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In vitro inhibitory effect of oriental melon (Cucumis melo L. var. makuwa Makino) seed on key enzyme linked to type 2 diabetes: Assessment of anti-diabetic potential of functional food

https://doi.org/10.1016/j.jff.2013.01.008Get rights and content

Abstract

As the world’s population continues to increase, the agricultural discards of plant origin have attracted considerable attention for various purposes in the pharmaceutical and food industry. The objective of present study was to evaluate the potential of oriental melon (Cucumis melo L. var. makuwa Makino) seed for management of hyperglycaemia-linked to type 2 diabetes. Ethanol and hexane extracts from oriental melon seed were used to evaluate their inhibitory activities against α-glucosidase and α-amylase. Low phenolic-containing hexane extract exhibited much higher inhibitory activities against α-glucosidase and α-amylase than ethanol extract. The GC–MS result revealed that hexane extract constituted linoleic acid (29.6%), oleic acid (17.3%), and palmitic acid (6.5%). At high concentration, hexane extract exhibited strong inhibitory activities against α-glucosidase (35.3%) and α-amylase (61.8%). These in vitro studies indicated that hexane extract of oriental melon seed could be used as a potent alternative for controlling type 2 diabetes.

Highlights

► This study reminds people to reconsider and reuse wastes of agriculture. ► It helps consumers correct selecting this plant to manage a determinate disease. ► It provided effectiveness for a given period of harvest time.

Introduction

Diabetes mellitus is a chronic disease caused by inherited and/or acquired deficiency in insulin secrete and/or by decreased responsiveness of the organs to secreted insulin (insulin resistance). One practical therapeutic approach to the management of diabetes is by controlling postprandial hyperglycaemia. This can be achieved by the inhibition of carbohydrate hydrolysing enzymes such as α-amylase and α-glucosidase present in the gastrointestinal tract (Oboh et al., 2012). It is well known that during the disease state of diabetes mellitus, α-glucosidase and α-amylase can be detrimental, due to the biochemical defect causing blood glucose levels to be elevated. The inhibition of α-glucosidase and α-amylase can significantly reduce the post-prandial increase of blood glucose and therefore can be an important strategy in the management of blood glucose level in type 2 diabetic and borderline patients. The α-glucosidase inhibitor, acarbose improves sensitivity to insulin and decreases postprandial hyperglycaemia. However, the most frequent side-effects observed with acarbose therapy are gastrointestinal symptoms (Laube, 2002). Currently, there is renewed interest in plant-based medicines (Nickavar et al., 2008) and functional foods modulating physiological effects in the prevention and cure of diabetes (Tadera et al., 2006).

Melon crops are much diversified and comprise six subvarieties, among which the oriental melons (Cucumis melo L. var. makuwa) are commercially important. They are widely grown in Korea, China and East Asian countries and favoured by consumers, largely due to their high qualities, special flavours and consumer demands. Many researchers have paid attention towards the Cucurbitaceae family. Oriental melon seeds were reported to possess therapeutic effect such as antioxidant, anti-inflammatory, and analgesic properties (Gill et al., 2009). Thus, this present work was carried out to discuss the inhibitory effects of α-glucosidase and α-amylase by oriental melon (Cucumis melo L. var. makuwa Makino) seeds.

Section snippets

Preparation of oriental melon seed extract

Two different solvents (hexane and ethanol) were used to obtain extracts with different compositions. Air-dried seeds were crushed into powder in a grinder (Ya Horng Electronic Co., Ltd., China) with a size range of 0.5–1.2 mm, sealed in a plastic bag and stored at 4 °C until extraction. The extraction procedure was as follows: first, 10 g of melon seeds powder extracted with 250 mL hexane solvent at 150 °C for 3 h and repeated twice for the removal of triacylglycerol matter, then, the defatted seed

Total phenolic and fatty acid content

The content of extractable phenolic compounds in the oriental melon seed extracts was determined through a linear gallic acid standard curve (y = 0.0225x + 0.0084; r2 = 0.9982). As seen in Table 1, the variation of phenolic content was quite large. Total phenolic content presented in hexane and ethanol extract were 0.2 and 171.2 mg GAE/100 g DM, respectively. Due to the different biological potentials of compounds with different polarity (Julkunen-Tiito, 1985), solvent extraction is frequently used for

Conclusion

Oriental melon seed (Cucumis melo L. var. makuwa Makino) which has always been considered as an agricultural waste was demonstrated to be an effective inhibitor of α-glucosidase and α-amylase. Although the inhibitory effect of seed extracts has been established in vitro, these findings provided a potent alternative for controlling diabetes. To determine the true efficacy of the oriental melon seed hexane extracts as α-glucosidase and α-amylase inhibitors, studies in human subjects are necessary.

Acknowledgement

This research was supported by the communal research project (Project No. PJ008300) of Rural Development Administration, Korea.

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