Natural Products Synthesis

Screening

1991. The larger objective of the program is tostlmulate research and development of poten­tial psychotherapeutic agents (synthetic ornatural). In addition to research grants. thisprogram administers two major contracts:3

• The Chemical Synthesis Program hasbeen ongoing since 1959 and provides alibrary ofunique research tools and drugs

:i~I

I U.8. Efforts in Natural Products Research

J. Cott

At the beginning of the 1990s. the Decadeof the Brain. l many neurobiological toolsneeded for a better understanding.of the myr­iad systems of the brain and behavior arebecoming aVailable. Despite improvements inthe necessary tools and advances made in thelast three decades (using chemical syntheticapproaches to drug design and sophisti~ated

structure-activity studies), significant prog­ress in the treatment ofmental dis-orders (particularly refractory dis­orders) has lagged. and the need issilll great for more effective medica­tions. While many thousands ofcompounds have been synthesizedand evaluated. many gaps remainin the therapeutic anmu,nentartumfor psychiatric disordef~.

A major reason for these gaps isthe relative lack of understandIngof theJundamentalneurobiologicalprocesses involved In human learn­ing. memory. emotions. and psy­chopathology. Since the phanna­ceuticalindustry Invests primartlyin areas of mental health researchwhere timely and significant com­mercial success Is l1kely, manyimportant areas remain where itleadership role for the NationalInstitute of Mental Health (NIMH) FIG~ I.-Organizational Chartcould be pivotal. PMDP: Psychotherapeutic Medication Development Program

Psychotherapeutic Drug Discoveryand Development Program

In 1990. the Psychotherapeutic Drug Dis­covery and Development Program was fonned.It is currently located within the DIvision ofNeuroscience and Behavioral Science (Fig. 1).A specific Program Announcement2 invitingresearch grant applications was released In

173

(Table 1). Custom syntheses ofinvestiga­tional compounds not currently In thel1brary are also available for psychophar­macology researchers In academia.Industry. and govC?rnment.

• The NIMH Screening Program contractfacllltates the phannacologIc profil1ng ofpotential new drugs and natural productextracts. This contract provides state-of­the-art. in Vitro assays for up to 100different cen~al nervous system (CNS)

Therapeutics

TABLE 1.-NIMH chemical synthesis program inventory

New additions, 1991-93 Catalog # New additions, 1991-93 Catalog #

N-Acetyl-4-0-methyldopamlne

N-Acetyl-3-0-methyldopamlne

N-Acetyl-O-methyltyramine

cis-3-Amlnocyclohexane carboxylic AcidGABA uptake inhibitor

4'-Amlno-PPHT HCI2-[N-(4-amlnophenyl)-N-propyl-S-hydroxytetralln(4'-amlno)-N-0434. Analog of the O2agonist PPHT"

Biotin-poly-O.L-Iyslneblotlnylated marker for living neurons, of sufficientsize (MW ca. 3000) that interneuronal diffusion is low

BTCP ,Dopamine uptake inhibitor; analog of ,,:-CP

5-Carboxamldotryptamlne maleateSHT, agonist

5-(S-Cystelnyl)-L-OOPAConjugate of L-DOPA which may be formed In vivo

1,2-0imethyllsoqulnollnlum iodide \

S(-)-OMBBS(-)·S-Ethyl-S-(1 ,3-dlmethylbutyl)barblturlcacid:sedative, hypnotic

R(+)-OMBBConvulsant

MH-P-701

MH-P-702

MH-P-703

MH-A-701

MH-P-706

MH-B-703

MH-B-701

MH-C-704

MH-C-702

MH-I-705

MH-B-704

MH-B-705

NAPSN-(-Amlnophenethylsplperone): 02 antagonistintermediate for photoafflnlty or radloUgands

(+)-Noreplnephrlne (+)-bltartrate

SKF-104,078Post-junclionally selective 2-adrenoceptorantagonist.

N6-p-SulfophenyladenosineWater-soluble trl.thylammonium salt, A,·adenosineagonist

Telenzepine amine congenerAnalog of the M, muscarinic antagonist telenzepine

UK-14.3045-Bromo-N-(4,S-dlhydro-1H-Imldazol-2-yl)-6­quinoxallnamine ~-adrenerglc agonist

YM-09151-2cls-N-(1-Benzyl·2-methylpyrrolidln-3-y/)·S·chloro-2­methoxy-4-methylaminobenzamlde: selectivedopamine O2antagonist

In process

A1lantoxanamldeEnantlomers of 7-hydroxy-DPATeH)-labeled R(+)-B-Hydroxy-OP~T5-lodo-6-nltroqulpazlne 1

MH-N-701 "

MH-N-702

MH-8-701

MH-A-702

MH-T-701

MH-U-701

MH-Y-701

MH-B-501MH-H-511MH-T-506

MH-A-501MH-H-S07MH-H-50BMH-H-509MH-H-510MH-T-502

MH-8-S02MH-D-50SMH-D-506MH-D-507

MH-D-50B

A1anine,3-(3-amlnonaphtyl)-Histidine, a-Methyl-, HCIHistidine, 2-methyl-, 2HCIHistidine, 4-methyl·, HC'4-Hydroxytryptophan hemiacetateTyrosine·O·sulfate, L-(-)- potassium salt

Available compounds preparedprior to 1991

Catechols and derivatives

Barbiturates/hydantolns

Amino acid derivatives

BarbituricAcid, 5-ethyl-5-(1·methyl-3-hydroxybutyJ)­Hydantoin, S-(2,4,5-trihydroxybenzyl)·2-ThlobarbituricAcid, 5-ethyl-S-(1·methyl-

3-hydroxybutyl)-

Benzoic Acid, 3,4-dimethoxy-S·hydroxy3,4-Dlhydroxyphenylethanol: trlethylenedlamlne3,4-Dimethoxy-5-hydroxybenzolc acida-Dimethyiamlno-3,4-dlhydroxy-acetophenone

methachlorlde4-(a.N,N-"Oimethylaminopropylamino)-1,2­

dihydroxybenzene 2HBr

MH-M-702

MH-I-704

MH-B-706

MH-E-701MH-E-702

MH-I-703

MH-I-702

(±)-OMBB

N-Ethyln~rnlcotlne

N-EthylnorcotlnineInternal standards for mass spectrometry.

