Introduction

In traditional medicinal systems of India, different parts of the plant have been claimed to have medicinal properties. The large number of herbal products including several metals and minerals has been reported for the care of diabetes mellitus in ancient literature¹. The plant drugs are considered to be less toxic and free from side effects than synthetic drugs ².The Syzygium cumini (jamun) is a large evergreen tree, grown widely in the indegangetic plains and also in the Cauvery delta of Tamilnadu ³. The jamun belongs to the family Myrtaceae and is botanically identified as Syzygium cumini Linn⁴ . Syzygium cumini (Jamun) seeds have hypoglycaemic^5,6,7 , anti-inflammatory ⁸, antipyretic ⁹, psychopharmacological ¹⁰ , hypolipidaemic ¹¹, and antioxidant ^{12, 13, 14} activities. It is reported that the jamun seed extracts given to animals with 5 g/Kg body weight was more effective than glibenclamide⁶ _, an  antidiabetic or hypoglycaemic drug mostly given orally in case of diabetes type-2. Glibenclamide is also glucoamylase inhibitor. Thus it controls the degradation of glycogen and maintains glucose level in the blood. Reports are available that a decoction of the dry leaves of the Syzygium cumini gives hypoglycaemic effect ¹⁵ . The oral administration of alcoholic seed extract of jamun has a hypoglycaemic effect which also reduces glycosuria ³. There is no report available on aqueous and alcoholic extracts of Syzygium cumini (Jamun) seed on glucoamylase and antibacterial activity. In the present work we have studied the effect of aqueous and alcoholic extracts of Syzygium cumini (Jamun) seed isolated at different temperatures on glucoamylase and antibacterial activity in vitro.

Material And Methods

Plant material

Syzygium cumini (Jamun) seeds were collected fresh from local market, and washed with distilled water and dried in presence of sunlight. The plant was identified and authenticated at the Blatter Herbarium ST. Xavier’s College, Mumbai-400 001, India, with specimen no. 1848 of G.L.Shah. The dried seeds were ground in electrical mill and the powdered seeds were kept separately in plastic containers in dark until used.

Preparation of aqueous Jamun seed extracts (JSEts) at different temperatures

A suspension of 10 g of seed powder in 100 ml of distilled water was stirred manually for half an hour at 4⁰C temperature. The suspension was centrifuged for 5 minutes at about 6000 rpm. The centrifugate was evaporated to dryness at 80⁰C in an oven. Similarly the aqueous extracts were prepared at 10, 15, 20, 25, 30, 35, 40, 45 and 50⁰C.

Preparation of methanolic Jamun seed extracts (JSEts) at different temperatures

A suspension of 10 g of seed powder in 100ml of methanol was stirred manually for half an hour at 4⁰C temperature. The suspension was centrifuged for 5 minutes at about 6000 rpm. The centrifugate was evaporated to dryness at 80⁰C in an oven. Similarly the aqueous extracts were prepared at 10, 15, 20, 25, 30, 35, 40, 45 and 50⁰C.

Antibacterial study

The aqueous and methanolic extracts obtained at different temperatures were tested against four microorganisms by agar cup method ¹⁶. All bioassays were carried out in triplicate and average values were taken.

Glucoamylase activity

1 mL of the reaction mixture containing 0.5 mL of starch solution (5 mg/mL prepared in 100 mM acetate buffer pH 4.5) and a suitable amount of enzyme (0.1 mL, 2 mg) were incubated at 37⁰C for 30 minutes. The reaction was terminated by keeping the test tubes in boiling water bath for 1-2 minutes, cooled under running tap water and the liberated glucose was estimated by DNS method ¹⁷. A unit activity is defined as the mg of glucose liberated per mg of protein per minute.

Results and Discussion

The oral administration of aqueous and alcoholic extracts of Syzygium cumini (jamun) seed resulted in a significant reduction in blood glucose level^{15, 18 , 19}. There is no report available for the study of aqueous and alcoholic extracts of Syzygium cumini (Jamun) seed isolated at different temperatures on glucoamylase and antibacterial activity. In the present project we have studied the effect of aqueous and alcoholic extracts of Syzygium cumini (Jamun) seed isolated at different temperatures on glucoamylase in vitro.

The percentage yield of aqueous and methanolic extracts of Syzygium cumini seeds are depicted in Table 1. The percentage yield of aqueous extracts of Syzygium cumini seeds were significantly elevated at different temperatures as compared to methanolic extracts. Maximum 18% yield with water whereas only 8% yield is obtained with methanol between +4 to 50⁰C.

Table 1: Percentage yield of aqueous and methanolic JSEts.

The inhibition of glucoamylase of aqueous and methanolic JSEts isolated at different temperatures is given in Fig. 1. In our study, we have found that the aqueous and methanolic JSEts inhibits the glucoamylase activity in vitro. The methanolic JSEts isolated at different temperatures are found inhibitors of glucoamylase activity as compared to aqueous JSEts. The aqueous JSEt isolated at 25^oC and the methanolic JSEt isolated at 10^oC shows 35% and 50% inhibition of glucoamylase respectively. It is also observed that the percentage inhibition is 5% and 25 % in case of aqueous and methanolic extract respectively isolated at 45⁰C. The possible mechanism by which JSEts bring about its hypoglycaemic action may be by affecting the activity of glucoamylase or by increasing the glycogen biosynthesis. The significant inhibition of glucoamylase suggests that the active hypoglycaemic compound present in aqueous and methanolic extracts of jamun seeds does not necessarily require the presence of functioning of β-cells for its favorable action seen in type-I. It means the aqueous and methanol JSEts may act in a variety of diabetic conditions with or without functioning of pancreatic β-cells. An antibacterial effect of methanolic and aqueous JSEts is given in Table 3 and Table 4 respectively. The methanolic JSEts shows  remarkable antibacterial activity as compared to aqueous JSEts.

Figure 1: Inhibitory action of aqueous and methanolic JSEts on glucoamylase in vitro.   Click here to View figure

Table 3: Antibacterial activity of methanolic extracts of seeds of Syzygium cumini.

Table 4: Antibacterial activity of aqueous extracts of seeds of Syzygium cumini

Acknowledgements

We kindly acknowledge the UGC, New Delhi, India for financial assistance. We are also thankful to the micro-analytical division, University department of chemistry, Mumbai, India for instrumental support.

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