Green synthesis and characterisation of natural antiseptic soaps from the oils of underutilised tropical seed

Sustainable Chemistry and Pharmacy 4 (2016) 32–39

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Green synthesis and characterisation of natural antiseptic soaps from the oils of underutilised tropical seed Olubunmi Atolani a,b,n, Elizabeth Temitope Olabiyi a, Abdullateef Abiodun Issa a, Hidiat Taiwo Azeez a, Ehi Gift Onoja b, Sulyman Olalekan Ibrahim c, Marili Funmilayo Zubair c, Olubunmi Stephen Oguntoye a, Gabriel Ademola Olatunji c a

Department of Chemistry, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria Department of Chemical Sciences, Redeemer's University, Ede, Nigeria c Department of Industrial Chemistry, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria b

art ic l e i nf o

a b s t r a c t

Article history: Received 30 March 2016 Received in revised form 22 July 2016 Accepted 24 July 2016 Available online 11 August 2016

The maintenance of beautiful skin and hair is the desire of many people all over the world, thus, the application of safe cosmetic products is inevitable. Natural cosmetics containing bioactive phytochemical compounds offer great deal of beauty and pharmacological effect with less toxicity to users and the environment. The principle of green chemistry was adopted for the preparation of herbal antiseptic soaps which were plant-based, biodegradable and free of artificial colourings/preservatives. Underutilised tropical seeds of Daniellia oliveri, Elaeis guineensis and Vitellaria paradoxa (Shea butter) were used as sources of oil or fat for the saponification processes while Moringa oleifera seed oil and leave extract served as sources of antimicrobial agents. Ocimum basilicum also served as source of fragrance as well as antiseptic agent. The oils were mixed at different ratio to obtain soaps with different properties. Physicochemical parameters which include colour, acid value, free fatty acid values, saponification values, hardness, pH, colour and foaming ability of the oil and soaps were determined as applicable. The fatty acids methyl esters of the oils were prepared via transesterification and subjected to GC–MS analysis to obtain the fatty acid composition of the oils. Daniellia oliveri oil contains 57% linolelaidic acid as the major fatty acid, while oleic acid (46%) and lauric acid (44%) were the most prominent in Shea butter and palm kernel oil respectively. The antimicrobial activity of the soaps determined using agar diffusion method indicated that the soaps made from the oil of Daniellia oliveri and Shea butter inhibited the growth Streptococcus aureus, Klebsiella granulomatis and Aspergillus niger. Shea butter soap has the highest activity against Klebsiella granulomatis (42 mm), while soaps made from blend of palm kernel oil and Shea butter had highest activity against Aspergillus niger (7.0). The production was highly cost effective when compared to selected commercial soaps. Therefore, the adoption of these natural resources for the preparation of eco-friendly herbal soaps would save the environment of the daily introduction of many hazardous synthetic chemical products whilst also finding utility for non-conventional seed oils and at the same time improving the economic status of the community. & 2016 Elsevier B.V. All rights reserved.

Keywords: Daniellia oliveri Moringa oleifera Elaeis guineensis Vitellaria paradoxa Saponification Transesterification

1. Introduction Everyone desires beautiful hair and skin. Therefore, since maintaining a beautiful skin and hair is a daily affair for many people all over the world, the application of appropriate and safe cosmetic is inevitable. Cosmetics from natural sources containing bioactive phytochemical compounds offer great deal of beauty and pharmacological effect with less toxicity to users and the

n Corresponding author at: Department of Chemistry, University of Ilorin, Ilorin, Nigeria. E-mail address: [email protected] (O. Atolani).

http://dx.doi.org/10.1016/j.scp.2016.07.006 2352-5541/& 2016 Elsevier B.V. All rights reserved.

environment. Following the principle of green chemistry, herbal soaps prepared from plant-based renewable sources would key into the United Nation 17 sustainable development goals to protect the planet, have good health, sustainable community, clean energy and make life on land and in water safer (UNDP-SDG, 2000). Cosmetics made from natural sources possess the ability of improving psychological, social and clinical impulses on users. Many artificial and synthetic constituents of cosmetics for skin and hair usually results in damaged skin, dry skin, brittle hair, browning of hair, itching among other things (Joshi and Pawal, 2015). For instance, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and parabens used as antioxidant and/or preservatives in cosmetics are known to induce allergic reactions

O. Atolani et al. / Sustainable Chemistry and Pharmacy 4 (2016) 32–39

O

O

CH2OH

CH2O-C-R1 + H2O

O

NaOH

O

Saponification

CH2OH

CH2O-CH-R

2

R1-C-O-Na+ +

R2-C-O-Na+ O

O

CH2OH

CH2O-C-R3 Triglyceride (oil/fat)

Glycerol

CH2OH KOH/MeOH Transesterification

R3-C-O-Na+ Sodium salts of fatty acids (Soap)