(+)-HA-966 MH-H-702R(+)-3-Amlno-1-hydroxy·2-pyrroUdlnone: antagonistof glycine modulatory site associated with NMOAreceptor "

4'-Methyl-MPP+ IodideDopamlnerglc neurotoxin

1-Methyl-TI01-Methyl-1,2,3,4,-tetrahydrolsoqulnollne:dopamlnerglc neurotoxin

TIO1,2,3,4-Tetrahydrolsoqulnollne

1-Methyl-lsoqulnollne

7-Hydroxy-OPAT MH-M-7017.Hydroxy·2-(N,N-dipropylamlno)telraUn: putative 03agonist

1-Hydroxytacrine maleate MH-H-703(Velnacrine) cholinesterase Inhibitor

IsoMHPG MH-I-7013-Hydroxy+methoxyphenylglycol: norepinephrinemetabolite

, 2'Methyl-MPP+ Iodide MH-M-701Dopaminergic neurotoxin

174

U.S. Efforts in Natural Products Research

TABLE 1.-NIMH chemical synthesis program inventory (continued)

Available compounds preparedprior to 1991 (continued) Catalog #

Available compounds preparedprior to 1991 Catalog #

Catecholsand derivatives (continued) Indoles (continued)

Drugs and other heterocyclic compounds

Adaplperazlne MH-A-5023-(2'-Aminobenzhydroxy)tropane MH-A-S033·(~·Aminoethyl)-S-hydroxybenzolblthiophene MH-A-5042-Amlnotetralln HCI - MH-A-50Sp-Azido-TFMPP MH-A-506Benzo(b)-thlophene,2-cyanomethyl·S-hydroxy- MH-B-S03CarboslyrY1,3-amlno-3,4-dihydro·7-hydroxy- MH...c-S3SHaldol MH-H-S14~·(5-Hydroxy-3·benzo[81thlenyl)-o:-amino-propionlcacid MH-H-S1S3-(3-Hydroxyphenyl)·N-n-propylplperldlne HBr MH-H-516Norcyclazoclne MH-N-S016-Qulrioxallnamine, 5·bromo·ethylthiocarbamate MH-Q-704Qulnoxallne,6-amino- MH-Q-701Qulnoxaline,6-amlno·S-bromo- MH-Q-702Qulnoxallne,5-bromo-6-isothiocyanate MH-Q-70SQulnoxaline,6·lsothiocyanate MH-Q-706Qulnoxallne,6-nitro- MH-Q-703W-S MH-W-501W-7 MH-W-502

Miscellaneous amlnes and derivatives

Hydrazlnoproplonlc acid, 3,4-dlhydroxybenzyl-, OL­3·(4-Hydroxy-3-methoxyphenyl)-1-propanol1-(3-Methoxy-4-hydroxyphenyl)·1-hydroxy·

2·aminopropane hydrogen oxalatePhenylacetic Acid, 2,4-dlbenzyloxy-S·methoxy­~erlne, 3-(3,4-dltlydroxyphenyl)-, O(+)-threo­Serine, 3·(3,4-dlhydroxyphenyl)-, L-(-)-threo­Phenylacetic Acid, 2,4-dlmethoxy·Phenylacetic Acid, 3,4,S·trimelhoxy-Pyruvic Acid, 3-methoxy-4·benzyloxyphenyl·

Imipramine and derivatives

Imipramine, 3-ehloro·, desmethy­Imipramine, dldesmethyl·, HCIImipramine, 2·hydroxy­Imlpramine,2-hydroxydesmethyl·

Indoles

5-Amlnotryptamine dlpicrateS,6-0lhydroxylndoleN-Oimethyl,lryptamlne, S,6,7-trlmethoxy­S-Hydroxyindole-3-~-propionlc acidS-Hydroxy-6-methoxylrypamlne creatinine sullate5-Hydroxy-7-methoxytryptamlne creatinine sulfate4·Hydroxylryptamine creatinine sUlfate6-Hydroxylryptamine creatinine sulfate7-Hydroxylryptamlne creatinine sulfate5-Methoxyindole, 3-(2-aminopropyl)-, HCI6-Methoxylryptamine creatinine sulfate

MH-H-512MH-H-S13MH-M-501

MH-P-S14MH-S-501,MH-8-S02MH-P-51SMH-P-S16MH-P-S17

MH-I-S01MH'-I-502MH-I-S03MH-I-504

MH-D-509MH-D-510MH-H-S01MH-H-502MH-H-S03MH-H-504MH-H-50SMH-H-506MH-M-S02MH-M-503

a-Methylserotonln hydrogen oxalate1-Methylserotonln maleateSerotonin O·sulfateS,6,7-Trihydroxylryptaminecreatinine sulfate

Melatonin

6-Chloro·2-methylmelatonin6·Methoxymelatonin

Acetoxyethyldlmethylethylammonlum IodideHistamine, 2-methyl-, dipicratea-Methylhlstamine oxalateAniline, (m-chlorophenyl)-N-

fy·N'-dlmethylamlnopropyl)-, HCI2-0Ibenzylamlnoproplophenone,4'-benzyloxyOlmethylaminoethyl acetate hydrogen maleate4-(y-N,N·Oimethylaminopropylamino)phenol dlmaleateHistamine, N-dlmethyl-, methyl IodideHistamine, N-methyl-, diplcrate2-Hydrazlno-3·(4-hydroxyphenyl)-propionic acid3-HydroxybenzylaminePlperazlne,N-(2·adamanlyl)-, HCIPlperazlne-dlacroleinTFMPP, p-amlno-, 2HCI3-(y-N,N-Trimethylamlnopropylamino)phenoI2HBr

