leaves of Icacina oliviformis and their cytotoxic activities.

Thirteen previously undescribed (9ß-H)-pimarane derivatives, icacinolides A-G (1-7) and oliviformislactones C-H (8-13), together with four known analogs (14-17), were isolated from the leaves of Icacina oliviformis. Their structures were constructed by extensive spectroscopic analysis, 13C NMR-DP4+ analysis, ECD calculation, single-crystal X-ray diffraction, and chemical methods. These structurally diverse isolates were classified into six framework types: rearranged 3-epi-17-nor-(9ß-H)-pimarane, rearranged 17-nor-(9ß-H)-pimarane, 16-nor-(9ß-H)-pimarane, 17-nor-(9ß-H)-pimarane, 17,19-di-nor-(9ß-H)-pimarane, and (9ß-H)-pimarane. Among them, compounds 1, 5, and 7 were the first examples of three rearranged 3-epi-17-nor-(9ß-H)-pimaranes featuring a unique (11S)-carboxyl-9-oxatricyclo[5.3.1.02,7]dodecane motif with contiguous stereogenic centers, whereas their C-3 epimers, compounds 2-4 and 6 were the second examples of four rearranged 17-nor-(9ß-H)-pimaranes. Additionally, compounds 8 and 12/13 represented the second examples of a 16-nor-(9ß-H)-pimarane and two 17,19-di-nor-(9ß-H)-pimaranes, respectively. In cytotoxic bioassay, compound 2 exhibited significant cytotoxic against HT-29 with IC50 values of 7.88 µM, even stronger than 5-fluorouracil, and 15 showed broad-spectrum cytotoxic activities against HepG2, HT-29, and MIA PaCa-2 with IC50 values of 11.62, 9.77, and 4.91 µM, respectively. Meanwhile, a preliminary structure-activity relationship suggested that 3,20-epoxy, 6,19-lactone, 2-OH, 7-OH, and 8-OH in (9ß-H)-pimarane derivatives might be active groups, whereas ring C aromatization may decrease the cytotoxic activities.

Further prenylated anthranoids from Harungana madagascariensis.

Ten undescribed anthranoids, including three anthraquinone acetals as racemic mixtures, (±)-kenganthranol G-I, and seven prenylated anthranols, (±)-kenganthranol J-M and harunganol G-I, together with thirteen known compounds, were isolated from the stem bark of Harungana madagascariensis. The structures of (±)-kenganthranol G and (±)-kenganthranol J were confirmed by X-ray crystallography. (±)-Kenganthranol G was separated into (+)-kenganthranol G and (-)-kenganthranol G by chiral HPLC and their absolute configurations were established by electronic circular dichroism. (±)-Kenganthranol L displayed α-glucosidase inhibitory activity with an IC50 of 4.4 µM.