O

R1-C-O-Me O

CH2OH

R2-C-O-Me

CH2OH

R3-C-O-Me

O Glycerol

Fatty acid methyl esters (FAMEs)

Fig. 1. Saponification and transesterification of lipid (fixed oils) from plant seeds.

in human skins and are have been classified as potential carcinogen by the international agency for research on cancer (Joshi and Pawal, 2015; Suzuki, 2010; IARC, 1978). Soap is the major product of chemical reaction between triglyceride (fixed oil from seed) and lye solution (Gunstone, 2004; Scrimgeour, 2005). The process is termed saponification (Fig. 1). The soap comes in solid moulded form, termed bars or in liquid usually termed liquid soap kept in dispenser now widespread in many public washrooms. In order to characterise the triglyceride composition of the oils from seeds, the lipid is usually transesterified (Fig. 1). Previous research effort has been directed to exhibit the potential of seed oils such as shea butter, neem seed oil and palm kernel oil for the production of soap of varied characteristics (Alander, 2004; Aliyu et al., 2012; Ameh et al., 2013; Getradeghana, 2000; Maranz et al., 2004; Warra et al., 2011). The production of soaps with unique properties needs a careful selection of oil type. The criteria for the selection of oil for industrial or domestic application in soap-making includes the presence of natural characteristic aroma, clarity, natural colour, low moisture content and absence of flat and rancid (unpleasant) odour (Okoye et al., 1999; Manji et al., 2013). Values that determine the quality of bar soaps include the hardness, cleansing power, conditioning, lathering potential and antiseptic nature. These qualities are attained by reacting various combinations of oils or fat in different proportion with lye (Manji et al., 2013). While many of the synthetic antiseptic soaps seems expensive and unaffordable especially in developing countries, herbal cosmetics offers an affordable and sustainable cheap means with comparative health and safety benefits (Joshi and Pawal, 2015; Sharma et al., 2008). The global dependence on herbal products seems to be on the increase. WHO estimated that about 80% of African population depend directly or indirectly on herbal or natural products (Ekor, 2014; Joshi and Pawal, 2015; WHO, 2002). In fact, the global market for herbal medicines was over $60 billion per annum with an estimate of 6.4% increase average annual growth rate. This is apparently due to the contribution of the significant health and economic values of herbal products (Inamdar et al., 2008; Sharma et al., 2008; WHO, 2002). Herbal cosmetics contain antioxidant, anticancer and antimicrobial agents that could help in the management of various skin and hair conditions. The presence of phytochemicals such as vitamins, proteins, tannins, terpenoids and other bioactive ingredients rejuvenate, freshen and protect the hair and skin from various skin and hair conditions such as psoriasis, eczema, skin dryness, skin cancers, sun burn, skin dryness, boil, solar keratosis, dermatitis, impetigo, candidiasis, athlete's foot, chicken pox, carbuncles, staph infections, cyst, abscess, cracking, dandruff, flaking

33

and others (Fathima et al., 2011; Kapoor, 2005; Joshi and Pawal, 2015). Increased attention has been given to the use of natural antioxidants for prevention of diseases caused by oxidative damage in human body and/or by lipid peroxidation in food (Teow et al., 2007). The traditional medical practice in Nigeria utilises many seed oils or medicinal plant extracts, which are cheaply sourced for skin and hair care products due to their abilities to rejuvenate, moisten and enhance strong skin and hair. The seeds produced from plants usually contain lipids, fatty acids, amines, proteins and esters which are essential for maintaining body skin function. In Nigeria, many valuable seeds that are oil-rich are allowed to perish each year because they belong to non-conventional oil seeds. Daniellia oliveri (Rolfe) Hutch & Dalziel of the family Caesalpiniaceae is a well-known plant in Africa and the Amazon region (Langenhein, 1983; Atolani and Olatunji, 2016). The plant is locally known as “emi ya” in south west Nigeria. It is a grossly underutilized tropical tree with many potential economic and health values. The plant is used as ornamental tree in many parts of south western Nigeria and it grows widely in the forest region. The tree exudate has been applied as a component of cosmetics and its potential as anti-wrinkle agent has been patented (Lamy et al., 2010). Polyalthic acid, a furano-terpene has been isolated from the exudate from the plant (Atolani and Olatunji, 2014), while the chemical composition of the resin have been examined (Atolani and Olatunji, 2016). Other seeded plants which include Shea butter tree (Vitellaria paradoxa) of the family Sapotaceae and Moringa oleifera of the family Moringaceae are widely reported in literature for various biological activities. The leaves, fruits, flowers, roots, seeds, bark and pods of Moringa oleifera have been reported to possess analgesic, antitumour, cardiac and blood circulation stimulatory activities (Makonnen et al., 1997; Sutar et al., 2008), antipyretic, antiepileptic, anti-inflammatory and antiulcer properties (Pal et al., 1995). Elaeis guineensis (family) is a well useful plant whose seed oil, known as palm kernel oil (PKO) is grossly applied for formulations of different cosmetic product especially, soap (Amira et al., 2014; Traitler and Dieffenbacher, 1985). The plant is readily available in Nigeria where its serves major economic purpose for the local users. Ocimum basilicum (family) is an important medicinal plant with varied application across tribes and regions (Grayer et al., 2004; Lawrence, 1988; Politeo et al., 2007). This present study aimed at producing herbal soaps with antiseptic properties that will possess the capacity of improving the natural beauty, attractiveness and appearance of African skin and hair from underutilised tropical seeds by adopting the principle of green chemistry in order to attain a pollution free environment.

