ABSTRACT
Abstract ................................................................................................. 189 4.1 Introduction .................................................................................. 189 4.2 Methodology ................................................................................ 194
4.2.1 Plant Collection and Extraction ....................................... 194 4.2.2 Antioxidant Assays .......................................................... 194 4.2.3 Determination of Total Phenolic Content (TPC) ............. 195 4.2.4 Pro-oxidant Assay ............................................................ 195 4.2.5 α-Glucosidase Inhibition Assay ....................................... 196 4.2.6 α-Amylase Inhibition Assay ............................................. 197 4.2.7 AR Inhibitory Activity ..................................................... 197 4.2.8 AGEs Formation InhibitoryActivity ................................ 198 4.2.9 MTT Viability Assay ........................................................ 198
4.2.10 3T3-L1 Pre-adipocyte Differentiation ............................. 199 4.2.11 2-NBDG Uptake in 3T3-L1 Adipocytes .......................... 200 4.2.12 Adiponectin Quantification .............................................. 200 4.2.13 Toxicity Evaluation .......................................................... 201 4.2.14 Isolation and Identification of Active Compounds
from S. aqueum Leaf ....................................................... 203
4.3 Discussion and Results ................................................................ 204 4.3.1 Taxonomic Classification of S. aqueum .......................... 204 4.3.2 Antioxidant Activity ......................................................... 204 4.3.3 Pro-oxidant Capability ..................................................... 206 4.3.4 Antidiabetic Activity of S. aqueum leaf Extract .............. 207 4.3.5 Viability of 3T3-L1 Cells ..................................................211 4.3.6 Differentiation of 3T3-L1 Pre-adipocytes ....................... 212 4.3.7 2-NBDG Uptake in 3T3-L1 Adipocytes .......................... 214 4.3.8 Increase in Adiponectin Secretion ................................... 216 4.2.9 Toxicity Evaluation of S.aqueum Leaf Extract ................ 217 4.3.10 Isolation and Identification of the Bioactive
Compounds from S. aqueum Leaf .................................... 222 4.4 Conclusion ................................................................................... 224 Keywords .............................................................................................. 224 References ............................................................................................. 225
ABSTRACT
The various parts of Syzygium aqueum (S. aqueum) has been used in traditional medicine. In this study, the leaf extracts have been shown to have significant compositions of phenolic compounds, protective activity against free radicals as well as having lipid peroxidation inhibition activity and low pro oxidant capability. This investigation also revealed its effectiveness in inhibiting the carbohydrate hydrolyzing enzymes, α-glucosidase and α-amylase at more significant levels than the drug acarbose. In addition, it was able to inhibit the key enzyme in polyol pathway, aldose reductase (AR) and prevent the advanced glycation end-products (AGEs) formation. We also found that non-toxic concentrations of S. aqueum leaf extract was able to induce differentiation in 3T3-L1 pre-adipocytes, enhance fluorescent deoxyglucose analog (2-NBDG) uptake into mature adipocytes in the absence and presence of insulin and was able to increase adiponectin secretion. In subacute toxicity studies, where leaf extract were administered to rats for 14 days did not result in death or show any adverse effects. No significant differences in body weight or relative organ weight and no gross or microscopic abnormalities were observed. Furthermore, all biochemical tests performed on the sera of the experimental animals was in the range of the normal control groups. In addition, the elemental content in the extract was far below the permissible level for nutraceuticals. Thus, the standardized ethanolic extract of S. aqueum leaf can be considered devoid of any toxic risk. Six flavonoid compounds, 4-hydroxybenzaldehyde (1), myricetin-3-O-rhamnoside (2), europetin-3-O-rhamnoside (3), phloretin (4), myrigalone-G (5) and myrigalone-B,and (6), were isolated from the ethanolic extract of S. aqueum leaf. The results strongly suggest the antioxidant and antidiabetic potential of S. aqueum leaf extract.
