How Plant Extracts are Prepared

The collected plant material (plant parts: stems, leaves, flowers, roots, bark etc.) is dried in a ventilated oven at 45 oC for 24 H, and subsequently milled to a fine powder by means of an IKA Universal Mixer M20 (or other type). An amount of 20.0 g of the dried plant powder is weighed in an Erlenmeyer of 100 ml to which 70 ml of hexane (purity grade 99 %) is added (the plant sample has to be submerged with solvent) for pre-extraction. The Erlenmeyer is placed in a sonicator-bath (Branson 8210 or some other type) and sonicated at a temperature 40 oC during 30 minutes. The mixture is filtered using paper filter, followed by washing the Erlenmeyer with 20 ml of hexane and then with 50 ml of hexane. The filtrate is poured in a round-bottomed flask and the solvent is concentrated in vacuo (at about 11 mm Hg) up to 5-10 ml by means of rotavapor, utilizing a water bath at 40 oC. This residue is brought in a 30-ml vessel to let the solvent evaporate. The open vessel is left overnight in a well-ventilated hood in order to evaporate the last traces of the solvent in the hexane pre-extract.

The solids, collected on the filter, are broken up and dried in the air overnight in the hood. The dried material is extracted in the same way with methanol-water (90:10). The dried material from the filters placed in an Erlenmeyer of 100 ml to which 70 ml of 90 % methanol is added. The mixture is sonicated as above at 40C during 30 minutes, after which it is filtered, followed by washing the Erlenmeyer with 20 ml of 90 % methanol. The filtrate is poured in a round-bottomed flask and the solvent is evaporated in vacuo completely. The dry 90% methanol extract is dissolved in as little as possible 100 % methanol by using the sonicator-bath and poured in a 30-ml vessel to let it evaporate overnight in the hood.