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