Enzyme inhibitory and antioxidant activities of traditional medicinal plants: potential application in the management of hyperglycemia.
BACKGROUND
Traditional Indian and Australian medicinal plant extracts were investigated to determine their therapeutic potential to inhibit key enzymes in carbohydrate metabolism, which has relevance to the management of hyperglycemia and type 2 diabetes. The antioxidant activities were also assessed.


METHODS
The evaluation of enzyme inhibitory activity of seven Australian aboriginal medicinal plants and five Indian Ayurvedic plants was carried out against α-amylase and α-glucosidase. Antioxidant activity was determined by measuring (i) the scavenging effect of plant extracts against 2, 2-diphenyl-1-picryl hydrazyl (DPPH) and 2, 2'-azinobis-3-ethylbenzothiazoline-6-sulfonate (ABTS) and (ii) ferric reducing power. Total phenolic and total flavonoid contents were also determined.


RESULTS
Of the twelve plant extracts evaluated, the highest inhibitory activity against both α-amylase and α-glucosidase enzymes was exerted by Santalum spicatum and Pterocarpus marsupium with IC50 values of 5.43 μg/ml and 0.9 μg/ml, respectively, and 5.16 μg/ml and 1.06 μg/ml, respectively. However, the extracts of Acacia ligulata (IC50 = 1.01 μg/ml), Beyeria leshnaultii (0.39 μg/ml), Mucuna pruriens (0.8 μg/ml) and Boerhaavia diffusa (1.72 μg/ml) exhibited considerable activity against α-glucosidase enzyme only. The free radical scavenging activity was found to be prominent in extracts of Acacia kempeana, Acacia ligulata followed by Euphorbia drummondii against both DPPH and ABTS. The reducing power was more pronounced in Euphorbia drummondii and Pterocarpus marsupium extracts. The phenolic and flavonoid contents ranged from 0.42 to 30.27 μg/mg equivalent of gallic acid and 0.51 to 32.94 μg/mg equivalent of quercetin, respectively, in all plant extracts. Pearson's correlation coefficient between total flavonoids and total phenolics was 0.796.


CONCLUSIONS
The results obtained in this study showed that most of the plant extracts have good potential for the management of hyperglycemia, diabetes and the related condition of oxidative stress.
Environment and Biotechnology Centre, Faculty of Life and Social Sciences, Swinburne University of Technology, PO Box 218, Hawthorn 3122 VIC, Australia.
Vandana
V
Gulati
Ian H
IH
Harding
Enzo A
EA
Palombo
D000975:Antioxidants / Q000032:analysis / Q000494:pharmacology* / Q000627:therapeutic use; D001315:Australia; D052160:Benzothiazoles; D001713:Biphenyl Compounds / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000201:enzymology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000032:analysis / Q000494:pharmacology* / Q000627:therapeutic use; D005290:Ferric Compounds / Q000378:metabolism; D005419:Flavonoids / Q000032:analysis / Q000494:pharmacology*; D065089:Glycoside Hydrolase Inhibitors; D006943:Hyperglycemia / Q000201:enzymology / Q000378:metabolism / Q000517:prevention & control*; D007194:India; D019684:Magnoliopsida / Q000737:chemistry*; D008515:Medicine, Ayurvedic; D018384:Oxidative Stress; D010636:Phenols / Q000032:analysis / Q000494:pharmacology*; D008517:Phytotherapy; D010851:Picrates / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D010946:Plants, Medicinal / Q000737:chemistry; D013451:Sulfonic Acids / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism; D000516:alpha-Amylases / Q000037:antagonists & inhibitors
D000975:Antioxidants; D052160:Benzothiazoles; D001713:Biphenyl Compounds; D004791:Enzyme Inhibitors; D005290:Ferric Compounds; D005419:Flavonoids; D065089:Glycoside Hydrolase Inhibitors; D010636:Phenols; D010851:Picrates; D010936:Plant Extracts; D013451:Sulfonic Acids; D013844:Thiazoles; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C004931:1,1-diphenyl-2-picrylhydrazyl; D000516:alpha-Amylases