Dears
I prepared seaweed extract in MeOH/water (70/30) and evaporated the solvent. Now I want dissolve dry extract in MeOH for stock and future analysis, but the extract dose not fully dissolve in methanol. We have 50 g seaweed yielding 14 g methanolic extract. I dissolve all 14g extract in 10ml MeOH, but it didn't fully dissolve and there is residuum like salt at bottom of tube. I weighted the unresolved (residue) extract. it was almost 10 g. now what can I do? Can anyone help me in this case?
Dear Salim,
Considering the quantity of residue taken, 14 g is too much to be solubilized in just 10 ml methanol. you can try using a little diluted extract probably 1g in 10 ml methanol. However there is one more thing you have to consider that the carbohydrates and high molecular weight tannins which are abundant in sea weeds are only partially soluble in pure methanol, so if you want a concentrated solution try using the same ratio of methanol:water.
Please follow this article
EVALUATION OF ANTIOXIDANT CAPACITY OF METHANOL EXTRACT AND ITS SOLVENT FRACTIONS OBTAINED FROM FOUR MOROCCAN MACRO ALGAE SPECIES
Halima Chernane, Cadi Ayyad University/ Morocco Mounir Mansori, Salma Latique, Prof. Mimoun El Kaoua Cadi Ayyad University, Department of Biology, Laboratory of Biotechnology, Protection of Agro-Resources, Morocco.
European Scientific Journal May 2014 edition vol.10, No.15 ISSN: 1857 – 7881 (Print) e - ISSN 1857- 7431
Preparation of seaweed extracts and fractions The pulverized moisture free seaweed material (20 g) was extracted in 250 mL of methanol in a soxhlet extractor for 7 hours at 40°C. The total extract was filtered and the obtained filtrate (crude extract) was concentrated in a rotary evaporator at 40°C to dryness. Dried extract was dissolved in 90% aqueous methanol for fraction. First fractionation was carried out with 100 ml petroleum ether (PE). PE fraction was collected and aqueous methanol phase was evaporated in a rotary evaporator to give a semisolid. A semisolid was dissolved in 200 mL of distilled water and Fractioned with 100 ml ethyl acetate (EA), dichloromethane (DCM) and n-butanol (BuOH). Resulting fractions including aqueous were evaporated to dryness. Dried fractions were dissolved in methanol and stored in coloured vials for further analysis.
As answered by Galvina Ferreira the solvent to extract ratio is not proportionate. Also, when you use water as solvents some salts (inorganic) may also get into your extract. You can prepare stock in aqueous methanol in the same proportion as that of your extraction, say 1:1 or 9:1. Good luck.
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