Analysis and Comparative Study of Essential Oil Extracted from Nigerian Orange, Lemon and Lime Peels

Transcription

1 Analysis and Comparative Study of Essential Oil Extracted from Nigerian Orange, Lemon and Lime Peels By V.I. Njoku B.O. Evbuomwan

2 Research Article Analysis and Comparative Study of Essential Oil Extracted from Nigerian Orange, Lemon and Lime Peels *V.I. Njoku, B.O. Evbuomwan Department of Chemical Engineering, college of Graduate Studies, University of Port Harcourt, Choba, Nigeria. ABSTRACT *Corresponding Author s letsbeconnected@yahoo.com, Phone: Essential oils are a product obtained from vegetable raw materials and are complex mixtures whose composition may include volatile terpenic compounds. In this study, the relationship between time and amount of essential oil extracted from the citrus peels using steam distillation was shown. Orange peel was shown to contain more amount of essential oil (20ml at 180minutes) than lemon (7ml at 180minutes) and lime (5ml at 180minutes).Using GC-MS analysis, 11, 12 and 24 chemical constituents were identified in orange, lemon and lime essential oil respectively. The 3 main components and their percentage compositions are D-Limonene (54.151%), Pulegone (11.652%) and L- Carvone (2-cyclohexen-1-one) (5.457%) for orange peel essential oil, D-limonene (64%), 2-cyclohexen-1-ol (6.21%) and β-pinene (3.822%) for lemon peel essential oil, and β-pinene (23.124%), D-limonene (17.07%) and α-pinene (10.399%) for lime essential oil. D-limonene was the most prevalent chemical constituent in orange and lemon essential oil, but β-pinene was the most prevalent in lime peel essential oil. Although lemon contained more D- limonene per unit volume of essential oil, application of these percentages on the volume of essential oil obtained from 370g of the peels at 180minutes showed that orange peel can deliver more D-limonene per unit mass of available peel. Hence, orange peel essential oil is a more economical source of D-limonene in Nigeria. Keywords: Quantitative, Analysis, Qualitative, Comparative, Extracted, Essential oil, Orange, Lemon, Lime. 1. INTRODUCTION Essential oil from citrus is a large type of natural flavours and fragrances, which is popularly used in food industries, daily chemical product and health care field (Sheng-min et al., 2012). The citrus species are a potential source of variable oil which might be utilized for edible and other industrial application (Maria et al., 2012). Essential oils are broadly used as pharmaceutical components, in nutritious supplements and for cosmetic industry and aromatherapy (Maria et al., 2012). Guenther (1955) also stated that the oil is also employed in perfumes, toilet waters, eaux de cologne, and in cosmetics to which it impacts a refreshing top note. Essential oils are a product obtained from vegetable raw materials (Berger, 2007), and are complex mixtures whose composition may include volatile terpenic compounds, which have the formula (C 5 H 8 ) n, where the compounds are monoterpenes if n=2, sesquiterpenes when n=3, diterpenes when n=4 etc (Smith et al., 2001). These are secondary metabolites in plants (Mazen, 2002) and responsible for the characteristic aroma on the fruit. Lemon essential oil are complex mixtures of chemical compounds like limonene, Y-terpinene, citral, linalool and β-caryophyllene among others, which can be represented by three main classes, namely terpenes, oxygenates, and sesquiterpenes (Benvenuti et al., 2001). The most significant flavour compound is citral, while linalool possesses highly distinctive organoleptic characteristics. In addition, limonene, myrcene, octanol, and Y- terpene among others contribute with high aroma flavour of lemon oil (Benvenuti et al., 2001). The composition of orange oil varies for several reasons. Region and seasonal changes as well as the method used for extraction lead to these variation. Gamarra et al. (2006) also stated that the quality of essential oil depends on different factors; among them are the chemotype and biotype of the plant, the climatic conditions as well as the extractive process. Several compounds have been identified in orange oil with gas chromatographmass spectrometry. Most of the substances are part of the terpene group (limonene, α-pinene, sabinene, β- pinene, myrcene and δ-3-carene) with limonene being the dominant one. Long chain aliphatic hydrocarbon alcohols and aldehydes like octanol, decanal, and octanal are second important group of substances (Verzera et al., 2004). Citrus fruits have a rough, robust and bright (green to yellow) coloured skin. They are usually 4 to 30cm long and 4 to 20cm in diameter, with a leathery surrounding rind or skin known as epicarp (or flavedo) that cover the fruits and protect it from damages. Citrus fruits are notable for their fragrance, partly due to flavanoids and limonoids contained in the rind (Manthey, 2004). The endocarp is rich in soluble sugar and contains significant 6

