analysis of essential oil from watermelon seedssospoly journal of science & agriculture, vol. 2,...

SosPoly Journal of Science & Agriculture, Vol. 2, (Dec., 2017) ISSN: 2536-7161

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Umaru Ali Shinkafi Polytechnic Sokoto, Nigeria

ANALYSIS OF ESSENTIAL OIL FROM WATERMELON SEEDS

Mansur Ahmad, Riskuwa Faruk, Kasimu Abubakar Shagari and Shehu Umar

Shehu Shagari College Of Education, Sokoto-Nigeria

[email protected]

ABSTRACT

Watermelon belongs to the family of Cucurbitaceae and it well known in Nigerian modern

and traditional system for its modern and traditional uses. The present investigation was

carried out to determine the chemical properties, proximate composition as well as the

possible bioactive components of watermelon seeds using GCMS analysis. The oil from the

seeds was extracted using soxhlet extraction procedure. Moisture was determined directly on

the seeds by oven drying at 105oC for 6 hours. The yield of the dry seeds from the sample was

determined. The ripened seeds and dry seeds were then ground in some blender, separately,

and placed in a vacuum oven at 60oC for 6 hours and finally stored in a desiccator until

analyzed. Proximate analyses were performed in triplicate in accordance with the AOAC

procedures (AOAC, 1990). The ash was determined by heating overnight at 500oC and the

protein content of the seeds by standard Kjeldahl (total %N) procedure. Wiss and Devine

(1961) method was adopted for the chemical analysis. Free Fatty Acid of the oil

(2.46±0.01%) which shows the better quality of the oil. The acid value (7.60mg/NaOH/g) fall

within acceptable limits for edible oils (≤10mg/NaOH/g). The GC-MS analysis was carried

out on a GC-MS-QP 2010 Shimadzu system using NIST database. Seven (7) components from

watermelon seeds were identified. The prevailing elements in the watermelon seeds were

palmitic acid, carbonic acid, oleic acid, Dioctylester, propanedioic acid, linoleic acid

chloride and delta-tocopherol. The presence of various bioactive compounds confirms the

applications of watermelon for multiple ailments by traditional and modern practitioners.

However, isolation of individual phytochemical constitutes may proceed to find a novel drug

or lead compound.

Keywords: Watermelon, Seeds, GC-Ms, Proximate Analysis, Essential Oil

INTRODUCTION

The use and dependence on plants as medicines by man has been in existence since time

immemorial, and man continues to search for plants as drugs for a particular disease within

his reach. Synthetic medicines are safe than herbal medicines because the phytochemical in

the plant extract target the biochemical pathway (Zaidan and Badrul, 2005). Medicinal plants

are an expensive gift from nature to human. The approval of traditional medicines as an

alternative form of healthcare and the improvement of microbial resistance to the existing

antibiotics has lead researchers to scrutinize the antimicrobial compounds (Parvathi, S.,

2010). Medicinal plants have been used all over the world for the treatment and prevention of

various ailments especially in developing countries where infectious diseases are endemic

and modern health facilities, and services are inadequate (Zaida and Badrul, 2005). The

medicinal actions of plants unique to particular plant species or groups are consistent with the

concept that the combination of secondary products for a specific plant taxonomically distinct

(Wink et at., 1999).

mailto:[email protected]


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Screening active compounds from the plant have led to the invention of new

medicinal drugs which have protection and treatment roles against various diseases including

cancer, Alzheimer‟s diseases (Sheeja and Kuttan, 2007). Plant remains a vital source of drugs

and nowadays much emphasis has been given to nutraceuticals.

Watermelon (Citrullus lanatus), family Cucurbitaceae is a vine-like flowering plant

originally from southern Africa. Its fruits, which is also called watermelon is a referred to by

botanists as a pepo, a berry which has a thick rind (exocarp) and fleshy center (mesocarp and

endocarp) pepos are derived from an inferior ovary and are characteristic of the

Cucurbitaceae. The watermelon fruit, loosely considered a type of melon-although not in the

genus Cucumis has a smooth exterior rind (green, yellow and sometimes white) and a sweet

interior flesh (usually pink, but sometimes orange, yellow, red and sometimes green if not

ripe). It is also commonly used to make a variety of salads, most notably fruit salad

(Pomeranz and Clifton, 1981).