2. Materials and methods 2.1. Collection of plant materials The seed of Daniellia oliveri (Rolfe), Ocimum basilicum and Vitellaria paradoxa (Shea butter nut) were collected during the fruiting season from the premises of the University of Ilorin, Ilorin, Nigeria while Moringa oleifera leaves and seeds were collected from the fruiting tree within Ilorin metropolis, Nigeria. The plant materials were identified and authenticated at the Herbarium of the Department of Plant Biology, University of Ilorin, Ilorin, Nigeria where voucher specimen numbers UIH 964, UILH/001/961 and UILH/002/1008 were obtained for Daniellia oliveri, Vitellaria paradoxa and Moringa oleifera respectively. The seeds were dried at ambient temperature, de-shelled and pulverised. The leaves of Moringa oleifera were also collected, dried

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O. Atolani et al. / Sustainable Chemistry and Pharmacy 4 (2016) 32–39

at ambient temperature and pulverised while the leaves of Ocimum basilicum were collected and used fresh when needed in order to preserve the fragrance content. All pulverised plant materials were kept in a cool dark place for further work.

were expressed in mMol/Kg. The peroxide value was calculated using the formula

Peroxide value=

( Vs − Vb) × molarity of titrant × 103 g / Kg WEIGHT OF SAMPLE ( g )

= meq/kg

where Vb ¼titre for blank; Vs ¼titre for sample; M¼Molarity.

2.2. Solvents and reagents 2.5. Transesterification of the oil Potassium hydroxide (KOH) and hydrochloric acid (HCl) used were analytical grade. n-Hexane and methanol were re-distilled before use when necessary while palm kernel seed oil (PKO) and honey were obtained from reliable commercial local retailers in Ilorin metropolis. 2.3. Extraction of seed oils The pulverised Daniellia oliveri seed (388.5 g) was subjected to soxhlet extraction using n-hexane as the extracting solvent at 60 °C for approximately 3 h. The extract was concentrated via distillation to obtain the oil. The oil yield was 59.15 g. A similar procedure was adopted for 235.9 g of the pulverised Vitellaria paradoxa seed to obtain 61.30 g shea butter while 180.4 g of the pulverised Moringa oleifera seed yielded 69.48 g of oil. 2.4. Determination of the physicochemical parameter of the oils The physicochemical parameters of the oils were determined using standard procedures with slight modification where applicable (Gerpen, 2005; Ibeto et al., 2012). Odour, colour, and physical state were determined by sensory evaluation. 2.4.1. Saponification value 1 g of each oil was weighed into a conical flask containing 25 mL of methanolic KOH and mixed together. The mixture was warmed in a water bath for 5 min, 3 drops of phenolphthalein were added to it and the content titrated against 0.5 M HCl until the pink colour disappeared. The discolouration indicates the end point. Saponification value was then calculated using the equation:

SV=

mLOF ( S − B) × M × 56. 1 g /mol WEIGHT OF SAMPLE( g )

= mgKOH/g

The oils were subjected to transesterification by treating 2 g of each oil with 0.2 M methanolic HCl. 2 g of the oil was poured into a beaker containing 10 mL of the prepared methanolic HCl. The mixture was refluxed for an hour and allowed to settle into layers in a separating funnel. The layers were separated and the aqueous layer was re-washed with hexane before discarding it. The organic phase was also washed with water and then concentrated to afford the fatty acid methyl esters (FAMES) which was dried over anhydrous magnesium sulphate and stored for GC–MS analysis. The yield of the transesterified oil was determined using the formula:

Percentage Yield=

weight of trans − esterified oil ×100 weight of lipid

2.6. GC/GC–MS analyses The fatty acid composition of the transesterified oils were analyzed using Agilent 19091S-433HP-5MS equipped with pH column of 30 m  250 mm  0.25 mm. The column was packed with 5% Phenyl Methyl Silox. The column temperature was initially held at 35 °C for 3 min with injection volume of 0.2 μL and then programmed to rise at the rate of 5 °C/min to 280 °C over a total run time of 62 min at a split mode of ratio 50:1. The heater was set at 300 °C, whereas the detector (mass spectrophotometer) temperature was maintained at 250 °C. Carrier gas, helium was at an average velocity of 44.3 cm/s and pressure of 11.604 psi. Ionisation mode was electron impact at a voltage of 70 eV. The identification of the chemical components was by matching mass spectral with those of NIST library. 2.7. Lye preparation

where B ¼ blank titre value (mL); S¼ sample titre value (mL); M ¼Molarity of KOH. Molecular weight of KOH was taken to be 56.1 g/mol.