3 amounts of vitamin C, pectin, fibres, different organic acids and potassium salt which give the fruits its characteristic citrus flavour (Ezejiofor et al., 2011). Citrus juice also contains a high quality of organic acids (citric, malic, acetic and formic acids). In Nigeria and other parts of the world, citrus sinensis (sweet orange) are cheaply available, thus serves as a major source of vitamins in diets. Orange fruit and its juice have several beneficial, nutritive and health properties (Okwu and Emenike, 2006). They are rich in vitamins especially ascorbic and folic acids. Over the last decades, many other virtues and medicinal benefits of orange fruits have been discovered besides their antiscurvy property (Rapisararda, 1999). There is convincing epidemiological evidence that the consumption of orange fruit is beneficial to health and contributes to the prevention of degenerative process, particularly lowering incidence of degenerative process, particularly cardio and cerebro- vascular diseases (Rapisararda, 1999). The protection that orange fruit provides against these diseases has been attributed to the various antioxidant phytonutrients contained in citrus species (Okwu and Emenike, 2006; Rapisararda, 1999). The current annual world production of citrus fruits is approximately 110 million tons, of which oranges constitute about 80 million tons (USDA, 2013). In Nigeria, about 930,000 tons of citrus fruits are produced annually from an estimate of 3 million hectares (FAO, 2008). The objective of the research was to: a. Determine the relationship between time and quantity of essential oils obtained from citrus peels, b. Compare quantitatively the composition of essential oils obtained from orange, lemon and lime peels, c. Determine the percentage of components present in the essential oils, d. Identify the major components present in the composition, and e. Determine the physicochemical properties of the essential oils. 2. MATERIALS AND METHODS a. Steam Distillation Oranges used in this work were bought from Rumuokoro market in Portharcourt, Rivers state, Nigeria. They were washed with de-ionized water, peeled and cut into small pieces. The orange peel was then weighed using RADWAG WAGI electronic top loading balance (AS 220/C/2) to obtain exactly 370grams. The orange peels were then pureed using MARLEX ELECTROLINE (Excella) blender. The pureed orange peel was then carefully transferred into a 1000ml flat bottom flask. 650ml of deionized water was measured using a 1000ml measuring cylinder and then added to the 1000ml flat bottom flask (distilling flask). Boiling chips was then added to the distilling flask to ensure that boiling occurs calmly without bumping. The experiment was then set-up as shown in Figure 1 below; Figure 1: laboratory set-up for the steam distillation of citrus peel. Heating of the distilling flask was then slowly commenced using STUART HOT PLATE/ MAGNETIC STIRER. The heat source was adjusted so that the distilling rate is approximately 20 drops per minutes. As the mixture boils and distils, de-ionized water was added via the separation funnel in the set-up just to keep the water level at