HISTORY

Watermelon is thought to have originated in southern Africa, where it is growing wild.

Alphonse de Candolle, in 1882 already considered the evidence sufficient to prove that

watermelon was indigenous to tropical Africa (North Carolina State University). Though

Citrullus cololyn this often supposed to be a wild ancestor of watermelon and is now found a

native in North and West Africa. (Dane and Liu, 2007) suggest by chloroplast DNA

investigations that the cultivated and wild watermelon appears to have diverged

independently from a common ancestor, possibly Citrullus ecirrhosus from Namibia.

It is not known when the plant was first cultivated, but Zohary and Hopf note

evidence of its cultivation in the Nile valley from at least as early as the second millennium

BC. Although watermelon is not depicted in any Egyptian hieroglyphic text nor makes any

ancient writer mention, it finds of the characteristically large seeds is reported in Twelfth

dynasty sites numerous watermelon seeds were recovered from the tomb of Pharaoh

Tutankhamen (Daniel and Maria, 2000). By the 10th

century AD, watermelons were

cultivated in China, which is today the world‟s single largest watermelon producer. By the

13th

century, Moorish invaders had introduced the fruit to Europe according to John Mariana

the Dictionary of American food and Drink.

Charles Fredric Andrus, a horticulturist at the USDA vegetable Breeding laboratory in

Charleston South Carolina, set out to produce a disease-resistant and wilt-resistant

watermelon. The result was that gray melon from Charleston. Its oblong shape and hard rind

made it easy to stack and ship. Its adaptability meant it could be grown over a wide

geographical area. It produced high yields and was resistant to the most severe watermelon

disease Anthracnose and Fusarium wilt.

In Japan, farmers of the Zentsuji region found a way to grow cubic watermelons by

planting the fruits in glass boxes and letting them naturally assume the shape of the

receptacle. The square is designed to make the melons easier to stack and store, but the

square watermelons are often more than double the price of normal ones. Pyramid shaped

watermelons have also been developed, and any polyhedral shape may potentially also be

used.


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VARIETIES

There are more than 1200 varieties of watermelons ranging from less than a pound to more

than two hundred pounds, with flesh that is red, orange, yellow or white (Baker Creek, 2008).

Several notable varieties are as follows:

Carolina cross: - This variety of watermelons produced the current world record melons

weighing 262 pounds (119kg). It has green skin, red flesh and commonly produces fruits

between 65 and 150 pounds (29 and 68 kg). It takes about 90 days from planting to harvest,

(Baker Creek, 2008).

Yellow Crimson: - Variety of watermelon that has a yellow colored flesh. This particular

type of watermelon is “sweeter” and more “honey” flavored than another red flesh

watermelon (Anioleka et al., 2007).

Orangeglo: - This variety has a very sweet orange pulp, and is a significant oblong fruit

weighing 9kg (20-30 pounds). It has a light green rind with Jaggiest dark green stripes. It

takes about 90-100 days from planting to harvest. The Moon and Stars variety of watermelon

has been around since 1926 (Moons and star, 2008). It has many small yellow circles with

purple-black rind, (Stars) and one or two large yellow circles (Moon). The watermelon

weights 9-23kg (20-50 pounds) (Johnson and Sahaya, 2012). The flesh is pink or red and has

brown seeds. The foliage is also spotted. The time from planting to harvest is about 90 days.

Cream of Saskatchewan: - This variety consists of small round fruits around 25cm (10

inches) in diameter. It has a quite thin, light green with dark green striped rind, with sweet

white flesh and black seeds. It can grow well in cold climates. This variety was brought to

Saskatchewan, Canada by Russian immigrants. These watermelons take 80-85 days from

planting to harvest.