The wood ash was collected from the University's restaurant was soaked in hot water for a day and then filtered using Wattman filter paper to obtain the lye, a brown coloured solution.

2.4.2. Acid value 1 g of each oil was weighed into a flask with 25 mL of methanol and 3 drops of phenolphthalein indicator was added to it. The mixture was warmed in a water bath for 5 min and titrated against 0.1 M KOH until the pink colour appeared which indicates the end point. Acid value was calculated using the equation:

2.8. Conductivity and turbidity tests

AV=

mLOFKOH × N × 56. 1 g /mol = mgKOH/g WEIGHT OF SAMPLE( g )

where AV ¼ Acid value; M ¼Molarity of KOH. 2.4.3. Peroxide value 0.5 g of each oil sample was weighed into a conical flask containing 1 g potassium iodide. The mixture of glacial acetic acid (13.5 mL) and chloroform (6.5 mL) was added to it. The conical flask was placed in a water bath for one minute after which 20 mL of 5% potassium iodide and 25 mL of water was added to it. The whole content was titrated against sodium thiosulphate solution (0.002 M) to colourless using starch as an indicator. The results

The conductivity of the lye solutions was determined using an EC 214 Conductivity Meter while the turbidity was determined using 2100N Turbidity Meter. 2.9. Saponification of oils The various oils were saponified using hot process since the cold process produced no instant saponification. 10 mL of the Palm kernel oil was heated to boiling in a beaker and 10 mL of prewarmed lye solution was added to the boiling oil with constant stirring. A thick dark-brown coloured semi-solid mass of soap was observed immediately. Where applicable, honey was added and the semi-solid mass was further stirred for about 10 min before it was allowed to cool and set for some weeks (Warra et al., 2011; Ogunsuyi and Akinnawo, 2012). In order to obtain soap of varied properties, the components, Palm kernel oil, D. oliveri oil, Moringa oleifera leaf extract and honey were mixed at different ratios.

O. Atolani et al. / Sustainable Chemistry and Pharmacy 4 (2016) 32–39

2.10. Inclusion of natural additives Additives which include 1 mL of aqueous moringa extract and 0.2 mL of honey were added after the saponification to the semisolid matter and stirred together. For the scent, approximately 0.5 g of the fresh leaves of Ocimum basilicum was inserted to the semi-solid matter to impart scent and antibacterial properties to the soap. The leaf was removed after few minutes before allowing the soap to set.

35

for bacteria and fungi respectively. The zone of inhibition was measure using a ruler. 2.17. Cost analysis of the soaps The production cost analysis of the soaps was carried out by estimating the amount of each reagent which includes the lye, oils and additives used for each soap. The cost was compared to that of commercial soaps.

2.11. Soap characterisations 3. Results and discussion All the prepared soaps were characterised by their pH, foaming ability, solubility and hardness whilst comparing their values with commercial soap samples using standard procedure (Ameh et al., 2013). Commercial bathing soaps which include Dettol soap, Lux soap and Dudu osun were used as standards for comparison. 2.12. Determination of pH of soaps The pH values of the soaps were determined using a pH meter (Inolab, WTW, Germany, pH 7310). 1 g of the soaps was weighed and dissolved in 10 mL distilled water and made up to 100 mL mark to afford 1% (w/v) homogeneous soap solution. The electrode of the pH meter was inserted into the solution and the value recorded. The steps were repeated for all the soaps as well as the commercial soaps used as standards. 2.13. Foaming ability tests 0.2 g each of the soap sample was put into a 100 mL measuring cylinder containing only 10 mL distilled water. The mixture was shaken vigorously so as to generate foams. After shaking for 2 min, the cylinder was allowed to stand for about 10 min and the height of the foam was then measured and recorded. The steps were repeated for the other prepared soap as well as the commercial soaps. 2.14. Solubility tests 0.2 g of each soap was added to a 100 mL measuring cylinder containing 10 mL of distilled water. The duration of the dissolution of the soap after continuous shaking was recorded. 2.15. Hardness tests The hardness of the soap was determined by inserting a regular hand-sewing needle (4.2 cm in length and 0.5 mm in diameter) to the soap. The needle was loaded at top with a weight of 370 g on lever system. The lever was raised and allowed to gently penetrate the soap within 30 s. The process was repeated three times and the average depth of the penetration of the needle was measured and recorded (Ameh et al., 2013). 2.16. Determination of soap sensitivity to microbes The antimicrobial sensitivity potential of the soap samples was studied using selected bacteria: Streptococcus aureus, Klebsiella granulomatis, and a fungus: Aspergillus niger. Agar diffusion method was adopted (Ameh et al., 2013). Media were autoclaved and 20 mL of the prepared sterilised Sabouraud Dextrose Agar was poured into sterile petri-dishes. The microorganisms of interest were inoculated following serial dilution of 1  106 CFU/mL. After the agar solidifies, 1 mL of 100 mg/mL of the sample solution prepared in water was pipetted into each hole in the petri dish bored aseptically. They were incubated at 37 °C for 48 h and 96 h

