Cancer is the major public health problem worldwide; consequently, the search for new chemotherapeutic drugs is constant. Most of these agents are derived from natural sources, which are the major consistent basis for the search for modern anticancer medicines. In this context, numerous studies indicate flavonoids as a potential new class of secondary metabolites for anticancer therapy. In this review, special attention was addressed to flavonoids present in Achyrocline satureioides, a widely used medicinal plant with several and a well established range of biological properties. Two of these flavonoids are extensively studied for anticancer therapy, quercetin and luteolin, followed by 3-Omethylquercetin. Achyrobichalcone, recently isolated from A. satureioides by our group, can also represent a promising chemotherapeutic biomolecule due to its similarity with other cytotoxic bichalcones to cancer cell lines. The anticancer properties of these flavonoids, specially quercetin and luteolin, type of cell death, mechanisms and molecular targets involved were described. In general, these effects were observed due to the inhibition of cell proliferation, cell cycle arrest, apoptosis, inhibition of angiogenesis, prevention of migration/metastasis and overcoming multidrug resistance, alone or in combination with commonly used chemotherapeutic drugs. All these successful findings in preclinical studies suggest that these flavonoids are promising biomolecules for the development of new anticancer drugs in the future.
Achyrobichalcone is a biflavonoid recently found in Achyrocline satureioides. This substance has unprecedented chemical structure and occurrence, but resembles other bioactive bichalcones, which have important pharmacological properties, such as anticancer activity. The major challenge for evaluation of the physicochemical and biological properties of this new molecule is the isolation step, which affects the purity and yield of the isolated product. Thus, the objective of this work was to develop a semi-preparative method for achyrobichalcone isolation from Achyrocline satureioides by high-speed countercurrent chromatography. The high-speed countercurrent chromatography separation was achieved in two steps. In the first step, an enriched fraction of achyrobichalcone from the freeze-dried extract was obtained, using the solvent system hexane-ethyl acetate-methanol-water 0.8:1:0.8:1, v/v. The purification of achyrobichalcone from the enriched fractions was achieved by further high-speed countercurrent chromatography fractionation with hexane-ethyl acetate-methanol-water 0.9:0.9:0.8:1, v/v. The final isolated product was obtained using preparative thin layer chromatography and crystallization procedure. A yellow semi-crystalline solid with purity close to 90% was obtained as the final product. The mass recovery of achyrobichalcone isolation was near 67%. The structural identification from spectroscopic and chromatographic techniques confirmed the achyrobichalcone structure. This is the first report of achyrobichalcone isolation on a semi-preparative scale by high-speed countercurrent chromatography. This method afforded achyrobichalcone in good yield and purity for further biopharmaceutical studies.
The new method developed affords evaluation of the quality of achyrobichalcone obtained by isolation, and indicates the stability of the molecule under various stress conditions.
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