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American Journal of Chemistry 2019, 9(1): 13-20
DOI: 10.5923/j.chemistry.20190901.02
Comparative Study on the Cosmeceutical Properties of
Oils from Dacryodes edulis (African Pear) and Persea
americana (Avocado) Fruits
Iniobong S. Enengedi1,*, Okon D. Ekpa2, Magdalene E. Ikpi2
1Department of Chemistry, Akwa Ibom State University, Ikot Akpaden, Akwa Ibom State, Nigeria
2Department of Pure and Applied Chemistry, University of Calabar, Calabar, Cross River State, Nigeria
Abstract Fruits are major sources of oils for human nutrition as well as for several industrial purposes. The properties of
Dacryodes edulis fruit oils from two locations (Uyo and Ikom) were compared to those of Persea americana, a widely used
oil in cosmeceutical formulations. All the oils extracted from each of these fruits were liquid at room temperature. The oil
yield of P. americana (18.55%) was low in comparison to those of D. edulis-Uyo (49.57%) and D. edulis-Ikom (52.49%). The
saponification value of D. edulis-Uyo, D. edulis-Ikom and P. americana oils were 189.33 mgKOH/g, 188.64 mgKOH/g and
185.13 mgKOH/g respectively, indicating their potential application in soap making. Fourier Transform Infrared (FT-IR)
spectra of P. americana and D. edulis oils appear very similar, however, they revealed slight differences. Soap produced with
D. edulis oil from Uyo gave the best quality soap considering the high fatty matter of 89.2% as compared to that of D. edulis
soap from Ikom oil (65.4%) and soap from P. americana oil (70.8%). The oils from these fruits could be used as emollients in
cosmeceuticals. The higher oil yield of the fruits of D. edulis than P. americana, with similar functional groups (C-HCH3,
C=O, C-O, C-HCH2 and -CH=CH), could project D. edulis oils as possible substitute for P. americana oil in cosmeceutical
formulations.
Keywords Dacryodes edulis, P. americana, Oils, Cosmeceutical formulations
1. Introduction
Vegetable oils have been used on skin for cosmetic and
medical purposes. They act as protective barriers to the skin
by occlusive effect, allowing the skin to retain moisture,
thereby, resulting in hydration of the skin [1]. Dacryodes
edulis (African pear) is an indigenous fruit tree in the humid
low lands and plateau regions of West, Central African and
Gulf of Guinea countries [2]. The fruits of D. edulis can be
eaten either raw, cooked in salt water, roasted in hot ash or
grilled in the oven [3]. D. edulis fruit could serve the dual
purpose of being a source of minerals and vitamins to human
nutrition and as a raw material for industries, if properly
harnessed. The pulp and seed of D. edulis had been found to
contain reasonable amounts of oil [4, 5]. [4] Reported the
percentage oil content in D. e. var. edulis and D. e. var.
parvicarpa to be 68.29% and 54.68% and [5] reported
32.56% oil content for unspecified variety of D. edulis. [2]
* Corresponding author:
iidung@yahoo.com (Iniobong S. Enengedi)
Published online at http://journal.sapub.org/chemistry
Copyright © 2019 The Author(s). Published by Scientific & Academic Publishing
This work is licensed under the Creative Commons Attribution International
License (CC BY). http://creativecommons.org/licenses/by/4.0/
Reported 32.62 - 35.05% oil content of D. edulis at different
stages of fruit development. [6] Reported the fatty
composition of D. edulis oil to be rich in saturated fatty acids,
having palmitic acid (44.31%) and stearic acid (8.07%), and
unsaturated fatty acids having oleic acid (42.45%) and
linoleic acid (5.17%). D. edulis oil from ripe fruits had been
used as a precursor for synthesis of surface coating driers [6].
