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1 Food Chemistry 120 (2010) Contents lists available at ScienceDirect Food Chemistry journal homepage: Extraction, separation and characterisation of sesame oil lignan for nutraceutical applications M.V. Reshma *, C. Balachandran, C. Arumughan, A. Sunderasan, Divya Sukumaran, Shiny Thomas, S.S. Saritha National Institute for Interdisciplinary Science and Technology (Formerly RRL), Council of Scientific and Industrial Research, Trivandrum, India article info abstract Article history: Received 27 March 2009 Received in revised form 17 October 2009 Accepted 23 November 2009 Keywords: Sesamum indicum Sesamin Sesamolin USM Nutraceuticals Nutraceutical aspects of sesame oil (SO) are well reported. However, an efficient process for commercial production has not yet been reported. In this study we have aimed at separating lignans from SO aiming at use as nutraceuticals. SO was subjected to sequential extraction with methanol under selected conditions of temperature (70 C), time (100 min) and solvent:oil ratio (1:1). Under the optimised conditions, the yields of pooled methanolic extract concentrate and residual oil were ± 1.0 g and 89.2 ± 1.0 g, respectively. On HPLC analysis, the methanol concentrate showed a total lignan content of 9.32 ± 0.19% (6.54 ± 0.12% sesamin and 2.78 ± 0.31% sesamolin). The concentrate was subjected to low temperature crystallization (4 C) for the separation of lignan crystals and 51% of the lignans in the oil with 94.4% purity. The crystal-removed methanolic concentrate was saponified and purified; the total lignan content (sesamin and sesamolin) in the unsaponifiable matter (USM) was 64%.The distribution of sesamin and sesamolin in the purified USM was in the proportion 46:54, unlike that in the pure crystals (84:16). Lipid classes (triglycerides, TG; free fatty acids, FFA; diglycerides, DG; monoglycerides, MG; polar lipid, PL) in SO, methanolic extract concentrate and residual oil were separated using thin-layer chromatography (TLC). The amounts of lipid classes were determined by relating the total area of the fatty acid peaks to the area of the peak for internal standard (methyl heptadecanoate), using gas chromatography (GC). The process reported here describes a simple and less cumbersome procedure to produce lignans with high yield and purity for nutraceutical applications. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Oil from sesame (Sesamum indicum Linn.), is markedly different from all other vegetable oil due to its high nutritional and therapeutic values and it is widely utilised in tropical and sub tropical regions. India and China are the major producers of sesame seed, contributing about 70% of the total world production of about 1.2 million metric tones (MMT). Sesame seed yields about 45 50% by weight of highly stable oil with a distinct flavour, and is widely used in Indian traditional medicine; Ayurveda and their medicinal applications are referred to in the traditional medical texts of India and China. Sesame oil (SO) is also used for culinary purposes and deoiled meal is mainly utilized as cattle feed. Several epidemiological and clinical studies have indicated a strong positive association of intake of dietary and non-dietary phytochemicals and health. In this context, several plant-based nutraceuticals are * Corresponding author. Fax: address: reshmamv2001@yahoo.co.in (M.V. Reshma). developed with health-protective roles. Plant materials that have been consumed as part of the diet or traditional medicines would require less rigorous screening protocols and can be used for nutraceutical development. Sesame seed/so, from this perspective, is a rich source of lignans, known for a variety of biological activities and has been used as food or medicine for ages by a large section of the population. Recent studies, using modern methods, have revealed potential health benefits of sesame, such as antioxidative (Shahidi, Liyana-Pathirana, & Wall, 2006) antihypertensive (Sankar, Sambandam, Rao, & Pugalendi, 2005) hypocholesteremic (Hirose et al., 1991), anticancer (Miyahara, Hibasami, Katsuzaki, Imai, & Komiya, 2001) and immunoregulation (Nonaka, Yamashita, Izuka, & Namiki, 1997). Beneficial health effects of sesame are primarily attributed to lignans and their glycosides. Lignans are a class of secondary plant metabolites produced by oxidative dimerization of two phenyl propanoid units. The main lignans in SO are sesamin and sesamolin and are reported to be in the concentration range %. They account for about 10% of the unsaponifiable matter (USM) in SO (Hemalatha & Ghafoorunissa, 2004). Perusal of the earlier reports related to recovery of lignans from sesame seed/so would reveal that none of them were industrially /$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi: /j.foodchem

