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‘Water apple’ extract may provide dietary support for diabetes

By Nathan Gray , 20-Jan-2012

Extracts of a Malaysian medicinal plant known locally as the ‘water jambu’ or ‘water apple’ could provide bioactive compounds that help to support people suffering from diabetes by reducing lowering blood sugar levels, suggest researchers.

According to research published in Food Chemistry , extracts of water apple (Syzygium aqueum) leaf may contain flavanoids that have the ability to stabilise or lower blood sugar levels – referred to as anti-hyperglycaemic activity.

The research team, led by Dr Uma Palanisamy, and based at Monash University in Malaysia, explained that the extract was found to contain six flavanoid compounds some of which were established to be more effective than certain anti-diabetes drugs in blocking the action of carbohydrate hydrolysing enzymes (that are key to blood sugar management).

“The results obtained in this study and our on-going work will provide the biochemical rationale to include specific S. aqueum leaf extract, or its bioactivity, as part of a dietary support for managing hyperglycaemia linked to Type-2 diabetes,” said Palanisamy and her colleagues.

“The active compounds of S. aqueum leaf were seen to inhibit α-glucosidase and α-amylase activity far better than the antidiabetic drug, acarbose,” they revealed.

Palanisamy and her team said their findings provide ‘a strong rationale’ to establish for the water apple’s capability as an anti-hyperglycaemic agent.

Study details

The research team found and isolated six flavonoid compounds from the leaf extract: 4-hydroxybenzaldehyde, myricetin-3-O-rhamnoside, europetin-3-O-rhamnoside, phloretin, myrigalone-G, and myrigalone-B.

“Our investigation revealed [the extracts] effectiveness in inhibiting the carbohydrate hydrolysing enzymes, α-glucosidase (EC50 = 11 μg/ml) and α-amylase (EC50 = 8 μg/ml), at significant level than the commercial drug acarbose (EC50 = 28 μg/ml, α-glucosidase; EC50 = 12 μg/ml, α-amylase),” wrote Palanisamy and her co-workers.

In addition, the water apple leaf extracts were found to inhibit aldose reductase (key enzyme in the polyol pathway), and prevent the formation of advanced glycation end (AGE) products by 89%. The researchers said that by blocking the enzyme and slowing AGE formation the extract could potentially help to control the development of diabetes complications.

The team added that the flavonoid compounds isolated from the extract are being tested in the laboratory, “to reveal its ability to reduce insulin resistance.”

“It should be noted that although having such a low yield of bioactive compounds (2.6%), the S. aqueum leaf ethanolic extract exhibited significant carbohydrate hydrolysing enzyme and aldose reductase inhibition activity as well as prevented AGEs formation,” said the Malaysian researchers.

Source: Food Chemistry
Published online ahead of print, doi: 10.1016/j.foodchem.2011.11.147 ,
Flavonoids isolated from Syzygium aqueum leaf extract as potential antihyperglycaemic agents”
Authors: T. Manaharan, D. Appleton, H.M. Cheng, U.D. Palanisamy

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