Persea americana (avocado) is a medium sized tree,
measuring about 9-20 meters in height. It is widely grown
worldwide for fruits on large scale in various subtropical
countries and are generally recognized as a popular and
healthy food source supplying proteins and lipids to the
human diet [7]. The fruit is not sweet but fatty, almost
distinctly, yet subtly flavoured, and of smooth, almost
creamy texture [8]. P. americana is a good source of oil,
containing monounsaturated fat. Its oil content varies
depending on its varieties and the period of extraction of the
oil by cold-press processs [9]. [9] Reported the oil content of
27.12%, pH of 5.7; iodine value of 37.26 g/100g and
saponification value of 219.20 mgKOH/g from the fruit pulp.
The binding of water in the stratum corneum can become
compromised and ineffective. In this case it is helpful to
reduce the transepidermal water loss by applying occlusive
films. Mineral oil should be used; however, the benefits of a
natural vegetable oil is preferred [10]. Natural oils are of
14 Iniobong S. Enengedi et al.: Comparative Study on the Cosmeceutical Properties of Oils
from Dacryodes edulis (African Pear) and Persea americana (Avocado) Fruits
significant nutritional importance and are also desirable
emollients for skin care applications. Natural oils are good
sources for tocopherols and phytosterols, components
offering both antioxidant activity and bioactivity for skin
care applications [11]. D. edulis and P. americana oils could
be of great importance in cosmeceuticals intended for daily
care of the face and body. Deficiency in oil could result in
excessive dryness of the skin. D. edulis and P. americana
oils could serve as a cosmetic base which would prevent
water loss through the skin, mainly by means of making a
protective layer on the epidermis. They could also soften the
skin, thereby reducing fine wrinkles.
This is the first comparative study to project D. edulis oils
as possible substitute for P. americana oil in cosmeceutical
formulations.
2. Materials and Methods
2.1. Sample Collection and Identification
D. edulis fruit was collected from Uyo (A) in Akwa Ibom
State and Ikom (B) in Cross River State, Nigeria. Also
P. americana fruit (C) was collected from Oron in Akwa
Ibom State, Nigeria. The samples were transferred into
polyethelene bags, labelled properly and taken to the
laboratory for identification and preparation. The fruits were
identified and authenticated by a Taxonomist in the
Department of Botany and Ecological Studies, University of
Uyo, Akwa Ibom State, Nigeria. Voucher specimens were
deposited at the herbarium with the number, UUH 3541 and
3546 for D. edulis and P. americana respectively.
A B C
Figure 1. Experimental samples: D. edulis fruits from Uyo (A), D. edulis
fruits from Ikom (B) and P. americana fruits (C)
2.2. Oil Extraction
Ripe fruits of D. edulis from Uyo and Ikom were washed
with water, put in polyethylene bags for 24 hours for the fruit
to soften. The pulps were removed and mashed using mortar
and pestle to have a smooth paste. Also, unripe fruits of
P. americana were kept for about 48 hours at room
temperature until they were ripened. The fruits were cut open
with a stainless-steel knife to remove the seed from the pulp,
and the skin was removed from the pulp. The pulps were
mashed using mortar and pestle to have a smooth paste. Each
of the mashed samples were spread on stainless-steel trays
and dried in the sun for 6 hours. The samples were scraped
from the trays into clean white cotton cloths, wrapped and
squeezed.
The yield of the oil was calculated using Equation (1),
expressed as percentage of the dry weight of the sample [12].
The oils collected were stored in airtight bottles in a
functional refrigerator for further use.
Yield (%) = A1/A2 x 100 (1)
Where A1 = weight of extracted oil (g)
A2 = weight of dry sample (g)
2.3. Characterisation of the Oils
The cold pressed oils of D. edulis fruits (from Uyo and
Ikom) and P. americana fruits were analysed without further
purifications for their physicochemical properties viz:
freezing point, melting point, pH, smoke point, moisture
content, acid value, iodine value and saponification value
using standard methods. All the determinations were done in
duplicates.