4 the operation level preventing the water level from going too low which can cause the sugar in the puree to caramelize and burn and also keeping the heat at a low steady level. The experiment was conducted for the following times; 60, 100, 140 and 180 minutes, in each case, the distillate was collected and transferred into a 250ml separating funnel. 20ml of diethyl ether was added to the distillate in the separating funnel to extract the oil. It was ensured that there was no flame source or hot plate on during the use of diethyl ether because diethyl ether is very, very flammable. The water layer in the separating funnel was then drained off. The diethyl ether layer was collected and small quantity of anhydrous magnesium sulphate was added to dry off the water content. The oil was then kept in a fume cupboard for 12 hours to allow all the diethyl ether vapourize. The oil extracted was then measured and recorded. b. Quantitative and qualitative analysis of citrus peel essential oils The quantitative and qualitative analysis of the citrus peel essential oil was done using (5975 Series MSD with an Agilent 7890A). 0.5 ml of each of the oil samples was diluted to 5 ml by the addition of 4.5 ml of methylene chloride (diluents). Helium was used as the carrier gas because of its inert nature EXPERIMENTS 3.1. Determination of the solubility of citrus peel essential oil in water Approximately 6 drops of water was added to the test tube containing 3 drops of orange peel essential oil. The test tube was stirred thoroughly with a glass stirring rod. Two separate phases was observed. The ph of the water was measured to determine if the essential oil is partially soluble in water and whether it has changed the ph of the water. It was observed that the ph paper did not change colour. Thus, the orange peel essential oil is a water insoluble compound. The above experiment was carried out on lemon and lime essential oil, and same result was obtained Determination of the boiling point of citrus peel essential oil 5ml of the essential oil was placed in a small test tube. A capillary, sealed at one end is placed open-end down into the essential oil. The test tube is firmly attached to a thermometer with a rubber band such that the thermometer bulb should be even with the test tube s bottom, and this entire assembly immersed in an oil bath (half filled 100ml beaker). As the temperature is slowly increased, a rapid evolution of bubbles from the end of the tube begins. Heating was continued for about 5-10 seconds to be sure that all of the air has been expelled from the capillary, and the vapours of the essential oil become equal to the atmospheric pressure. As the temperature decreases, the bubbles slowed down and the essential oil starts rising into the capillary. At the point when the bubble stops, the thermometer was read and recorded. The above process was repeated 2 more times, and the temperature reading in each case was recorded. The above experiment was carried out on orange, lemon and lime essential oil at atmospheric pressure Determination of specific gravity of orange peel essential oil Density bottle was used for determining the density of the oil. A clean and dry bottle of 25ml capacity was weighed (W 0 ) and then filled with the oil, stopper inserted and reweighed to give (W 1 ). The oil was substituted with water after washing and drying the bottle and weighed to give (W 2 ).The above experiment was done using orange, lemon, and lime essential oil Determination of refractive index of citrus peel essential oil The Abb's refractometer was used for the determination of refractive index. It gives values up to the 4th decimal place. The refractive index is denoted by n D 25 where n is the refractive index at 25 C taken with sodium light (D - line). First, the refractometer was standardized with distilled water which has refractive index of n D 29.5= Then it was cleaned with acetone and dried with cotton. After this, a drop of orange peel essential oil was placed between the prisms of refractometer. The telescope was rotated to bring the border line of total refraction to the junction of cross-wire in the telescope. The refractive index was recorded at room temperature. The above experiment was repeated for lemon and lime peel essential oil. 8

