I am extracting black pepper oil using Soxhlet method (hexane as solvent). The solvent with extract was filtered before running it in rotary evaporator to remove the solvent from the oil. After rotavap, the oil and solvent were collected separately but I am curious what is this that solidified in the flask? The texture is like a house paint and somehow wax-like. Picture 1 is a minute after it touch the waterbath. Picture 2 is what's left in the flask. It was pure liquid before rotavap.
Hexane dissolves waxy compounds, as ethanol, methanol .... So it is not strange. The waxy compounds in peper are extracted along with other compounds like terpenes ...
As Hoseini said, you are extracting anything soluble in hexane, including the phospho- and triacyl-glyceride lipids. You may also be getting some lipopolysaccharides and lipoproteins. The lipids are soluble in hexane, but their melting point may be above RT. It is highly likely that they are precipitating during hexane evaportation to create a semi-solid tar-like substance. You can try to sapponify the lipids then run a FAME-GC method to ID the fatty acids. You can also try to dissolve in 1% SDS and run a PAGE gel to see if there are lipoproteins. you could do an Iodine assay to see if there is any polysaccharide content.
Compounds get concentrated by evaporating solvent in rotary evaporator.
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