Department of Biology, Gandhigram Rural Institute-Deemed University, Gandhigram 624302 Dindigul (TN), India
Received: 27 Jan 2017, Revised and Accepted: 20 Apr 2017
Objective: The present investigation comprises, in vitro antidiabetic activity such as α-amylase and α-glucosidase inhibitory activities and in vivo antidiabetic activity of methanolic extract of Pleurotus florida.
Methods: The fruiting bodies of Pleurotus florida were obtained from Mushroom Unit, Department of Biology, Gandhigram Rural Institute-Deemed University, Gandhigram, Dindigul, Tamil Nadu, India. Sample preparation, qualitative phytochemical analysis, in vitro antidiabetic activities namely α-amylase and α-glucosidase inhibitory activity and in vivo antidiabetic activity namely evaluation of alloxan induced diabetic rats were carried out following the methods reported previously.
Results: In vitro and in vivo antidiabetic activity of P. florida exhibited significant results for its α-amylase (94.93±1.75 % at 1000 µg/ml) and α-glucosidase inhibitory activity (84.90±0.42 % at 1000 µg/ml) in a dose-dependent manner. The extract also showed significant antidiabetic activity on in vivo (p<0.05) at the tested dose level (200 mg/kg b. w) this was comparable to Glibenclamide, a standard antidiabetic drug.
Conclusion: The presence of phytochemicals namely phenols, flavonoids, saponins, tannins and terpenoids may be responsible for such antidiabetic activity. These results reveal that P. florida can be used as a potential antidiabetic agent.
Keywords: Pleurotus florida, Phenols, Flavonoids, Antidiabetic activity, Antidiabetic agent
© 2017 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Diabetes mellitus is a metabolic disorder due to absolute or relative insulin deficiency . According to World Health Organization  bout 10 % of the total population and about one out of five persons above the age of 50 suffer from this disease and it is a major cause of morbidity and mortality. The increasing worldwide incidence of diabetes mellitus in adults constitutes a global public health burden. It is predicted to be doubled by the year 2030 to about 380 million where in India, China, and the United States will have the largest number of people with diabetes . Diabetes mellitus may present with characteristic symptoms such as thrust, polyuria, blurring of vision and weight loss . The long-term effects of diabetes mellitus include progressive development of the specific complications of retinopathy with blindness, nephropathy that may be lead to renal failure or neuropathy with risk of foot ulcers, amputation, Charcot joints and sexual dysfunction . Currently, available therapy for diabetes includes insulin and various oral antidiabetic agents such as sulfonylurea, biguanide, metformin, α-glucosidase inhibitors, troglitazone but these are known to have a number of serious adverse effects in patients [5-7].
Plants and fungi are the main sources of natural compounds used for medicine. They have attracted considerable interest because of their wide variety of bioactive metabolites . The mushrooms are being developed as nutriceutical and nutraceutical to garner the essence of mushrooms and to make consumption easy. Further, scientific validation of traditional knowledge bears evidence of the many positive effects of consuming mushrooms fresh or processed on human health. A wide variety of bioactive compounds isolated from many species of mushrooms have been identified .
Pleurotus florida, commonly known as the white oyster mushroom is one of the most economically important edible mushrooms that grow predominantly in tropical regions and it is considered as the valuable health food with high content of protein . Moreover, this mushroom has been demonstrated to possess various valuable biological properties including antioxidant , antimicrobial , anti-inflammatory , antitumor  as well as antidiabetic activities [15-17]. Till now most studies have been focused on in vitro antidiabetic activities of P. florida concerning α-amylase and α-glucosidase activities. Although a wide range of model systems are available for evaluation of antidiabetic activities, the choice mainly depends on the nature of the substances under investigation. There is evidence for discrepancies in antidiabetic activities of substances when tested in vitro and in vivo. Therefore, in the present study, the methanolic extract of P. florida was subjected to the qualitative analysis of phytochemicals and also for its antidiabetic activities using in vitro studies namely, α-amylase, α-glucosidase, and in vivo antidiabetic activity of alloxan induced diabetic rats were carried. The investigation of the local species may yield mycochemicals with novel medicinal properties that can be used for the development of therapeutic agents in diabetes and for other ailments.
The fruiting bodies of Pleurotus florida were obtained from Mushroom Unit, Department of Biology, Gandhigram Rural Institute-Deemed University, Gandhigram, Dindigul, Tamil Nadu, India. Sample preparation ,qualitative phytochemical analysis , in vitro antidiabetic activities namely α-amylase  and α-glucosidase  inhibitory activity and in vivo antidiabetic activity namely evaluation of alloxan induced diabetic rats were carried out following the methods reported previously .