2.3.1. Determination of Moisture Content
The method described by [13] was used to determine the
moisture content of the oils. A well labelled crucible was
dried in an oven at 105°C. The crucible was allowed to cool
in a dessicator and weighed to a constant weight. Each of the
oils (2 g) was added to the crucible, the weight of the crucible
with the oil was taken and dried in an oven at 105°C. The
crucible with the oil after drying was cooled in a dessicator
and weighed to a constant weight. Percentage moisture
content was calculated using Equation (2).
% moisture content =
bc
x 100
ba
−
−
(2)
Where
a = weight of empty crucible (g)
b = weight of crucible + oil before drying (g)
c = weight of crucible + oil after drying (g)
2.3.2. Determination of Freezing Point
The oil (10 cm3) in a test tube was inserted in a cup
containing ice blocks, the temperature at which the oil began
to freeze was recorded using a thermometer [14].
2.3.3. Determination of Melting Point
The melting point of the oil was determined by the method
described by [13]. The oil (10 cm3) in a test tube was inserted
in a cup containing ice blocks and left to solidify. The
solidified oil in the test tube was removed from the ice block,
the temperature at which the oil began to melt was recorded
using a thermometer.
2.3.4. Determination of Smoke Point
The oil (10 cm3) was measured into a clean dried crucible
and heated on a hot plate. The temperature at which the oil
started to form a bluish smoke was recorded using a
thermometer [15].
American Journal of Chemistry 2019, 9(1): 13-20 15
2.3.5. Determination of pH of oil
The oil (50 cm3) was measured into a clean dried beaker
and the probe of a digital pocket-sized pH meter was
introduced into the oil and pH recorded at room temperature
[16].
2.3.6. Determination of Acid Value (AV)
The acid value of the oils was determined by using ASTM
D465-05 standard method [17]. The individual oils (1 g) was
measured into separate conical flasks, followed by addition
of 25 cm3 of carbon tetrachloride (CCl4). Two (2) drops of
phenolphthalein indicator were also added to the mixture.
The mixture was titrated with 0.1 M alcoholic potassium
hydroxide (KOH) solution until a colour change was
obtained. A blank titration was also carried out without the
oil. The acid values of the oils were computed using
Equation (3).
Acid value (AV) =
VxMx 56.1
W
(3)
Where
M = concentration of standard KOH solution (moldm-3)
V = volume of KOH used for sample (cm3)
W = Weight of the individual oils (g)
56.1 = Molar mass of KOH
2.3.7. Determination of Saponification Value (SV)
The ASTM D464-05 standard method [17] was used to
determine saponification value. Two grams (2g) of the
individual oils were weighed separately in a conical flask
and 25 cm3 of 0.5 M ethanolic potassium hydroxide solution
was added. Each flask was heated in a steam bath, refluxing
for 30 minutes with occasional swirling. The resultant
solutions were then titrated with 0.5 M hydrochloric acid
(HCl) using 2 drops of phenolphthalein indicator until the
pink colour just disappeared. A blank determination, that is,
without the oil, was carried out under similar conditions. The
saponification values were calculated using the Equation 4.
Saponification value (SV) =
( )
M B A
56.1 x C
−
(4)
Where
M = Concentration of standard HCl (moldm-3)
C = weight of the individual oils (g)
B = volume of HCl used in the blank titration (cm3)
A = volume of HCl used in the test titration (cm3)
2.3.8. Determination of Iodine Value (IV)
The ASTM D5768-02 standard method [17] was used to
determine the iodine value of the individual oils. To 0.5 g of
the individual oils in a separate conical flask, 20 cm3 of
carbon tetrachloride was added to the oil. The resultant
solution was mixed with 25 cm3 Wijs solution. Each flask
with its content were stoppered, swirled to mix, and allowed
to stand in the dark for 1 hour at room temperature. Then 20
cm3 of 10% aqueous potassium iodide and 100 cm3 of water
were added to the contents in each of the flasks. The content
of the flask was titrated with 0.1 M sodium thiosulphate
solution until the yellow colour almost disappeared. Starch
indicator (1 cm3 of 1%) was added and the titration continued
by adding more sodium thiosulphate solution until the
blue-black colouration disappeared after vigorous shaking. A
blank determination was carried out in the same manner
under similar conditions. The iodine value for the oils were
determined using (5).
