Dissertation Report on

Antibacterial activity of Aloe vera gel extracts andidentification of Antibacterial compounds from Aloe vera

gel extracts.

AT

FICCI Research & Analysis Centre, Dwarka

Submitted in partial fulfillment of

M.Sc. Biotechnology

Semester IV

Amity Institute of Biotechnology

Amity University Rajasthan2013

Supervised By: Submitted By:

Dr. Sujata Pandit Aanchal Gupta[ Head, Amity University,Research & Development Rajasthan

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FICCI Research &Analysis Centre] M.Sc Biotechnology

IV Semester

Dr. Neetu Mishra[Lecturer,Amity Institute Of Biotechnology,Amity University, Rajasthan]

INTRODUCTION

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Aloe vera is a stem less or very short-stemmed succulent plant growing to 60–100 cm (24–39 in) tall, spreading by offsets. The leaves arethick and fleshy, green to grey-green, with somevarieties showing white flecks on the upper andlower stem surfaces. The margin of the leaf isserrated and has small white teeth. The flowers areproduced in summer on a spike up to 90 cm (35 in)tall, each flower being pendulous, with a yellowtubular corolla 2–3 cm (0.8–1.2 in) long[26].

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The Aloe vera plant has been known and used forcenturies for its health, beauty, medicinal andskin care properties. The name Aloe vera derives fromthe Arabic word “Alloeh” meaning “shining bittersubstance,” while “vera” in Latin means “true.”2000 years ago, the Greek scientists regarded Aloevera as the universal panacea. The Egyptians calledAloe “the plant of immortality.” 

The botanical name of Aloe vera is Aloe barbadensismiller. It belongs to Asphodelaceae (Liliaceae)family, and is a shrubby or arborescent, perennial,xerophytic, succulent, pea- green color plant. Itgrows mainly in the dry regions of Africa, Asia,Europe and America. In India, it is found inRajasthan, Andhra Pradesh, Gujarat, Maharashtra andTamil Nadu[2].

The plant has triangular, fleshy leaves withserrated edges, yellow tubular flowers and fruitsthat contain numerous seeds. Each leaf is composedof three layers: 1) An inner clear gel thatcontains 99% water and rest is made ofglucomannans, amino acids, lipids, sterols andvitamins. 2) The middle layer of latex which is thebitter yellow sap and contains anthraquinones andglycosides. 3) The outer thick layer of 15–20 cellscalled as rind which has protective function andsynthesizes carbohydrates and proteins. Inside therind are vascular bundles responsible fortransportation of substances such as water (xylem)and starch (phloem)[23].

The efficacy of Aloe liquid as an antibacterialagent is shown to have a wide range against gram

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positive and gram negative bacteria. Theantimicrobial agents of Aloe vera gel was reported toeffectively reduce the growth of Staphylococcus aureus,Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli,Helicobacter pylori and Salmonella typhi [13,17,19,24].

Whole leaf components are proposed to have directantibacterial propertied include anthraquinones andsaponin [19,24]; while polysacchrides have beenattributed within direct bacterial activity throughthe stimulation of phagocytic leucocytes todestroybacteria[13,17].

Due to the increasing development of antibioticresistance, the purpose of this study is to testAloe vera gel against a comprehensive panel ofmicrobes to characterise its antibacterialactivities furthermore, this project details theisolation, fractionation and partial identificationof antibacterial components from Aloe vera leaf gel.

Objectives of project :

Sampling of plant material.

Extraction of gel from plant leaves.

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Preparation of gel extract.

Determination of antibacterial activity of extract.

Purification of compounds present in extract.

Determination of antibacterial compounds.

Identification of antibacterial compounds by GC-MS.

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REVIEW OFLITERATURE

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Image 1 : Homegrown Aloe vera plantTaxonomic Classification:[27]

Kingdom: Plantae

Subkingdom: Tracheobionta

Superdivision: Spermatophyta

Division: Magnoliophyta

Class: Liliopsida

Subclass: Liliidae

Order: Liliales

Family: Aloaceae

Genus: Aloe

Species: Aloe vera

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Aloe vera contains 75 potentially activeconstituents: vitamins, enzymes, minerals, sugars,lignin, saponins, salicylic acids and aminoacids[3,20].Vitamins: It contains vitamins A (beta-carotene), Cand E, which are antioxidants. It also containsvitamin B12, folic acid, and choline. Antioxidantneutralizes free radicals.

