CHAPTER ONE

1.0: INTRODUCTION

1.1: PHARMACOGNOSY- A GENERAL OVERVIEW

Pharmacognosy, the modern science of natural medicines, is based on traditional medicines used in different parts of the world. Traditional medical heritages of Ayurveda, Traditional Chinese Medicine, Greco European Medicine, Egyptian Medicine, Kampo medicine and others are important precursors for the development of Pharmacognosy and Pharmaceutical Sciences. Pharmacognosy is composed of two Greek words, i.e. pharmakon (a drug) and gignosco (to acquire knowledge of) or gnosis (knowledge). Thus, literally Pharmacognosy is to acquire knowledge of drugs (Kinghorn et al.,2015).

Pharmacognosy can also be defined, as the ―pharmaceutical science, that deals with the discovery, characterization, production and standardization of drugs of natural origin (Bart, 2016). According to Heinrich et al.,(2009) contemporary Pharmacognosy deals with medicinal plants, crude drugs, extracts, pure compounds and foods having health benefits and it is, in fact, the ―science of biogenic or nature derived pharmaceuticals or poison (Swati Pund, et al.,2016). Furthermore, Pharmacognosy is also defined as a molecular science that explores naturally occurring structures and activity relationships with a drug potential (Marcy and Kinghorn, 2005). The American Society of Pharmacognosy defines Pharmacognosy as the study of physical, chemical, biochemical and biological properties of drugs, drug substances or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources (Bart, 2016). Thus, in a contemporary context, Pharmacognosy has become a multidisciplinary science of natural drugs and drug substances and it deals with medicinal plant cultivation, crude drug production, chemical; biological; pharmacological and molecular analysis of crude drugs and drug substances to assure their production, potency, purity and safety as well as to assist new drug discoveries (Marcy and Kinghorn, 2005).

The study of medicinal plants has attracted many researchers, owing to the useful applications of plants for the treatment of various diseases in human and animals. To date, medicinal plants have been used in all cultures as a source of medicine for the treatment of various diseases including stomach complaints, malaria, depression and cancer (Hoareau and Da Silva, 1999). Available literature reveals that there are about 250,000 flowering plants in the world, out of which more than 50,000, are used for medicinal purposes (Schippmann et al.,2002 ). According to Dr O. Akerele, program manager, Traditional Medicine, Division of Drug Development and Policies, World Health Organization(WHO), Geneva, Switzerland, ‘’for countries to make full use of their heritage of traditional medicine, including the wealth of medicinal plants which most of them possess, they must have a special interest in funding ethno-medical studies, bringing together botanists, clinicians, pharmacologists and others for the purpose of assessing and realizing the full potential of development in this area’’(Akerele, 2000).

The role of medicinal plants in national development cannot be overemphasized. The attention paid by authorities and administrations to the use of medicinal plants has increased although, considerably, for different reasons and in different settings. In developing countries, this has resulted largely from a decision to take traditional forms of medicine more seriously and explore the possibility of utilizing them in primary health care delivery. In other countries, health authorities have been compelled to react to the great surge of public interest in the use of herbs and plants (Akerele, 2000).

1.2: Standardization and quality control of herbal medicines

According to the WHO, standardization and quality control of herbals is the process involved in the physicochemical evaluation of crude drug covering aspects, such as selection and handling of crude material, safety, efficacy and stability assessment of finished product, documentation of safety and risk based on experience, provision of product information to consumer and product promotion. Herbal materials are categorized according to sensory, macroscopic and microscopic characteristics (Sucker et al; 2012). An examination to determine these characteristics is the first step towards establishing the identity and the degree of purity of herbal materials. They are carried out before any further tests are undertaken (Emil, 1902). Visual inspection provides the simplest and quickest means by which to establish identity, purity and possibly quality. If a sample is found to be significantly different from the specifications in terms of colour, consistency, odour or taste, it is considered as not fulfilling the requirements (Kubelka, 2014).