Iodine value (IV) =
()
M B V
12.69 x S
−
(5)
Where
M = concentration of standard Na2S2O4 (moldm-3)
S = Weight of individual oils (g)
V = Volume of Na2S2O4 used in test titration (cm3)
B = Volume of Na2S2O4 used in blank titration (cm3)
2.3.9. Infrared Spectroscopy (IR)
Fourier Transform Infrared (FTIR) spectra of the
individual oils were obtained using IR Affinity-1S Fourier
Transform Infrared spectrophotometer. A horizontal
attenuated total reflectance (ATR) sampling accessory
equipped with zinc selenide (ZnSe) cell was employed. The
cold-pressed oils were used without further purification.
Approximately 20 mg of the individual oils were placed in
the sampling accessory obtaining the best contact with the
crystal. The approximate total time required for spectral
collection was 5 min. All spectra were recorded within a
range of 4000-650 cm-1 with a 4 cm-1 resolution. Analyses
were performed in dry atmosphere (18 ± 0.5°C). Each
spectrum was calculated as the average of 20 scans and
subjected to background subtraction.
2.4. Soap Production and Analysis
The method of [18] was used for soap production. The
individual oils (100 g) of D. edulis-Uyo, D. edulis-Ikom and
P. americana respectively were weighed into separate 500
cm3 beakers, heated to about 100°C and saponification was
initiated by adding 20 cm3 of 23.5% sodium hydroxide
(NaOH) solution. To the resulting solution, 60 g of NaOH
pellets dissolved in 100 cm3 of deionised water was added
gradually while stirring until completion of saponification.
NaCl (8 g) dissolved in 30 cm3 of deionised water was added
to grain soap. The salt was added to separate the spent lye in
the bottom, while saponified mass floats on the surface to
reduce the soap viscosity and to separate the glycerol water
in the bottom. The glycerol water was removed by siphoning.
The soap paste was washed with 10 cm3of hot water (90°C)
to reduce excess sodium hydroxide and sodium chloride and
any impurities found in the soap paste. The soap obtained
was washed again with 10 cm3 of distilled water, filtered
using a linen cloth, then a small amount of water was added
to soften it whilst heating. The soap was placed in a mould
and allowed to dry.
16 Iniobong S. Enengedi et al.: Comparative Study on the Cosmeceutical Properties of Oils
from Dacryodes edulis (African Pear) and Persea americana (Avocado) Fruits
2.4.1. Determination of Total Fatty Matter (TFM)
Total fatty matter of individual soap produced was
determined using the method of [18]. Each soap (10 g) was
weighed in a beaker and 150 cm3 of deionised water, 20 cm3
of 15% tetraoxosulphate (VI) acid (H2SO4) solution were
added. The mixture was heated until the soap dissolved to
form a clear solution. Fatty acid on the surface of the
resulting solution was solidified by adding 7 g of candle wax
and reheated. The solution was allowed to cool to form a
cake on the surface of the solution. The cake was removed
and left at room temperature to dry to a constant weight. The
cake was weighed to obtain the total fatty matter using the
Equation (6).
% TFM =
AB
x 100
W
−
(6)
Where A = weight of wax + oil (g)
B = weight of wax (g)
W = weight of soap (g)
2.4.2. Determination of Free Caustic Alkali
Free caustic alkali was determined using the method of
[18]. Produced soap (5 g) was weighed into a conical flask
and 30 cm3 of ethanol was added and the mixture heated until
a clear solution was obtained. Barium chloride (10 cm3
of 20%) was added and the solution turned cloudy milky,
which later turned pink with addition of few drops of
phenolphthalein indicator. The resulting solution was titrated
against 0.05 M H2SO4 solution. Free caustic alkali was
calculated using Equation (7).
NaOH =
A
0.31 x V
W
(7)
Where VA = volume of acid used (cm3)
W = weight of soap (cm3)
2.4.3. Determination of Moisture Content
A crucible was dried in an oven at 105°C to a constant
weight. The crucible was removed and cooled in a desiccator.
