INTRODUCTION:

Cashew tree exudates are gums obtained from various species of cashew tree (Anacardium occidentale) as a result of tree bark injury. Cashew gum is produced in the epithelial cells of the plant. The gum is fluid in nature and dries up by evaporation of water on exposure to the environment.

The cashew gum has been found to have a variety of industrial uses .It can be used as a substitute of gum Arabic. In paper industry it can be used as a substitute for liquid glue .In pharmaceutical industry it can be used as an agglutinant for capsules and pills. It can be used as a stabilizer for fruit juices in food industry.

Cashew gum has a high molecular mass and on hydrolysis yields galactose and galacturonic acid[1]

Cashew gum has been reported to have an antitumor activity[2]. Cashew gum exudates has been reported as a potential chromatographic matrix as a bioaffinity ligand for proteins[3].

EXPERIMENTAL:

All the solvents used were of AR grade. Weighing was done on a Contech single pan balance with 1 mg sensitivity. All the chemicals used were of AR and were used after thorough drying in the oven. pH measurements were done on a digital pH meter.

Gum exudates were collected from cashew tree barks by inducing superficial injury to the bark. The exudates were pulverised to a fine powder form. 100 gms of the powder was soaked in 500 cc of distilled water at room temperature. The dispersion was then filtered to remove undissolved matter (which was mainly the material from the bark of the tree).The gum was then precipitated using ethanol. The precipitated gum was filtered and air dried to constant weight before storing in air tight containers.

The pH , moisture and ash contents were determined by AOAC methods⁴Protein content was measured by the Kjeldahl method⁴.The insoluble matter was determined as per the method specified by British Pharmacopoeia⁵.The total sugar was determined by the phenol sulphuric acid method⁶.Inorganic ions were determined by Atomic Absorption Spectroscopy.

The microbial load was determined by using Mac Conkey agar and Sabouraud dextrose agar. 1 gm of the gum was dissolved in 25 cc of sterile distilled water and the pour plate method⁷ was used to determine the microbial count. The antimicrobial activity was determined against commonly occurring pathogenic species of bacteria namely Escherichia coli, Staphylococcus aureus, Pseudomonas aeuroginosa, Klebsiella spp and fungus Candida albicans. The method used was well diffusion method[8, 9]. Swelling index was calculated as per the method specified in British Pharmacopoeia[5].

RESULTS AND DISCUSSION:

The crude gum appeared brownish in colour. Most of the impurities were due to the presence of fibrous material from the bark of the tree. Purified gum was however crystalline, yellowish white in colour, tasteless and odourless.

The purified gum sample was used for determining the ash value. Ash value of 1.47% indicates presence of low amount of inorganic matter.

The pH value was found to be 4.36.

Acid insoluble ash value of 0.27% is an indication of good mineral content and a low amount of silica based impurities.

The protein content as determined by the Kjeldahl method was found to be 1.65%.

Percentage of insoluble matter was 2.6%This is in accordance with Glicksman[1]. A low value of insoluble matter indicated that the gum exudates obtained from the particular plant has good water solubility.

The amount of sugar determined in selected cashew gum sample was 0.0076%.This indicates a lower proportion of carbohydrates.

The results for analysis of minerals indicated that the gum sample had an ample proportion of essential minerals

The calcium and iron content was 1659 mg/kg and 297 mg/kg respectively. Sodium, potassium and zinc were

310, 905 and 2.96 mg/kg respectively.

The swelling index value of 0.5 is an indication that the gum tends to dissolve in water rather than forming a viscous gel.

The results are tabulated in table 1 and 2

Table 1: Physical and chemical parameters of cashew gum

Sr No	Parameter	Result
1	Moisture	9.05%
2	Ash value	1.47%
3	Acid insoluble ash	0.27%
4	Insoluble matter	2.6%
5	Protein content	1.65%
6	Sugar content	0.0076%
7	Swelling index	0.5
8	pH	4.36

Table 2:Inorganic ions in cashew gum

Sr No	Metal ion	Concentration(mg/kg)
1	Calcium	1659
2	Potasssium	905
3	Zinc	2.96
4	Sodium	310
5	Iron	297
6	Nickel	Absent
7	Cadmium	Absent
8	Arsenic	Absent

Biological Studies on exudates:

The crude gum extract and the purified extract were compared with respect to their microbial load and their antimicrobial activity.

It was found that the bacterial as well as fungal count of the gum reduced on purification.

The crude as well as purified gum did not show any antibacterial activity against the commonly used pathogenic bacteria Escherichia coli, Staphylococcus aureus, Pseudomonas aeuroginosa, Klebsiella spp and fungus Candida albicans, at concentrations ranging from 20mg/ml to 50mg/ml

The results are summarised in table 3 and 4.

Table 3: Microbial count in crude and purified gum sample

Organism	Count in crude gum	Count in purified gum
Aerobic bacteria	4×10³ cfu/gm	1×10³ cfu/gm
Fungi	495 cfu/gm	90 cfu/gm
E.coli	Absent	Absent
Staphylococci	Present	Absent
Pseudomonas spp	Absent	Absent
Klebsiella spp	Absent	Absent
Salmonella spp	Present	Absent
Note : Present indicates only very few organisms were found Absent indicates total absence of the corresponding organism

Table 4: Antibacterial activity of the cashew gum sample

Organism	Concentration of the purified gum sample used
	20mg/cc	30mg/cc	40mg/cc	50mg/cc
Escherichia coli	--	--	--	--
Staphylococcus aureus	--	--	--	--
Pseudomonas aeuroginosa	--	--	--	--
Klebsiella spp	--	--	--	--
Candida albicans	--	--	--	--
indicates no zone of inhibition on the inoculated solid medium with wells containing the respective concentration of gum

CONCLUSION:

Cashew gum has a good amount of inorganic minerals and protein content. It can be thus used in food industry as a nutrient supplement and as an additive in various processed foods. Its ease of storage, non toxic nature and non reactive nature would mean that it can be used in pharmaceuticals as an excepient.

Absence of any antibacterial activity suggests that it has a limited use as a therapeutic agent.

Thus Cashew gum can be used as an economical substitute to gums and agglutinants in food and pharmaceutical industry.

REFERENCES:

1 Glicksman M,Gum Technology in Food industry, Academic press journal USA, 11-16. 1969

2 Cheila Mothe, Ivone A De Souza,Glicia M T Calazaris,Agro food Industry,Vol 19, 50. 2008

3 Da Silveira Noguiera Lima R, Rabelo Lima J, Rebiero De Salis C, De Azevedo Moreira R, Lecithin and Glycoconjugates Laboratory, Federal University of Ceara, Brazil.

4 AOAC Official Methods of Analysis, 15th Ed., Association of Official Analytical Chemists, Inc., Arlington, VA.1990.

5 British Pharmacopoeia,. Vol IV, Her Majesty Stationery Office, London, pp: A260. 2005

6 British Pharmacopoeia, Vol I Her Majesty Stationery Office, London, pp: 372009.

7 Dubois, M., Giles, K. A., Hamilton, J. K., Rebers, P. A. and Smith,FAnal. Chem. 28, 350–356,1956

8 Mehrotra, Samboli Principles of Microbiology,Tata Mc Graw Hill Publication,pg 109,2009

9 Cappucino, Microbiology: Laboratory manual, Pearson publication.

Received on 07.03.2014 Modified on 28.03.2014

Asian J. Research Chem. 7(4): April 2014; Page 404-406