The Cerrado biome is the world’s largest and most
diversified
tropical savanna. Despite its diversity, there remains a paucity of
scientific discussion and evidence about the medicinal use of Cerrado
plants. One of the greatest challenges is the complexity of secondary
metabolites, such as flavonoids, present in those plants and their
extraction, purification, and characterization, which involves a wide
range of approaches, tools, and techniques. Notwithstanding these
difficulties, the search for accurately proven medicinal plants against
cancer, a leading cause of death worldwide, has contributed to this
growing area of research. This study set out to extract, purify, and
characterize 3-O-methylquercetin isolated from the
plant Strychnos pseudoquina A.St.-Hil.
(Loganiaceae) and to test it for antiproliferative activity and selectivity
against different tumor and nontumor human cell lines. A combined-method
approach was employed using 1H and 13C nuclear
magnetic resonance, thermogravimetric analysis, differential scanning
calorimetry, single-crystal X-ray diffraction, Hirshfeld surface analysis,
and theoretical calculations to extensively characterize this bioflavonoid.
3-O-methylquercetin melts around 275 °C and
crystallizes in a nonplanar conformation with an angle of 18.02°
between the pyran ring (C) and the phenyl ring (B), unlike quercetin
and luteolin, which are planar. Finally, the in vitro cytotoxicity
of 3-O-methylquercetin was compared with data from
quercetin, luteolin, and cisplatin, showing that structural differences
influenced the antiproliferative activity and the selectivity against
different tumor cell lines.