Question

Alkaloids can be extracted from plant tissues using dilute hydrochloric acid. Why does the use of acid enhance their water solubility?

Answer 1

Alkaloids are usually nitrogen-containing organic compounds and are mostly alkaline in nature. They are usually combined with organic acids such as oxalate, citrate, etc. to form a salt. The presence of organic moieties (more hydrophobic than inorganic moieties) in both the component of the salt make them very less soluble in water. To increase their solubility in water and to increase the extraction yield, these organic acid salts are replaced with inorganic acid salts. Thus when dilute HCl is added to the plant sap for alkaloid extraction, the anionic component of alkaloid salt is replaced by chloride ion leading to an increase in their solubility in water and better extraction yield.