The produced soap (3 g) was accurately weighed using
analytical balance into the dried crucible and dried in an oven
at 105°C and cooled in a desiccator to a constant weight [18].
The % moisture content was calculated using Equation (8)
% Moisture =
Cs Ch x 100
Cs Cw
−
−
(8)
Where
Cw = weight of crucible (g)
Cs = weight of crucible + sample before heating (g)
Ch = weight of crucible + sample after heating (g)
2.4.4. Determination of pH of Soap
The soap (2.0 g) was weighed into a clean beaker, 20 cm3
of water was added to dissolve the soap in order to prepare
10% aqueous solution of soap. The pH of 10% aqueous
solution of the soap was measured by using a pocket-sized
digital pH meter at room temperature [19].
3. Results and Discussion
The physicochemical properties of oil from D. edulis-Uyo,
D. edulis-Ikom and P. americana fruits namely: yield,
freezing point, melting point, pH, smoke point, moisture
content, acid value, iodine value and saponification value are
shown in Table 1.
Table 1. Characterization of Oil from D. edulis-Uyo [D. e (U)], D.
edulis-Ikom [D. e (I)] and P. americana [P. A] Fruits
Test Sample
D. e (U) D. e (I) P. A
Yield (%) 49.57 52.49 18.55
Saponification value (mgKOH/g) 189.33 188.64 185.13
Acid value (mgKOH/g) 5.610 5.049 3.927
Iodine value (gI2/100g) 51.78 50.25 65.99
pH 5.7 6.2 4.9
Smoke point (°C) 210 212 216
Freezing point (°C) 22 18 15
Melting point (°C) 23 19 16
Moisture content (%) 1.22 1.14 1.24
The oil yield of P. americana was low in comparison to
those of D. edulis. This low yield of the P. americana oil than
D. edulis can be attributed to high moisture content in the
pulp or due to genetic factors of the plants. The high oil yield
for D. edulis implies that, processing of D. edulis oil for the
personal care Industry or edible purposes will be more
economical as fruits of D. edulis contain more oil than fruits
of P. americana. It had been established that oil contents of P.
americana varies depending on its varieties and the period of
extraction of oil by cold-press processs [9]. The oil yield of D.
edulis fruits-Uyo was lower than that reported [4] in D. e. var.
edulis and D. e. var. parvicarpa but higher than that reported
by [2, 5]. The oil yield of D. edulis-Ikom was lower than that
reported for D. e. var. edulis but close to that reported for D.
e. var. parvicarpa [4] but was higher than that reported by
[2, 5]. The oil yield of P. americana was lower than that
reported by [9].
The pH of D. edulis-Uyo, D. edulis-Ikom and P.
americana oils were 5.7, 6.2 and 4.9 respectively. This
reveals that the oils were weakly acidic, hence, they contain
low amount of fatty acids making them fit for edible
purposes [16]. High levels of free fatty acids especially
linoleic acids are undesirable in finished oils because they
can cause off-flavours and shorten the shelf life of oils [20].
However, linoleic acid strengthens the lipid barrier of
epidermis in dry skin, protects against transepidermal loss of
water and normalises the skin metabolism [21]. The pH of
the oils was within the skin pH, so the oils could be applied
on skin with no irritation.
Moisture contents of D. edulis-Uyo, D. edulis-Ikom and P.
americana oils were 1.22%, 1.17% and 1.24% respectively.
American Journal of Chemistry 2019, 9(1): 13-20 17
Water is an unusual component of oils and fats, as the two
are non-miscible and the presence of water can be
compatible only at very low proportions. However, even
very low moisture contents can prove to be harmful to oils
and fats products, as water is a catalyst of almost all chemical
degradation reactions. Moisture content generally provides a
good indication of the level of the other quality parameters of
oil and can also prove very helpful to forecast subsequent
variation upon storage. The presence of high moisture
content enhances oxidative degradation [22]. The moisture
content of these oils were low, indicating that they will
maintain their quality parameters for a long time. Lower
moisture content of oil implies good shelf-life.
