WHO Monographs on Selected Medicinal Plants.pdf

Chapter- 1

Bulbus allii sativi

Definition

Bulbus Allii Sativi consists of the fresh or dried bulbs of Allium sativum L. (Liliaceae)

Synonyms

Porvium sativum Rehb.

Selected vernacular names

It is most commonly known as "garlic". Ail, ail commun, ajo, akashneem, allium, alubosa

elewe, ayo-ishi, ayu, banlasun, camphor of the poor, dai toan, dasuan, dawang, dra thiam,

foom, Gartenlauch, horn khaao, horn kia, horn thiam, hua thiam, kesumphin, kitunguu-

sumu, Knoblauch, kra thiam, krathiam, krathiam cheen, krathiam khaao, I'ail, lahsun, lai,

lashun, lasan, lasun, lasuna, Lauch, lay, layi, lehsun, lesun, lobha, majo; naharu, nectar

orthe gods, ninniku, pa-se-waa, poor man's treacle, rason, rasonam, rasun, rustic treacles,

seer, skordo, sluon, stinking rose, sudulunu, ta-suam, ta-suan, tafanuwa, tellagada,

tellagaddalu, thiam, toi thum, turn, umbi bawang putih, vallaip- pundu, velluli, vellulli

Description

A perennial, erect bulbous herb, 30-60 cm tall, strong smelling when crushed. The

underground portion consists of a compound bulb with numerous fibrous rootlets; the

bulb gives rise abovc ground to a number of narrow, keeled, grass- like leaves. The leaf

blade is linear, flat, solid, 1.0-2.5cm wide, 30-60 cm long, and has an acute apex. Leaf

sheaths form a pseudostem. Inflorescences are umbellate; scape smooth, round, solid, and

coiled at first, subtended by membraneous, long-beaked spathe, splitting on one side and

remaining attached to umbel. Small bulbils are produced in inflorescences; flowers are

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variable in number and sometimes absent, seldom open and may wither in bud. Flowers

are on slender pedicels; consisting of perianth of 6 segments, about 4-6mm long, pinkish;

stamens 6, anthers exerted; ovary superior, 3-locular. Fruit is a small loculicidal

capsule..Seeds are seldom if ever produced

Plant material of interest: fresh or dried bulbs

General appearance

Bulbus Allii Sativi consists of several outer layers of thin sheathing protective leaves

which surround an inner sheath. The latter enclose the swollen storage leaves called

"cloves". Typically.. the bulb possesses a dozen sterile scathing leaves within which are

6-8 cloves bearing buds making a total of 10-20 cloves and 20-40 well-developed but

short and embedded roots. The cloves are asymmetric in shape, except for those near the

centre.

Organoleptic properties

Odor strong, characteristic alliaceous taste very persistently pungent and acrid.

Geographical distribution

Bulbus Allii Sativi is probably indigenous to Asia ( India) but it is commercially

cultivated in most countries.

General identity tests

Macroscopic and microscopic examinations and microchemical analysis are used to

identify organic sulfur compounds, thin-layer chromatographic

analysis to determine the presence of alliin.

Chemical assays

Qualitative and quantitative assay for sulfur constituents (alliin, allicin etc.) content by

means of high-performance liquid chromatography or gas chromatography-mass

spectroscopy methods.

Major chemical constituents

The most important chemical constituents reported from Bulbus Allii Sativi are the sulfur

compounds. It has been estimated that cysteine sulfoxides (e.g. alliin )and the non-

volatile y-glutamylcysteine peptides make up more than 82% of the total sulfur content of

garlic.

The thiosulfinates (e.g. allicin) ajoenes (e.g. E-ajoene, Z-ajoene). vinyldithiins (e.g. 2-

vinyl-(4H)-1,8-dithiin [5], 8-vinyl-(4H)-1.2-dithiin [6]), and sulfides (e.g.diallyl disulfide,

diallyl trisulfide), however, are not naturally occurring compounds,. Rather, they are

degradation products from the naturally occurring cysteeine sulfoxide, alliin . When the

garlic bulb is crushed, minced, or otherwise processed, alliin is released from

compartments and interacts with th eoenzyme alliinase in adjacent vacuoles. Hydrolysis

and immediate condensation of the reactive intermediate (allylsulfenic acid) forms alicin

