Antioxidant and Antidiabetic Activities of Cucumis Melo Var. Flexuosus Leaf Extract

Cucumis melo var. flexuosus (C. melo var. flexuosus) is one of the ancient horticultural crops in many parts of the world. However, there has been no study reported its effects on diseases. Therefore, the aim of present study was to investigate antioxidant and antidiabetic activities of C. melo var. flexuosus leaf. First, the antioxidant activity of snake melon leaf extract was determined. Then the biochemical parameters for diabetic rats treated with snake melon (30, 60 and 120 mg/kg b.w) were investigated. The leaf extract showed a high antioxidant activity. Further, diabetic rats treated with snake melon leaf extract showed a significant decrease in the levels of blood glucose, total cholesterol, triglycerides and low-density lipoprotein cholesterol, lactate dehydrogenase, liver enzymes, and malondialdehyde and a significant increase in insulin, body weight, high-density lipoprotein cholesterol, total protein, catalase and superoxide dismutase levels. This study demonstrated the antioxidant and antidiabetic activities of leaf extract of snake melon. J Physiol Pharmacol 2018; 62(4) : 445–452 *Corresponding author : Tel. : +2 01063410190; Fax: +2 0133222578; E-mail address: Doaa.mohamed@fsc.bu. edu.eg (Received on July 1, 2018) and their low side effects (7). Cucumis melo L. (melon) is one of the most popular horticultural crops worldwide which belongs to the Cucurbitaceae family (8). Many studies were done on different plants of this family due to their nu t r i t iona l , m edic ina l , e thnoveter inary and ethnomedicinal values (9). Cucumis melo var. flexuosus is a member of this famous family that was known from ancient Egyptians and Romans (10). C. melo var. flexuosus has several names such as snake melon, Armenian cucumber, agoor, snake cucumber, and furious (11, 12). Its fruit is usually slender and is almost always bent and twisted (13). Immature fruits are harvested and consumed as a raw vegetable for salad and for medicinal use (8). Despite the fame of this plant as a vegetable used by many peoples, but its effect on our bodies is still Introduction Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and hypoinsulinemia or insul in res is tance (1) leading to a lo t of complications (2). It is supposed that oxidative stress plays an essential role in the development of diabetic complications (3). But, antioxidants stand as a protective shield against the risk of oxidative stress (4, 5). The plants are famous for containing a variety of bioactive compounds, such as antioxidants (6) 446 Ibrahim and El-Maksoud Indian J Physiol Pharmacol 2018; 62(4) expressed as mg of quercetin equivalent (QE/g of extract dry materials). The whole experiment was repeated three times. DPPH radical scavenging activity The method of Chew et al. (16) has been used for the scavenging ability of DPPH (2, 2-diphenyl-1p ic rylhydrazyl ) an t iox idant tes t wi th s l igh t modification. 1 ml of different concentrations of diluted extracts of the plant parts in ethanol was added to 1 ml of DPPH (0.15 mM in ethanol). 1 ml DPPH with 1 ml ethanol was prepared as a control. The reaction mixtures were mixed very well by hand and then incubated in the dark at room temperature for 30 min. The absorbance was measured at 517 nm with a UV-Visible spectrophotometer. The ascorbic acid was used as a positive control and the ethanol was used as a blank. The DPPH scavenging ability of plant extracts was calculated using the following equation : % scavenging activity = [(Abs control / Abs sample)]/ (Abs control)] ×100 The Abs control is the absorbance of DPPH + ethanol; Abs sample is the absorbance of DPPH + sample. All measurements were done in triplicate. Acute toxicity study The mean lethal dose (LD50) of the aqueous ethanolic extract of C. melo var. flexuosus leaf was determined in rats using the method described by Lorke (17). Experimental animals Male Wistar albino rats weighing 123–124 g were purchased f rom Helwan Farm o f Egypt ian Organization for Vaccine and Biological Preparations, Egypt. The rats were fed a standard chow diet and al lowed to dr ink water ad l ib i tum dur ing the experimental period (30 days). The rats were housed in animals cages under standard environmental conditions (22±1°C, 12 h light/12 h dark cycle). Animals were acclimatized for a period of 7 days in our laboratory condition prior to the experiment. unknown. Therefore, the present study was aimed to evaluate the possible antioxidant and antidiabetic activities of C. melo var. flexuosus leaf extract. Materials and Methods Plant material and preparation of extract Leaves of snake melon were collected from Benha, Egypt, in Augustus 2017 and authenticated by Dr. Mahran El Nagar (Department of Horticulture, Faculty of Agriculture, Benha University, Benha, Egypt). The fresh leaves (3.5 kg) were dried in the shadow, crushed to get 300 g of homogeneous fine powder and then extracted with 70% ethanol using a Soxhlet apparatus. The aqueous ethanolic extract was concentrated at 35-40°C using a rotary evaporator to give 30 g of solid extract. After that, the extract was stored at –10oC for experimental use. Determination of total phenolic content (TPC) Total phenolic content in the extract was determined by Folin-Ciocalteu reagent (14). Leave extract (200 μg/ml) was mixed with the Folin Ciocalteu reagent (400 μl) and 1.5 ml of 20% sodium carbonate. The mixture was shaken thoroughly and made up to 10 ml of distilled water. After 2 h, the absorbance at 765 nm was determined. The concentration of total phenolic content was determined as mg of gallic acid equivalent (GAE) per g of dry weight of plant powders. The whole experiment was repeated three times. Determination of total flavonoid content (TFC) Total flavonoid content was determined according to the method described by Kumaran (15). 1 ml of plant extract in ethanol (200 μg/ml) was mixed with 1 ml aluminum trichloride in ethanol (20 mg/ml) and a drop of acetic acid and then diluted with ethanol to 25 ml. The absorption at 415 nm was read after 40 min. Blank samples were prepared from 1 ml of plant extract and a drop of acetic acid and then diluted to 25 ml with ethanol. The total flavonoid content was determined using a standard curve of quercetin and Indian J Physiol Pharmacol 2018; 62(4) Antioxidant and Antidiabetic Activities of Cucumis Melo Var. 447 Induction of diabetes The overnight fasted rats were injected with a single dose of streptozotocin or STZ (60 mg/kg body weight in 0.1 M citrate buffer, pH 4.5). After 72 h of STZ administration, the tail vein blood was collected to determine fasting blood glucose level and only rats with blood glucose higher than 200 mg/dl were considered diabetic and included in the experiment