The melting and freezing points of D. edulis-Uyo, D.
edulis-Ikom and P. americana oils were 23°C, 19°C, 16°C
and 22°C, 18°C, 15°C respectively. P. americana oil had the
lowest melting and freezing points followed by D.
edulis-Ikom oil and D. edulis-Uyo oil had the highest
melting and freezing points. The variation in melting (23°C,
19°C, 16°C) and freezing (22°C, 18°C, 15°C) points for
D. edulis-Uyo, D. edulis-Ikom and P. americana oils
respectively could be due to differences in fatty acid
composition or free fatty acids in the oil.
The smoke point of D. edulis-Uyo, D. edulis-Ikom and P.
americana oils were 210°C, 212°C and 216°C respectively.
This reveals that D. edulis oils’ smoke point are comparable
with P. americana oil. Smoke point is the temperature at
which oil starts to be visibly smoking in the pan of the oil. It
provides a useful characterization of its suitability for frying.
The smoke point of an oil increases as free fatty acid content
decreases. Heating an oil produces free fatty acids and as
heating time increases, more free fatty acids are produced,
thereby decreasing smoke point [23]. A healthy oil becomes
unhealthy when it reaches its smoke point. When an oil
reaches its smoke point, the structure of the oil begins to
break down, nutrients are lost, flavour is changed and most
dangerously, compounds can be created that are damaging to
health. This result implies that these oils could be used for
frying but not above their respective smoke points so as not
to create free radicals, which are damaging to health.
The saponification value of D. edulis-Uyo, D. edulis-Ikom
and P. americana oils were 189.33 mgKOH/g, 188.64
mgKOH/g and 185.13 mgKOH/g. The saponification value
of D. edulis-Uyo and D. edulis-Ikom oils are comparable
with P. americana oil. The saponification value of these oil
can be compared to the value (188.8 mgKOH/g) obtained by
[13]. Saponification value of oil serves as an important
parameter in determining the suitability of oil in soap making.
The high saponification values of the oils in this research is
an indicative of high proportion of medium fatty acids and
potential application in soap production [24]. [29] Reported
low saponification values of some oils, indicating that they
contain high proportion of long chain fatty acids.
The acid values obtained in D. edulis-Uyo, D. edulis-Ikom
and P. americana oils were 5.610 mgKOH/g, 5.049
mgKOH/g and 3.927 mgKOH/g respectively. Acid value
gives an indication of the quality of fatty acids in oil. Low
acid value in oil indicates that the oil will be stable over a
long period of time and protect against rancidity and
peroxidation. Acid value is used as an indicator for edibility
of an oil and suitability for use in the paint and soap
industries.
The level of unsaturation measured by iodine value is one
of the most important properties of triglyceride oils that
determine its industrial applications. Iodine value could be
used to quantify the amount of double bonds present in the
oil which reflects the susceptibility of the oil to oxidation
[20]. The iodine value obtained in D. edulis-Uyo, D.
edulis-Ikom and P. americana oils were 50.25 gI2/100g,
51.78 gI2/100g and 65.99 gI2/100g respectively. This
indicates that P. americana oils may have more unsaturated
bonds than D. edulis. The iodine value of P. americana was
higher than the values for D. edulis-Uyo and D. edulis-Ikom
but none of their values was more than 100 gI2/100g. This
implies that these oils could be classified as non-drying oils,
and could be used as emollient to soften the skin. Non-drying
oils are not suitable for ink and paint production due to their
non-drying characteristics but may be useful in the
manufacture of soaps and can be regarded as liquid oil [20].
Non-drying oils are slow to oxidize and so remain liquid for
a long time. This quality makes them particularly useful as
lubricants and as a fuel for lamps. This implies that D. edulis
and P. americana oils can be used on skin to protect the skin
barrier by occlusive effect, allowing the skin to retain
moisture, resulting in decreased transepidermal water loss.