Melitopolski: - This variety has small round fruits roughly 28-30cm (11-12 inches) in

diameter. It is an early ripening variety that originated from the Volga River region of Russia

are known for the cultivation of watermelons. This watermelon is seen piled high by vendors

in Moscow in summer. This variety takes around 95 days from planting o harvest.

Densuke: - This variety has round fruit up to 25 16 (11 kg). The rind is black with no stripes

or spots. It can only grow on the Island of Hokkaido, Japan, where up to 10,000 watermelons

are produced every year. In June 2008, one of the first harvested melons is being sold at an

auction for 650,000 yen (6300 USD) making the most expensive watermelon ever sold. The

average selling price is generally around 25,000 yen (250 USD) (Vohra and Kaur, 2011).

LITERATURE REVIEW

Definition of Fats and Oils

Fats and oils can be defined by layman as the substances that are clearly fatty in nature,

greasy in texture, and are immiscible with water biochemically , fats and oils are defined as

substances that are insoluble in water and can be extracted by organic solvents of low polarity


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such as petroleum ether chloroform, methanol, n-hexane, etc. Chemists defined fats and oils

as the triglycerides of fatty acids in which one molecule of glycerol combined with three

molecules of long chain fatty acid with the elimination of water molecule.

Sources of Fats and Oils

Fats and oils from plants are found mostly in fruits and seeds while in animals it‟s stored as

fatty tissues which protect certain parts of the body and as insulation against cold. Synthetic

fats and oils are produced by oxidation of hydrocarbons to fatty acids, which are then

esterified with glycerol, or synthesis of fatty acids from carbohydrates by microorganisms.

Essential Oils

Essential oils are highly volatile substances isolated by physical process from an odoriferous

plant of a single botanical species. Therefore the fragrance of buds flowers leaves or bark,

and terminal branches of individual plants is due to the presence of these volatile oils. They

bear the name of the plant from which it is derived from example peppermint oil or rose oil.

Such essentials oil was thought to represent their very essence of odor and flavor. After many

years of research, it is now known that these essential oils are a mixture of up to twenty or

more fragrance chemical compounds of highly aromatic substances mostly benzene straight

chain hydrocarbons compounds of intermediate molecular lengths and terpene derivatives.

ECONOMIC IMPORTANCE OF WATERMELON

Nutritive Values

Watermelon raw (edible part) has the total energy of about 127kj (30kcal), Carbohydrates

content 7.55g, Sugars (6.2g), Dietary fiber (0.4g) Fat (0.15g) Protein (0.61g) Water (91.45g),

Vitamin A equivalent to 28µg (3%), Thiamin (Vit.B1) 0.033mg (3%), Riboflavin

(vit.B2)0.021mg (1%), Niacin (Vit.B3) 0.178mg (1%), Pantothenic acid (B5) 0.221mg (4%),

Vit.B6 0.045mg (3%), Folate (Vit. B9)3.4g (1%), Vit.C 8.1mg (14%), Calcium 7mg (1%) Iron

0.24mg (2%), Magnesium 10mg (3%), Phosphorus 11mg, Potassium 112mg (2%), Zinc

0.10mg (1%), (Iakshmi and Kaul, 2011).

Sources of Other Compounds/Substances

Watermelons contain a significant amount of citrulline, and after consumption of several

kilograms of watermelon, an elevated concentration is detected in the blood plasma, this

could be mistaken for citrullinaemia or other urea cycle disorders (Martin and Negro, 2007).

Watermelon rinds usually a light green or white color is also edible and contains

many hidden nutrients that most people avoid eating due to its unappealing flavor. They are

sometimes used as a vegetable (Martin and Negro, 2007)

In China, watermelons are stir-fried, stewed or more often pickled. When stir-fried the

skinned and fruited rind is cooked with olive oil, garlic, chili peppers, scallions, sugars, and

rum. Pickled watermelon rind is also commonly consumed in the southern us. Watermelon

juice can also be made into wine. Watermelon is also mildly diuretic and contains significant

amounts of beta-carotene. Watermelon with red flesh is a significant source of lycopene,

(Hdider and Lenucci, 2011).