Natural Products and Derivatives

Isosalsollne HCIKawalnReserpine, 1-(~-dlethylamlno)ethyl-, dlplcrateSalsollne HCI

Nucleosides

6-Amino-2-chloro-9-(2'·methylsullonyl-~-D·

xylofuranosyl)-9-H-purlne

.Phenethylamines

2-Amino-1-(3,4,S·trimethoxyphenyl)-ethanol2-Amino-1-(3,4-dimethoxyphenyl)-ethanol HelAla-Ala-6-hydroxydopamine HCIBoc-Ala·Ala-6·hydroxydopamine, 0(-)-

N-Acelyloctopamlne, OL·2-Chloropropadrine HCI~-(p-Chlorophenyl) alanine, OL­p-Chloroamphetamine HCI3,4-0ibenzoyloxyphenylalanlne, L·(+)-2,4-0ihydroxyphenylalanlne

MH-M-504MH-M-50SMH-8-S03MH-T-S03

MH-c-S36MH-M-506

MH-A-S08MH-H-517MH-M-S07MH-A-509

MH-D-S11MH-D-512MH-D-513MH-H-S18MH-H-519MH-H-520MH-H-521MH-P-S18MH-P-S19MH-T-504MH-T-SOS

MH-I-SOSMH-K-501MH-R-501MH-8-S04

MH-A-514

MH-A-510MH-A-511~H-A-S12

MH-A-513

MH-e-537MH-C-S38MH~-S39

MH-D-514MH-D-515

175

Therapeutics

r!jiI

TABLE 1.-NIMH chemical synthesis program inventory (continued)

Available compounds preparedprior to 1991 (continued) Catalog #

Available compounds preparedprior to 1991 Catalog #

176

I,I

-j

I!j

!.~\I

-)

1I

'\

II~

I

MH-P-510MH-P-S11MH-P-50SMH-P-S12MH-P-513MH-T-501MH-T-511

MH-H-528MH-P-S28

4-HydroxyphenylglycolPropylene glycol. 4-hydroxy-3·methoxyphenyl·,

diazablcyclo(2.2.21 octane salt, DL·

Phenylgylcols

Chlorpromazine, 7-acetoxy-, hydrogen maleate MH-C-S04Chlorpromazlne,8·benzyloxy·7-methoxy. MH-C-S05Chlorpromazine, 7.8-dlacetoxy Hydrogen Maleate MH-C-S06Chlorpromazine, 7,8-diacetoxy-7-semlcarbazone-, HCI MH-C-507Chlorpromazlne,7,8-dibenzyloxy· MH-C-50SChlorpromazine, dldesmethyl-, HCI MH-C-S09Chlorpromazine.6,9·dihydroxy· MH-C-S10

•Chlorpromazine, 7,8-dlhydroxy-, HCI MH-C-S11Chlorpromazine, 7,S-~ihydroxydldesmethyl-HCI MH-C-S12Chlorpromazine,7,8-dimethoxy-HCI MH-C-S13Chlorpromazlne,7,S-(dimethylmethylenedloxy)· MH-C-S14Chlorpromazlne,7.S-dloxo-HCI MH-C-S1SChlorpromazine. 7,8-dioxodidesmethyl-, HCI MH-C-S16Chlorpromazine,6·hydroxy- MH-C-S17Chlorpromazine,7-hydroxy-HCI MH-C-S1SChlorpromulne,7-hydroxy-glucuronide MH-C-S19Chlorpromazine, 7-hydroxydesmelhyl·, HCI MH-C-S20Chlorpromazine, 7·hydroxy-methiodide MH-C-S21Chlorpromazlne,9-hydroxy- MH-C-S22Chlorpromazine-S-oxide HCI MH-C-S24Chlorpromazlne-N-Oxlde MH-C-S25Chlorpromazine sulfone HCI MH-C-526Chlorpromazine sulloxide HCI MH-C-S27Chlorpromazine sulfoxide, 7-hydroxy- MH-C-528nor1.Chlorpromazine sulloxlde HCI MH-C-S32nor2-Chlorpromazlne, 7-hydroxy-B-methoxy-, HCI MH-C-S31nor1.Chlorpromazlne HCr MH-C-S29nor2-Chlorpromazine HCI MH-C-S30nor1-Chlorpromazlne sulloxide, N-acetyl·7-acetoxy- MH-C-S33Compazine, 3-hydroxy-, desdimethyl MH-C-5342,4-Dlchloropromazine HCI MH-D-5293,7-Dichlorophenothiazlne MH-D-530Perphenazlne, 7.8-dihydroxy•• 2HCI MH-P-501Phenothiazine. 2-chloro·7·hydroxy-S-methoxy- MH-P-507Phenothiazine, 2-chloro-1 O-(2-dlnlElthylamlnoethyl)-. HCIMH-P-S03Phenothiazine, 2-chloro-1 O-(3-amlnopropyl)- MH-P-S02Phenothlazine,2·chloro-6,9-dioxo- MH-P-50SPhenothlazlne,2-ehloro·7,8-dioxo· '\ MH-P-S06Phenothiazine, 2-methoxy· MH-P-509Phenothiazine, 2-ehloro-1 O-(3-dlmethylamlno-2- MH-P-S04

·hydroxypropyl)·, maleatePhenothiazine. N-methyl-Phenothiazine, N·methyl·2-(trifluoromethyl)­Phenothiazine, 3-hydroxy·Phenothlazlne·5-0xldenor1-Promazlne Sulfoxide HCITrlfluoperazlne-S·OxideTrlfluorpromazlne, desmethyl-. HCI

MH-H-52SMH-H-S26MH-H-527

MH-D-516MH-D-517MH-D-518MH-D-S19MH-D-S20MH-D-521

MH-D-S22MH-D-523MH-D-524MH-D-S2SMH-D-526MH-D-S27MH-D-528MH-D-501MH-D-502MH-D-S03MH-D-504MH-G-501MH-G-S02MH-H-S22MH-H-S23

MH-M-S08MH-M-S09MH-M-510MH-D-S01MH-N-502MH-P-701MH-P-702MH-P-703MH-P-520MH-P-521MH-P-S22MH-P-S23MH-P-S2SMH-P-S26MH-P-527MH-T-S07MH-T-S08MH-T-509MH-T-S10