. One milligram of alliin is considered to be equivalent to 0.45mg of allicin. Allicin itself

is an unstable product and will undergo additional reactions to form other derivatives

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(e.g. products), depending on environmental and processing condition. Extraction of

garlic cloves with ethanol at <0 o C gave alliin; extraction with ethanol and water at 25o

C led to allicin and no allin; and steam distillation (100o C) converted the alliin totally to

diallyl sulfides. Sulfur chemical profiles of Bulbus Allii Sativi products reflected the

processing procedure: bulb, mainly alliin, allicin; dry powder, mainly alliin. allicin;

volatile oil, almost entirely diallyl sulfide, diallyl disulfide, diallyl tisul fide, and diallyl

tetrasulfide; oil macerate, mainly 2-vinyl-[4H]-1.8-dithiin, 8-vinyl-[4H]-1,8-dithiin, E-

ajoene, and Z-ajoene .The content of alliin was also affected by processing treatment:

whole garlic cloves (fresh) contained 0.25-1.15% alliin, while material carefully dried

under mild conditions contained 0.7-1.7% alliin.

Gamma-glutamylcysteine peptides are not acted on by alliinase. On prolonged storage or

during germination, these peptides are acted on by y-glutamyl transpeptidase to forn1

thiosilfinates.

Dosage forms

Fresh bulbs, dried powder, volatile oil, oil macerates, juice, aqueous or alcoholic extracts,

aged garlic extracts (minced garlic that is incubated in aqueous alcohol (15-20%) for 20

months, then concentrated), and odorless garlic products (garlic products in which the

alliinase has been inactivated by cooking; or in which chlorophyll has been added as a

deodorant; or aged garlic preparations that have low concentrations of water-soluble

sulfur compounds).

The juice is the most unstable dosage form. Alliin and allicin decompose rapidly, and

those products must be used promptly.

Dried Bulbus Allii Sativi products should be stored in well-closed containers, protected

from light, moisture, and elevated temperature.

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Medicinal uses

Uses supported by clinical data

As an adjuvant to dietetic management in the treatment of hyperlipidaemia, and in the

prevention of atherosclerotic (age-dependent) vascular changes. The drug may be useful

in the treatment of mild hypertension.

Uses described in pharmacopoeias and in traditional systems of medicine

The treatment of respiratory and urinary tract infections, ringworm and rheumatic

conditions. The herb has been used as a carminative in the treatment of dyspepsia.

Uses described in folk medicine, not supported by experimental or clinical data

As an aphrodisiac, antipyretic, diuretic, emmenagogue, expectorant, and sedative, to treat

asthma and bronchitis, and to promote hair growth.

Pharmacology

Experimental pharmacology

Bulbus Allii Sativi has a broad range of antibacterial and antifungal activity.The essential

oil, water, and ethanol extracts, and the juice inhibit the in vitro growth of Bacillus

species, Staphylococcus aureus , Shigella sonnei , Erwinia carotovora , Mycobacterium

tuberculosis , Escherichia coli , Pasteurella multocide , Proteus species , Streptococcus

faecalis , Pseudomonas aeruginosa , Candida species , Cryptococus species , Rhodotorula

rubra, Toruloposis species, Trichosporon pullulans , and Aspergillus niger .Its anti

microbial activity has been attributed to allicin, one of the active constituents of the drug.

However, allicin is a relatively unstable and highly reactive compound and may not have

antibacterial activity in vivo. Ajoene and diallyl trisulfide also have antibacterial and anti

fungal activities. Garlic has been used in the treatent of roundworm ( Ascaris

strongyloides ) and hookworm (Ancylostoma caninum and Necator americanus) (44=45).

Allicin appears to be the active anthelminthic constituent, and diallyl disulfide is not

effective.