Biodegradable antiseptic herbal soaps have been produced from natural renewable sources in line with the principles of green chemistry. The use of auxiliary raw materials such as sodium hydroxide, sodium silicate, sodium sulphate and artificial perfumes, colourants, preservatives and synthetic antimicrobial agents were avoided. Sodium hydroxide has been linked to the cause of skin irritation and cancer. They strip the skin of oil, and sometimes raise the pH beyond tolerable limit of the skin's microflora (Tarun et al., 2014; IARC, 1978). The soaps were made from natural renewable and sustainable raw materials such as oils from underutilised tropical seeds, wood ash which is a huge waste of the baking and cooking industries. Ashes of plants contain potassium carbonate (K2CO3) and sodium carbonate (Na2CO3). The carbonate ion present in both of these compounds reacted with water to form an alkaline solution. Natural scent was incorporated directly from plant source i.e. leaves of Ocimum basilicum. Many modern commercial antiseptic soaps contain synthetic chemicals such as triclosan, trichlorocarbanilide and chloroxylenol, most of which are known to be carcinogenic, mutagenic and able to generate allergic reactions (Ameh et al., 2013). As a result, many of the modern soaps could cause increased bacterial resistance and also introduce or cause the release of metabolism hazardous compounds such as endocrine disruptors to the environment. Many cosmetic preservatives such as parabens are now considered as emerging contaminants because of their ability to disrupt the endocrine systems (Gore et al., 2015; Joshi and Pawal, 2015). Natural antiseptic soaps produced in this study are expected to be environmentally benign with less or no interference with hormone functions. Many of the herbal plant used in cosmetics have natural beneficial effects which could be of tremendous importance to human. Olive oil used in lotions and shampoos contains beta-sitosterol and tocopherol which acts as antioxidants (Rabasco and Gonzalez, 2000), Aloe vera contains leucine and saponin glycosides that provides vitamins, antioxidant and moisturising activities (Basmatekar et al., 2011) while neem seed (Azadirachta indica) contains phytochemicals that produces antifungal, antibacterial, pain-relieving, wound healing and anti-dandruff effects (Anand et al., 2010). 3.1. Physicochemical characteristics of the oils The D. oliveri had a lower yield (18.44%) compared to the oil obtained from the shea butter nuts (62.9%) (Table 1). However, the D. oliveri oil had higher saponification value and yield of transesterified product compared to that of shea butter. The D. oliveri oil had saponification value of 280.5 (mgKOH/g), peroxide value of 7.025 (meq/kg) and acid value of 1.12 (mgKOH/g). The analytical values obtained for the physicochemical properties were significantly in favour of the utilisation of the oil from the indigenous seeds of Daniellia oliveri and shea nut for soap production on commercial scale. The physicochemical parameters of the oil/fat are shown in Table 1.

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O. Atolani et al. / Sustainable Chemistry and Pharmacy 4 (2016) 32–39

Table 1 Physicochemical characteristics of the oils. Parameter

D.oliveri

Palm kernel oil

Shea butter

%Yield of oil from seed Saponification value (mgKOH/g) Acid value (mgKOH/g) % Free fatty acid Peroxide value (meq/kg) Physical state at room temperature Colour

18.44 280.5 1.122 91 7.025 Liquid

– – – – – Liquid

62.9 152 22.44 11.24 – Solid

Light Yellow 75

Brownish Yellow Pale yellow

%Yield of the transesterified oil

91

62.9

3.4. Oil mixing ratio for soap production The saponified products were obtained by using different proportion of the oils in order to determine the various properties of oils. The mixing ratios, soap colour and washing efficiency of the soap are shown in Table 4. The soap made from the D. oliveri was pale brown while that of shea butter was cream colour. The soaps with the highest washing efficiency based on physical observation were the ones produced solely of D. oliveri oil and shea butter, without mixing with any oil. The incorporation of Palm kernel oil to form oil blends for the soap preparation lower the washing efficiency.