MH-C-S01MH-C-S02MH-C-503

Phenethylamines (continued)

(+/-)-3,4-Dihydroxyphenylalanyr-GABA(-)-2,4-Dlhdroxyphenylalanlne4,5-Dihydroxyphenylalanlne, 3:Cl1loro-, DL-, HBr2,3-Dihydroxy-p·phenethylamine HBr2,4-Dihydroxyphenethylamine HCI3,4-DI-(p-trlmethylammonlum-ethoxy)phenethylamine

dichloride HCI3,4-Diethylcarbonatophenethylamlne carbamate3,4-Dihydroxyphenethylamine, N-acetyl­3,4-Dihydroxyphenylalanine, 2-chloro-, Dt-. HBr3,4-Dihydroxyphenylalanlne. 6-chloro-. DL-, HBr2,4-Dlhydroxyphenylalanlne, DL­3,4-Dihydroxyphenylalanyl-GABA Ethanol, DL­Dimethyladrenaline methlodide, DL-Dopamine, 6-hydroxy-, HBrDopamine, 6-hydroxy-, HCIDopamine, 2-methyl-6-hydroxy-, HBrDopamine, 4-0-sulfate-y-Glutamyl dopamine4-0-(P-D-Glucopyranusiduronlc acld)-dopamine2-Hydroxy-p-phenethylamlne HCI3-Hydroxy-(p-dlmethylaminoethoxy)

phenethylamlne 2HCI4-Hydroxyphenethylamine. 2-amino-, 2HBrthreo-p-p-Hydroxyphenylserlne4-Hydroxy-3(-p-trimethylammonium methoxy)-

-phenethylamlne chloride HCI3-Methoxy-a-methyldopa-4-0-sulfate potassium saltN-MethylphenethanalamlneN-Methyltyramlne hydrobromideOctopamine, 0(-)-Norepinephrine,6-fluoro-oxalatePhenethylamlne, N-acetyl-3-hydroxy-4-methoxy­Phenethylamlne, N-acetyl-4-hydroxy-3-methoxy­Phenethylamine. N-acetyl-4-methoxy­Phenethylamine 3,4-di-(p-dlmethylamlnoethoxy) 3HCIPhenethylamine. 3,4-dibenzyloxy-. HCIPhenethylamlne. 2,S-dlmethoxy-Phenethylamine, N-acetyl-3.4-dihydroxy·Phenylalanine. -1l-3,4-dihydroxy-2-methyl-. DL·Phenylalanine, 3-hydroxy-4-methoxy-, DL­Phenylethylamlne, 2,4-dlmethoxy-2,3,4-Trlhydroxyphenethylamine HC11-2,3,4-Trihydroxyphenylalanine, D-Tyramine O-sulfateTyrosine, 2-amlno-

Phenothiazines

2-Chlorophenothiazlne, 10-carboethoxy­2-Chlorophenothlazlne. N-ethyl­Chlorpromazine

p

U.S. Efforts in Natural Products Research

TABLE 2.-Avallable receptor binding andenzyme activity assays

Amino acids

aulsqualate Glycine (nonstrychnlne)Kainate Glycine (strychnine)MK-801 GABAANMDA GABABPCP Benzodiazeplne

Biogenic amines*

Adrenergic (a, ~, & Serotonergic (1, 1A,subtypes) and 2)

Muscarinic (M1-3) Histaminergic (H1, H2)

Peptldes

Angiotensin II Arg-vasopressin V1Bombesin CCKcentrai

Substance P Substance KNeurotensin Neuropeptide Y

VIP Somatostatin

Peptide factors Channel proteins

ANF Calcium (N,T,L)NGF ChlorideEGF Potassium

Second messengers Miscellaneous

Forskolln Adenosine (A1,A2)Phorbol ester Opiate (nonselective)

Inositol triphosphate AIDS (e;g., gp120)~igma

Enzyme assays

Monoamine oxidase I Acetylchollnestrase

• Initial ligands nonselective followed by selective for subtype

receptors (examples of basic assays InTable 2). Samples that are active (hits) Inone or more receptor assays are tested Ina functional bioassay to determine ago­nist or at:ltagonlst activity CTable 3). Thescheme. for processing and evaluatingsamples Is depicted In Figure 2. To date.more than 600 pure· synthetic sampleshave been promed for receptor activity. Asummary of the receptor binding activityofthese compounds Is shown In Figure 3.

177

NIMH Interest in Natural ProductsResearch

I~ North America. half of all prescriptionsWritten are for plant products or for productsbased on plants. In the early 1900s. manypharmaceutical firms and academic investiga­tors were Involved In collecting and testingnatural products for biological activity. Psy­chopharmacologists.ln particular. were Inter­ested In natural products research. primarUybecause of the hallucinogens. During the1960s, these naturally occurring substances.which Induced unique states of conscious­ness. were the subject of thousa~ds ofresearch papers and sclentlflc symposia- anotable one sponsored by NIMH.4 Once thepha,rmacology of the hallucinogens was betterunderstood and their use became megal.ethnopharmacologlc research virtually halted.Aniong the other reasons for the decl1ne Innatural products research. low rates of payoffand high costs of discovery. development. andformulation were probably the mostimportant.

Recent global economic and environmentalpressures. however. are resulting In a renewedinterest In natural products research. Perhapsthe most c6mpell1ng Is the rapid disappear­ance of the flora and fauna of the tropical rainforests. If these natural sources of fuedlclnalchenucals are not explored now. they maydisappear forever. A second development hasbeen the technical advancement of high­capacity. In vitro assays that greatly Increasethe speed and decrease the cost ofdrug screen­Ing for precisely speCified pharmacologicactivities.