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Health Benefits of Watermelons

Watermelon has plenty of potassium that is useful in cleansing the toxic depositions of

kidneys. Additionally, it‟s helpful in lowering amount of uric acid in the body, thus reducing

the risk of kidney problems and development of renal calculi. Besides these, being loaded

with water contents, it encourages frequent urinating; again it‟s useful for kidney cleansing.

Furthermore, the antioxidants in the watermelons ensure the well-being of kidneys.

A great deal of magnesium and potassium found in the watermelons are incredibly

effective in reducing the blood pressure level. The carotenoids contained in the fruit protect

walls of arteries and veins from hardening, thus helping to lower blood pressure level,

(Poduri et al., 2012).

Alongside tomatoes, watermelon has moved up to the front of the line in recent

research studies on high-lycopene foods. Lycopene is a carotenoid phytonutrient that is

especially important for our cardiovascular health, and an increasing number of scientists

now believe that lycopene is an important for bone health as well. Among whole, fresh fruits

that are commonly eaten in the U.S., watermelon now accounts for more U.S. intake of

lycopene than any other fruit, (Saha and Poduri, 2012).

Health scientists are becoming more and more interested in the citrulline content of

watermelon. Citrulline is an amino acid that is commonly converted by our kidneys and other

organ systems into arginine (another amino acid). The flesh of a watermelon contains about

250mg of citrulline into arginine. In particular, if a person‟s body is not making enough

arginine, higher levels of arginine can help improve blood flow and another aspect of our

cardiovascular health, (Azevedo et al., 2007).

There is also some preliminary evidence from animal studies that greater conversion of

citrulline into arginine may help prevent excess accumulation of fat in fat cells due to a

blocked activity of an enzyme called alkaline phosphatase, or TNAP, (Saha et al., 2012).


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MATERIALS AND METHODS

MATERIALS: The material used includes the fruits of fresh watermelons.

CHEMICALS

REAGENTS MANUFACTURER %PURITY

Petroleum ether B.O.H Chemical Ltd. England 99.8%

Sulphuric acid B.O.H Chemical Ltd. England 97%

Sodium hydroxide B.O.H Chemical Ltd. England

Conc. HCl B.O.H Chemical Ltd. England 99%

Phenolphthalein B.O.H Chemical Ltd. England

Pyridine B.O.H Chemical Ltd. England 96%

Ethanol B.O.H Chemical Ltd. England 99.9%

Starch C. Gerhard Gmbu Company

Potassium iodide B.O.H Chemical Ltd. England 97%

Iodine James Borough Puy Ltd. London 99%

Chloroform B.O.H Chemical Ltd. England 99.4%

Sodium thiosulphate B.O.H Chemical Ltd. England 98%

Glacial acetic acid B.O.H Chemical Ltd. England 99.8%

Potassium chloride B.O.H Chemical Ltd. England 97%

Ammonium sulfate B.O.H Chemical Ltd. England 98%

Boric acid indicator B.O.H Chemical Ltd. England

Sodium sulfate B.O.H Chemical Ltd. England 96%

Copper sulfate B.O.H Chemical Ltd. England 95%

APPARATUS

APPARATUS TYPE/MODEL COMPANY

Spatula Glass Pyrex glass England

Volumetric flask Glass Pyrex glass England

Measuring cylinder Glass Pyrex glass England

Burette Glass Pyrex glass England

Conical flask Glass Pyrex glass England

Tripod Metallic Pyrex glass England

Soxhlet set

Hot air oven Metallic, HQ4400 Muttle, Switzerland

GC-MS machine QP 2010 Shimadzu, Japan

Crucibles Ceramic Muttle, Switzerland


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Sampling

Watermelon fruits were purchased from Ramen-Kura, a local market for vegetables in Sokoto

state, in the northern part of Nigeria. The flesh is removed and the seeds collected were

washed and dried for easy removal of the epicarp.

