Abstract
BackgroundThere is a need to develop potential new therapies for the management of diabetes and hypertension. Australian medicinal plants collected from the Kuuku I’yu (Northern Kaanju) homelands, Cape York Peninsula, Queensland, Australia were investigated to determine their therapeutic potential. Extracts were tested for inhibition of protein glycation and key enzymes relevant to the management of hyperglycaemia and hypertension. The inhibitory activities were further correlated with the antioxidant activities.MethodsExtracts of five selected plant species were investigated: Petalostigma pubescens, Petalostigma banksii, Memecylon pauciflorum, Millettia pinnata and Grewia mesomischa. Enzyme inhibitory activity of the plant extracts was assessed against α-amylase, α-glucosidase and angiotensin converting enzyme (ACE). Antiglycation activity was determined using glucose-induced protein glycation models and formation of protein-bound fluorescent advanced glycation endproducts (AGEs). Antioxidant activity was determined by measuring the scavenging effect of plant extracts against 1, 1-diphenyl-2-picryl hydrazyl (DPPH) and using the ferric reducing anti-oxidant potential assay (FRAP). Total phenolic and flavonoid contents were also determined.ResultsExtracts of the leaves of Petalostigma banksii and P. pubescens showed the strongest inhibition of α-amylase with IC50 values of 166.50 ± 5.50 μg/mL and 160.20 ± 27.92 μg/mL, respectively. The P. pubescens leaf extract was also the strongest inhibitor of α-glucosidase with an IC50 of 167.83 ± 23.82 μg/mL. Testing for the antiglycation potential of the extracts, measured as inhibition of formation of protein-bound fluorescent AGEs, showed that P. banksii root and fruit extracts had IC50 values of 34.49 ± 4.31 μg/mL and 47.72 ± 1.65 μg/mL, respectively, which were significantly lower (p < 0.05) than other extracts. The inhibitory effect on α-amylase, α-glucosidase and the antiglycation potential of the extracts did not correlate with the total phenolic, total flavonoid, FRAP or DPPH. For ACE inhibition, IC50 values ranged between 266.27 ± 6.91 to 695.17 ± 15.38 μg/mL.ConclusionsThe tested Australian medicinal plant extracts inhibit glucose-induced fluorescent AGEs, α-amylase, α-glucosidase and ACE with extracts of Petalostigma species showing the most promising activity. These medicinal plants could potentially be further developed as therapeutic agents in the treatment of hyperglycaemia and hypertension.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-016-1421-5) contains supplementary material, which is available to authorized users.
Highlights
There is a need to develop potential new therapies for the management of diabetes and hypertension
The tested Australian medicinal plant extracts inhibit glucose-induced fluorescent advanced glycation endproducts (AGEs), α-amylase, αglucosidase and angiotensin converting enzyme (ACE) with extracts of Petalostigma species showing the most promising activity. These medicinal plants could potentially be further developed as therapeutic agents in the treatment of hyperglycaemia and hypertension
We investigated the effect of selected Australian medicinal plant extracts for α-amylase, α-glucosidase, and ACE inhibition and antiglycation related to hyperglycaemia
Summary
There is a need to develop potential new therapies for the management of diabetes and hypertension. Type II diabetes mellitus is a chronic disease characterised by high blood glucose level or hyperglycaemia. Non-insulin dependent hyperglycaemia characterises the early stages of type II diabetes due to the increased breakdown of starch by α-amylase and absorption of glucose by α-glucosidase [6, 7]. The inhibition of these enzymes can significantly decrease the postprandial increase in blood glucose level after a mixed carbohydrate diet, it is an important strategy for the management of hyperglycaemia linked to type II diabetes [7]. One of the long-term complications of type II diabetes is arterial hypertension, which may eventually result in cerebrovascular accidents and cardiovascular diseases
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