The 1988 National Advisory Mental HealthCouncil (NAMHC) Report to Congress on theDecade of the Brain1 provides the backgroundfor the current Interest and activities In natu­ral products research. Specifically. theNAMHC recommended that NIMH:

• Cooperate with the National Cancer Insti­tute (NCI) to obtain representative sam­ples that are being collected under theirnatural products collection program

• Formulate speclflc plans for a naturalproducts screening program to be im­plemented through a series of contracts.

Therapeutics

Valuable Medicinals

Agency for International Develop­ment to release a Request for Appli­caUons entitled "InternationalCooperative BIodiversIty Groups."6The purpose of such groups Is tosearch for new medications fromnatural sources. The program Isadmin1stered by the Fogarty Inter­national Center.

An apprecIation of the history ofphannacology Involves...an apprecI­ation of naturally occurring com­pounds. ThIs research Is enrichedby other dIscIplInes such asethnobotany (the study of the rela­tionship between man and his am­bIent vegetation) and ethnophar­macology (the study of the use ofplants and animals for their toxicor medicinal properties by local cul­tures and peoples). PharmacologyItselfbegan with attempts to under­stand the valuable bIological prop­erties ofmedicinal plants. The "dis­covery" and introduction ofpsycho­active products such as curare,atropine, ouabain. morphine. res­erpine, and digitalis Into modernmedicIne were the genesIs of thediscipline of psychophannacology.

While Western medIcine adoptedmost of these drugs dUring the1950s, many of them are ancIentmedIcInals. ReserpIne use datesback almost 3000 years to theancient Hindu Ayurvedic medIclneas a treatment for InsanIty andother disorders. The first Western

sclentlftc description oflts use as a tranquWzerwas In 1931.7 The active alkaloIds were firstIsolated In root extracts of Rauwolfiaserpentina In 1952,8 and Its structure wasdescribed In 1954.9 Nathan KlIne pIoneered Itsuse In the Western world In 1954.10

Astute clInical observations have played amajor role In discovering the therapeutic useofsynthetic compounds. Examples Include theantipsychotic effects of chlorpromazInell and'the antidepressant activity of lmlprarnine12

(both developed originally as antlhlstamlnes

178

TABLE 3.-Receptor binding and functional assays·

Receptor affinity (ligand) Functional assay

Adenosine A1 ~H-bPCPX) cAMPAdenosine A2 ~H-CGS 21680) rat vas deferens~-adrenerglc ~H.prazosln) rat vas deferens~-adrenerglc ~H-rauwolscine) rat vas deferensp-adrenerglc (3H-DHA) mouse anticonvulsantAngiotensin II (1261-angiotensin II) G.P. tracheaBenzodlazeplne (3H.flunltrazepam) I.C.V.Bradykinin (BKS- 3H.bradyklnln) G.P.lleumDopamine 0 1 ( H·SCH 23390) G.P. atriaDopamine O2 ~H-racloprlde) cAMPCa++ (l) ~H-nitrendiplne) rat portal veinCCKA (3H.L-364718) G.P.lleumCCKB (3H-CCK-S) G.P.lleumGABAA (3H.mucimol) mouse anticonvulsantGlycine (3H·glycine) I.C.V.Glutamate (3H.glutamate) IP3Histamine H1 ~H-pyrilamine) gastric acidity in vivoInterleukln.1cx (1261-IL-1a) G.P.lleum5-HT1 (3H·S.HT) fibroblast PGE2 release5-HT1A (3H-S-OH-DPAT) G.P;i1eum5~HT2 (3H.ketanserln) IP35-HT3(3H.GR-65630) rat aortaKain81e ~H.kalnlc acid) G.P.lleumLeukotrlene B4 (3H-LTB4) mouse anticonvulsantleukotriene 04 ~H-LTD4l neutrophil enzyme releaseMuscarinic M1 (3H.pirenzipine) G.P.lleumMuscarinic M2 (3H-NMS) G.P.lleumMuscarinic M3~H.NMS) G.P. atriaNeurokln!n 1 ~H.substa!1ce P) G.P.lleumNeuropeptlda Y ~H-NPY) G.P.lleumNM~A (3H-CGS 19755) G.P. atriaPCP (3H·TCP) G.P. vas deferensPhorbol'Ester ~H-PDBu) platelet aggregationPlatelet Activating Factor ~H-PAF) r:.abbit ,platelet aggregationQuisqualate ~H·AMPA) mouse anti.convulsantNa+ (Site 2, 3H.batrachotoxln) G.P. atriaK+ rat portal veinSigma ~H-DTG) G.P. vas deferens

* Ugands and bloassays are representative examples only.

These ,requests have both been addressed.The Psychotherapeutic Drug Discovery andDevelopment Program has recently focused onstimulating natural products research. ThIsnew emphasIs was recently profiled IIi theWashtngton Insight Natural Products Newslet~,

ter.5 , Also, recognizIng that a fundamentalmechanism for managing bIodiversIty may beto link conservation with economic diversIty,on June 1. 1992. NIl\4H joIned with theNational Institutes of Health (NIH), theNational.Sclence Foundation. and the U.S.