Enzymes: It contains 8 enzymes: aliiase, alkalinephosphatase, amylase, bradykinase,carboxypeptidase, catalase, cellulase, lipase, andperoxidase. Bradykinase helps to reduce excessiveinflammation when applied to the skin topically,while others help in the breakdown of sugars andfats.

Minerals: It provides calcium, chromium, copper,selenium, magnesium, manganese, potassium, sodiumand zinc. They are essential for the properfunctioning of various enzyme systems in differentmetabolic pathways and few are antioxidants.

Sugars: It provides monosaccharides (glucose andfructose) and polysaccharides:(glucomannans/polymannose). These are derived fromthe mucilage layer of the plant and are known asmucopolysaccharides. The most prominentmonosaccharide is mannose-6-phosphate, and the mostcommon polysaccharides are called glucomannans[beta-(1,4)-acetylated mannan]. Acemannan, aprominent glucomannan has also been found.Recently, a glycoprotein with antiallergicproperties, called alprogen and novel anti-

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inflammatory compound, C-glucosyl chromone, hasbeen isolated from Aloe vera gel.

Anthraquinones: It provides 12 anthraquinones, whichare phenolic compounds traditionally known aslaxatives. Aloin and emodin act as analgesics,antibacterials and antivirals.

Fatty acids: It provides 4 plant steroids;cholesterol, campesterol, β-sisosterol and lupeol.All these have anti-inflammatory action and lupeolalso possesses antiseptic and analgesic properties.

Hormones: Auxins and gibberellins that help inwound healing and have anti-inflammatory action.

Others: It provides 20 of the 22 humanrequired amino acids and 7 of the 8 essential aminoacids. It also contains salicylic acid thatpossesses anti-inflammatory and antibacterialproperties. Lignin, an inert substance, whenincluded in topical preparations, enhancespenetrative effect of the other ingredients intothe skin. Saponins that are the soapy substancesform about 3% of the gel and have cleansing andantiseptic properties.

The aloe leaf can be divided into two major parts,namely the outer green rind, including the vascularbundles, and the inner colourless parenchymacontaining the aloe gel. Description of the innercentral part of the aloe leaf may sometimes beconfusing, due to the different terms that are used

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interchangeably such as inner pulp, mucilagetissue, mucilaginous gel, mucilaginous jelly, innergel and leaf parenchyma tissue. Technically, theterm ‘pulp’ or ‘parenchyma tissue’ refers to theintact fleshy inner part of the leaf including thecell walls and organelles, while ‘gel’ or‘mucilage’ refers to the viscous clear liquidwithin the parenchyma cells[16].

The raw pulp of A. vera contains approximately 98.5%water, while the mucilage or gel consists of about99.5% water[8]. The remaining 0.5 – 1% solidmaterial consists of a range of compounds includingwater-soluble and fat-soluble vitamins, minerals,enzymes,polysaccharides, phenolic compounds andorganic acids[5]. It has been hypothesized thatthis heterogenous composition of the Aloe vera pulpmay contribute to the diverse pharmacological andtherapeutic activities which have been observed foraloe gel products[21].

Aloe barbadensis Miller (Aloe vera) has a longhistory of use as a therapeutic agent with manyreported medicinal properties. Amongst itstherapeutic properties, it has been shown to haveanti-inflammatory activity[4], immunostimulatoryactivity[18] and cell growth stimulatory activity[22].

Furthermore, activity against a variety ofinfectious agents has been attributed to Aloe vera;for instance, antibacterial[9], antiviral[11] andanti fungal[12].

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Ferro et al. (2003) have shown that Aloe vera leafgel caninhibit the growth of the two Gram-positivebacteria Shigella flexneri and Streptococcusprogenes[9].

Specific plant compounds such asanthraquinones[7,10] anddihhydroxyanthraquinones[25], as well assaponins[19], have been proposed to have directantimicrobial activity.

Despite the therapeutic possibilities of thisplant, there have been limited reports on theantimicrobial effects of isolated Aloe veracomponents.

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