Separation of hydroxycitric acid lactone from fruit pectins and polyhydroxyphenols on polybenzimidazole weak-base resin.

Polybenzimidazole (PBI) free-base resin has been used for selective sorptio n and recovery of hydroxycitric acid lactone (HCAL) from aqueous solutions containing also significant proportions of polyhydroxyphenols and fruit pec tins, because the study has relevance to the problem of separation and reco very of HCAL, a potent antiobesity substance,from aqueous extracts of Garci nia cambogia fruits, grown largely in coastal areas of South India. PBI res in has the saturation sorption capacity of 315 mg/g dry resin for HCAL, com pared with 131, 138, and 293 for catechol, pyrogallol, and pectin, respecti vely, in individual sorptions from aqueous solutions. The resin selectivity for HCAL over catechol, pyrogallol, and pectin in binary sorptions varies with pH, the separation factor of HCAL being maximum over catechol and pyro gallol at a pH of 1.7-1.8 and infinite over pectin at pH < 1.8. Under vigor ous agitation the initial uptake of HCAL is very fast with 30% of the equil ibrium sorption taking place in 10 s, followed by a significantly lower rat e, leading to an overall 75% attaimnent of equilibrium sorption in 30 min. In continuous column operations with PBI resin and influent containing HCAL , polyhydroxyphenols, and fruit pectins, a proper combination of relatively low flow rate, a relatively low substrate pH (1.7-1.8), and "dead-end" str ipping with alkali, which involves use of less than the theoretical amount of stripping agent necessary for complete stripping, produces an excellent separation and good yield of HCAL from the mixed influent.