U.S. Efforts in Natural Products Research

! (active)

2...:s percent of total 1-2 percent of total

active~

FlOURE 2.-Chemlcalsample flowsheet

for use as sedatives); the antidepressant actlv-.ity ofmonoamine oxidase inhibitors (developedfor the treatment of tuberculosis)l3; and theant1manic effects ofllthium (discovered dUringattempt~ to solubilize urates in guinea pigs). 14

Pursuit of the mechanism of action of reser­pine lead Arvid Carls,son, at the UIiiversity ofGoteborg, Sweden, to the .discovexy of a newbrain transmitter, dopamine.1~ PreViouslybell~ved to be orIly a precursor in the synthesisofnorepmephrine, Carlsson provided evidencethat dopanline was not only a transmitter butthat its .insufficiency resulted in the mysteri­ous neurological disturbances in. Parkinson'sdisease, and its ovemctlvity might be associ-'ated with schizophrenia. His fortunate discov­erY of chlorpromazine's activity in sch1zophre­rna led him to investigate the mechamsm ofthis dIJ1g, and in 1963, he proposed that the"ne~roleptic" mechanism '\\Tas a blockade ofbrain dopamine recepiPrs. 16

Thus, the study of psychoactive medicinalplants has prOVided opportunities forunpredicted discoveries in neurobiology,including neurotransmitters, receptor sub­stances, second 'messengers, ion channels,and soon. A sign1ftcant scientific constmlnt isplaced on drug development when we mustl1m1t our search to chemicals that interact with

biological systems in predicted ways. Truly'urnque medications are unllk~ly to emerge.nus is especially true for research in areaswith. no effective drug treatments, such ascognitive disorders. nus lack impedes even theincremental ~me too" advances associated withpurely synthetic approaches. A final advantagefor further development of herbal medicine isthat it lends itself to standard methods ofpharmacologic evaluation already in use. Thesame cannot be said for many other types ofpotentially beneficial, alternative medicalpractices.

Natural Products Workshop

A workshop was held in April 1992 entitled"The Potential for Derivtng New Psychothera."peutic Medications From Natural Sources."nus workshop assembled many notable natu­ral product scientists from the Urnted Statesto help in the planning of an expanded initia­tive. Many topics were discussed at the meet­ing, and all were pleased to see that NIMH hadagain become interested in natural products.The participants made several conclusionsand recommendatitms:

179

"1404.--.-----'------··----·· ---,------.- ----.---..---------"---

UIO r-------.-------------------~tested. Govern~ent

Agencies, phannaceuti­cal companies, privatebotanical museums,and Independent inves­tigators with an Interestin natural prodnchcould seNe as sourcesfor plant and animalsamples that havealready been collected.For example, John Dalyofthe National Instituteof Diabetes, Digestiveand Kidney Disorders,reported an animalproduct with very inter­esting and novel phar­macologic properties. 17A new peptide from frogskin enhanced .thebinding ofadenoslne Alreceptors, while otherassociated compoundsantagonized' these

same receptors. Effects of this drug inman were unUke any other described sofar.

• As a followup to the first NAMHC recom­mendation, proposals for ways in whi~h

to effect a mutually ben~ficial 'use ofresources was discussed with representa­tives from NCI. NIMH will explore meth­ods for. preselecting compounds from theNCI natural products libraxy and requestsamples for psychoactive screel)ing by anNIMH contractor. One specific e?ffiII1plewould be to match compounds in thelibraxy that the ,~atural product database. NAPRALERr. suggests have psy­chother~peuticutility.

• Many "naturopathic" remedies such asthose found commercially in health foodstores have been shown to possess signif­Icant biological activity. Usually, the fewactive compounds identified have notbeen evaluated by modern phannacologlcmethods. This may provide a. startingplace for the NIMH screening program.Tests should probably be done with prop­erly identified. fresh plant samplesextracted by standardized procedures

o

20,.....,....__.::=:::~-·::::-,~::••····_·:::~:::::=:::::_::::·-.::::_:::::_:::::-:::._.::::-::::_:::~_::::._.::::-:::::-:::::_:::-:::::-:::::_::::_:~:_:::::_:::~_.:::_:::::_:::::_::::'_'::::_:::::_:::::_:::'_':::'-':--1.. ::1: .. ::I:.::I::::::::I~:i::~::.~::::::::Ii:;:::::::=:~:~~:::::.:~~':;,: ::.::::::::'::::::::

I ,

~S~~~ij~§~~~~~i~~~;~~~~~~;~~!~~~~~~ ~~z ~ ~ ~~~m~ 0 ~~~~w ~ ~~8 ~~ ~ ~ g8~~ ~ QZ ~~

. 0 mz ~ ~o ~ (/l

• Wh1le inexpensive, high-capaCity screensare available for'CNS drug development,in vitro screens such as receptor bindingare generally l1mited' to the identlficationof compounds similar to those alreadyavailable. due to their reliance on stan­dard receptor mechanisms. An idealscreen would not depend on predeter­mined notions of mechanism, e.g., wouldbe one that measures a more complexfunctional activity such as whole animalbehavior. One could then work backwardto unravel a potentially novel mechanism.of action.

• Extraction procedures should not onlyoptlm1ze the alkaloid fraction but retain thepolar, water soluble compounds. An Initialcrude extmct With methanol would reducethe possibility of extmctlng amino acidsthat could result In false positives In recep­tor binding. A water extract of the remain­ing material should also be prepared.Molecu~sizing would be unnecessaty.

• While plants would be the major focus.any samples that have shown interestingactivity. either in preliminaxy screens orby ethnopharmacologlc data. should be

Therapeutics

~

.~ 120

~ 100I-tll ----.--~-~--------------iu.o 80',.....,1--··_....._....._....._....._...._... _..._... ..-.-.._._._....-.. ..--...:~

a:wlD60,-tII...·_··_·-····..:,···;·-·····-····-·····-·····_····_··.._•..._....._...._....._....._....._....._...._....._....._....._...._....._....,_...._....._....._...._...··..,...·····_·····"-7......:.·····_·····_·····_····_·.•._.... .:...'••._.•• _._~

::e:;) .. .. ,..:::~::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::~::::::::::::::::::::::::::::::::::::~::::::::::::::::::: .. :.:: .Z40-tI--I-lI--I-..----------..--...:..--...:.....:............::.:.....:.....:....:.::.::....:.::.::....:.::.:~

. ASSAYFIGURE 3.- Receptor-BlndJng Activity ofSynthetic Compounds. Receptor proftle fromNovaScreen ofapproxImately 550 compounds submItted to the rrogram through theend of 1992. -Hits- indicate at least 50-percent displacement 0 the radIollgand atafinal assay concentration of 10-5 M.

t. ;,

!,I .~,J'1

ii,JilII:/

~II

l

180

U.S. Efforts in Natural Products Research

rather than usIng the commercIally avaIl­able extracts.

