Effect of solvents and extraction methods on forskolin content from coleus forskholii roots

Abstract

Coleus forskohlii roots are mainly used for extraction of the bioactive diterpenoid, forskolin, which has enormous biological activities. In this study, impact of the solvent and extraction method on forskolin content from Coleus forskohlii root powder was investigated. Nine solvents from different polarity group were tested for forskolin extraction. It was found that the efficiency of the solvents used to extract forskolin varied considerably (0.18 to 2.91 %). The average values indicated that among all the extractives, forskolin content was significantly higher in methanol (2.91 %), followed by ethanol (2.59 %), and least content was found in water (0.18 %). Low polarity solvents were not found very effective for forskolin extraction. Further three different extraction methods (Soxhlet/refluxing, ultrasound and microwave-assisted solvent extraction) were also compared using safest and most effective solvent for forskolin yield. As ethanol exhibited good extraction efficiency for forskolin and is a safe solvent, it was chosen for further optimization of extraction method. Soxhlet extraction technique gave higher yield of forskolin (0.17 to 2.83 %) compared to microwave-assisted solvent extraction (0.09 to 2.29 %) and ultra sound-assisted extraction (0.08 to 1.47 %). From these results it was evident that the extraction of forskolin depended on extraction process as well as the solvent useds.