2 1042 M.V. Reshma et al. / Food Chemistry 120 (2010) feasible and economical. Shinmen et al. (1993) used an immiscible organic solvent for extracting the lignans from sesame and obtained a lignan content of only 32.23% in the extract, based on total lignans in oil. They also tried supercritical extraction of oil and also different chromatographic techniques for isolating desired lignans from the extract. However, the yields and purities by these techniques have not been reported. Namiki, Kobayashi, and Hara (2001) subjected SO to supercritical extraction and the reported % yield of extracts ranged from 21% to 24%; the lignan content in the extract was only %. Akimoto, Shinmen, Yamada, Shimizu and Sugano (1994) extracted SO using organic solvent and administered it to animals and reported that the composition showed inhibitory effects and could be used in treatment of inflammation, thrombosis or hypertension. However, the yield and purity were not reported. Similarly, other techniques have also been tried, wherein the oil was subjected to liquid extraction, followed by saponification and precipitation at 4 C; again the yield of extraction was very poor (Dachtler, VandePut, Stijn, Beindorff, & Fritsche, 2003). The objective of the present work was to develop a commercially feasible and economical process to produce a range of products containing lignans of 60 95% purity for nutraceutical applications with emphasis on maximising recovery of the oil for reuse. 2. Methods 2.1. Raw material and chemicals White SO was supplied by M/s. Arjuna Natural Extracts Limited (Aluva, Kerala, India). Standards of fatty acids methyl esters (FAME), methyl heptadecanoate, sesamin and sterols (Stigmasterol, campesterol and b-sitosterol) were purchased from Sigma (St Louis, MO, USA). c-tocopherol was purchased from Merck (Darmstadt, Germany). HPLC-grade solvents from Merck (Darmstadt, Germany) were used for HPLC analysis. All other chemicals were of laboratory grade from Ranbaxy (New Delhi, India) Experimental apparatus and extraction procedure Hundred grams of SO were mixed with methanol in different ratios (1:1, 1:2 and 1:0.5 w/v), and was then placed in an extraction vessel (1 l) consisting of a three necked flask equipped with a motor-driven stirrer, reflux condenser, thermometer assemblage and heating mantle. The mixture of SO and methanol, in different ratios, as described, was then subjected to continuous stirring at different extraction temperatures (50, 60 and 70 C) for 10 min, after which the mixture temperature was lowered to 50 C. The mixture was then transferred into a separating funnel and, after 15 min of settling time, the methanol extract and residual oil were separated. The separated residual oil from the first extraction was stripped of solvent and subjected to a second extraction with a fresh batch of methanol, as has been described and, likewise, 10 sequential extractions were performed. The methanolic extracts separated from the 10 sequential extractions were pooled and stripped of solvent using a flash evaporator to obtain the methanolic extract concentrate. The resultant residual oil from the 10 sequential extractions was also concentrated and yields were determined by gravimetry. The sequential extraction process was repeated with three batches of fresh SO at an oil to solvent ratio of 1:1(w/v) and temperature of 70 C Crystallization of lignans from methanolic extract concentrate The methanolic extract concentrate, as obtained above, was dispersed in petroleum ether (1:0.5 w/v) and the mixture was subjected to cryoscopic temperature conditons of 4 to 10 C for a time duration of h in order to facilitate crystallization of the lignans. The lignan crystals were separated from the mixture by vacuum-filtration, washed with chilled petroleum ether until oil-free, dried in a vacuum oven at a temperature below 60 C for 1 h and weighed Separation of lignans from methanolic extract concentrate by saponification Saponification of the crystal-removed methanolic extract was carried out by adding (1:1 w/v) of potassium hydroxide (KOH) in water (60:40 w/v) and ethanol (1:6 v/v) to the extract and then refluxing it in a boiling water bath for 1 h. After completion of saponification, water (1:4 v/v) was added to the mixture which was then extracted with petroleum ether (1:10 v/v) six times, each time separating the petroleum ether phase. The separated petroleum ether fractions from the six extractions were pooled and then washed with 10% ethanol until alkali-free. The combined alkalifree petroleum ether extract was flash-evaporated under reduced pressure and then dried in a vacuum oven at a temperature below 60 C for 30 min to 1 h to get the USM Purification of USM Purification of USM was carried out by washing it with petroleum ether (1:0.7 w/v) 10 times, followed by vacuum-filtration to remove the impurities and it was then dried in a vacuum oven below 60 C for 1 h to obtain the purified USM Analytical methods Lignans, tocols and sterols Lignans (sesamin and sesamolin), tocol and sterols analyses were performed with a Shimadzu HPLC (Kyoto, Japan) with LC- 10 AD model pump, a 7125 model Rheodyne injector (Cotati, CA) fitted with a 20 ll sample loop, and a SPD-10 A ultraviolet (UV) visible detector. The peaks were recorded using a C-R7Ae plus integrator. Reverse-phase HPLC equipped with a Luna 5 lm C 18 (2) column ( mm), was used for the analysis of lignans in samples (oil, methanol extract concentrate, residual oil, crystal and USM). Lignans were separated using methanol/water (70:30 v/v) at a flow rate of 1 ml/min. The UV detector was set at 290 nm (Hemalatha & Ghafoorunissa, 2004). Quantitation of separated peaks was done by calibration with standard sesamin. The peak identified at a retention time of 12.9 min was confirmed as sesamin in comparison with standard sesamin, and that at a retention time of 17.3 min was confirmed as sesamolin, based on earlier reports, and was quantitated using the response factor of sesamin. For the analysis of tocols, a Phenomenex NH 2 (M) column (25 cm 4.6 mm id 5 lm, Kyoto, Japan) was used in the normal phase with the solvent system n-hexane/isopropanol (92:8 by vol) at a flow rate of 1 ml/min. The UV detector was set at 297 nm (Renuka Devi, Suja, Jayalekshmy, & Arumughan, 2000) and the peaks were identified and quantitated using tocol standards. For the analysis of sterols, a reverse-phase Zorbax ODS column (25 cm 4.6 mm id 5 lm) was used with solvent system methanol/water (96.5:3.5 by vol) at a flow rate of 1.2 ml/min. The UV detector was set at 206 nm (Holen, 1985) and the separated peaks were identified and quantitated using sterol standards Separation of lipid classes About 20 mg of SO, methanolic extract concentrate and residual oil were spotted and separated into triacylglycerols (TG), free fatty acid (FFA), diacylglycerol (DAG), monoacylglycerol (MG) and polar lipid (PL) classes by thin-layer chromatography (TLC) on a 1 mm

3 M.V. Reshma et al. / Food Chemistry 120 (2010) thick silica gel G adsorbent with a hexane/diethyl ether/acetic acid (80:20:1,v/v/v) solvent system. Plates were prewashed and equilibrated prior to development as in standard chromatographic procedures. Lipid bands were detected by exposure to iodine vapour and were identified using reference compounds. TG, DG, MG and FFA fractions were eluted from the gel with chloroform and the PL band with chloroform/methanol/water (5:5:1, v/v/v) (Christie, 1987). Fatty acid methyl esters (FAMEs) of the separated lipid classes were prepared by esterifying with alcoholic sulphuric acid reagent, according to the International Union of Pure and Applied Chemistry (IUPAC) procedure (IUPAC, 1987). Methyl esters were analysed on a 2010 Shimadzu GC (Japan) with a flame Ionization Detector (FID) and a DB-23 Column (30 m 0.32 mm id 0.25 lm film thickness). Injector and detector temperatures were maintained at 250 and 300 C, respectively. The carrier gas was nitrogen. The oven temperature was maintained at 100 C for 10 min and increased to 180 C at the rate of 5 C/min, then maintained at that temperature for 20 min. The amount of lipid classes were determined by relating the total area of the fatty acid peaks to the area of the peak for internal standard (methyl heptadecanoate). A correction factor, calculated from average molecular weight of fatty acids, determined from the fatty acid composition, was used to convert the total amount of fatty acids to weight of the corresponding lipid class. 3. Results and discussion 3.1. Optimisation of conditions for maximum lignan extraction An efficient process for commercial production of lignans has not yet been reported. The prior arts on lignan extraction were mainly aimed at in vivo and in vitro studies, using the extracted lignans. Considering the bioactivity of lignans reported, in this study we have aimed at separating the lignans from sesame for use as nutraceuticals. The process reported here describes a most economical method to produce lignans with high yield and purity. SO was sequentially extracted with methanol in the ratio 1:1 at different temperatures (60, 70 and 80 C) and time durations (10 Weight (g) Total Lignans extracted Lignans in Res Oil Lignans in Extract Time (min) Fig. 1. Effect of temperature (70 C) on extraction of lignans from SO. 100 min). The methanol extract thus obtained was analysed every 10 min for total lignan (TL) content by HPLC. From the results of HPLC, it was observed that time, temperature and number of extractions affected lignan extraction. At all temperatures tested (60, 70 and 80 C) lignan content in the methanolic extract increased with increasing extraction time and no significant increase was observed in the lignan content of the methanolic extract beyond 100 min. Accordingly, the lignan content in residual oil also decreased. Retention of lignans in residual oil was greater at 60 C than at that at 70 C and 80 C. By changing the SO solvent ratios from 1:1 to 1:2 and 1:0.5, no beneficial effect in lignan extraction could be observed (data not shown), from that of 1:1. With 1:0.5 solvent ratios, for an extraction duration of 10 min, the TL recovery was only 7%, as against 17% with 1:1. Thus, temperature, time and solvent ratio for sequential extraction were found to be critical and were optimised as 70 C, 100 min and 1:1, respectively, as shown in Fig. 1. Table 1 shows the % yield of lignan and sterol and tocol contents of SO, methanol extract and residual oil. Under these