Sample Preparation

The melon seeds were then subjected to sun-drying the melon seeds of 100g were dry-milled,

and the oil content was extracted by Soxhlet extraction method before being subjected to

chemical, proximate and GC- MS analyses respectively.

Extraction of Oil from Watermelon Seeds

From the grounded sample of watermelon seeds, 50g was weighed into an empty thimble

which was placed in a Soxhlet extraction set. 250ml of n-hexane solvent was then poured into

the extraction flask. The bottom of the extractor containing the sample was connected to the

extraction flask and placed on the heating mantle. As temperature increased steadily n-hexane

boiled and formed a vapor which was condensed by the condenser formerly attached to the

extractor and then dropped into the thimble dissolving and extracting oil present in the

powdered seeds. The extraction was carried out continuously for 6 hours.

After the extraction procedure, the thimble was removed then the n-hexane formed a

vapor which condensed and was collected in the receiver of the Soxhlet extractor while the

oil remained in the flask allowed to cooled and weighed. The procedure was repeated for the

remaining grounded sample of the watermelon seeds, and the oil was obtained.

Reagents Preparation

Na2S203.5H20 (0.1M)

Six (6.0g) of sodium thiosulphate was dissolved in a volumetric flask and made up to mark

250cm3 with distilled water.

Starch Indicator (1%)

One (1.0g) of starch was dissolved in 5sm3

distilled water and then made up to 100cm3

volumetric flask with hot distilled water refluxed for 5minutes and then allowed to cool.

KI (10%)

Ten (10g) of KI was dissolved in a beaker containing 90ml distilled water and then made up

to 100cm3

mark volumetric flask with distilled water.

KOH (0.1M)

One and a half i.e. (1.5g) of KOH was dissolved in distilled water and made up to mark

250cm3

distilled water.

Alcoholic KOH (0.1M)

A pellet of (1.4g) of KOH was dissolved in 50cm3 of ethanol and made up to mark 250cm

3

with distilled water.

HCl (0.5M)

About 10.6cml of concentrated HCl was poured into a beaker containing distilled water and

made up to 250cm3 with distilled water.

Phenolphthalein (1%)


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One gram (1.0g) of phenolphthalein was dissolved in 100cm3 of ethanol.

Solvent Mixture

The solvent mixtures were prepared by mixing 125cm3 of each of toluene and isopropyl

alcohol and 4cm3

of 1% phenolphthalein in isopropyl alcohol.

Na0H (0.25M)

One gram, i.e. (1.0g) of Na0H was dissolved in a 1dm3 volumetric flask and made up to mark

with distilled water.

ICI (Iodine Monochloride)

Pyridine 8.2ml by volume and 6ml of conc. H2S04 was mixed in 20ml cooled glacial acetic

acid, and 26ml of bromine was added to this solution. The mixture was then diluted to Idm3

with glacial acetic acid and was kept in the dark.

ANALYSIS AND DETERMINATIONS: PROXIMATE ANALYSIS

Determination of Moisture

The moisture content of melon seeds was determined by putting freshly obtained seeds in an

oven at 1050C. The moisture content was also determined by drying the rind and finding the

loss in weight.

Procedure

An empty crucible was weighed; 2g of fresh seeds were considered into it and placed in an

oven at 1050C for 24 hours. After 24 hours they were removed allowed to cool and weighed.

2g of the fresh seeds were weighed and shed dried and reweighed.

Determination of Ash Contents

Ash is the non-volatile inorganic matter of the sample that remains after subjecting it to high

temperature.

Procedure: - An empty crucible was weighed. 2g of the fresh sample was weighed and

transferred into the pre-weighed crucible. It was then heated in a muffle furnace at a

temperature of 6000C for s2 hours. It was allowed to cooled and weighed again.

Determination of Crude Protein

The Kjeldahl method was used for crude protein determination.

Principle

The method is based on the transformation of protein nitrogen and other nitrogenous

compounds other than nitrate and nitrite into ammonium sulfate by acid digestion with strong

acid usually concentrated H2S04 i.e.

