Applications of Cytisine Extraction and Detection in Biological Materials for Clinical Medicine
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Acta Poloniae Pharmaceutica ñ Drug Research, Vol. 76 No. 5 pp. 797ñ804, 2019 ISSN 0001-6837 DOI: 10.32383/appdr/109895 Polish Pharmaceutical Society APPLICATIONS OF CYTISINE EXTRACTION AND DETECTION IN BIOLOGICAL MATERIALS FOR CLINICAL MEDICINE 1 2 3 DOROTA BARTUSIK-AEBISHER *, DAVID AEBISHER , RYAN J. COURTNEY , 4 5 6 ANDRZEJ SOBCZAK , ZUZANNA BOBER , RAFA£ PODG”RSKI , PATRYCJUSZ KO£ODZIEJCZYK5 and PIOTR TUTKA1,3,5 1University of RzeszÛw, Department of Experimental and Clinical Pharmacology, Faculty of Medicine, Al. Kopisto 2a, 35-959 RzeszÛw, Poland 2University of RzeszÛw, Department of Photomedicine and Physical Chemistry, Faculty of Medicine, Warzywna 1a, 35-959 RzeszÛw, Poland 3National Drug and Alcohol Research Centre, University of New South Wales, Sydney, NSW, Australia 4Medical University of Silesia, Department of General and Inorganic Chemistry, School of Pharmacy with the Division of Laboratory Medicine, Poniatowskiego 15, 40-055 Katowice, Poland 5University of RzeszÛw, Centre for Innovative Research in Medical and Natural Sciences, Warzywna 1a, 35-959 RzeszÛw, Poland 6University of RzeszÛw, Department of Biochemistry, Faculty of Medicine, Warzywna 1a, 35-959 RzeszÛw, Poland Abstract: Tobacco use is a leading cause of preventable mortality worldwide. New cost-effective smoking ces- sation treatments are needed especially in some low-to-middle income countries where smoking rates are ris- ing, and current pharmacotherapy treatments remain cost-prohibitive. Since the 1960ís, cytisine has been used as an effective nicotine substitution agent to aid in smoking cessation albeit limited to a selected few Eastern/Central Europe and Central Asian countries. Cytisine is a biologically active alkaloid of plant origin and is known to be a ligand of nicotinic acetylcholinergic receptors (nAChRs). For several decades, the prop- erties of cytisine have been investigated and reported in the biomedical and pharmaceutical literature. Due to the beneficial impact of cytisine on smoking cessation and its costly multistep synthesis, there is a growing interest in extraction from natural sources as well as in analytical identification and quantification for clinical medicine and forensic toxicology. In this paper, we present several current analytical approaches to cytisine extraction and identification from biological samples of plant and human origin. The development of extraction techniques will allow for the widespread use of the drug in experimental and clinical pharmacology, toxicolo- gy and forensic medicine. Keywords: smoking cessation, cytisine extraction, biopharmacy, biomedicine, chromatography Tobacco use causes 6 million deaths per year quently, tobacco remains a significant threat to pub- worldwide, and the World Health Organization lic health and intensified efforts to reduce smoking (WHO) has projected that tobacco use will cause an and promote cessation are needed. A recent editori- additional 8 million deaths annually by 2030 (1). al published in The Lancet stated that the current Recently, a comprehensive 187-country survey on anti-tobacco strategy was failing. Subsequently, The the prevalence of daily smoking between 1980 to Lancet commissioned ìThe World Without Tobacco 2012 found a large reduction in smoking at a global in 2040î campaign (3). However, a trend analysis of level for both men and women. However, due to the projected reduction in the number of cigarette population growth, the number of daily smokers smokers suggests that a tobacco-free world by 2040 worldwide has significantly increased (2). Conse- may be ambitious (4). Based on medicinal reports, * Corresponding author: e-mail: [email protected] 797 798 DOROTA BARTUSIK-AEBISHER et al. α β smokers die 10 years earlier than non-smokers albeit the 4 2 nAChR at nanomolar concentrations (12, this time may be significantly decreased by quitting, 13) with Ki values ranging from 0.45 to 2.4 nM (14, especially before age 40 (5). 15) which are sufficient to activate these receptors Despite attempts to control tobacco using a even with limited blood-brain barrier penetration broad spectrum of interventions, breaking the nico- (14). Cytisine is thought to aid smoking cessation by tine habit remains very difficult. The best results in reducing the severity of withdrawal symptoms (via α β the treatment of nicotine addiction are achieved its partial agonist action on 4 2* nAChR) and by when a combination of pharmacotherapy and non- reducing the reward and satisfaction associated with pharmacological treatments are used (6). However, smoking (via antagonistic action against nicotine at α β despite their advantages, current pharmacotherapies 4 2* nAChR) (6). are too expensive