**Abstract**

Diabetes is one of the leading cause of death globally. One of the strategies towards managing diabetes is the antidiabetic drugs which has recorded a huge success but accompanied with different degrees of side effect, hence, the use of natural plants products is encouraged. Several reports of antidiabetic medicinal plants have flooded literature but few has led to identification of active ingredient in such. *Cucumis sativus* is one of such plants reported to have antidiabetic property but there is little or no data on the active agent. This chapter therefore provides report on the active principle and mechanism of action underlying the antidiabetic activity of *C. sativus.*

**Keywords:** diabetes, *Cucumis sativus*, flavonoids, kaempferol

#### **1. Introduction**

Diabetes is a disorder where the body cells cannot use glucose effectively due to low insulin (Type 1 diabetes) or insulin insensitivity (Type 2 diabetes), therefore the blood glucose level increases [1]. It is characterized by a fasting blood glucose level higher than 126 mg/dL. It is one of the top 10 causes of death globally. About 463 million adults are living with diabetes; by 2045 this will rise to 700 million and Diabetes caused 4.2 million deaths in 2019 [2].

In 2017, total estimated cost of diagnosed diabetes in the U.S. was \$327 billion [3]. Some complications of diabetes are oxidative stress, dyslipidaemia, endoplasmic reticulum (ER) stress [4, 5], retinopathy [6], neuropathy [7], nephropathy [8], cardiovascular complications [9], and ulcerations [10].

The management of diabetes has involved many approaches in order to enhance the availability of insulin, boost insulin sensitivity and reduce alpha glucosidase activity [11].

From research, people with excess weight can greatly manage diabetes by engaging in moderate and considerate weight loss plan, also exercise can help control blood sugar levels, reduce glycated hemoglobin and reduce insulin resistance.

Antidiabetic drugs are pharmacological substances that are employed in treating hyperglycemia when life style modifications do not bring desired effects [12]. They are categorized into different classes and they work either to enhance synthesis of insulin or reduce blood glucose level using different strategies.

These antidiabetic drugs are very effective in treating hyperglycemia, but despite this success, there has been increased side effects accompanying their use. Therefore, there is increased search for antidiabetic agents from medicinal plants with little or no adverse effects. Experimental reports have validated the presence of antidiabetic substances in medicinal plants [13–15]. One of such plants reported to have antidiabetic property is *Cucumis sativus*. Saidu *et al*.'s study reported the hypoglycemic property of methanolic fruit pulp extract of *Cucumis sativus* [16].

This chapter focuses on the antidiabetic principle identified in *Cucumis sativus* L.

### **2. Flavonoids**

Flavonoids are a class of plants secondary metabolites made up of polyphenolic structures that contribute to the color and fragrance of fruits and flowers, therefore, they constitute a significant part of the human diet [17]. As a large class, flavonoids are subdivided into groups based on the structure of their carbon rings and these include flavanols, flavones, chalcones, flavonones, flavanonols and isoflavones. They are abundantly distributed in vegetables, fruits and some beverages. Flavonoids possess a wide range of health-promoting properties like the antioxidant effect, anti-carcinogenic, anti-inflammatory and antidiabetic capabilities. They display these properties by modulating the functions of some cellular enzymes as well as inhibition of different enzymes like lipo-oxygenase, cyclo-oxygenase, phosphoinositide 3-kinase and xanthine oxidase [18, 19]. Therefore, they are indispensable components in various pharmaceutical, cosmetics and medicinal applications. One of the flavonoids that possesses antidiabetic property is kaempferol.

#### **3.** *Cucumis sativus* **L***.*

*Cucumis sativus* L*.* also known as Cucumber is a creeping plant in the family Cucurbitaceae. It is a fruit native to India and widely cultivated around the world. It is consumed fresh in salads, fermented (pickles) and as cooked vegetable [20].

**Figure 1.**

*High pressure liquid chromatographic profiling of the antidiabetic principle derived from Cucumis sativus fruit juice.*

**15**

**Figure 2.**

*Structure of Kaempferol.*

*Antidiabetic Principle in* Cucumis sativus *L. DOI: http://dx.doi.org/10.5772/intechopen.96393*

ethanol and slightly soluble in water.

kaempferol from *Cucumis sativus* L. [26].

**5. Biosynthesis of kaempferol**

flavonoid called kaempferol using HPLC (**Figure 1**).

3-O-glucoside [28].

**4. Kaempferol**

*Cucumis sativus* L. as a fruit, in addition to its nutritional value, has been reported to have some biological activities as anti-aging [21], antioxidant [22], and antidiabetic [23]. These properties have been linked to the presence of some phytochemical substances detected in *Cucumis sativus* L. like cucurbitacins [24], ascorbic acid [25], cucumerin, apigenin [26], lutein [27], quercetin 3-O-glucoside and kaempferol

Recent studies validated the presence of antidiabetic agents in *Cucumis sativus L.* Ibitoye *et al* [29] identified the antidiabetic agent in *Cucumis sativus* L. as a

Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one also known as kaempferol-3, **Figure 2**) is a yellow crystalline flavonoid having a molecular weight of 286.23 with a melting point of 276–278 °C. It is soluble in hot

It has been isolated from different parts of different plants. Yang *et al*. separated kaempferol and its derivatives from the methanolic crude extract of *Neocheiropteris palmatopedata* by repeated column chromatography, using a Sephade*x* LH-20 column [30]. Orhan et al. reported the bioactivity-guided fractionation of *Calluna vulgaris* and isolated kaempferol galactoside using successive column chromatography techniques [31]. Ibitoye et al. also reported the bioactivity guided isolation of

Kaempferol and its derivatives are synthesized in plants by different types of enzymes. Kaempferol is synthesized by condensation of 4-coumaroyl-CoA with tripropionyl-CoA to produce naringenin chalcone, this reaction is catalyzed by chalcone synthase [32]. Naringenin chalcone is then converted into a flavanone called naringenin, which is thereafter hydroxylated by flavanone 3-dioxygenase to produce dihydrokaempferol [33]. Finally, the introduction of a double bond at the

There is no much data on the pharmacokinetics of Kaempferol, however, flavonoids are extensively metabolized by the colonic microflora [34, 35].

C2-C3 position of dihydrokaempferol produces kaempferol.

*Antidiabetic Principle in* Cucumis sativus *L. DOI: http://dx.doi.org/10.5772/intechopen.96393*

*Cucumis sativus* L. as a fruit, in addition to its nutritional value, has been reported to have some biological activities as anti-aging [21], antioxidant [22], and antidiabetic [23]. These properties have been linked to the presence of some phytochemical substances detected in *Cucumis sativus* L. like cucurbitacins [24], ascorbic acid [25], cucumerin, apigenin [26], lutein [27], quercetin 3-O-glucoside and kaempferol 3-O-glucoside [28].

Recent studies validated the presence of antidiabetic agents in *Cucumis sativus L.* Ibitoye *et al* [29] identified the antidiabetic agent in *Cucumis sativus* L. as a flavonoid called kaempferol using HPLC (**Figure 1**).