The skin will then be moisturized, thereby making the skin to
be soft and pliable, reducing fine wrinkles.
Figure 2. FTIR of P. americana (P A), D. edulis-Uyo (D E U) and D.
edulis-Ikom (D E I)
The FT-IR analysis of D. e (U), D. e (I) and P. A oils is
shown in Figure 2 and the functional groups identified in the
FTIR spectra of the oils are shown in Table 2.
18 Iniobong S. Enengedi et al.: Comparative Study on the Cosmeceutical Properties of Oils
from Dacryodes edulis (African Pear) and Persea americana (Avocado) Fruits
Table 2. Functional Groups Identified in P A, D E U and D E I Oils
Frequency
(cm-1) Functional group Intensity
3450 (k) OH stretching Weak
3007 (j) Cis C=CH stretching Medium
2922 (i) C-HCH2 asymmetric stretching vibration Very strong
2852 (h) C-HCH2 symmetric stretching vibration Very strong
1743(g) Carbonyl C=O from ester Very strong
1463 (f) C-HCH2 scissoring bending medium
1377 (e) C-HCH3 scissoring bending Weak
1234 (d) C-HCH2 scissoring bending Weak
1161 (c) -CH in plane medium
1114 (b) C-O from ester Weak
721 (a) -CH=CH- bending out of plane Medium
FTIR Spectroscopy is a very good method to analyse the
authenticity of fat and oil because it exhibits finger print
characteristics. The FTIR spectra of P. americana (P A), D.
edulis-Uyo (D E U) and D. edulis-Ikom (D E I) oils (Figure 2)
appear very similar; however, they revealed slight
differences. The peak at 721 cm-1 was present in all the three
oils, it indicates the presence of CH=CH functional groups.
They are attributed to alkenes’ functional groups in the oils.
They can be part of fatty acids with unsaturated bond in the
oils. The spectra of all oils revealed weak peaks at 1114 cm-1
which indicate C-O group from ester. The three oils also
revealed weak peaks at 1377 and 1234 cm-1, indicating
C-HCH3 and C-HCH2 functional groups respectively. The
strongest peak at 1743 cm-1 was present in the three oils,
indicating C=O ester functional group. The peaks located at
2922 cm-1 and 2852 cm-1 indicate C-HCH3 and C-HCH2
functional groups stretching vibrations respectively. These
peaks were present in all the oils’ spectra and were very
strong. These groups indicate the presence of methyl and
methylene functional groups in the oils. The differences are
seen in the weak broad peak at 3450 cm-1 indicating -OH
group only on the spectrum of D. edulis-Ikom (D E I) oil.
This -OH group may be from water, and it implies that the
cold pressed D. edulis-Ikom (D E I) oil contained a little
moisture. Also the intensity of D. edulis-Uyo (D E U) oil at
3007 cm-1 is not as sharp as that of the other oils. It could be
that D. edulis-Uyo (D E U) oil has fewer unsaturated bonds
than the other oils. These functional groups (C-HCH3, C=O,
C-O, C-HCH2 and -CH=CH) identified in Figure 2 are
typical of fats and oils. The FT-IR of D. edulis oils were
comparable to that of P. americana. P. americana oil is
highly priced in the cosmetic industry for its countless skin
healing properties. This implies that D. edulis oils can also be
used in personal care products for the treatment of dry skin,
among other applications. It can even be more economical
since D. edulis fruits contain more oil than P. americana
fruits.
Moisture content is a parameter that is used in assessing
the shelf life of a product. High moisture content in soap
would lead to reaction of excess water with unsaponified fat
to give free fatty acid and glycerol in a process called
hydrolysis of soap on storage. From Table 3, D. edulis-Uyo
oil soap had the lowest moisture content (10.33%), followed
by D. edulis-Ikom oil soap (15.33 %), P. americana had the
highest moisture content (21.33 %). The moisture content of
D. edulis-Uyo oil soap was lower than 12.63% of neem soap
[18]. This result implies that D. edulis-Uyo oil soap would
have a longer shelf life than D. edulis-Ikom oil and P.
americana oil soaps.