optimised conditions of sequential extraction, the yields of pooled methanolic extract concentrate and residual oil from 100 g of SO were ± 1.0 g and 89.2 ± 1.0 g, respectively. On HPLC analysis, SO used in the present study showed a TL content of 1.08 ± 0.04%, in which the distribution of sesamin and sesamolin was 70:30 (0.75 ± 0.01% and 0.32 ± 0.05%, respectively). The methanol concentrate showed a TL content of 9.32 ± 0.19%, of which 6.54 ± 0.12% was sesamin and 2.78 ± 0.31% was sesamolin; thus, 87.04% of TL present in SO was extracted under the optimised conditions. The distribution of sesamin and sesamolin was similar to that observed in SO (70:30). The resultant oil had a residual lignan content of 0.15 ± 0.02%, indicating that the optimised conditions favoured maximum extraction of lignans. Total phytosterol and tocol contents of SO, methanol extract and residual oil were also checked and it was observed that the oil used contained 0.44 ± 0.05% of total phytosterols, of which the most abundant was b sitosterol (0.31 ± 0.02%). SO, a relatively poor source of tocols, contained only 0.04 ± 0.01% of c tocopherol. The extractability of sterol by methanol is comparatively lower (38%) than those of lignans and tocols. Eighty-six percentage of the tocol present in the original oil was extracted by methanol. These lignans, sterols and tocols can contribute to the antioxidant properties of the methanol concentrate. Lee and Choe (2006) extracted lignan compounds from roasted sesame oil and studied their effects on lipid autooxidation by using a methyl linoleate model system and reported that the autooxidative stability of methyl linoleate could be improved by the addition of sesamol, sesamin or sesamolin extracted from the roasted sesame oil Crystallization Sequential extraction trials were conducted with 1000 g of SO under the above mentioned optimised conditions for 100 g oil (Fig. 2). The separated, pooled methanolic extract from the sequential extraction was concentrated ( ± 10 g) and dispersed in petroleum ether in the proportion 1:0.5 to facilitate crystallization at 4 10 C for h. Dispersion volume of petroleum ether be- Table 1 Lignan contents of SO, methanol extract and residual oil. Oil/extract % Yield Lignans (g/100 g) Phytosterols(g/100 g) c-tocopherol (g/100 g) Sesamin Sesamolin Total lignans Stigma sterol Campe sterol b-sitosterol Total sterols SO ± ± ± ± ± ± ± ± 0.01 Methanol extract ± ± ± ± ± ± ± ± ± 0.02 Residual oil 89.2 ± ± ± ± ± ± ± ± ± 0 Each value in the table represents average (±SD) of four analyses from three replications.

4 1044 M.V. Reshma et al. / Food Chemistry 120 (2010) Sesame Oil, 1000g Sequential Extraction with 1:1 (w/v) Methanol at 70 ºC Pooled Methanol Concentrate g ± 10.0 g Residual oil 870 g ± 10.0 g Crystallization with 1:0.5 pet ether at 4 o C Residual Methanol extract, g ± 10.0 g Crystals, 5.52 g ± 0.6 g (94.36 % purity) Saponification USM, 6.04 g ±0.5 g 58 % purity Cold Petroleum Ether wash ( 2 ml x10 times) Washed USM, 5.49 g ± 0.5 g 64 % purity Petroleum ether extract Fig. 2. Optimised flow diagram for recovery of lignans from SO. low and above 1:0.5 proportions was shown to affect the crystal yield adversely. The most significant finding was that, through the crystallization step of the methanolic concentrate, 51.1% of lignans in the oil could be separated with high purity. The bioactive lignan crystals (TL 2) weighed 5.52 ± 0.6 g. HPLC analysis of the TL 2(Fig. 3) showed 94.36% purity, with lignan constituents comprising sesamin (4.63 ± 0.2 g) and sesamolin (0.89 ± 0.2 g) in the proportion of 84:16 in the crystal mixture, as shown in Table 2. Also, the resultant residual oil (870 g) could be preserved by desolventization to get the starting material, i.e. SO, to the extent of 90% (Fig. 2) Saponification Fig. 3. HPLC of lignan crystals. Saponification of the crystal-removed methanolic concentrate (109.2 ± 10.0 g) for different time durations revealed that 1 h of saponification was sufficient to complete the reaction. Washing of the USM (6.04 ± 0.5 g) with chilled petroleum ether was found to increase the lignan content in the USM due to the removal of pigments from the USM. By this purification step, the total lignan content in USM (TL 3) was increased from 58% to 64%, along with a 9% loss in USM weight (5.49 ± 0.5 g). HPLC analysis revealed that the distribution of lignan constituents, sesamin (1.63 ± 0.3 g) and sesamolin (1.89 ± 0.14 g) in the purified USM Table 2 Yield, purity and composition of lignan products obtained from SO following the process optimised. Product Code Sesame oil/product Yield of product (g) Lignans Purity (%) Lignans (%) Distribution Lignan recovery based on TL in sesame oil (%) Sesamin Sesamolin SO Sesame oil (100 g) ± ± :30:00 a TL 1 methanol extract ± ± ± :30: a TL 2 Lignan crystals from methanol extract 0.55 ± ± ± :16: a TL 3 b USM from residual methanol extract 0.55 ± ± ± :54: a TL 4 b USM from whole methanol extract 1.09 ± ± ± :20: Each value in the table represents average (±SD) of four analyses from three replications. a TL, Total lignan. b USM, unsaponifiable matter.

