Natural Pharmaceuticals and Green Microbial Technology

Health Promotion and Disease Prevention

Debarshi Kar Mahapatra, Ravindra S. Shinde, Aishwarya A. Andhare, A. K. Haghi

• Publisher: Apple Academic Press
• Year: 2021
• ISBN:
  9781000754476
• Edition: 1
• Topic: Médecine
• Subtopic: Théorie, pratique et référence de la médecine

This volume presents some of the latest research and applications in using natural substances and processes for pharmaceutical products. It presents an in-depth examination of the chemical and biological properties of selected natural products that are either currently used or have the potential for useful applications in the chemical and pharmaceutical industries. It covers emerging technologies and case studies and is a source of up-to-date information on the topical subject of natural products and microbial technology. It provides an applied overview of the field, from traditional medicinal targets to cutting-edge molecular techniques. Natural products have always been of key importance to drug discovery, but as modern techniques and technologies have allowed researchers to identify, isolate, extract, and synthesize their active compounds in new ways, they are once again coming to the forefront of drug discovery.

CHAPTER 1

Green Solvents for Pharmaceuticals

GOKUL S. TALELE¹ and HITESH V. SHAHARE²*

¹NGSPM, College of Pharmacy, Anjaneri, Nashik, Maharashtra, India

²SNJB’s Shriman Sureshdada Jain College of Pharmacy, Chandwad, Nashik, Maharashtra, India

*Corresponding author. E-mail: [email protected]

ABSTRACT

The use of petrochemical solvents is the key for various chemical and organic processes without severe implications on the environment. Green solvents were developed as an alternative to petrochemical solvents which is reducing the use of petrochemical solvents in outlook of green chemistry. Green solvents or bio-solvents are environment friendly, which are derived from the processing of agricultural crops. The class of green solvents is involving water, supercritical fluids, ionic liquids, non-toxic liquid polymers and their varied combinations. These are characterized by low toxicity, convenient accessibility, and possibility of reuse as well as great efficiency.

1.1 INTRODUCTION

Nowadays, almost all manufacturing and processing industries depend on the extensive use of solvents, which is reflected in the nearly 15 billion kilograms of yearly produced organic and halogenated solvents worldwide. These horrendous numbers finally raised international concern in the 1960s and led to the U.S. Pollution Prevention Act in 1990. “Green Chemistry” or “Sustainable Technology,” as it is known today, can be shortly defined as a chemical working process, utilizing raw materials, eliminating waste and avoiding the use of toxic and hazardous reagents and solvents. Furthermore, high product selectivity at an economical reaction rate should be achieved, thereby minimizing the amount of solvents, reagents and promoters. Although the most commonly used solvents cause serious environmental and health problems, solvents in general have been proven beneficial for temperature control of solutions by the boiling point, heat supply for exothermic and endothermic reactions, purification, extraction, recrystallization, azeotropic distillation, chromatography, alteration of reaction rates, and selectivity of the reaction.¹

Generally speaking, there exist three different approaches to mitigate the release of solvents and contaminated water into the ecosystem.

1) Solvent reduction or recycling. Many industries made remarkable progress in implementing “closed-loop systems” that reduce solvent or water use and thus improve their ability to recycle.

2) Switching to solvent free processes could be another beneficial step towards a “greener environment”. Elimination of organic solvents and other volatile organic compounds (VOC) from paints and coatings, resulting in dry powder coatings and solid ultraviolet curable coatings display a good alternative.

3) However, not many reactions can be carried out under solvent less condition, which leads to the third approach to reduce the release of solvents into the ecosystem. This especially applies to industries that are dependent on operations involving coatings, separations and reactions, as many processes have been shown to require “liquids” of some kind.

They include water, ionic liquids, fluorous solvents, organic carbonates, carbon dioxide as well as biosolvents, as shown in Figure 1.1, each with its own advantages and drawbacks.²

FIGURE 1.1 Various green solvents.

1.2 GREEN SOLVENTS

1.2.1 WATER

Water is most important solvent in green chemistry. It is non-flammable, nontoxic, and not expensive which is amply available. As a protic and polar solvent, it plays an important role in view of green chemistry. Supercritical water behaves like a nonpolar solvent and exists at pressures above 221 bar and temperatures above 374°C. The non-polarity is caused by the loss of hydrogen bonding; hence salts are no more soluble in supercritical water, whereas O₂ and non-polar solvents are. Therefore, oxidation reactions in supercritical water have been developed and studied since the 1970s, mainly for the disposal of organic waste. Unfortunately, there has not been a solution for the occurring corrosion problems due to halogen traces yet, leading to the fail of commercialization of this method. On the other hand, the high polarity of common water also has a lot of advantages in regard to reactivity and selectivity, like in organometallic catalysis. It is possible to recover and recycle the catalyst in an aqueous biphasic system via phase extraction whereas the product stays dissolved in the organic phase.³

1.2.2 IONIC LIQUIDS

Ionic liquids are molten salts with very low vapor pressure. Additionally, many of them have low combustibility, exceeding thermal stability as well as solvating qualities and they are electrically conductive. Hence, there is an increasing interest in replacing volatile organic solvents with ionic liquids.⁴ They serve as solvents or reaction media for many separation or catalytic processes regarding the fact that there is a wide range of organic, inorganic as well as polymeric molecules which are well soluble in ionic liquids. Their solvating properties are depending on the smaller anions and larger organic cations.⁵ The ionic liquids consist of:

1. Anions: Examples are formate, benzoate, acetate, halides, nitrate, hydrogensulfate, tosylate, hexafluorophosphate, phosphate, thiocya-nate, tetrafluoroborate, and trifluoromethanesulfonate methanesulfonate anions.

2. Cations: Examples are phosphonium, pyridinium, ammonium, pyrrolidinium, and imidazolium cations.

They are stable over a wide range of temperature and can be used in biphasic systems due to the immiscibility with some organic solvents. After extraction with an organic solvent, the catalyst remains in the ionic liquid and can easily be reused.^6,7

1.2.3 BIOSOLVENTS

Biosolvents have been developed as an alternative to VOC, which are usually harmful to the environment and to human health.⁸ The most important chemical classes of biosolvents are shown in Figure 1.2:

FIGURE 1.2 Various bio-solvents.

These compounds offer the a...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• About the Editors
• Table of Contents
• Contributors
• Abbreviations
• Preface
• 1. Green Solvents for Pharmaceuticals
• 2. Abutilon indicum and Prosopis juliflora as a Source of Antibiotic and Herbicidal Agents
• 3. Pharmacological Perspectives of Eugenol in Modern Context
• 4. Predictive In Silico Global Metabolism Analysis: Disease Mechanism
• 5. Intracellular Proteolysis and Neoplasia: Ubiquitin-Proteasome System, Cell Cycle, and Cancer
• 6. Vitamin D, Analogues, Drugs, and their Relevance to Cancer Inhibition
• 7. Stem Cells and Their Connection with Cancer: Prostate Disease
• 8. MEK/ERK Pathway Overactivation in Liver Tumors: TGF-β Death
• 9. Chalcone Scaffold Bearing Natural Antigout Agents
• 10. Double-Pole Electrode in New Devices and Processes for Direct Electrochemical Oxidation of Blood Inside the Blood Vessel
• 11. Advanced Development in the Synthesis of Biologically Active Heterocyclic 1, 2, 3, 4 Tetrahydropyrimidine-2-Ones
• Index