Development and Validation of a Method to Quantify Flavonoids in Leaves of Lithospermum officinale (Boraginaceae)

The common gromwell Lithospermum officinale L. is a valuable medicinal plant that has been used in traditional medicine since ancient times. A method to quantify flavonoids in L. officinale leaves by differential spectrophotometry was developed taking advantage of the flavonoid reaction with aluminum chloride. The optimum duration of the reaction was determined, as well as the optimum volume-to-volume ratio between an aqueous ethanolic extract of L. officinale leaves and 2% aluminum chloride (aqueous ethanolic solution). Rutin was used as a standard. The method was validated in terms of specificity, linearity, precision, and accuracy and proved suitable for analytical purposes. The flavonoid content expressed in terms of rutin was found to exceed 2% of the absolutely dry weight in L. officinale leaves over different years of cultivation.