Sample nitrogen + H2S04 (NH4)2 SO4

The ammonia present is digested with the help of sodium hydroxide and distilled out and

collected into receiving flask containing a boric acid indicator which changed color from

pink to green.

(NH4)2S04 + Na0H 2NH3 + H20 + NaS04

NH3 + H3BO NH+

4 + H2B03


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The nitrogen content was thus estimated by titration the content in the receiving flask with

standard acid (H2 S04).

H+

H2B03 H3B03

The amount of H+ consumed in the reaction is equivalent to the amount of nitrogen present

in the sample.

The amounts of protein were then estimated by multiplying the concentration of

nitrogen in the sample by a conversion factor of 6.6 which is equivalent to 16gN/100g

protein.

Procedure

From the dried grounded sample, 2grams was weighed into Kjeldahl digestion flask,

and a catalyst mixture was added (NaS04, CuS04 and Selenium oxide in the ratio 10:5:1).

The content was heated in the sulfuric acid (H2S04). The content was heated in the Kjeldahl

digestion unit until the digestion was completed (approximately 30minutes). The flask was

cooled, diluted volumetric flask and made up to the mark with distilled water. 10ml of the

aliquot was then taken into the digestion flask, and 20mls of 45% Na0H solution was added.

The content was diluted to about 200ml with distilled water and distilled using Kjeldahl

distillation apparatus.

The distillates were received into receiving flask containing 10mls boric acid solution

indicator. After distillation, the distillate was titrated with standardized 0.1M HCl to the

endpoint. The blank was determined in the same way without the sample.

DETERMINATION OF CRUDE FIBRE (AOAC 1990)

Procedure

From the grounded sample, 2grams was weighed and placed in a conical flask containing

200ml of 1.15% H2S04 sulphuric acid and boiled gently for 39 minutes. The content was

filtered, and the residues were scraped into the container with a spatula. The oxidant 1.25%

sodium hydroxide Na0H was added and allowed to boil gently for 30minutes. The content

was then filtered and washed thoroughly with hot distilled water.

The precipitate was allowed to dry, and the residue was scraped into a crucible and

dried overnight at 105OC in a hot air oven. It was then removed and cooled in a desiccator.

The sample was then weighed and ashed at 6000C for ninety minutes in a furnace. This was

finally cooled in a desiccator and weighed.

DETERMINATION OF CRUDE LIPID

Soxhlet extractor used for crude lipid determination. 2grams each of the dried grounded

samples were weighed into a porous thimble and its mouth covered with cotton. The thimble

was then placed in an extractor chamber, which was suspended above a receiving flask

containing petroleum ether (boiling point 40-600C). The flask was heated on a hot mantle and

the oil extracted.


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The extraction continues for about eight hours (8) after which the thimble was

removed from the soxhlet, and the apparatus was reassembled and heated on water-bath

apparatus for solvent recovery. The flask containing the crude oil was then disconnected,

cleaned up and placed in an oven at 1000C for thirty minutes (30). The flask was then cooled

in a desiccator and weighed.

DETERMINATION OF CARBOHYDRATES

To obtain the % carbohydrate content, all the above proximate analysis parameters have to be

summed and subtracted the value obtained out of 100. The remaining value obtained after

substitution is our percentage carbohydrate content in the sample. %CH0= 100- (% Ash +%

crude protein +% crude fiber + % crude lipid).

ANALYSIS AND DETERMINATION

PHYSICO-CHEMICAL ANALYSIS

DETERMINATION OF PEROXIDE VALUE

Peroxide value is an index of lipid deterioration expressed as peroxide per kg of fat or mili-

equivalent. It is the first products of unsaturated oil when peroxide value reaches a certain

level; complex change occurs with formation of ketone, aldehyde and hydroxyl group all

these are volatile and responsible for odor and flavor.