5 3.5. Determination of peroxide value of orange, lime and lemon essential oil 30ml of acetic acid chloroform solution was measured into a flask containing 2g of the oil sample. A 0.5ml saturated solution of potassium iodide was then added, followed closely by the addition of 30ml of distilled water. The flask content was then titrated against 0.1M sodium thiosulphate (Na 2 S 2 O 3 ) until the yellow colour almost disappeared. 0.5ml starch indicator was added and the titration continued until the end-point (where the blueblack colour just disappeared). A blank titration was also performed. Where S and B represent sample and blank titrations respectively. The peroxide value is thus calculated; PEROXIDE VALUE = ( ). Where S= Sample titration. B= Blank titration Determination of saponification value of citrus peel essential oil g of orange peel essential oil were weighed into a conical flask separately. 25ml of 0.1N ethanolic potassium hydroxide was added to the conical flask, and content constantly stirred for 1 hour followed by reflux. Phenolpthalein indicator was then added to the conical flask and titrated with 0.5M HCl till the solution changes to colourless. The same procedure was repeated for the blank. The above experiment was repeated using g of lemon and g of lime essential oil Determination of acid value of citrus peel essential oil 25ml of diethyl ether and 25ml of ethanol was mixed in a 250ml beaker. The resulting mixture was added to g orange peel essential oil in a 250ml conical flask, and few drops of phenolphthalein were added to the mixture. The mixture was then titrated with 0.1M KOH to the end point with consistent shaking for which a dark pink colour was observed and the volume of 0.1M KOH (V o ) was noted. The above experiment was repeated using g lemon and g lime essential oil. 4. RESULTS AND DISCUSSION a. Steam distillation The time and quantity of essential oil extracted from the citrus peels are presented in Tables 1, 2 and 3, and Figure 2, 3, 4, and 5 for orange, lemon and lime respectively. From Table 1, 2 and 3 for orange, lemon and lime respectively, it was observed that the volume of essential oil extracted from the peels increases with time. It was also noticed that more essential oil (20ml) at 180 minutes of heating was extracted from 370g of the orange peels than from equal mass of lemon and lime peel at the same time of heating, while lime had the least quantity of essential oil extracted (5 ml). These observations are in agreement with the findings of Kamal et al.(2011) who reported that among the citrus species tested, C. Sinensis exhibited the maximum oil yield ( %) followed by C. reticulata ( %) and C. paradisii ( %). Gamarra et al. (2006) stated that the quality of essential oil depends on different factors; among them are the chemotype and biotype of the plant, the climatic conditions as well as the extractive process. Soumaya et al.(2012) also reports that essential oil yield varied during ripening to reach maximum values during the middle stage of maturity (stage 2) for mandarin and orange, while the highest lemon yield was found at the beginning of fruit maturation and decreased after that. Also Des Gachons et al. (2005) stated that water supply during ripening was reported to influence considerably the essential oil content with an enhancement of yield under moderate water shortage conditions. All these will possibly be responsible for the high yield of orange essential oil over that of lemon and lime. 9

6 Table 1: Variation of volumes of essential oil extracted from orange peel. S/N Plant Weight Volume of Time of Temp.( 0 c) Volume of material (gm.) distilled water(ml) heating(min) essential oil (ml) 1 ORANGE PEEL Volume of orange Oil (ml) Volume of Lemon oil (ml) Volume of Lime oil (ml) 0 60 mins 100 mins 140 mins 180 mins Figure 2: Volume of essential oils extracted from citrus following different extraction periods. a. Physicochemical properties of citrus peels Table 2: Physicochemical properties of citrus peel essential oils. Properties Orange Lemon Lime Specific gravity Boiling point ( O C) Refractive index Solubility in water Insoluble Insoluble Insoluble Saponification value ( mg KOH/g oil) Acid value ( mg KOH/g oil) Peroxide value b. Quantitative and qualitative analysis of citrus peel essential oils The orange, lemon and lime peel essential oils contained a total of 11, 12 and 24 components, respectively. Table 3 shows the total components and their percentage composition for orange, lemon and lime, essential oils. The GC-MS chromatogram for orange, lemon and lime are shown in Figures 3, 4 and 5, respectively.

7 Figure 3: Gas chromatographic plot for orange peel essential oil. Figure 4: Gas chromatographic plot for lemon peel essential oil.

8 Figure 5: Gas chromatographic plot for orange peel essential oil. Table 3: Components and percentage composition in orange, lemon and lime peel essential oil. COMPONENT COMPOSITION (%) ORANGE LEMON LIME 1R-α-Pinene Cyclohexene D-Limonene (Z)-3-Carene ,3,8-p-Menthatriene Pulegone Methylcyclohexa-1,3-diene ,3-Cycloheptadiene Cyclohexen-1-ol ,4-Cyclohexadiene Cyclohexen-1-one (L β-phellandrene β-pinene ,4-Cyclohexadiene Cis-p-Mentha-2,8-dien-1-ol methyl-5-(1-methylethenyl) Cyclohexen-1-ol α-phellandrene Ocimene Bicyclo[4.1.0]hept-2-ene Carene Bicyclo[3.1.0]heptan-3-ol Cyclohexene-1-methanol E,Z-4-Ethylidenecyclohexene Cyclohexen-1-ol Cyclohexen-1-one ,6-Octadienal ,3-Cyclohexadiene