Table 2 Conductivity and turbidity test of lye (wood ash). Parameter

Wood Ash lye

Conductivity (mS) Turbidity (NTU)

0.2 185

3.2. Conductivity and turbidity The conductivity and turbidity results of lye solution are shown in Table 2 below. 3.3. Fatty acids composition of the oils The fatty acids compositions of D. oliveri seed oil, Palm kernel oil and shea butter used in preparation of the soaps were determined by subjecting the transesterified oils to GC/GC–MS analyses. The results (Table 3) indicated that the predominant fatty acid in the D. oliveri oil is linolelaidic acid, an omega-6 trans-fatty acid (TFA). The D. oliveri contains 57% linolelaidic acid as the major fatty acid, while oleic acid (46%) and lauric acid (44.60%) were the most prominent in Shea butter and Palm kernel oil respectively. Stearic acid a, monounsaturated fatty acid was also prominent (40.10%) in the shea butter while palmitic acid (17.94%), a C-16 Table 3 Fatty acid compositions of D. oliveri oil, shea butter and Palm kernel oil. % RA of Palm kernel oil

% RA of Shea butter

– – 3.43 –

44.60 17.94 11.70 3.50

– – 4.32 –

18:2 18:1 18:1 18:2 18:2

56.57 8.11 19.67 – –

– – – – 1.86

– 40.10 46.33 7.70 –

20:0 21:1 21:1 22:0 24:1

0.88 – – 5.1 6.24 9.41 90.59 34.02 56.57

– 2.97 15.90 1.53 – 79.27 20.73 18.87 1.86

1.55 – – – – 5.87 94.13 86.43 7.70

Peak no. Fatty acids

Saturation % RA of D. oliveri

1 2 3 4

12:0 14:0 16:0 18:0

5 6 7 8 9 10 11 12 13 14

Lauric acid Myristic acid Palmitic acid Methyl 16methylheptadecanoate Linolelaidic acid Stearic acid, cis-Oleic acid Linoleic acid Methyl 9-cis,11-transoctadecadienoate Eicosanoic acid Heneicosanoic acid Monoolein Docosanoic acid Tetracosenoic acid Total Saturate Total Unsaturate Monounsaturate Polyunsaturate

saturated fatty acid was high in the palm kernel oil. Only palm kernel oil had lauric and myristic acids in the oil as they were not within detectable limit in both the D. oliveri oil and shea butter. Both D. oliveri oil and shea butter had above 90% unsaturation while Palm kernel oil had only 20.73% unsaturation. The high percentage of the saturated C-12 and C-14 fatty acids in the palm kernel oil and the low concentration of the unsaturated fatty acids might be responsible for the observed low quality (washing efficiency, forming ability) of the soap produced from palm kernel oil. The linolelaidic acid which was the major constituent of the D. oliveri oil has also been reported to be…

%RA indicates percentage relative abundance (peak area relative to the total peak area).

3.5. The physicochemical characteristics of the soaps The pH values (Table 5) of the soaps were determined at two different stages which include the day the oils were saponified and after the soaps had cured (after about three months). All the pH values of the cured soaps fell within acceptable range (9–10) that is permitted by a regulating authority especially in Nigeria except the soap made from palm kernel oil only which had pH slightly above 10 (Oyedele, 2002). The pH values obtained are also in agreement with literature results (Ogunsuyi and Akinnawo, 2012; Vivian et al., 2014). The obtained pH values indicate that the soaps would be less corrosive and is expected to produce less skin reaction when used. High pH values are usually obtained (most often when industrial sodium or potassium hydroxides are used) as a result of incomplete hydrolysis which results from saponification process. The high alkalinity is overcome by the addition of excess fat or oil or any other super fatting agent to reduce the harshness of soap (Warra et al., 2011). The alkalinity favours detergency (Kaoru, 1998). More so, The use of high alkaline soaps can neutralise the body's protective acid mantle that acts as a barrier against bacteria and viruses since a healthy human skin has a pH range of 5.4–5.9 (Mak-Mensah and Firempong, 2011). The use of soap with high pH value causes an increase in skin pH, which results into an increase in dehydration, irritation and destruction of the bacterial flora (Tarun et al., 2014). The application of wood ash as the source of alkali in this work produced less alkaline soaps which would be more body-friendly. Soaps A3 and B3 which are soaps made from only D. oliveri oil and Shea butter respectively had the highest foaming ability (Fig. 2). Their foaming abilities were superior to the commercial soaps namely; dudu osun, lux and Dettol soaps. The two, A3 and B3 also had moderate solubilities (Fig. 3) and higher hardness properties (Fig. 4) compared to the commercial soaps and other soaps with mixtures of oils. The solubility and hardness of the soaps is an indication of the ability of the soaps to last longer when used due to its ability to slowly dissolve in water. Shea butter had been reported to contain some unsaponifiables that do not react with lye which thus remain in soap to nourish the skin. Shea butter gives soap with hardness, conditioning, stable lather, and a silky feel. Shea butter is known to help in removing skin blemishes, dry skin, and wrinkles (Manji et al., 2013). The high