Table 3. Chemical Characteristics of the Prepared D. edulis-Uyo (D E U),
D. edulis-Ikom (D E I) and P. americana (P A) Soaps
Characteristics D E U
(100 %)
D E I
(100 %)
P A
(100 %)
Total fatty matter (%) 89.2 65.4 70.8
Moisture content (%) 10.33 15.33 21.33
pH 10.1 10.4 10.3
Free caustic alkali (%) 0.07 0.09 0.02
From Table 3, the pH value of D. eduli-Ikom oil soap
(10.4) was higher than the pH values of D. edulis-Uyo oil
soap (10.1) and P. americana oil soap (10.3). The pH values
of the three soaps compare with the value 10.4 of neem soap
[18] and fall within the recommended range for bathing soap
of 9-11 [18]. These values are slightly higher than 9.38 for
cotton seed oil soap [25] and 9.11-9.99 for neem-shea
butter soaps reported by [26]. The high values could be
due to incomplete alkali hydrolysis resulting from the
saponification process. It can be overcome by the addition of
excess fat or oil or any other superfatting agent to reduce the
harshness of the soap [25]. Alkaline substances neutralize
the body’s protective acid mantle that acts as a natural barrier
against bacteria and viruses. Healthy skin has a pH 4 to 6
[27], while alkalinity favours detergency.
Table 3 reveals the percentage total fatty matter (TFM) of
D. edulis-Uyo oil soap (89.2%), D. eduli-Ikom oil soap
(65.4%) and P. americana oil soap (70.8%). The TFM of D.
edulis-Uyo oil, D. eduli-Ikom oil and P. americana oil soaps
were higher than 63.75% of neem soap as reported by [18];
and TFM of D. edulis-Uyo oil soap was higher than 71% -
84% of washing soaps obtained by [28]. Total fatty matter is
an indication of soap quality. The more the fatty matter, the
better the quality of the soap. The lower TFM value of D.
eduli-Ikom oil soap could be due to the presence of unreacted
sodium hydroxide in the mixture [29]. This implies that D.
edulis-Uyo oil gave the best quality soap. Dry skin needs
soap with high TFM of about 80%. This helps to re-hydrate
the skin, making it smooth, and the high oil content within
the soap acts as a lubricant throughout the day [18].
Free caustic alkali is the amount of alkali free to prevent
soap from becoming oily. Free caustic alkali in D.
edulis-Uyo oil, D. eduli-Ikom oil and P. americana oil soaps
were 0.07, 0.09 and 0.02 respectively (Table 3). Ghana
Standards require toilet soaps to have free alkali of 0.07 [18].
D. edulis-Uyo oil soap compares well with Ghana standards.
P. americana oil soap was lower than the Ghana standard
American Journal of Chemistry 2019, 9(1): 13-20 19
while D. eduli-Ikom oil soap was higher than the Ghana
standard. Excess free caustic alkali causes skin itching and
clothes wear out. This implies that the amount of free caustic
alkali in D. edulis-Uyo oil and P. americana oil soaps may
not have any adverse effect on cloth or skin compared to D.
eduli-Ikom oil soap.
4. Conclusions
Cold pressed oils extracted from D. edulis-Uyo, D.
edulis-Ikom and P. americana fruits could be classified as
non-drying oils and could be used as emollients in
cosmeceuticals. The higher oil yield of the fruits of D. edulis
than P. americana, with similar functional groups (C-HCH3,
C=O, C-O, C-HCH2 and -CH=CH), could project D. edulis
oils as possible substitute for P. americana oil in
cosmeceutical formulations.
Comparatively, D. edulis-Uyo oil soap with lowest
moisture content (10.33 %), lowest pH (10.1), highest Total
fatty matter (89.2%) and free alkaline of 0.07, was the best
quality soap produced from the three oils. This was followed
by P. americana oil soap with D. edulis-Ikom oil soap
having the least quality.
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