• When consIderIng eventual commercIaldevelopment ofan active compound, syn­thetic capab1l1ty would be the Ideal. ThIsIs especIally Important when current reg­ulatory requIrements are consIdered.However, If total synthesIs Is economI­cally unfeaSIble, partial synthesIs couldbe an option. In addItion. communica­tions with the U.S. Food and DrugAdmin­istration should be established to explorethe possibiJities for development of stan­dardized extracts.

• The cost of Implementing a modest drug­screening program depends on the degreeof cost-sharlhg by other.instltutions andby whatever financIal incentives can beprovided to prIvate-sector firms inter­ested In drug development.

• This inItiative in pharmacognosy must becombined with ethnopharmacology toincrease the likelihood ofobtaining usefulmedictnals that are collected. extracted.and ~adm1nistered in the ,proper fashion(e.g., as a tea) to faCilitate extraction oftheactive cOl}stituent(s). The way the com­pound is handled may also give prelimi­nary information about its stability (e.g.,dried root, whIch is good for months:fresh leaf preparation for each use).

• An important aspect for the chemist is tohave a readily avaIlable screening proce­dure (in vivo or in vitro) that can be usedto follow the activity dUrlhg the isolationprocess as fractionation and purIficationproceeds.

Topics discussed that clearly need addi­tional work include the identlftcation of usefulscreening methods for novel psychoactivecompounds. Future NIMH workshops will dealwith this subject in greater depth. '

( -

Current Program Activities

NIMH is evaluating several natural productsreported to have therapeutic properties in thecentral nervous system. The literature regard­.ing ethnopharmacologic approaches to thetreatment of memory disorders such as

AlzheImer's disease show that several plantsare extensively used for thIs purpose. Many areavaIlable in the United.States in health foodstores as extracts and as the powdered plants.One of the most widely studied natural cogni­tive enhancers in recent years is Ginkgo biloba.Extracts from the leaves of the ginkgo treecontaIn pharmacologically active glycosidesand ginkgolides. They are reported to enhancememory and to increase cerebral blood perfu­sion. 18- 21 A patented extract contaIning stand­ardized amounts of the active constituents ismarketed In Germany and France. Gotu kola(Centella asiatica) is also used as a memoryenhancer and Is often sold in combination Withginkgo. These and a few other locally avaIlable"dietary supplements" with reported behav­ioral activity in animals or plants were ana­lyzed in the NIMH-NovaScreen receptor bind­ing assays. Preliminary' results of receptorbinding with the crude extr;lcts are shown inTable 4. Note that 25 additionalreceptors werealso tested at -6 /-lg/ml of these extracts butwere inactive (data not shown).

These affinity estimates assume startingmaterial to be approximately 1 g/ml freshplant (yielding approximately 20 mg/ml crudeextract), which is then diluted 10: 1 In 4-per­cent dimethylsulfoxide and 10: 1 agaIn in assaybuffer. At a final concentration of 20 /-lg/ml inthe Initial screening assay. samples inhibitingbinding at least 50 percent are then tested atconcentrl:\,tions of 20, 2, 0.2, and 0.02 /-lg/ml.This yields an approximate ICso. Assumingthat the crude extract contains 5 percent oftheactive compound(s) by weight, the affinity forthese receptors would be in the low nanomolarrange-well withIn pharmacologically relevantconcentrations. .

While the apparent in vitro activity of theseextracts is consistent with. the behavioral

>. effect~ reported in anImals. additional studiesusing standardized extraction and fraction­ation techniques will be necessary to confirmthese estimates. A graphic summary of' theresults of receptor-binding profiles for themore than 100 natural product samples pro­filed by the ·NIMH screening program as ofDecember 1992 is shown in Figure 4.

A collaborative effort for identlftcatioh anddevelopment of antiagmg. memory-enhancingdrugs has been ongoing since 1991 with Dr.Renuka Misra of NIH. This consists ofscreening

lSI

70-y---- -;- -,

ASSAYFlOURE 4. - Receptor-BlndJng Activity ofNatural Products. Receptor profile fromNovaScreen ofapproximatelY 150 compounds submitted to the program throuldtthe end of 1.992. -Hits- IndJcate at least 50-percent displacement of tileradloligand at concentrations between 40 and 300 Jlg/mlln the final assay.

TOTAL SCREENED. 146

NIMH, together with the NUl Offic~ for theStudy ofAlternative Medical Practice~ and theFogarty International Center, 'isspoIisodngworkshops and conferences on various aspectsof natural products research during 1993 and1994.

Current research initiatives ideal for jointIndo-U.,S. natural products research includepharmacologic characterization. isolation, and

~ 60-!--------------···-------------IZ:J 50 .....----------.oQ.::E 4O.tI-__-~-------.-I!!!!!I!!!!!!!!'I!!!!!!!!I!!!~!!!!!!I!!!!!!I!!!!!!!~.'-..-.--Ioo 30..-..._----------------------fW " ..

>.~ 20-t-.....-I1---------------=--:::--:-:-:".=....=.. ---:::=1o< lo-t-.=-FIFI~...Flir_=:=.:.:.:.:....-::..----------:::··:-:·'="':--"--:"-="-:"::-~-:-I'*"

crude plant extracts based on AyUlveda andAyur-vedic crude drugs used in the traditionalsystem of mediCine in India. Dr. Misra devel­oped this collaborative progriun with Dr. SukhDev, Indian Institute ofTechnology, under theUnited Natlons Development Program throughthe Council of Scientific and IndustrialResearch. More than 100 plant samples andseveral Ayurvedic drugs (Rasayan) were col­lected and extracted in coldmethanol' for screening. Sev­eral crude extracts and frac­tions have lnltially shown sig­nificant receptor activity inseveral assays.

A computer search of theethnopharmacology data base(NAPRALER11 at the Univer­sity of Illinois in Chicago isongoing. Potentially fruitfulareas for psychotherapeuticdrug developme.nt gleanedfrom this data base will resultin more detailed plans foradditional research. The NCIbotanical library has agreed tosupply any plant materialsalready available in theirlibrary for NIMH evaluation.

