Quantitative high performance liquid chromatographic analysis of diterpenoids in Agni-casti fructus

Pharmacological data have indicated that part of the dopaminergic activity of Vitex agnus-castus is attributed to the labdan diterpenoids found in the fruits. Therefore an analytical method for the standardization of rotundifuran (1), vitexilactone (2) and 6 beta,7 beta-diacetoxy-13-hydroxy-labda-8,14-diene (3) was developed. Because of the time-consuming and expensive isolation of the diterpenoids, p-cymene was chosen as an internal standard. The concentration of rotundifuran in different extracts and trade samples of the drug varies between 0.04 and 0.30% in the drug and between 1.04 and 2.23% in the extract. The concentration of vitexilactone was generally lower between 0.016 and 0.167% for the drug and between 0.34 and 1.01% for the extract. The determined concentration of 6 beta,7 beta-diacetoxy-13-hydroxy-labda-8,14-diene in the drug was in the range of 0.02 and 0.10% and in the extract in the range of 0.18 and 0.80%. Determination of the factors of correction of p-cymene gave 5.63 for rotundifuran, 2.73 for vitexilactone and 3.74 for 6 beta,7 beta-diacetoxy-13-hydroxy-labda-8,14-diene.