Procedure

From the extracted oil, 2g was weighed into a conical flask, and 25ml of glacial acetic acid

and chloroform was added. 1ml of KI solution was added and allowed to stand in the dark for

1 minute so that the solution becomes straw yellow. 35 ml of distilled was also added and

then followed with ten drops of 1% starch indicator. This was titrated against 0.004M

Na2S203.5H20 till blue color disappeared. The procedure was done in triplicate and blank was

estimated without adding oil.

DETERMINATION OF ACID VALUE

It is the percentage of free fatty acid expressed as oleic acid.

Principle

Acid value of oil is determined by titration of known weight of oil against 0.25N Na0H using

phenolphthalein as indicator

C17H33COOH + Na0H C17H33C00Na +H20

Procedure

From the extracted watermelon seed oil, 1g was weighed in a conical flask 50ml of denatured

alcohol was then added and shaken and two drops of phenolphthalein indicator were added to

the mixture then titrated against 0.25M Na0H with vigorous shake until the permanent light

pink color was observed.


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SAPONIFICATION VALUE

William and Devine's method was used (1961). Saponification number is the amount of

milligram of potassium hydroxide (KOH) required to completely saponify (I.0g) of oil.

Principle

When oils are treated with excess alcoholic (KOH), the oil gets saponified, and a definite

amount of (KOH) is used up. The excess KOH left unused may then be found by titrating

against 0.5M HCl.

Procedure

From the oil extracted 0.5g was weighed in a quick-fit-reflux flask, and 25ml alcoholic KOH

was then added. It was refluxed for 30minte so that it gets simmered. The flak was allowed to

cool, and 1ml of phenolphthalein indicator was then added and titrated against 0.5M HCl.

IODINE VALUE

The method described by Devine and Williams (1961) was used. This is the percentage of

iodine monochloride (ICI) regarding iodine absorbed by the oil.

Principle

The method is based on the treatment of a known weight of oil or fat with a known volume of

a standard solution of iodine monochloride (ICl). Estimation of ICI is by titrating iodine

liberated by adding excess potassium iodide. Titration was done against sodium thiosulphate

(Na2S203.5H20) with starch as indicator.

ICI + KI KCI +I

2Na2S203+ I2 Na2S406+2NaI

Procedure

From the oil extracted, 0.3g was weighed, and 10ml of carbon tetrachloride (CCl4) was then

added. Also, 25ml of Wiss solution was added the flask was shaken and allowed to stand in

the dark for one hour. 15ml of 10% potassium iodide and 100ml of distilled water was added

to the mixture. The mixture was titrated against (0.1M) Na2S203.5H20 until the blue

coloration disappeared which indicated an endpoint. The blank solution was also titrated at

the same time without oil.

DETERMINATION OF PERCENT FREE FATTY ACID

From the oil extracted, 10g was weighed and then boiled with 50ml ethanol, allowed to cool

and two drops of phenolphthalein indicator were added. The mixture was then titrated against

0.1M Na0H until the pink color was obtained.

Gas Chromatography-Mass Spectrometry (Gc-Ms) Analysis

The GC-MS analysis was carried out on a GC-MS-QP 2010 plus Shimadzu system and gas

chromatograph interfaced to a mass spectrometer (GC-MS) instrument employing the


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following conditions: column Elite – 1 fused silica capillary column (30m x 0.25mm 1D x µI

composed of 100% (dimethyl-polysiloxane).

For GC-MS detection, an electron ionization system with ionization energy of 70 eV

was used. Helium gas (99.999%) was used as the carrier gas at constant flow rate 1ml/min,

and an injection volume of 2µl was employed (split ratio of 10:1) injector temperature-

2500C ion-source temperature 280

0C the oven temperature was programmed from 110

0C

(isothermal for 2min.) to 280oC/min, ending with a 9min isothermal at 280

0C. Mass spectra

were taken at 70 eV; a scan interval of 0.5 sec and fragments from 40 to 550 Da. Total GC

running time was 36minutes. The relative percentage amount of each component was

calculated by comparing its average peak area to the entire areas; software adapted to handle

mass spectra and chromatogram was a turbo mass. The detection employed the NIST Ver. 2.0

the year 2009.