Fresh garlic, garlic juice, aged garlic extracts, or the volatile oil all lowered chlesterol and

plasma lipids, lipid metabolism, and athero9genesis both in vitro and in vivo. In vitro

studies with isolated primary rat hepatocytes and human HepG2 cells have shown that

water-soluble garlic extracts inhibited cholesterol biosynthesis in a dose-dependent

manner . Anti hyperchlesterolaemic and anti hyperlipidameic effects were observed in

various animal models (rat, rabbit, chicken, pig) after oral (in feed) or intragastric

administration of minced garlic bulbs; water, ethanol, petroleum ether, or methanol

extracts, the essential oil; aged garlic extracts and the fixed oil. Oral administration of

allicin to rats during a 2-month period lowered serum and liver levels of total lipids,

phospholipids, triglycerides, and total cholesterol.Total plasma lipids and cholesterol in

rats were reduced after intraperitoneal injection of a mixture of diallyl disulfide and

diallyl trisulfide .The mechanism of garlic's anti hypercholesterolaemic and anti

hyperlipidaemic activity appears to involve the inhibition of hepatic

hydroxymethylglutaryl-CoA (HMG-CoA) reductase and remodeling of plasma

lipoproteins and cell membranes.At low concentrations (<0.5mg/ml), garlic extracts

inhibited the activity of hepatic HMG-CoA reductase, but at higher concentrations

(>0.5mg/ml)cholesterol biosynthesis was inhibited in the later stages of the biosynthetic

pathway (68). Alliin was not effective, but allicin and ajoene both inhibited HmG-CoA

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reductase in vitro (IC 50 = 7 and 9 mmol/l respectively) . Because both allicin and ajoene

are converted to allyl mercaptan in the blood and never reach the liver to affect

cholesterol biosynthesis, this mechanism may not be applicable in vivo. In addition to

allicin and ajoene, allyl mercaptan (50mmol/l) and diallyl disulfide (5mmol/l) enhanced

palmitate-inducedinhibition of chgolesterol biosynthesis in vitro. It should be noted that

water extracts of garlic probably do not contain any of these compounds; therefore other

constituents of garlic, such as nicotinic acid and adenosine, which also inhibit HmG-CoA

reductase activity and cholesterol biosynthesis, may be involved.

The anti hypertensive activity of garlic has bee demonstrated in vivo. Oral or intragastric

administration of minced garlic bulbs, or alcohol or water extracts of the drug, lowered

blood pressured in dogs, guinea pigs, rabbits, and rats. The drug appeared to decrease

vascular resistance by directly relaxing smooth muscle.The drug appears to change the

physical state functions of the membrane potentials of vascular smooth muscle cells.

Both aqueous garlic and ajoene induced membrane hyperpolarization in the cells of

isolated vessel strips. The potassium channels opened frequently causing

hyperpolarization, which resulted in vasodilatation because the calcium channels were

closed.The compounds that produce the hypotensive activity of the drug are uncertain.

Allicin does not appear to be involved, and adenosine has been postulated as being

associated with the activity of the drug. Adenosine enlarges the peripheral blood vessels,

allowing the blood pressure to decrease, and is also involved in the regulation of blood

flow in the coronary arteries; however, adenosine is not active when administered orally.

Bulbus Allii Sativi may increase production of nitric oxide, which is associated with a

decrease in blood pressure. In vitro studies using water or alcohol extracts of garlic or

garlic powder activated nitric-oxide synthase, and these results have been confirmed by

in vivo studies

Aqueous garlic extracts and garlic oil have been shown in vivo to alter the plasma

fibrinogen level, coagulation time, and fibrinolytic activity. Serum fibrinolytic activity

increased after administration of dry garlic or garlic extracts to animals that were

artificially rendered arteriosclerotic. Although adenosine was thought to be the active

constituent, it did not affect whole.

Garlic inhibited platelet aggregation in both in vitro and in vivo studies. A water,

chloroform, or methanol extract of the drug inhibited collagen-, ADP-, arachidonic acid-,

epinephrine-, and thrombin-induced platelet aggregation in vitro. Prolonged

administration (intragastric, 3 months) of the essential oil or a chloroform extract of

Bulbus Allii Sativi inhibited platelet aggregation in rabbits. Adenosine, alliin, allicin, and

the transformation products of allicin, the ajoenes; the vinyldithiins; and the

dialkyloligosulfides are responsible for inhibition of platelet adhesion and aggregation. In

addition methyl allyl trisulfide, a minor constituent of garlic oil, inhibited platelet

aggregation at least 10 times as effectively than allicin. Inhibition of the arachidonic acid

cascade appears to be one of the mechanisms by which the various constituents and their

metabolites affect platelet aggregation. Inhibition of platelet cyclic AMP

phosphodiesterase may also be involved.

Ajoene, one of the transformation products of allicin, inhibited in vitro plate-let

aggregation induced by the platelet stimulators-ADP, arachidonic acid, calcium

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