Syzygium aqueum leaf extracts for possible antidiabetic treatment

Syzygium aqueum, a species in the Myrtaceae family, has been welldocumented as a medicinal plant. In this study, we show Syzygium aqueum leaf extract to protective activity against free radicals as well as having low pro-oxidant capability. Recent attention has been focused on plant extracts and plant derived compounds to treat type 2 diabetes. Plants that serve both as antioxidant scavengers as well as antidiabetic agents would be ideal to treat diabetes and its complications. Our investigations revealed the effectiveness of Syzygium aqueum leaf extract in inhibiting the carbohydrate hydrolyzing enzymes, α-glucosidase and α-amylase at more significant levels than the commercial drug acarbose. In addition, the extract was able to inhibit the key enzyme in the polyol pathway, aldose reductase and prevent the AGE formation. It is also highly desirable to find natural antidiabetic alternatives that stimulate adipogenesis and glucose uptake in adipocytes but, unlike TZDs, do not induce obesity or other side effects. We found that non-toxic concentrations of the extract was able to induce differentiation in 3T3-L1 preadipocytes, enhance glucose uptake in mature adipocytes and was able to increase adiponectin secretion. Sub-acute toxicity studies using Sprague Dawley rats showed no toxicity effects of the extract up to concentrations of 2000 mg/kg. The structural characterization of the active compound(s) in plant extracts could thus lead to the formulation of new therapeutic drug to treat diabetes mellitus. Six flavonoid compound 4-hydroxybenzaldehyde, myricetin-3-O-rhamnoside, europetin-3-O-rhamnoside, phloretin, myrigalone-G, and myrigalone-B, were isolated from the extract of S. aqueum leaf. Our results strongly suggest the antioxidant and antidiabetic potential of S. aqueum leaf extract. There are plenty of opportunities for nutraceutical and pharmaceutical industries to use S. aqueum leaf for the management of diabetes mellitus.