Identification Of Components

The interpretation of mass spectrum of GC- MS was done using the database of National

Institute of Standard and Technology (NIST) having more than 62,000 patterns. The mass

spectrum of the unknown components was compared with the mass of the known elements

stored in the NIST library. The name, molecular weight, and structure of the parts of the test

material were ascertained.

RESULTS

Proximate Analysis

The moisture content of the seed is quite low (4.56+ 0.04%) and falls within the range of

moisture content of similar seeds as shows from the table below. The ash content (4.20

+0.02%) obtained is higher than the established value for animal feed. The fat, crude protein,

and nitrogen-free extract are also high.

TABLE: 1 PROXIMATE COMPOSITION OF WATERMELON SEEDS

Parameters Composition

Moisture 4.50+0.04

Crude lipid 41.46+0.03

Crude Protein 25.50+05

Crude Fiber 6.34+0.01

Ash 4.20+0.02

Free Nitrogen 14.97+0.08

CHEMICAL ANALYSIS

Free Fatty acid (FFA) value for the watermelon seeds oil is (2.46 + 0.01%). The

saponification value and iodine value were all slightly higher in the oil.


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TABLE 2: PHYSIC-CHEMICAL PROPERTIES OF WATERMELON SEEDS OIL

Iodine value %Acid value saponification value free fatty acid peroxide

value

55.42+0.07 7.60+0.3 112.58+0.5 2.46+0.01 17.47+0.4

GC-MS ANALYSIS

The components present in the watermelon seeds oil were identified by GC.MS analysis as

shown in the table (3) below.

The active compounds with their molecular formula, molecular weight, retention time

(RT) and their percentage compositions are presented in table (3). Seven (7) compounds were

identified in the oil and the prevailing compounds are Palmitic acid (Hexadecanoic acid)

3.80%, Octyl propyl ester (1.03% Delta-Tocopherol (5.16%), Oleic acid (9-octadecenoic

acid) (17.84%), Propanediol acid (Dicyclohexyl ester) 3.74% Dioctyl ester (1, 2-

Benzenedicarboxylic acid) (0.98%) and Linoleic acid chloride 13.77% the spectrum profile

of seven major components with their respective retention time were shown in the table. The

mass spectrum of the compound with retention time 22.50 and 13.77 gave the primary peak.

Table 3.Detected components in watermelon seeds oil using GCMS technique.

SN Name of compound Mole formula Mole weight RT % composition

1 Palmitic acid C16H3202 256 18.H 3.80

2 Carbonic acid (Octadecylpropy ester C22H4403 356 6.51 1.03

3 Delta-Tocopherol C27H 4602 402 5.7 5.16

4 Oleic acid (9 octadecenoic acid ) C18H3404 282 19.8 17.84

5 Propanedioc acid C15H2404 268 6.18 3.74

6 Dioctyl ester C24H3804 390 23.10 0.98

7 Linoleic acid chloride (19,12-

octadecadienoyl chloride)

C18H31Cl0 298 22.50 13.77

unidentified compounds 53.68

Total % composition 100


14


The Chromatogram of the compounds detected from the watermelon seed oil

Structures of some of the identified compounds using GC-MS analysis

Oleic acid


15


DISCUSSION

The low moisture content of watermelon seed is advantageous regarding the shelf life of the

grain, with less moisture content seeds able to be preserved for a more extended period. From

literature, ash content for nuts, seeds, and tubers should fall within acceptable limits for

edible oils (1.5-2.5%) to be suitable for animal feed. The high quantity of oil content is an

indication that watermelon seed is another ready source of oil like the peanuts and soybean

seeds. The high protein content of the oil has a pleasant implication a society with high

protein deficiency. Fatty acid value of oil is highly essential in considering the quality of oil

because of the lower the free fatty acid, the better the quality of the oil which is (2.46%) and

acid value (7.60mg/Na0Hg) which fall within acceptable limits for edible oils


16


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