O. Atolani et al. / Sustainable Chemistry and Pharmacy 4 (2016) 32–39

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Table 4 Mixing ratio of the oils/fat used for the saponification. Samples

Oils/fat and additives mixing ratio

Mixing ratios

Soap colour

Washing efficiency

A1 A2 A3 B1 B2 B3

PKOþD. oliveri oilþ Moringa leaf extractþ Honey PKOþD. oliveri oil D. oliveri oil PKOþShea butterþ Moringa leaf extractþHoney PKOþShea butter Shea butter

0.89:0.05:0.05:0.01 0.95:0.5 1 0.89:0.05:0.05:0.01 0.95:0.5 1

Dark brown Dark brown Pale brown Dark brown Dark brown Cream

Good Good Very good Good Good Very good

where A1: PKOþD. oliveri oilþ M. oleifera leaf extractþ Honey; A2: PKOþ D. oliveri oil; A3: D. oliveri oil; B1: PKOþ Shea butter þM. oleifera leaf extractþ Honey; B2: PKOþShea butter; B3: Shea butter.

Soap sample

A1 A2 A3 B1 B2 B3 PKO only Dudu Osun Lux Dettol

pH before curing

pH after curing

Foam height (cm3)

Solubility (sec)

9.99 10.13 – 10.11 9.46 – 10.91

8.75 8.52 8.72 9.48 8.64 9.78 10.10

3.11 2.53 4.50 2.53 2.77 5.00 2.29

420 420 420 620 600 540 300

1.55 0.35 0.30 2.30 1.30 0.20 1.40

Hard Very hard Very hard Soft Hard Very hard Hard

–

9.17

3.61

360

2.20

Soft

– –

9.73 9.08

3.69 3.48

780 600

1.30 1.30

Hard Hard

Hardness (cm)

Texture

where A1: PKOþD. oliveri oilþ M. oleifera leaf extractþ Honey; A2: PKOþ D. oliveri oil; A3: D. oliveri oil; B1: PKOþ Shea butterþ M. oleifera leaf extractþHoney; B2: PKOþShea butter; B3: Shea butter.

Foaming height (cm)

6 5 4 3

Hardness (cm)

2.5

Table 5 The physical characteristics of the Soap samples.

2 1.5 1 0.5 0 A1

A2

A3

B1

B2

B3

PKO only Dudu Osun

Lux

Dettol

Soap samples

Fig. 4. Hardness of the soaps. Where A1: PKO þD. oliveri oilþ M. oleifera leaf extractþ Honey; A2: PKOþD. oliveri oil; A3: D. oliveri oil; B1: PKOþShea butterþ M. oleifera leaf extractþ Honey; B2: PKOþShea butter; B3: Shea butter.

concentration of the short chain saturated C-12 and C-14 fatty acids in the PKO is suspected to have led to the production of less quality soaps when compared to the D. oliveri oil and Shea butter soaps. Fatty acids with only 10 or fewer carbons are not the favourite in soaps making because they produces soaps that possesses obnoxious odours and also irritates the skin (Chalmers and Bathe, 1978; Vivian et al., 2014). The chemical nature of the lipophilic part of soap plays the largest role in determining the performance of finished soap (Viorica et al., 2011). The physicochemical characteristic of soap which includes moisture content, total fat matter (TFM), pH, free caustic alkalinity depends largely on several factors such as the strength and purity of alkali, the type of oil used, degree of saponification, constituent of the oil and many others (Roila et al., 2001; Vivian et al., 2014).

2 1

3.6. Result of antimicrobial sensitivity tests

0 A1

A2

A3

B1

B2

B3

PKO Dudu only Osun

Lux

Dettol

Soap samples Fig. 2. Foaming ability of the soaps. Where A1: PKO þD. oliveri oil þM. oleifera leaf extractþ Honey; A2: PKOþD. oliveri oil; A3: D. oliveri oil; B1: PKOþ Shea butter þM. oleifera leaf extractþ Honey; B2: PKOþ Shea butter; B3: Shea butter.

All the prepared soaps showed appreciable level of microbial activity (Table 6) against some of tested organisms. A broad activity was recorded in sample A3, that is, the soap prepared from D. oliveri oil only. It showed sensitivity against three organisms; Streptococcus aureus, Klebsiella granulomatis, Aspergillus niger and a

Solubility

Table 6 Sensitivity of microorganisms to the prepared soaps.