182

-

u.s. E;fforts in Natural Products Research.

structuralldentlftcat10n of active molecules Inmedicinal plants used In herbal medicine (e.g.,the AyUlveda). Thempeutlc areas of Interestwould include depression, psychotic disor­ders, anxiety disorders, and memory disor­ders. However, AyurvedIc d1agnosls and treat­ment of mental diSorders would likely useother tennlnology.Care must be taken tounderstand the prepamtlon and method ofadmJnistrat10n of medicinal plants. For obvi­ous reasons, single plant prepamtlons are pre­ferred for testing, and their botanical Identitymust be known.

REFERENCES

1. NIMH. Approaching the 21st centwy: Opportu­nlties for NIMH Neuroscience Research. DHHSPub. No. (ADM)88-1580. Washington, DC:Supt; of Docs., Govt. Print. Off., 1988.

2. Psychotherapeutic Drug Discovery and Devel­opment Program, PA-92-15, 1991.

3. Haigler, H., Cott, J.M., RUdorfer, M.,Schoenfeld, RI., Potter, W.Z., Vitiello, B., andEverist, H.D. Psychophann Bull 29:241-247,1992.

4. Efron, D.H., Holmstedt, B., and KI1ne, N.S.-Ethnophannacologic Search for PsychoactiveDrugs.- Proceedings of a -Symposium held inSan Francisco, CA, January 28-30, 1967.

183

5. Persinos, G.J., ed. Washington Insight, 5(4):7,1992.

6. International Cooperative Biodiversity Groups,RFA 1W-92-Ql, 1992.

7. Sen, G., and Bose, K.C. Indian Med World2:194, 1931.

8. Muller. J.M., SchUtter, E., and Beln, H.J.Experlentia 8:338, 1952.

9. Dorfman, L., Furlenmeler, A, Huebner, C.F., etaI. Hew GhtmActa 37:59, 1954.

10. KI1ne, N.S. Ann NYAcad Sci 59:107, 1954.11. Lehmann, H.E., and Hanrahan, G.E.AMAArch

Neural Psychiatry 71:227, 1954.12. Kuhn, RAm J Psychiatry 115:459, 1958.13. KI1ne, N.S. J GUn Exp Psychopathol 19(suppl):

72-78, 1958.14. Cade, J.F.J. MedJAus 2:349, 1949.15. Carlsson, A Pharmacal Rev 11:490, 1959.16. Carlsson, A, and Llndqvlst, M. A~ta Pharmacal

Toxtcol 20: 140, 1963.17. Daly, J.W.• Caceres,J.• Monl, RW.,et al. Proc

NatlAcad Sci 89:i0960, 1992.18. Gessner, B., Voelp, A, and Klasser, M.Arznetm·

Forsch/Drug Res 35: 1459, 1985.19. Vorberg, G. GUn TIials J 22:149, 1985.20. De Feudls. F.V. Ginkgo bUobaExtract (EGb 761).

Amsterdam: Elsevier, 1991.21. UlI, T.M., Le Bars; P.• Eralp, E., and Itll, K.Z.

Presented at the American College of Neuro­psychophannacology, San Juan, Puerto Rico,1992.

DECADE .OF THE BRAIN

India/USA R:~search in, (.~ .

Mental Health and Neurosciences

Editors

Stephen H. KoslowR. Srinivasa Murthy

George V. Coelho

u.s. DEPARTMENT OF HEALTH AND HUMAN SERVICESPUblic Health Service

National Institutes of Health

National Institute of Mental Health5600 Fishers Lane

Rockville, MD 20857

;.:.

ACKNOWLEDGMENTS

These proceedings and the Decade of the Brain Symposium could not have beensuccessfully completed without the diligent contributions from many individualsin,I1?;,Pia ~fl ~e, U,Jli~ed ~~tes of A1J,)erica. Spec~aI thapks ~e pu~ ~ membe~pfth~ ,DePaibne,lltsof, '~sychiatry;· N,a~onal Institute qf:Meiltal Hea!~ and NeuroSclences;"'Babgalbre. 'India:;' tlie hosts for the meeting. in particular. Mrs. P.V.Bhargavi. for coordinating the meeting and collating the Indian contributions andDrs. T.G. Sriram and Kishore Kumar for documentation support and organizationof the scientiflc sessions.

The US delegation Is extremely indebted to Mrs. Delores Dorman. Division ofNeuroscience and Behavioral Science. National Institute of Mental Health.National Institutes ofHealth. USA. for her scrupulous attention to the details andarrangements to coordinate all of the needed documents and schedules for travelto and from1ndia. and 'coordination of the editing of the final volume.

, .": • . ' ,;;,. 'i.' • , ."'. j ".

Special thanJtS are due to the US Embassy staff. in partlc;ular the Scientiflc"tA~ta9~e. Mr:qray' Handley ,and':'his as!'lstant Mr. ,M~ohan ("Bllla") Saxena"Without whose' guidance and care this Symposium would not have been the greatsuccess it was.

Ftnally. great appreciation Is due to the staff of the Office of International Healthof the Office of the Assistant Secretary ~or ~ealth. In particular. to Mrs. LindaVogel. Director. Office ofInternational Health. and Ms. Tina Chung. Public HealthAdviser for providing technical guidance and admtnistrative support throughoutall stages of the preparation for, the US delegation's travel to India.

COPYRIGHT STATIJS

The table and figures appearing on pages 44-52. 54. 73. 75. 78. 87. 132. 187.206-209. and 216 are copyrighted and are reproduced herein with permission ofthe copyright holder. Further reproduction of these copyrighted materials Isprohibited without specIfic permission of the copyright holder. All other materialcontained In this volume is in the public domain and may be used or reproducedwithout permission from the Institute or the authors. Citation of the source isappreciated.

Printed 1995

~ . 1,·1