The processes and procedures for the standardization and quality control of herbal medicines are highlighted below:

1.2.1: Macroscopic and microscopic evaluation

The macroscopic identity of herbal materials is based on shape, size, colour, surface characteristics, texture, fracture characteristics and appearance of the cut surface. However, since these characteristics are judged subjectively and substitutes or adulterants may closely resemble the genuine material, it is often necessary to substantiate the findings by microscopy and/or physicochemical analysis (Olanipekum M.K. et al., 2016). Microscopic inspection of herbal materials is indispensable for the identification of broken or powdered materials; the specimens are treated with chemical reagents. An examination by microscopy alone cannot always provide complete identification, though when used in association with other analytical methods it can frequently supply invaluable supporting evidence (Babajide, 2016). Comparison with a reference material reveals, characteristics not described in the requirements which might otherwise have been attributed to foreign matter, rather than normal constituents (M.K.et al; 2016).

1.2.2: DNA Barcoding

The traditional system of medicine utilizes medicinal plants to cure various ailments but the herbal industry suffers from substitution and adulteration of medicinal herbs with closely related species (Herbert, 2003). The efficacy of the drug decreases if it is adulterated, and in some cases, can be lethal if it is substituted with toxic adulterants (Herbert, 2003). Authentication at the DNA level provides more reliability because, in contrast to RNA, DNA is a stable macromolecule that is not affected by external factors and is found in all tissues (Bolstein et al., 1999). Therefore, development of DNA-based marker is important for authentication of medicinal plants (Sucker et al., 2012). The novel technique of identifying biological specimens using short DNA sequences from either nuclear or organelle genome is called DNA barcoding Figure 1.0 The term DNA barcode‘as taxon identifiers was first proposed by Paul Hebert of University of Guelph in 2003 (iBOL conference, 2017)

Following initial in-silico and laboratory-based assessment of different loci from chloroplast and nuclear genomes led to the conclusion that no single locus plant barcode exist, and soon it was realized that, multi-locus barcodes are requisite for plant barcoding. Subsequently a number of loci were being tested for their suitability as plant barcodes and many multi-locus combinations were suggested. The Consortium for the Barcode of Life Plant Working Group (CBOL) evaluated seven chloroplast genomic regions across the plant kingdom and proposed a combination of matK and rbcL as plant barcodes. High universality but less species resolution is provided by rbcl whereas matK affords high resolution but less universality. A combination of these two can help to achieve maximum species discrimination. Nevertheless, in closely related species, the discriminating ability of these two markers is low Therefore, the China Plant BOL Group proposed the addition of nuclear ITS (Internal Transcribed Spacer) to the matK+rbcL combination as plant barcode in order to achieve maximum identification rates even in closely related species( De-Zhu Li, et al., 2011).

Fig 1.0: Major steps in DNA Barcoding (Researchgate.net).

1.2.3: Physicochemical analysis

Ash of any organic material is composed of their non- volatile inorganic components. Controlled incineration of crude drugs results in an ash residue consisting of an inorganic material (metallic salts and silica) (Vesalus, 1996). A high ash value is an indication of contamination, substitution, adulteration in the crude drug (Hedberg, 1982). The ash remaining following ignition of herbal materials is determined by three different methods which measure total ash, acid-insoluble ash and water-soluble ash. The total ash method is designed to measure the total amount of material remains after ignition. The total ash usually consists of carbonates, phosphates, silicates and silica which includes both physiological (ash-derived from plant tissue) and non-physiological ash (residue of the adhering material to the plant surface, eg. sand and soil). Acid-insoluble is the residue obtained after boiling the total ash with dilute hydrochloric acid and igniting the remaining insoluble matter. This measures the amount of silica present, especially as sand and siliceous earth. Water-soluble is the difference in weight between the total ash and the residue after treatment of the total ash with water.