900 800 700 600 500 400 300 200 100 0 A1

A2

A3

B1

B2

B3

PKO Dudu Lux Dettol only Osun

Soap samples Fig. 3. Solubilities of the soaps. Where A1: PKO þD. oliveri oilþ M. oleifera leaf extractþ Honey; A2: PKOþD. oliveri oil; A3: D. oliveri oil; B1: PKOþ Shea butter þM. oleifera leaf extractþ Honey; B2: PKOþ Shea butter; B3: Shea butter.

Sample code ZI ofStreptococcus aureus (mm)

ZI ofKlebsiella granulomatis (mm)

ZIAspergillus niger (mm)

A1 A2 A3 B1 B2 B3 Ampicillin Tetracycline

31 42 29 3.0 NI 42 40 25

NI NI 3.0 7.0 1.0 NI 3.0 11

NI NI 1.0 NI 5.0 4.0 14 9.0

where ZI: Zone of Inhibition; NI: No inhibition; A1: PKO þD. oliveri oil þM. oleifera leaf extractþHoney; A2: PKOþD. oliveri oil; A3: D. oliveri oil; B1: PKOþ Shea butterþ M. oleifera leaf extractþ Honey; B2: PKOþ Shea butter; B3: Shea butter.

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O. Atolani et al. / Sustainable Chemistry and Pharmacy 4 (2016) 32–39

Table 7 Estimated production cost analysis of prepared soaps. Soap sample

Cost (USD) per 1 g

A1 A2 A3 B1 B2 B3 PKO only Dudu Osun Lux Dettol

0.0025 0.0023 0.0020 0.0030 0.0025 0.0023 0.0018 0.0040 0.0050 0.0085

where USD means United State Dollars; A1: PKO þ D. oliveri oilþ M. oleifera leaf extractþ Honey; A2: PKOþ D. oliveri oil; A3: D. oliveri oil; B1: PKOþ Shea butter þM. oleifera leaf extractþ Honey; B2: PKOþShea butter; B3: Shea butter.

seeds. The adoption of these techniques and natural resources for the preparation of herbal soaps would save the environment of the daily introduction of many hazardous chemical products which results from the utilisation of commercial synthetic soaps. The soaps prepared avoided the inclusion of auxiliary raw materials such as sodium silicate, sodium sulphate, sodium silicate and artificial perfumes, colourants, preservatives and synthetic antimicrobial agents. Soap made from Daniellia oliveri seed oil, which is usually an undervalued stock in the environment had the best properties in terms of hardness, forming ability, texture, colour, antimicrobial activity and commercial rating. The adopted method helps in the conversion of agro waste products in the environment to commercial utility products thereby improving the economic status of the community.

Conflict of interest Authors declared that there is no conflict of interest.

lower activity recorded against Klebsiella granulomatis. B3, Shear butter showed complete inhibition of the Klebsiella granulomatis bacteria which was comparable to the inhibition using standard drugs like ampicillin and tetracycline. The antimicrobial result indicates that the soap produced from the natural underutilised product has potential of inhibiting related microbial infections. Other seed oils such as neem oil (Azadirachta indica) has been reported to show broad spectrum antimicrobial activity (Sairam et al., 2000). However, a wider range of anti-microbial tests would be necessary to ascertain the potential of the soaps to inhibit a broad spectrum of organisms. The use of the soaps may help in the prevention of skin infections and communicable diseases. The application of antiseptic or medicated soaps for washing the body is the first line of defense against bacteria and other pathogens that can cause colds, the flu, skin infections and even deadly communicable diseases (Larson, 1988; Mwambete and Lyombe, 2011). However, the inoculum sizes of both pathogenic and non-pathogenic microorganisms would be reduced by the use of medicated soaps (Nester et al., 2002). Although, it has been highlighted that overuse of antiseptic soaps can have the negative effect by making users vulnerable to opportunistic skin infection and thereby spreading diseases instead of preventing them. Synthetic antimicrobial agent such as triclosan in soaps has been linked to the incidences of induced clinical antimicrobial resistance (Russell, 1998; Chuanchen et al., 2001; Levy, 2001; White and McDermott, 2001; Poole, 2002). Hence, the adoption of benign natural antimicrobial agents in soaps and cosmetics may assist in reversing the trend. 3.7. Production cost analysis of prepared herbal soaps Table 7 shows the cost of production of the prepared herbal soaps from the selected natural sources. The cost per gram of the soap was estimated and compared to the market cost of commercial soaps. All materials used were given a relative value and the cost of production thus calculated. The cost analysis was based on cost of raw materials vis-à-vis the relative yield of the soaps. The D. oliveri oil-made soap and the Shea butter-made soap had lower cost of production when compared to others that have other additives such as honey and Moringa oleifera seed oil.

4. Conclusion Following the principles of green chemistry, herbal antiseptic eco-friendly soaps have been prepared from underutilized oil

Acknowledgement Authors gratefully acknowledges TWAS research grant: 15-244 RG/CHE/AF/AC_G – FR3240287031 which supports this work.

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