9 1S-α-Pinene H-Cycloprop[e]azulene Caryophyllene Trans-α-Bergamotene Bicyclo[3.1.1]hept-2-ene Caryophyllene oxide The three highest occurring components in orange peel essential oil are D-limonene (54.15%), pulegone (11.65%) and L-carvone (2-cyclohexen-1-one) (5.46%). The three highest occurring components in lemon peel essential oil are D-limonene (64%), 2-cyclohexen- 1-ol (6.21%) and β-pinene (3.82%), and the three highest occurring components in lime peel essential oil are β- pinene (23.12%), D-limonene (17.07%) and α-pinene (10.40%). The amount of lemon peel essential oil for D- limonene and β-pinene is in agreement with Soumaya, et al. (2012) findings that D-limonene ( %), β- pinene ( %), γ-terpene ( %), and p-cymene ( %) were the highest ones in lemon. However percentage composition of sweet orange did not agree with that of Soumaya et al. (2012), which had a percentage of ( %). Figueiredo et al. (2008) and Schmidt (2010) also stated that it needs to be kept in mind that the chemical composition may already vary in the raw material, being influenced by plant health, growth stage, habitat including climatic, edaphic factors, as well as harvest time. Widmark and Blohm (1957) also stated that oxygen consumption upon storage of different monoterpenes has been recorded. El. Nikeety et al. (1998); Turek and Florian (2013) went further to state that changes in composition as well as physicochemical properties of essential oils were generally more pronounced in half-filled containers than when only little or no headspace was present. Asnaashari et al. (2010) stated that the GC-MS analysis of the essential oils of lime (C. aurantifolia) was also performed and approximately 22 main components, with Limonene (28.27%) being the principal one, were identified and quantified, as against 24 components identified in this work with β-pinene (23.12%) being the principal one, and Limonene (17.07%) being the next most abundant. However, from Table 3, it can be deduced that lemon peel essential oil has the highest percentage of D- limonene (64%) when compared to the same quantity of the three oil samples. But, from Table 1, it can also be seen that orange peel produced the highest volume of essential oil when compared with same mass of the three citrus peels and same time of distillation. Therefore, taking the longest time of heating (180 minutes) in Table 1 and the percentage composition of D-limonene in the citrus peels in Table 3, orange peel produced 20 ml of essential oils, whereas lemon produced 7 ml and lime 5 ml. Working out the quantity of D-limonene in the volume of essential oil obtained from the citrus peels after 180 minutes, using the percentage of D-limonene in the citrus peels as shown in Table 3, lime peel essential oil contained 0.85 ml D-limonene, lemon 4.48 ml D-limonene, while orange peel essential oil contained ml D-limonene. 5. CONCLUSION The results obtained showed that lemon peel contains more amount of D-limonene per unit volume of essential oil, while orange peel contains more amount of essential oil than lime and lemon per unit mass of peel. However, by obtaining percentage of D-limonene in volume of essential oil obtainable from unit mass of peel, it was concluded that orange peel is a more viable and economical source of essential oil which is very rich in D- limonene. 6. RECOMMENDATION The shelf life of citrus peel essential oil have been established from literature to be greatly affected by its storage conditions such as wrong storage containers, storage temperature and head space in storage containers. Thus, citrus essential oil should be stored in amber bottles, and below room temperature, with the avoidance of headspace in storage containers. Further research to evaluate the effect of fertilizer application on; a) The physicochemical properties of orange peel essential oil. b) The chemical constituents in orange peel essential oil. c) Volume of essential oil in orange peel. d) Pectin content in orange peel. 13

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