Determination of water soluble and alcohol soluble extractive is used as a means of evaluation of the crude drugs for the presence of active constituents in the plant material. This method determines the amount of active constituents extracted with solvents from a given amount of herbal material. It is employed for materials for which as yet no suitable chemical or biological assay exists. Extraction of any crude drug with a particular solvent yields a solution containing different phyto-constituents. The composition of these phyto-constituents in the particular solvent depends upon the nature of the drug and the solvent used.

An excess of water in herbal materials will encourage microbial growth, the presence of fungi or insects and deterioration following hydrolysis. Limits for water content should therefore be set for every given herbal material. This is especially important for materials that absorb moisture easily or deteriorate quickly in the presence of water. Moisture is an inevitable component of crude drugs, which must be eliminated as far as practicable, to aid in their preservation. The test for loss on drying determines both water and volatile matter.

Drying can be carried out either by heating to 100–105 °C or in a desiccator over phosphorus pentoxide under atmospheric or reduced pressure at room temperature for a specified period of time. The desiccation method is especially useful for materials that melt to a sticky mass at elevated temperatures. Many medicinal plant materials contain saponins that can cause persistent foam when an aqueous decoction is shaken. The foaming ability of an aqueous decoction of plant materials and their extracts is measured in terms of foaming index (AOAC official methods of analysis).

1.3: ANALGESICS

The term ‘analgesic’ refers to a medication that provides relief from pain without putting one to sleep or causing them to lose consciousness. Analgesics are medicines that are used to relief pain. They are known as painkillers or pain relievers. Pain which arises from a wide range of conditions such as headache, infection, sprains, toothache, wounds cleansing, trauma, surgery, poor posture, pain syndromes, migraines, menstruation, rheumatoid arthritis, e.t.c., is a recurrent episode in the present day life of the industrialized and civilized world (NPC USA, 2015).Many different types of medicines have pain-relieving properties and experts tend to group together medicines that have the same mechanism of action and would necessarily elicit the same effect. Two of the most common groups of pain killers are Non-steroidal Anti-Inflammatory Drugs (NSAIDS) and opiods (narcotics, which are generally classified as strong agonists, antagonists, mild to moderate agonists and mixed agonist-antagonists) (C.E Fookes 2018). It is therefore of great interest to have a plant that would both serve as food and as a potent analgesic.

1.4: OVERVIEW OF ANALGESICS

1.4.1: NSAIDS

The non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for the treatment of minor pain and for the management of oedema and tissue damage resulting from inflammatory joint disease (arthritis). A number of these drugs possess antipyretic activity in addition to having analgesic and anti-inflammatory actions, and thus have utility in the treatment of fever. Most of these drugs express their therapeutic actions by inhibition of prostaglandin biosynthesis as described in the sections that follow. Some of the primary indications for NSAID therapy include:

• Rheumatoid Arthritis (RA): No one NSAID has demonstrated a clear advantage for the treatment of RA. Individual patients have demonstrated variability in response to certain NSAIDs. Anti-inflammatory activity is shown by reduced joint swelling, reduced pain, reduced duration of morning stiffness and disease activity, increased mobility, and by enhanced functional capacity (demonstrated by an increase in grip strength, delay in time-to onset of fatigue, and a decrease in time to walk 50 feet).

• Osteoarthritis (OA): Improvement is demonstrated by increased range of motion and a reduction in the following: Tenderness with pressure, pain in motion and at rest, night pain, stiffness and swelling, overall disease activity, and by increased range of motion. There are no data to suggest superiority of one NSAID over another as therapy for OA in terms of efficacy and toxicity. NSAIDs for OA are to be used intermittently if possible during painful episodes and prescribed at the minimum effective dose to reduce the potential of renal and gastro intestinal toxicity. Indomethacin should not be used chronically because of its greater toxicity profile and its potential for accelerating progression of OA.

• Acute gouty arthritis, ankylosing spondylitis: Relief of pain; reduced fever, swelling, redness and tenderness; and increased range of motion have occurred with treatment of NSAIDs.