for many smokers, especially in Plasma concentrations of cytisine in humans low-to-middle income countries (LMICs), and are have been reported in single-dose and during 25-day not widely disseminated to the general population of standard regimens by Jeong et al. (17-19). Cytisine smokers. Therefore, there is an urgent need for alter- was found to have a simple pharmacokinetic profile native, more efficacious, safe and cheaper pharma- with maximum concentrations reached at 2 h post- cotherapies for health care systems and smokers. dose, and a half-life of 4.8 h. During day 1 of the 25- One such promising smoking cessation agent is the day regimen, a plasma concentration of 50.8 ± 4.7 alkaloid cytisine ((-)-Cytisine, (1R,5S)-1,2,3,4,5,6- ng/mL was measured suggesting a high oral bio- Hexahydro-1,5-methano-8H-pyrido[1,2a][1,5]dia- availability of cytisine (18). Cytisine remains intact zocin-8-one) which is a biologically active metabo- from ingestion to elimination and no associated lite of plant origin known to be a ligand of nicotinic metabolites have been detected which reduces the acetylcholinergic receptors (nAChRs). Despite its potential for competitive inhibition of drug-metabo- surprising popularity in some parts of the world, lizing enzymes. To date, no drug-drug interactions cytisine has been absent from almost all existing with cytisine have been reported. Furthermore, even reviews of antismoking treatments. Recent high- if cytisine is metabolized, its metabolites will be quality studies on the efficacy and safety of cytisine present in very low concentrations that are unlikely for smoking cessation established cytisine as a to be pharmacologically active. As a partial agonist α β promising alternative to currently available smoking of the 4 2* nAChR, cytisine exerts central and cessation drugs (7-10). Interest in the development peripheral effects that resemble the effects of nico- of cytisine extraction and detection methodologies tine. Peripheral effects are manifested after adminis- has been increasing due to its importance as a smok- tration of cytisine at doses that are 1/4 to 2/3 lower ing cessation agent as well as the need for improved than the doses of nicotine required to cause the same analytical methods for pharmacokinetics, measure- effect (20). Cytisine administration at therapeutic ments of clinical dosage, and toxicology. doses does not appear to significantly affect blood pressure, heart rate or respiratory rate. Pharmacological characteristics of cytisine Cytisine is a pyridine-like alkaloid (Fig. 1) that Cytisine for smoking cessation possesses promising pharmacological properties. As Cytisine is considered to be the oldest medica- a potent drug, cytisine is involved in biological tion used for smoking cessation (8, 21). Smoking processes, specifically in binding to nAChRs (11). cessation services providing behavioral support (e.g. α β Cytisine is a partial agonist of the 4 2* nAChR and face-to-face or telephone counseling) are effective α β a full agonist of receptors containing 7 and 4* but long-term quit rates remain too low (22). α β (12). The 4 2* subtype of nAChRs mediates, at Alternatively, more than 80% of smokers using least partially and probably mainly, the rewarding Nicotine Replacement Therapy (NRT), the most and reinforcing effects of nicotine. Cytisine binds to popular pharmacotherapy fail in their quit attempt (22). Cytisine has several advantages compared to existing smoking cessation pharmacotherapies including: (i) it has low cost being half to a twenti- eth the cost of other cessation drugs; (ii) it is well- tolerated by smokers with a low rate of adverse events [21]; (iii) it is relatively inexpensive to pro- duce) (23, 24); and (iv) importantly, it requires a shorter treatment period (i.e. 25 days) compared to Figure 1. The structure of (-)-cytisine 56 to 84 days for the nicotine replacements products, Applications of cytisine extraction and detection in biological materials... 799 Figure 2. The number of articles published on cytisine per year from 1992 to present based on a search of PubMed bupropion and varenicline (23, 24). A particular dis- comparison exists with varenicline (21, 27). Recent advantage was reported to be a higher incidence of modeling suggests cytisine may produce substantial gastrointestinal problems such as stomach aches costs savings for global health care systems com- which occurred more frequently in the cytisine pared with current pharmacotherapies (28). This group in comparison to placebo in a double-blind modeling relied on the results from one placebo- study (25). controlled trial (25) and the authors (along with a Despite cytisineís long history as a smoking Health Technology Assessment commissioned by cessation aid (21, 24) most clinical studies were per- the NHS) concluded that confirmatory trials