Variation in the contents of four flavonoid glycosides in edible Dendrobium officinale leaves during different harvesting periods and optimization of the extraction process

Despite being recognized as a specialty food in four Chinese provinces with established safety standards, <i>Dendrobium officinale</i> Kimura et Migo (Orchidaceae) leaf physicochemical indices overlook vital flavonoid glycoside components. Given the inconsistency in flavonoid quality under current standards, we devised a quantitative analysis targeting vicenin 2, vicenin 3, rutin, and isoviolanthin. Our analysis revealed significant seasonal variations, with harvests yielding the highest total content of these four flavonoid glycosides in February (1.6378 mg/g) and July (2.0642 mg/g). This finding provides a scientific basis for optimal collection timing, enhancing quality control and utilization. Furthermore, we optimized the extraction conditions (59.63 °C, 22.44 min, 1:37.91 g/mL solid-to-liquid ratio, 43.24 % ethanol) to maximize the flavonoid glycoside content. This study lays a foundation for refining <i>D. officinale</i> leaf quality standards and advancing related product development in China.