(3'R)-hydroxytabernaelegantine C: A bisindole alkaloid with potent apoptosis inducing activity in colon (HCT116, SW620) and liver (HepG2) cancer cells.
BACKGROUND
Tabernaemontana elegans Stapf. (Apocynaceae) is a medicinal plant traditionally used in African countries to treat cancer.


OBJECTIVE
To discover new apoptosis inducing lead compounds from T. elegans and provide scientific validation of the ethnopharmacological use of this plant.


METHODS
Through fractionation, (3'R)-hydroxytaberanelegantine C (1), a vobasinyl-iboga bisindole alkaloid, was isolated from a cytotoxic alkaloid fraction of the methanol extract of T. elegans roots. Its structure was identified by spectroscopic methods, mainly 1D and 2D NMR experiments. Compound 1 was evaluated for its ability to induce apoptosis in HCT116 and SW620 colon and HepG2 liver carcinoma cells. The cell viability of compound 1 was evaluated by the MTS and lactate dehydrogenase (LDH) assays. Induction of apoptosis was analyzed through Guava ViaCount assay, by flow cytometry, caspase-3/7 activity assays and evaluation of nuclear morphology by Hoechst staining. To determine the molecular pathways elicited by 1 exposure, immunoblot analysis was also performed.


RESULTS
(3'R)-hydroxytaberanelegantine C (1) displayed strong apoptosis induction activity as compared to 5-fluorouracil (5-FU), the most used anticancer agent in colorectal cancer treatment. In the MTS assay, compound 1 exhibited IC50values similar or lower than 5-FU in the three cell lines tested. The IC50value of 1 was also calculated in CCD18co normal human colon fibroblasts. The lactate dehydrogenase assay showed increased LDH release by compound 1, and the Guava ViaCount assay revealed that 1 significantly increased the incidence of apoptosis to a further extent than 5-FU. Moreover, the induction of apoptosis was corroborated by evaluation of nuclear morphology by Hoechst staining and caspase-3/7 activity assays of 1 treated cells. As expected, in immunoblot analysis, compound 1 treatment led to poly(ADP-ribose) polymerase cleavage. This was accompanied by decreased anti-apoptotic proteins Bcl-2 and XIAP steady state levels in all three cancer cell lines tested.


CONCLUSIONS
Compound 1 showed remarkable induction of apoptosis in HCT116, SW620 and HepG2 cells. Together, the results suggest that compound 1 is a promising lead structure for inducing apoptosis.
Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. Electronic address: apaterna@ff.ulisboa.pt.
Angela
A
Paterna
Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. Electronic address: segomes@ff.ulisboa.pt.
Sofia E
SE
Gomes
Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. Electronic address: borralho@ff.ulisboa.pt.
Pedro M
PM
Borralho
Centro de Estudos Moçambicanos e de Etnociências (CEMEC), Faculty of Natural Sciences and Mathematics, Pedagogical University, 21402161 Maputo, Mozambique. Electronic address: smulhovo@hotmail.com.
Silva
S
Mulhovo
Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. Electronic address: cmprodrigues@ff.ulisboa.pt.
Cecília M P
CM
Rodrigues
Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. Electronic address: mjuferreira@ff.ulisboa.pt.
Maria-José U
MU
Ferreira
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D029062:Apocynaceae / Q000737:chemistry; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D006801:Humans; D026121:Indole Alkaloids / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D017550:Spectroscopy, Fourier Transform Infrared
C000617431:3'-hydroxytabernaelegantine C; D000972:Antineoplastic Agents, Phytogenic; D026121:Indole Alkaloids; D053148:Caspase 3; D053179:Caspase 7
Anticancer; Apocynaceae; Apoptosis induction activity; Bisindole alkaloid; Tabernaemontana elegans