 • Dysmenorrhea: Excess prostaglandins may produce uterine hyperactivity. These agents reduce elevated prostaglandin levels in menstrual fluid and reduce resting and active intrauterine pressure, as well as frequency of uterine contractions. Probable mechanism of action is to inhibit prostaglandin synthesis rather than provide analgesia (DeRuiter, 2002).

Mechanism of Action of NSAIDs

The major mechanism by which the NSAIDs elicit their therapeutic effects (antipyretic, analgesic, and anti-inflammatory activities) is inhibition of prostaglandin (PG) sythesis. Specifically NSAIDS competitively ( for the most part) inhibit cyclooxygenases (COXs), the enzymes that catalyze the synthesis of cyclic endoperoxides from arachidonic acid to form prostaglandins (DeRuiter, 2002),Two COX isoenzymes have been identified: COX-1 and COX-2. COX-1, expressed constitutively, is synthesized continuously and is present in all tissues and cell types, most notably in platelets, endothelial cells, the GI tract, renal microvasculature, glomerulus, and collecting ducts. Thus COX-1 is important for the production of prostaglandins of homeostatic maintenance, such as platelet aggregation, the regulation of blood flow in the kidney and stomach, and the regulation of gastric acid secretion. Inhibition of COX-1 activity is considered a major contributor to NSAID GI toxicity. COX-2 is considered an inducible isoenzyme, although there is some constitutive expression in the kidney, brain, bone, female reproductive system, neoplasias, and GI tract. The COX-2 isoenzyme plays an important role in pain and inflammatory processes (DeRuiter, 2002). Generally, the NSAIDs inhibit both COX-1 and COX-2. Most NSAIDs are mainly COX-1 selective (eg, aspirin, ketoprofen, indomethacin, piroxicam, sulindac). Others are considered slightly selective for COX-1 (eg, ibuprofen, naproxen, diclofenac) and others may be considered slightly selective for COX-2 (eg, etodolac, nabumetone, and meloxicam). The mechanism of action of celecoxib and rofecoxib is primarily selective inhibition of COX-2; at therapeutic concentrations, the COX-1 isoenzyme is not inhibited thus GI toxicity may be decreased (DeRuiter, 2002).

Classification and Examples of NSAIDs

Non-steroidal anti-inflammatory drugs can be classified by action (effect on the COX enzymes) and chemical structure as traditional, non-selective COX inhibitors or as selective COX2 inhibitors.

Non-selective COX inhibitors 

• Acetates: diclofenac, indomethacin, sulindac
• Fenamates: mefenamic acid
• Oxicams: piroxicam
• Propionates: ibuprofen, ketoprofen, naproxen
• Pyrazolones: phenylbutazone
• Salicylates: aspirin, diflunisal. (Dyall-Smith, 2010).

Selective COX2 inhibitors

• More COX2 selective: meloxicam, nimesulid
• Coxibs:

o    First generation, highly selective: celecoxib 

o    Second generation, highly selective: etorcoxib, valdecoxib. (Dyall-Smith, 2010).

Another way to classify them is by half-life.

• Short-medium half-life (< 6 hours): aspirin, diclofenac, ibuprofen, indomethacin, ketoprofen

Long half-life (> 10 hours): diflunisal, naproxen, phenylbutazone, piroxicam, sulinda. (Dyall-Smith, 2010).

Adverse effects of NSAIDS

Common side effects

•     Gas

•     Bloating

•     Heartburn

•     Stomach pain

•     Nausea

•     Vomiting, diarrhea, or constipation

•     Mild headache

•     Dizziness. ( Lynn and Sinha, 2015).

Severe side effects

•     Swelling of the mouth, face, lips, tongue, ankles, feet, lower legs, hands, or eye area

•     Ringing in the ears (tinnitus)

•     Itching

•     Severe rash or hives

•     Red, peeling skin

•     Unexplained bruising and bleeding

•     Unusual weight gain

•     Stools that are bloody, black, or tarry

•     Bloody or cloudy urine

•     Blurred vision

•     Severe stomach pain

•     Vomit that looks like coffee grounds

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