im currently in the phase of extracting metabolites, specifically for antibacterial screening from endophytic fungi. i tried ethyl acetate, but after 1 week it's still not dry.
It's better to use a rotary evaporator. However, everything depends on the thermal stability of the active metabolites that you're planning to extract. As some of the secondary metabolites are not stable above the physiological temperature, usually the solvent evaporations are performed under reduced pressure conditions. Therefore we have to use rotary evaporators. But, if your compounds of interest are not thermally labile, you can use higher temperatures to evaporate the solvent. (As we do not know the exact metabolites in it, such harsh conditions are not usually recommended).
Check https://www.tandfonline.com/doi/full/10.1080/21501203.2018.1481154
Check https://bmccomplementmedtherapies.biomedcentral.com/articles/10.1186/s12906-021-03269-3
It is true that rotary evaporator and freeze dryer are the best options for concentrating your extract especially when considering the possible present of thermo labile constituents, however if due to financial constraint your lab cannot own any of these, you can improvised by using water bath at a control temperature of 45-50 oC, since you extract with ethylacetate, it will dry within two days. Again if you have a good fume cupboard, you can place the extract inside it in broad glass container, but if there is no functional one, you can place the extract in a braid glass container under a high speed fan in a place that people will not be exposed to the fumes from the solvent. Many of us make use of these improvised methods in our labs but we don't want to face realities. Try any of these, it will concentrate your extract without altering the constituents.
I also recommend to use rotary evaporator. As boilling point of ethyl acetate is comparatively high, you can't evaporate using normal conditions. If you heat it upto 70-80 C, most of your natural compounds may decompose and you wont able to evaluate accurate activity of your extract. Also if you keep it outside for days, most probably compounds may oxidized in air. If you are not isolating compounds, you can get small amount of extract in to a vial and can purge nitrogen to evaporate solvent. You can use that for initial bioassay evaluations. (mg quantities are enough for antibacterial assays) But you cant do this for isolation process.
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