This invention relates to a process for preparing highly water soluble double salts of hydroxycitric acid particularly alkali and alkaline earth metal double salts.
Fruits, particularly the rind of fiuits, of the plant belonging to Garcinia species are a rich naturally occuring source of hydroxycitric acid. Garcinia species grow abundantly in India and in the south East Asian countries. *Kdajm' an extract of Garcinia fiuits is used in in^iarting tart flavour to dishes, particularly meat and fish dishes. Ayurveda, the traditional hatal medicinal system, considers Garcinia as om of the herbs that k beneficial to heart Garcinia or malabar tamarind has also received considerable attention in recent times as a nutraceutical for effective obesity c(»itrol.
Hydroxycitric acid has been known to be baieficial for the control and reduction of mammalian body wei^ In particular, the (-) hydroxycitric acid isomer and derivatives thereof are found to inhibit fatty acid and cholesterol synthesis. These con^unds also function as a natural anorectic agent in mammals. This particular stereoiserties of hydroxycitric acid and its derivatives are not ideally suited for their use as nutraceuticals. For instance, hydroxycitric acid exhibits very strong scwir taste while its calcium sak thougjb not very pungent in taste is poorly soluble in water thereby reducing its bioavailability; the trip(Aassium salt of this acid is highly hygroscopic and is alkaline in nature. These undesirable diaract^stics such as taste and solubility affect the bioavailability or biological use of these compc^nds. It has been found that the double salt of Ca/K or Ca/Na of (-) - hydroxycitric acid are ideal for biological use, particularly, because of their ideal physical characteristics. Further, desirable properties of these double salts are their low sodium content in Ca/K double salt and balanced pH.
These double salts are hi^y water soluble, have no strong or undesirable taste and are practically odouriess. These sahs are therefore ideal for a variety of applications inclu^ng^beverages. Preparation of these double salts are disclosed in PCT WO 0015051 published on 23 March 2000 having priority in US patent application no.892414 filed on 14 July 1997; US patent no,6160172 dat^ 12 December 2000 and US patent no.6395296 dated 28 May 2002.
The processes of preparingjhe-double sah disclosed in the jwrior art are tedius and the final {u-oduct obtaified may cont^n harmful ccmtaminants, thus limiting its utility value. For instance, me-prtJcedure disclosed in PCT WO 0015051 consists of converting calcium salt of (-) - HC A into free HCA and the free (-) HC A is partially neutralized by the addition of Ca (OH)2 followed by con^lete neutralization with KOH. Removal of calcium phoi^hate and unreacted {^oi^horic acid from the reaction mixture is a cumbersome procedure. Indian patent no. 182487 involves conv^^ion of the calcium sah of (-) HCA into free HCA with oxalic acid. Hie

liberated HCA is treated with sodium hydroxide followed by partial replaceni^nt of sodium by calcium by treating with calcium chloride. Removal of calcium oxalate and excess oxalic acid fix>m the reaction mixture limits the utility of this method. US patent no.5656314 discloses cotiv^sion of calcium salt of hydroxycitric acid and into free acid with sulj^uric acid. Purification of the final product obtained by this process also involves tedious procedure.
Thus, the object of this invention is to conv^ calcium salt of hydroxycitric acid into a hi^y water soluble calcium, potassium o£ calcium, sodium dcmble salt using a simple cost effective process. Inorganic or organic acids are not used in this process of conversion ccmsequ^tly, removal of undesired by-products and excess acid from the reaction mixture is avoided. Surprisingly, it is observed that the Ca/K double salt is largely free of the lactone form of hydroxycitric add and when dissolved in water, the salt does not equilibrate between the free form and the lactone tbrm. Further, desirable properties of the Ca/K double salt i& its balanced pH and a low (<1%) sodium cafatiles the purified Garcinia extract used is obtained by tieating an aqueous extract of the fiuit rind with acetone. Settled mass firom the extract has been filtered off and the filtrate has been used for adjusting the pH.
invention also includes calcium potassium or calcium sodium double salts of hydroxycitric acid.

WE CLAIM:
1. A process fc^* preparing highly water soluble alkaline earth and alkali metal double salts of hydroxycitric acid; comprising the steps of precipitating sparingly soluble alkaline earth metal salts of hydroxycitric acid from an aqueous extract of the plants belonging to Garcinia species, dissolving said alkaline earth metal salts in aqueous alkali, adjusting the pH of said alkaline solution by adding an extract of purified Garcinia fruit extract thereto, purifying and drying the same thereafter to obtain highly soluble double salts of hydroxycitric acid.
2. The {M-ocess as claimed in claim 1, v^erein calciimi sah of hydroxycitric acid is precipitated from the aqueous extract of Garcinia plant by adding calciimi hydroxide thereto.
3. The process as claimed in claim 1, \^ereiti calcium salt of hydroxycitric acid is precipitated from the aqueous extract of Garcinia plant by adding a solution of sodium hydroxide thereto followed by adding a solution of calcium chloride.
4. The process as claimed in claims 1 to 3, wherein the Garcinia plant is Garcinia atroviridis, Garcinia cambogia or Garcinia indica.
5. The process as claimed in claims 1 to 4, wherein the fruit rind of Garcinia species is subjected to aqueous extraction.
6. The process as claimed in claims 1 to 5, wherein said calcium salt is treated
. with KOH solution having a concentration of 5 to 50%, preferably 5 to 15%
weight/volume.

The process as claimed in claims 1 to 6, wherein said purified Garcinia fruit extract is obtained by treating the aqueous extract thereof with acetone, and separating the insolubles therefrom.
The process as claimed in claims 1 to 7, wherein said aqueous extract containing the double salt is purified by treatment with activated charcoal, filtered and then spray dried.
The process as claimed in claim 8, wherein the filtrate is concentrated and dried under vacuum.
A process for preparing highly water soluble alkali and alkaline earth metal double salts of hydroxycitric acid substantially as herein described and exemplified.