Animal experiments were carried out according to the guidelines of the Committee for the purpose of control of experiments on animals and approved by the Institutional Animal Ethics Committee (Reg. No.: CPCSEA/265).
The results were expressed as mean values and standard deviation (SD). Linear regression analysis was used to calculate IC50 value. Data were analyzed using One-Way Analysis of Variance (ANOVA) followed by Turkey's multiple comparison post hoc tests using SPSS software 16.0 versions.
Values of p<0.05 were considered as statistically significant.
Qualitative phytochemical screening
Methanolic extract of P. florida was qualitatively analyzed and presented in table 1. Among the various phytochemicals assessed, the presence of phenols, flavonoids, saponins, tannins and terpenoids were detected.
In vitro antidiabetic activity
The methanolic extract of P. florida showed significant inhibition of α-amylase (94.93±1.75 % at 1.0 mg/ml) and α-glucosidase (84.90±0.42 % at 1.0 mg/ml) inhibitory activity in a dose-dependent manner and the concentrations required for 50 % of the above inhibition (IC50) were 35.96±0.35 µg/ml and 202.02±3.84 µg/ml, respectively (table 2).
In vivo antidiabetic activity
In vivo antidiabetic study revealed the significant reduction of blood glucose, serum cholesterol, serum triglyceride, LDL levels and significant increase of HDL level in P. florida treated diabetic rats in 14 d’s trials (table 3).
Table 1: Qualitative phytochemical screening of Pleurotus florida
|S. No.||Test for extracts||Inference|
Table 2: It shows in vitro antidiabetic activities of Pleurotus florida inhibition of α-amylase and α-glucosidase inhibitory activity
|α-amylase inhibition activity (%)||
|α-glucosidase inhibition activity (%)||
Data represent the mean ± SEM (n = 3) (p<0.05)
Table 3: It shows in vivo antidiabetic study blood glucose, serum cholesterol, serum triglyceride, LDL and HDL levels of Pleurotus florida treated diabetic rats in 14 d trials
Pleurotus florida is a good source of extractable phytochemicals with inhibitory potentials against key enzymes namely, α-amylase and α-glucosidase linked to Type 2 diabetes mellitus. In vitro tests can play a very important role in the evaluation of antidiabetic activity of drugs as initial screening tools, where the screening of a large number of potential therapeutic candidates may be necessary. They might provide useful information on the mechanism of action of therapeutic agents [22-24]. The therapeutic approach for treating Type 2 diabetes is to decrease the post-prandial glucose levels. This could be done by retarding the absorption of glucose through the inhibition of the carbohydrates hydrolyzing enzymes, α-amylase and α-glucosidase, present in the small intestinal brush border that is responsible for the breakdown of oligosaccharides; disaccharides into monosaccharides suitable for absorption [25-28]. Inhibitors of these enzymes, like acarbose, delay carbohydrate digestion and prolong overall carbohydrate digestion time, causing a reduction in the rate of glucose absorption and consequently blunting the postprandial plasma glucose rise . Jumepaeng et al.  reported that the α-amylase inhibitory activity was significantly higher as compared to acarbose drug currently administrated for controlling glucose levels in diabetic patients. Natural products from plants have shown lower inhibitory activity against the α-amylase activity and stronger inhibitory activity against noninsulin dependent diabetes mellitus (NIDDM) with minimal side effects. This is a positive result since as explained earlier, the excessive inhibition of α-amylase results in the abnormal bacterial fermentation of undigested carbohydrates in the colon, which in turn results in abdominal digestion, flatulence, meteorism and possibly diarrhoea .
Alpha-amylase inhibitors are copious in fungi, higher plants, and animals . These living beings create a large number of diverse protein inhibitors of α-amylases in order to regulate the activity of these enzymes. Like amylase inhibitors which are also well-known as starch blockers as they avoid dietary starches from being digested and absorbed by the body. This could be helpful for treating obesity and diabetes mellitus . The presence of inhibition to α-glucosidase activity in the extracts of P. florida could be caused by the presence of carbohydrate and protein (flavanols) which are suspected to be the competitive inhibitors for the α-glucosidase enzyme. This is appropriate with the substrate of α-glucosidase, which is a food starch and carbohydrate (glycogen) . Alpha-glucosidase inhibitors focusing on reducing the digestion of carbohydrate are the most common and efficacious agents utilized for the treatment of Type 2 diabetes [34, 35]. Since α-glucosidase inhibitors prevent the hybridization of carbohydrates into glucose, a lot of carbohydrates remain in the intestine. Therefore the bacteria will digest carbohydrates, which may cause gastrointestinal side effects such as flatulence and diarrhoea .