5 M.V. Reshma et al. / Food Chemistry 120 (2010) Lipid classes of SO, methanol extract and residual oil Fig. 4 shows the TLC pattern of lipid classes in SO, methanolic extract concentrate and residual oil and standards (TG, FFA, DG, MG, PL), lipid classes were identified by comparing the R f values of standards. Table 3 represents the effect of extraction conditions on the lipid classes in SO, methanol extract and residual oil. TG constituted the major fraction (86.26 ±.31%) of the total lipid in the SO. In Fig. 5, the gas chromatogram of TG is shown, indicating the presence of fatty acids myristic acid (peak1), palmitic acid (peak 2), stearic acid (peak 4), oleic acid (peak 5) and linoleic acid (peak 6). Peak 3 represents the internal standard. Extraction conditions (time 100 min, temperature 70 C) caused hydrolysis of TG, leading to proportional increases in FFA, DG and MG in the MeOH extract. In the residual oil, ± 0.86% was TG, followed by DG, FFA and PL; MG was not detected. 4. Conclusion Fig. 4. TLC plate of lipid classes in SO, residual oil (RO), methanol extract (ME) along with standards triglycerides (TG), free fatty acid (FFA), diglyceride (DG), monoglyceride (MG) and polar lipid (PL). was in the proportion of 46:54, unlike that observed in the pure crystals, i.e., 84:16. Thus 32.59% of the lignans was retained in the USM of the residual methanol extract. Alternatively, studies on the direct saponification of the methanolic concentrate by sequential extraction, without the aforementioned crystallization step, was also attempted. This revealed that USM (TL 4) with 72.9% purity, comprised of lignan constituents sesamin and sesamolin in the proportion 80:20, could also be obtained (Table 2/ Fig. 2). Thus the USM from whole methanol extract retained 73.33% of the lignans from the oil. The process reported here describes a simple and less cumbersome procedure, utilising extraction and crystallization techniques, with saponification only as an additional step making the process most economical and effective for producing lignans with high yield and purity. Under the optimised conditions of time, temperature and solvent ratio, maximum extraction of lignans was achieved, at the same time preserving the starting raw material. The lignan crystals obtained through this process were 94.36% pure and about 51.1% of the lignans in the original oil could be separated through the first step. Saponification of the crystal-removed desolventized methanolic concentrate and further washing yielded USM with 64% lignan. The distribution of sesamin and sesamolin in the purified USM was in the proportion 46:54, unlike in the pure crystals (84:16).These lignan compounds, either in the form of crystals or in the USM can thus be used for nutraceutical applications which take advantage of Table 3 Lipid composition (wt.%) of lipid classes of SO, methanol extract and residual oil. Sample Lipid Classes (wt.%) Triglycerides Free fatty acids Diglycerides Monoglycerides Polar Lipids SO ± ± ± ± ± 0.68 Methanol extract ± ± ± ± ± 0.14 Residual oil ± ± ± 1.66 a ND 0.67 ± 0.20 Each value in the table represents average (±SD) of four analyses from three replications. a Not detected Intensity min Fig. 5. GC of fatty acids in triglycerides (TG) of SO. 1, myristic acid; 2, palmitic acid; 3, methyl heptadecanoate (internal standard), 4, stearic acid; 5, oleic acid; 6, linoleic acid.

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