Plant Material and New Perspective of Nanoparticles as an Antidiabetic Agent
In spite of the significant advancements made in the control and treatment of diabetes mellitus by conventional hypoglycaemic agents, there are still some limitations and side effects that are associated with synthetic antidiabetic drugs. Effective diabetes management without side effects remains a major challenge to the healthcare system. The common side effects linked to oral hypoglycaemic drugs include hypoglycaemia, weight gain, gastrointestinal disorders, lactic acid intoxication, peripheral oedema and impaired liver function (Dai et al., 2018; Liu and Yang, 2019; Ganesan and Sultan, 2020). Traditional medicines are w'idely used and preferred because of their perceived efficacy, relatively fewer side effects and comparatively lower costs.
Some Antidiabetic Plant Extracts and Their Bioactive Compounds
Antidiabetic plant extracts and their bioactive compounds target the liver, pancreas, intestine, adipose tissue and muscle, where they exert their respective modes of action. Some factors negatively affect the bioavailability of plant-based products in living systems (Samadder and Khuda-Bukhsh, 2014; Furman et al., 2020). Crude plant extracts from several plant species belonging to varied plant families, including Aegle marmelos L. (Rutaceae), Balanites aegyptiaca L., Del. (Zygophyllaceae), Boerhavia diffusa (Nyctaginaceae), Camellia sinensis L. (Theaceae), Helicteres isora Linn. (Sterculiaceae), Melissa officinalis L. (Lamiaceae), Phaseolus vulgaris L. (Fabaceae), Rosmarinus officinalis L. (Lamiaceae), Khaya senegalensis (Desr.) A. Juss. (Meliaceae), Tamarindus indica L. (Fabaceae), Mitragyna inermis (Willd) О Ktze. (Rubiaceae) and Vaccinium myrtillus L. (Ericaceae), have exhibited significant hypoglycaemic activity (Funke and Melzing, 2006; Ayodhya et al., 2010; Moradi et al., 2018; Hamza et al., 2019). Numerous antidiabetic compounds such as beta-pyrazol-l-ylalanine, epigallocatechin gallate, roseoside, cinchonain lb, glycyr- rhetinic acid, leucocyandin 3-O-beta-n-galactosyl cellobioside, dehydrotrameteno- lic acid, leucopelargonidin-3-O-alpha-L-rhamnoside, strictinin, pedunculagin and isostrictinin and epicatechin, demonstrated significant insulin-mimetic and antidiabetic activity with varied modes of action and some with greater efficacy than conventional hypoglycaemic agents (Saxena and Vikram, 2004; Bnouham et al., 2006; Ко et al., 2007; Qa’dan et al., 2009; Ayodhya et al., 2010; Chauhan et al., 2010; Frankish et al., 2010; Liu et al., 2020).
Green Synthesis of Nanoparticles as Potential Antidiabetic Agents
Green synthesis of nanoparticles has added advantage when it is combined with metal precursors to give the metal nanoparticles. The stability of green synthesis metal nanoparticles is achieved using plant extracts which act as both reducing and stabilizing agents (Ashwini and Mahalingam, 2015; Latha et al., 2015). The resources are obtained from plant materials (Saravanakumar, et al., 2017). The plant extracts employed in the normal decoction method are more suitable for the green metal nanoparticle as a capping and stabilization agent, requiring no external stabilizers (Jha and Prasad, 2010; Ashwini and Mahalingam, 2015). The reduction of metal nanoparticles with the help of plant extracts biomolecules is an eco-friendly and a low-cost approach without any side effects (Ashwini and Mahalingam, 2015; Latha et al., 2015). Nanoparticles using plant materials, algae, fungi and several useful microorganisms are in focus in the present scientific world (Patra et al., 2019). Conventional physical and chemical method is one of the beneficial green technology methods, as it provides an environmentally friendly way of synthesizing nanoparticles, with no requirement of toxic and harmful chemicals, and uses a cost-effective approach (Patra and Baek., 2014; Veerasamy et al., 2011; Nadaroglu et al., 2017).
FIGURE 2.1 General methods of nanoparticle synthesis.
Figure 2.1 shows general methods of nanoparticle synthesis. Microorganisms and plant molecules such as phenolic compounds, proteins, alkaloids, enzymes, amines and pigments perform nanoparticle synthesis by reduction (Nadaroglu et al„ 2017).
Nanoparticle can limit fluctuations, reduce side effects, decrease dosage frequency and also improve patients’ compliance (Souto et al., 2019). Nanoparticles are currently being explored in an attempt to achieve improved bioavailability and prolonged desired effects of antidiabetic herbal remedies in targeted organs. Studies by Samadder and Khuda-Bukhsh (2014) show that potential antidiabetic properties of nano-encapsulated forms of Gymnema sylvestre and Syzygium jam- bolanum have relatively more anti-hyperglycaemic effects than unencapsulated counterparts in various experimental models. According to Jamdade et al. (2019), nature has an infinite collection of therapeutic plants, which serve as a repository of bioactive principles that form the foundation to complementary and alternative medicine. Natural products are currently being explored in the plant-mediated green synthesis of nanoparticles, and the approach is developing into a new and essential branch of nanotechnology. The use of plant extracts in the production of silver nanoparticles has drawn attention due to its rapid, eco-friendly, non-patho- genic and single-step technique for the biosynthetic processes (Bagyalakshmi and Haritha, 2017).
Silver nanoparticles and Pterocarpus marsupium are found to be effective for antidiabetic activity (Bagyalakshmi and Haritha, 2017). The study by Prabhu et al. (2018) shows that AgNPs and leaf extract of Pouteria sapota have efficient antidiabetic activity in the rat model of diabetes and might have the potential for development of medical applications. Zinc oxide nanoparticles synthesized using plant extracts of Tamarindus indica and Moringa oleifera showed higher antidiabetic activity, inhibiting a-glucosidase and a-amylase, which are the important enzymes in carbohydrate metabolism (Rehana et al., 2017). Silver nanoparticles (AgNPs) using stem extracts of Musa paradisiaca were also effective against diabetes in the streptozotocin-induced diabetes rat model (Anbazhagan et al., 2017).
Garg et al. (2016) reported that AgNPs using Zingiber officinale ethanolic extract had a notable effect on blood glucose lowering in rats with STZ-induced diabetes. Some of the metal nanoparticles syntheses using extracts of different plants and antidiabetic activity are shown in Table 2.2.
Biologically synthesized AuNPs using plant extracts showed remarkable antidiabetic activity extracts of Turbinaria conoides, Gymnema sylvestre, Sargassum swartzi, Chamalcostus cuspidatus, Hericium erinaceus, Sambucus nigra and Cassia fistula (Badeggi et al., 2020). Studies done by Malapermal et al. (2015) and Elobeid (2016) show that gold/silver NPs of cinnamon and Ocimum basilicum extract lower glucose levels. Guavanoic acid, curcumin, hesperidin, diosmin and naringin, phlo- ridzin, an antidiabetic agent found in fruits and its escin, gymnemic acid resveratrol and aglycon, are responsible for the biosynthesis of AuNPs (Badeggi et al., 2020). Tyrosine, tryptophan, chondroitin sulphate and chitosan are some of the compounds that have been used in the formation of AuNPs with antidiabetic properties (Badeggi et al., 2020).