In the present study, in vitro antidiabetic studies revealed the inhibition of α-amylase and α-glucosidase activity. The percentage inhibition at 200, 400, 600, 800 and 1000 μg/ml concentrations of P. florida on α-amylase and α-glucosidase showed a concentration dependent reduction in percentage inhibition. Therefore, the antidiabetic effect of P. florida might attribute to its inhibitory effect against α-amylase and α-glucosidase that delaying the digestion of carbohydrate to delay the postprandial rise in blood glucose. In the in vivo studies, blood glucose levels were assessed from 0 and 14th days in normal rats; diabetic-induced rats; mushroom extracts treated rats and also glibenclamide-treated rats. There is a significant reduction in all antidiabetic parameters on the 14th day in the rats treated with P. florida extracts. In the in vivo studies, alloxan-induced diabetic rats showed the significant increase in the levels of blood glucose than the diabetic rats (p<0.05). Blood glucose level was measured in normal and diabetic rats on day 0 and 14th day of drug treatment. After treatment with both species at 200 mg/kg b. w, the blood glucose levels on day 14th were significantly reduced compared to those on day 0 (p<0.01). The glibenclamide-treated rats also showed the significant reduction in serum glucose level (p<0.05). P. florida and glibenclamide administration attenuated hyperglycemia, while no significant changes were observed in normal and diabetic groups (p>0.05).
Mushrooms have been shown to be useful in supporting healthy cholesterol levels and have been shown to improve circulation; also they have been shown to help in maintaining blood sugar balance via blood sugar lowering effects, elevation of plasma insulin levels and enhanced liver metabolism of glucose and increase cellular insulin sensitivity . Hyperglycemia caused by diabetes is known to be a cause of oxidative stress that leads mainly to the enhanced production of mitochondrial ROS. Oxidative stress induced by hyperglycemia leads to the activation of stress-sensitive signaling pathways, which worsen both insulin secretion; action and promote the development of Type 2 diabetic mellitus [38-41]. Fasting hyperglycemia is a hallmark of diabetic mellitus. It has been postulated but is still debated that the fasting hyperglycemia in noninsulin-dependent diabetic mellitus arises from the hepatic overproduction of glucose .
Wi et al.  suggested that the post-absorptive hyperglycemia in Streptozotocin-diabetic rats is largely due to decreasing peripheral glucose clearance, while increased hepatic glucose output might also be a contributing factor at a very high Streptozotocin dose. Krishna et al. stated that polysaccharide extracted from P. citrinopileatus showed blood glucose lowering effect in rats. These findings suggest that mushrooms are promising antidiabetic nutriceuticals, but there is the lack of enough clinical evidence. Khan et al.  have reported that oral administration of P. ostreatus given to rat’s leads to blood glucose lowering effect in both insulin-dependent and insulin-independent diabetic conditions. Prabu and Kumuthakalavalli  experimentally found that methanolic extract of C. indica exhibited antidiabetic activity by lowering the levels of blood glucose, serum cholesterol, serum triglyceride, LDL levels and significant increase of HDL level. Antidiabetic effects of ethanolic extract of P. ostreatus on alloxan induced diabetic rats was extensively studied and reported as an effective antidiabetic regimen .
The methanolic extract of P. florida with its significant antidiabetic activity in rats, suggests its therapeutic potential for the prevention and control of diabetics; moreover, the mushroom species can be used as an easily accessible source of natural antidiabetic and as a possible food supplement or in the pharmaceutical industry. However, more intensive and extensive investigations are needed to exploit their valuable therapeutic potentials and the chemical characteristics of the antidiabetic components in the extracts should be further investigated.
The authors express their sincere thanks to the Principal, and the Head, Department of Pharmacology, The Periyar College of Pharmaceutical Sciences, Tiruchirapalli, for providing laboratory facilities.
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How to cite this article
Prabu M, Kumuthakalavalli R. Antidiabetic potential of the oyster mushroom Pleurotus florida (mont.) singer. Int J Curr Pharm Res 2017;9(4):51-54.