Cytotoxic and Genotoxic Activities of Alkaloids from the Bulbs of Griffinia gardneriana and Habranthus itaobinus (Amaryllidaceae)

Abstract

Background: Amaryllidaceae plants are known to be a great source of alkaloids, which are considered an extensive group of compounds encompassing a wide range of biological activities. The remarkable cytotoxic activities observed in most of the Amaryllidaceae alkaloids derivatives have prompt the chemical and biological investigations in unexplored species from Brazil. Objective: To evaluate the cytotoxic and genotoxic properties of alkaloids of Griffinia gardneriana and Habranthus itaobinus bulbs and study the role of caspase-3 as a molecular apoptosis mediator. Methods: Methanolic crude extracts of Griffinia gardneriana and Habranthus itaobinus bulbs were submitted to acid-base extraction to obtain alkaloid-enriched fractions. The obtained fractions were fractionated using chromatographic techniques leading to isolation and identification of some alkaloids accomplished via HPLC and 1H-NMR, respectively. Molecular docking studies assessed the amount of free binding energy between the isolated alkaloids with the caspase-3 protein and also calculated the theoretical value of Ki. Studies have also been developed to evaluate in vitro cytotoxicity and genotoxicity in such alkaloids and apoptosis activation via the caspase pathway using both tumor and normal cell lines. Results: Seven alkaloids were isolated and identified. Among these, 11-hydroxyvittatine and 2-α-7- dimethoxyhomolycorine were not cytotoxic, whereas tazettine, trisphaeridine, and sanguinine only showed activity against the fibroblast lineage. Lycorine and pretazettine were 10 to 30 folds more cytotoxic than the other alkaloids, including cancerous lines, and were genotoxic and capable of promoting apoptosis via the caspase-3 pathway. This result supports data obtained in docking studies wherein these two compounds exhibited the highest free energy values. Conclusion: The cytotoxicity assay revealed that, among the seven alkaloids isolated, only lycorine and pretazettine were active against different cell lines, exhibiting concentration- and time-dependent cytotoxic actions alongside genotoxic action and the ability to induce apoptosis by caspase-3, a result consistent with those obtained in docking studies.